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Optics Central

Locality: Melbourne, Victoria, Australia

Phone: +61 1300 884 763

Address: 8/23 Cook Road, Mitcham VIC 3132 Melbourne, VIC, Australia

Website: http://www.opticscentral.com.au

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24.01.2022 One of the most common questions people ask me is about magnification on telescopes. For visual telescopes, magnification is the ratio of the focal length of the telescope to the focal length of the eyepiece you're using. But people also ask me about magnification when you're using a camera. And that's more complicated. Rather than thinking about magnification, it's more helpful to think about field of view and resolution. Both of these are partly determined by focal length, ...but there are other things involved too. Field of view (FOV) is the area of the sky you actually get in your photo. It's determined by your telescope's focal length and the size of your sensor. My FOV of 1.8 by 1.3 can easily get both the Horsehead and Flame nebulas in, but not the whole of the Rosette nebula in. The size of the Rosette image is determined only by my focal length. That image cast onto my sensor is just a little larger than the sensor itself. Bummer. A camera with a large sensor will have a much wider FOV than one with a small sensor. This might look like less magnification, but again it's not that simple, because sensors with smaller pixels can pack more in. With this, you can blow up the image a bit more afterwards. It makes a mockery of the whole "magnification" concept. Resolution is a measure of how much of the sky a single pixel on your camera can cover. It's measured in arc seconds per pixel, and known as pixel scale. The pixel scale is your camera's pixel size (in microns, or m) divided by the telescope's focal length (in millimetres) multiplied by a constant: 206.265. So magnification is less meaningful than your field of view and the resolution you can get in that field. In combination, these things will give you more information what you can photograph and to what detail.

23.01.2022 The International Space Station is now 20 years old. It orbits the Earth every 90 minutes or so, and while it doesn't go past everyone every time, there are quite a few opportunities to see it - as long as you don't live in Canada, Northern Russia or anywhere in Scandinavia. Mike from Port Macquarie got a fantastic photo earlier this month. It's the best one I've seen so far. I contacted Mike to find out how he did it. ... and you can take a photo like this yourself!... The ISS is about 110 metres across. When it goes over soon after sunset or soon before sunrise, it stands out against a dark sky. If the light is at just the right angle, it can be brighter than Venus. The ISS moves at about the apparent speed of an airliner, but it makes no sound, and has no flashing lights. It's quite serene. But Mike's photo was a challenge. It's a bit like photographing an A380 from Melbourne while the plane is flying over Devonport in Tasmania! Mike uses an app called ISS Spotter to alert him of upcoming flyovers. There are quite a few similar apps, and a website (http://spotthestation.nasa.gov). To take the photo, Mike used a remarkably simple setup (see the photos), but has a well-practiced technique. He has an 8" manual Dobsonian telescope, a camera (an Olympus DSLR) and a 2x Barlow. The effective focal length is 2400mm, which is like a very long lens. The DSLR has a remote shutter button and was set to take photos continuously. Mike used 1/1000s exposures and ISO 1250. Once the camera was focused, all he had to do was physically manhandle the Dobsonian, hold the shutter button in his hand, line up the ISS in the red dot finder (a Telrad) and - to quote him - machine-gun the ISS when it was in the frame. Of course, "all he had to do" belies the fact that it's quite a job to juggle all that heavy and delicate equipment and get good shots. He got around 200 photos, of which 10 or 12 were usable. It's an incredible image, and beautifully captured. Well done Mike!

21.01.2022 The Christmas conjunction between Jupiter and Saturn is nearly here! The Astronomical Society of Victoria intends to hold a public viewing of the conjunction at Caulfield Racecourse staring at 8:30 on Thursday the 17th, Saturday the 19th and Monday the 21st of December. Check out the details, and get tickets at http://asv.org.au/. Bookings are essential! If you've been looking towards the west during the evening, you will have noticed that bright Jupiter dominates. It's the b...rightest thing in the sky right after sunset. Nearby, upwards and to the right (if you're in Australia, at least) you'll see a much dimmer Saturn. I've attached one of my own photos - taken last week through glass, so there's horrible reflections of the freeway lights - sorry! Each evening, Saturn and Jupiter have been edging closer to each other, and they'll be at their closest on the 21st. And I mean close. They're right up against each other. I've attached a couple of simulations of the sight at 9pm on the 21st. As you can see, it's after sunset but before the sky gets fully dark. The pair set at about 10:30 so there's a very limited window of opportunity for viewing. The wide field shows that the pair are only 18 degrees above the horizon at 9pm, and about the same distance to the left of true West. As they set, they'll drift further to the left, because we're in the Southern Hemisphere. By 10pm they'll be just 12 degrees above the horizon (which is very difficult to see). The eyepiece view simulation shows how close the planets will be at 9pm. As you can see, they're so close that their moons are entangled. I'll be helping out at the ASV event on the Monday night - so I might see you there!

19.01.2022 The other day I showed a photo of a circuit board I took though a dissecting microscope using a camera and a microscope adapter. A dissecting microscope has a large space for the specimen and low enough magnification for you to move it about while watching through two eyepieces. The other common type of microscope is for biological work. Because the bottom lens can get closer, magnification is higher, often up to 1600 times. You use a biological microscope for looking at thin...gs like plant or animal cells, or tiny things like insect parts - anything you can get onto a microscope slide, really. Using the adapter and my camera, I took photos with two more biological microscopes. The first was a saxon RBT Researcher Compact, which is a high-magnification stereo microscope. The camera went into the trinocular. You can see the set-up photo. The two photos here are the same: one is the whole frame and one is a detail, cropped for Facebook. I had to take a few test shots in manual mode before I was happy with the lighting. You can also see that the image was smaller than the size of the camera sensor, resulting in a dark shadow around the outside. This is called vignetting. I could also have spent more time on fine focusing. The second biological microscope was a much cheaper saxon SBM ScienceSmart. This is a single eyepiece microscope with lower magnification, so I attached the camera to the eyepiece holder. You can see the whole frame photo and its detail. I was very pleased with the image I got, even though it showed a little vignetting. If nothing else, it shows that the slides we use for our display models need to be cleaned! Overall, I'm pretty pleased with these photos. I'm reasonably used to photographing things through optical equipment, but the fact that I got these photos in a half hour shows it's not difficult for you to do. The ability to take high resolution photos through a microscope is useful for a lot of people. For others, its just a lot of fun.

19.01.2022 We've just received a pile of QHY cameras. I'm taking the opportunity to have a better look at some of them. This weekend, I looked at a QHY5III 178C planetary camera. I intend to post photos in the near future, but at this stage I haven't really come to grips with it. You see, the 178C is a colour camera and I'm used to monochrome.... There's a difference? CCD and CMOS sensors work by counting photons that land on each pixel. As an analogy, the pixels on the sensor can be thought of as buckets. Photons from stars fall in these buckets and get counted. However, the sensors only count photons - they can't tell what colour (or wavelength) the photos is vibrating at. What this means is that at their heart, all camera sensors are monochrome. To make their camera record true colour, monochrome users (like me) capture the image several times, through filters that only pass red, green and blue light. I reintegrate the shots later to make the final image. Colour cameras such as the QHY5III 178C work in a slightly different way. An array of tiny red, green and blue filters (called a "Bayer" filter) is put in front of the sensor, so that each pixel has its own filter. Groups of pixels get bundled together to form colour pixels. In effect, the camera takes the photo through the three filters simultaneously. The trick is to know which pixels are blue, green and red, so you can put them back together correctly. When it's right, each colour pixel on your computer screen displays the same levels of red, green and blue that fell on the sensor in the first place. So, to your eye, it's just that right shade of chartreuse! The QHY5III 178C has an RGGB Bayer pattern. I haven't mastered it yet, but I understand that the image is captured using SharpCap or similar can be saved either as a single monochrome layer (along with the Bayer key) or as three separate layers, one for each colour. But, like so many things in this hobby, it's not simple. It takes time and practice!

19.01.2022 Hooray, hooray, it's Black Fri-yay! Yes, we were only able to hold out against international peer pressure for so long. Optics Central's Black Friday sale is now on! Equatorial mount owners - are you a fan of polar scopes? Love kneeling for hours in the wet grass searching for stars you just can't see? No? Well, embrace the technology and get a QHYCCD Pole Master and adapter! Today, with the 5 per cent discount, it's just $531.90 - and shipping is free! ... Christmas is coming! Looking for a great gift for someone with a scope? The Celestron Powerseeker Eyepiece and Filter Kit is just $79.95 - that's a whopping 36 per cent off our normal price! Need a pair of binoculars for bird watching, hunting, or just admiring the view? During the Black Fri-yay sale there's free shipping on selected binoculars. Remember, the sale ends on Monday night, so get in quick! https://www.opticscentral.com.au/black-friday-sale

18.01.2022 I'm not sure how QHY labels their cameras. This is a QHY 268PH-C, the new APS-C colour camera (the one with all the bells and whistles: cooling, back illumination, zero amp-glow, 16-bit analogue-digital conversion). It comes in a couple of varieties, and this one is the photographic one. If you want the one with optical connectors, you'll have to order that specially (and get a computer that's capable of communicating with it). We've got a couple in stock now, and I pulled on...e out to take a photo, and found that it simply says "QHY268". I guess you just have to know.

18.01.2022 COVID trading arrangements for at least the next six weeks: You probably know that we’re located in Melbourne, which means we’re under a very strict COVID lockdown until at least mid-September. First, the good news: our website is open and we’re continuing to send optical equipment out through the mail. Also, we’re on the phone, on live chat and on the email on weekdays between 9am and 5pm, so we can help you out with whatever you need.... However, there’s less good news: we might be here, working away shipping products out, but customers are not permitted in the showroom. It’s locked, so please don’t turn up to browse. If you want to get information about telescopes, microscopes, binoculars, or anything optical, call us on 1300 884 763. For eligible orders only, we are open for click and collect pickups, but the majority of dispatches will be through AustPost or couriers. Finally, because of these restrictions, we’re closing on Saturdays for the next six weeks. I know this is inconvenient for everyone, and we're doing as much as we can to meet your needs, but there are forces in action that we aren't able to control (that is, the Coronavirus as well as external regulations put in place to combat the spread).

16.01.2022 I get asked a lot of questions from a lot of people. All of these questions are good, but some are so good they get asked a lot. This is one of those questions. The magnification of a telescope is how much bigger your target looks compared to looking at it without the telescope. If you like, it's how much closer the target is going to look. Magnification is expressed in multiples, so if your telescope has a magnification of "50 times", it means that whatever you're looking at... will look 50 times closer, or will appear 50 times bigger than without the scope. Remember that your telescope can have several eyepieces. Changing eyepieces changes the magnification. So, for watching the Moon, your 25mm eyepiece might give you just the view you want. However, if you want to look at Jupiter, all you get with a 25 is a dot, so you need more magnification. The 10mm eyepiece will give you a much closer image. But to calculate it, there's some mathematics involved. Your telescope, regardless of eyepiece, has a defined "focal length". You're likely to see this reported as, say, "F=650" on a sticker on the side of the scope. Typically, refractors or reflectors have focal lengths between 500mm and 1000mm, with Dobsonians being a bit longer, say, 1200mm. Cassegrains and Maksutovs (the ones with mirrors at both ends) can be much longer, up to 2800mm or even more for the giants. Your magnification depends on both the focal length of your telescope and the focal length of the eyepiece you're using. In fact, the magnification is the ratio of the two. So if you've got a scope with a 900mm focal length, and you're using a 25mm eyepiece, your magnification is 900/25=36 times. Change to the 10mm eyepiece and the magnification becomes 900/10=90 times. If nothing else, this explains why the higher number eyepieces have lower magnification! I know you're itching to ask about how to calculate magnification for photography. Err, it's complicated. I'll get to that another time.

15.01.2022 I know that for a lot of you, microscope photography is second nature, but being the astrophotographer, this is something that's new to me. We sell a range of microscopes. They start at very basic microscopes - essentially for kids and students, and go up to what I might call a middle-range professional instrument, suitable for engineering laboratories, vets, botanists, pest controllers, etc. Nothing like cutting-edge university labs or electron microscopes, sorry. We've also... got a number of ways of getting an image from a microscope. We'd prefer to use a separate imager, which is essentially a camera sensor that slides into the eyepiece holder or trinocular head. We've even got a few entirely digital microscopes, both hand-held or with a screen on a microscope body. If pushed, we can even get a mobile phone camera to the eyepiece. But the other day, a customer asked about how to attach a DSLR to a microscope. I've never really considered putting something as large as a DSLR onto one. It all comes down to the humble t-thread. This is an industry-standard, used to connect all manner of diverse things. Going through this thread, you can connect DSLRs, CMOS cameras, filters, eyepiece projectors, etc. onto telescopes, spotting scopes, filter wheels, and, as it turns out, microscopes. From the camera side, you need an adapter that fits onto your DSLR's bayonet mount. When you take your lens off, this little jigger goes onto the camera body. Which one you need depends on your camera, of course, but they all end in a female t-thread. From the microscope side, you need a second adapter that slides into the eyepiece holder or trinocular head. This adapter ends in a male t-thread. In this case, the adapters I needed were my own t-ring for a Pentax, and the saxon 1" to T2 Microscope Adapter. As you can see in the attached photo, the camera slots neatly into the trinocular on the microscope. You can also see the resulting photo (and the 100% crop to show the detail).

15.01.2022 I've mentioned the dwarf planet Ceres in my posts before, but only in passing. it's a little hard to introduce Ceres, due to changing nomenclature. It used to be considered the largest asteroid, but it's now called a dwarf planet. It's certainly the largest object found in the asteroid belt between Mars and Jupiter. It's also the only defined dwarf planet this side of Neptune. We've known about Ceres since the start of the 19th Century. Astronomers had been looking for planet...s between Mars and Jupiter, and discovered a number. They called this group "asteroids", meaning things that are "almost, but not quite, entirely unlike stars". But the thing that's most interesting about Ceres is those white dots. Hubble got a few photos of odd bright patches on Ceres back in 2004. Aliens! The Dawn mission, when a probe orbited Ceres, found that these were patches of sodium carbonate. These had probably formed when salty water bubbled up from Ceres' "muddy" interior, the water then sublimating into space. Judging from the amount of mixing the surface gets from meteorites, the percolation of brine to the surface is still happening, meaning Ceres is still volcanically active. You can see Ceres. It's a bit of a challenge, though. Ceres is magnitude 7.7, so you're going to need a medium sized telescope, a tracking mount and a camera. Currently, Ceres is between Aquarius and Sculptor. It rises after 6pm (Melbourne time) and sets at about 9am, meaning it's perfectly placed for observation. If you've got a go-to mount, find a star called SAO 191585. To see Ceres, take an exposure of about 30 seconds while your mount is tracking. Then about an hour later, come back and take another one. Better still, keep taking images for a few hours. Ceres will be the dot that moves slowly across the face of the other stars. My field is about 1.8 wide, and Ceres takes about 10 days to cross this. It doesn't move quickly. Good luck! ...and apologies to Douglas Adams. NASA images/Stellarium

14.01.2022 Telescope mirrors are delicate, right? So what happens when you shoot one with a gun? Reflector telescopes are a great way of getting some serious aperture onto a deep-space object like a nebula or galaxy. The 10-inch Dobsonians we have give a relatively inexpensive, no-nonsense and, frankly stunning view of those hard-to-see, dim fuzzies, especially from a dark sky location. New owners of reflector telescopes always ask me how often do they need to clean the mirror. They see...m surprised when I tell them that with care, they probably won't ever have to. Mirrors, particularly large ones, are very forgiving. How's this for a case in point? The Harlan J Smith Telescope in Texas is a 107 inch Cassegrain (with a Caudé option as well, for the technical). To put that into perspective, the ASV's monster in Central Victoria is "only" 40 inches in diameter. On commissioning in 1968, it was the third-largest telescope in the world. But in February 1970, there was an "incident". A member of staff appears to have had some sort of mental health episode, and directed his anger (along with a hammer and most of the clip from a 9mm pistol) at the mirror. He succeeded in shooting the mirror seven times, the damage being 3-5cm craters in the surface. Thankfully, apart from some understandable trauma, nobody was hurt. The telescope was relatively unscathed and was able to be used the very next night. It's been in continuous use ever since, with the mirror undergoing regular maintenance. The damage is still visible, and has reduced the light-gathering ability of the mirror by about 1 per cent. Diffraction from the craters is minimised using matt-black coatings. So next time you peer at your mirror and consider if you should clean those specks of dust off, think again. You're more likely to scratch it and cause diffraction spikes. https://www.nytimes.com//texas-man-fires-into-a-telescope- Image: McDonald Observatory

14.01.2022 Today's summer solstice post is overshadowed a little by the Grand Conjunction between Jupiter and Saturn. Of course, you're all out watching that - weather permitting, of course. Saturn and Jupiter will move behind the Sun, but Mars is still high, although it's beginning to get small as it moves away from the Earth. I've added a couple of pretty clusters to my list this time, M41 and M47. I got both of them from my light-polluted back yard a week or two back.... I've included my photo of M41, which I took using a saxon 1021 doublet refractor and my DSLR. Some of you got one of these for Christmas. The list is ordered by rough transit time - the time on the 21st when it's highest in the sky. That means roughly from West to East, and I'd advise looking at them in that order or some will set before you get to them. Globular cluster: NGC 104 - 47 Tucanae (07:55 PM) Galaxy: M 31 - Andromeda Galaxy (08:09 PM) Galaxy: NGC 253 - Sculptor Galaxy (08:09 PM) Galaxy: NGC 292 - Small Magellanic Cloud (08:24 PM) Galaxy: M 33 - Triangulum Galaxy (09:07 PM) Galaxy: M 74 - Phantom Galaxy (09:07 PM) Double star: Rho Eridani - Cat's Eyes (09:07 PM) Double star: Zeta Reticuli (10:48 PM) Galaxy: NGC 1365 - Great Barred Spiral Galaxy (11:02 PM) Open cluster: M 45 - Pleiades (11:16 PM) Open cluster: Mel 25 - Hyades (12:00 AM) Galaxy: ESO 56-115 - Large Magellanic Cloud (12:43 AM) Globular cluster: M 79 (12:43 AM) Bright nebula: M 1 - Crab Nebula (12:57 AM) Bright nebula: M 43 - De Mairan's Nebula (12:57 AM) Diffuse Nebula: M 42 - Orion Nebula (12:57 AM) Bright nebula: NGC 1977 - Running Man Nebula (12:57 AM) Bright nebula: NGC 2070 - Tarantula Nebula (12:57 AM) Dark nebula: B 33 - Horsehead Nebula (01:12 AM) Diffuse nebula: NGC 2024 - Flame Nebula (01:12 AM) Variable Red Star: Betelgeuse - Alpha Orionis (01:26 AM) Double star: Canopus - Alpha Carina (01:55 AM) Bright nebula: NGC 2237 - Rosette Nebula (01:55 AM) Open Cluster: M41 - Little Beehive (02:09 AM) Open Cluster: M47 (03:07 AM)

14.01.2022 An astroterrestrial photo is one that includes a star field as a background with something in the foreground to provide a subject. It can be a tree, a building, or anything the photographer chooses. In this case it was James. James lives in Canberra, and last May, was celebrating the end of the local lockdown with a weekend at Lake Eucumbene with his girlfriend Loz. James normally takes deep-sky nebula photos, so he took a 12" go-to Dobsonian with him, which is quite a task.... His intended targets were the Lagoon and Trifid nebulas, which were rising just after midnight. But setting up, he found that they weren't high enough to be much good. For targets near the horizon, you're looking through the boiling, dust-ridden soup that is the Earth's atmosphere. It wasn't until 2am that a photo was possible. But at that point, the dew was getting heavy and the secondary mirror on the Dob was starting to fog over. Such is life for the astrophotographer. The night wasn't a total write-off though. Earlier, Loz had taken this shot of James standing face-to-face with the setting Orion. And by "face-to-face", I'm being almost literal. Most people recognise the constellation of Orion by the three belt stars and the three sword stars. (In the Southern Hemisphere, people also know this asterism as "the saucepan".) Below the belt and sword, Orion's feet are the two stars Rigel and Saiph. Above the belt, Orion's shoulders are marked by Betelgeuse and Bellatrix. Have a look at the Stellarium diagram I've attached. What all this means is that Orion's head is traditionally thought as being the star Meissa, and this is what James is looking right at. For the technically-minded, this is a single 20 second exposure at ISO 3200 using a Canon 200D mk 2 which has been modified to allow near-infrared light from nebulas through. I'm not sure if the infrared had much of an effect in this image apart from brightening the sunset, but it sure is pleasing. Great result, Loz and James!

14.01.2022 The other night was the first night in weeks where it wasn't cloudy. Of course, there was a mad scramble when Melbourne-based astrophotographers were all running outside to take photos. Naturally, I was one of them. We couldn't run far though. The Melbourne Coronavirus lockdown prevented anyone from leaving their homes. On the night in question, the Moon was about three quarters full (waxing gibbous, if you're into that sort of thing), and not far from Jupiter and Saturn. Mar...s was up later. The Helix Nebula was around half way between Saturn. and Mars, and the Sculptor Galaxy followed. But imaging under moonlight is challenging, especially if you're after deep-sky targets like nebulas or galaxies. Moonlight washes out the really faint light from these targets, meaning the signal (nebula light) to noise (moonlight) ratio is really low. You can drag out these details using many subexposures, or use light pollution or narrowband filters, but at best you'll get an image which still isn't as good as one you'd get at a dark sky site. So I didn't go for the Helix or Sculptor. Instead I went for the dwarf planet Ceres. While I was doing that, I thought I'd also try something that took advantage of the moonlight, rather than fighting against it. I used the light pollution as a light source. This is when you use a long exposure to take photos in darkness, using different and unusual light sources. I'm no expert at this, but there are some who are masters at light painting (and I'm looking at YOU, Deanne!). In this case, the Moon was providing my photons. I put the camera on the tripod, set the timer to take a series of 30 second exposures, and went back to watching Ceres. The photo shows my "office", with me, my computer, mount and scope. The subtle moonlight is casting shadows downward onto the grass, but the fence is casting a shadow sideways. It's the neighbour's porch light which is also shining on the house behind. Shadows can be a bit puzzling, really.

13.01.2022 Melbourne seems to be making progress in getting the Coronavirus outbreak under some control, finally. However, for the moment we're still in lockdown and can't get out of the city for astronomy. Light pollution plays havoc with astronomy, and especially astrophotography. Light pollution is when light from street lights, house lights, sports stadiums, outdoor advertising and all those other reasons for turning lights on gets reflected off any dust in the air above us. It turn...s into a barrier separating us and the sky, effectively blotting out all the dim and interesting things out there. But that doesn't mean we can't see anything. Right now, even if the Moon isn't in the right spot (it changes all the time, of course) Jupiter and Saturn are nicely available. They're both high overhead soon after sunset. If you stay up much later, Mars will rise in the East, and because it's near opposition, it'll look good in a long focal-length telescope like an Novo 909. But we can also look for star clusters. These are pretty, largely immune from light pollution, and can be seen in inexpensive telescopes. I've shown a few over the past few weeks, and here's another one. M25 (sadly, it doesn't seem to have a common name) is high in the north west after sunset now. It's quite observable, even from the city. Finding it might be a challenge, though. Using the map I've attached, start from yellow Saturn and hop to very bright Jupiter, then turn a little to the left and make another, sightly larger hop. With experience, you might be able to see the "teapot" asterism that is Sagittarius and use this as an extra signpost. I've attached my own photo on which I've put some circles showing the field of view of some small telescopes and their eyepieces. This might give you an idea of how big it'll look in your own scope. I've also reprocessed the same photo, enhancing the star colours a little. If you want to see a pro's photo, have a look at https://apod.nasa.gov/apod/ap090831.html

11.01.2022 Being a nebula guy, I'm no expert at this, I assure you. This is pretty rough, but it'll get you started with some ideas. This was back in January 2017, and we were down at Sorrento with the family. It was a pleasant time, pre-Covid. On one of the evenings, my daughter and I went down to Diamond Bay to get some shots. We were looking North a half hour before midnight. You can tell that from the stars.... This is a single 30s exposure, f/3.5 at ISO 3200. I had a Pentax fisheye lens, which I don't like much. You can see horrible chromatic aberration if you look closely at the brighter stars. I used no tracking, just a tripod. I wanted to keep it as simple as possible. Some people take separate images for foreground and background, and there are advantages in this, such as foreground focus as well as background stacking. You can see the unprocessed original. Back home, I processed it in Photoshop (or you can use GIMP for free). I've un-distorted the image slightly, and rotated it a little to make it look more natural. I split the image into foreground and background so I could process them separately. I feathered the edges between the two layers to make it hard to tell where the cut is. For the foreground, I lightened the darkness using the levels tool. I brutally shoved the midpoint of the histogram to the left, and nothing more. Doing something as violent as this made the heavily lightened ground look very noisy and grainy. To counter this, I added a Gaussian blur rather than trying to reduce the noise. For the background, I had a lot of light pollution to cope with, as we were looking straight at Melbourne. I pushed the saturation to the max, which allowed me to adjust the colour balance before decreasing the saturation to a realistic level. Then I added some vibrance. I found that I didn't need to play around much with the levels. I didn't do anything about the chromatic aberration. That's it. Go and try it yourself. All you need is a camera and a lens.

11.01.2022 Black Fri-yay! Yes, it's on again for 2020! In celebration of some festival in anther country, we're having a sale! (Does it sound like an excuse? You betcha!) We've knocked 5 percent - and the shipping - off astronomy cameras and astrophotography accessories, and up to 50 percent off "selected sale items", by which we mean miscellaneous stuff that we think you might be interested in.... On an unrelated note, if you pick up a qualifying pair of binoculars, we'll pay for the shipping - Australia wide! See the banners for details, but as an example, how about a QHYCCD Mini Guide Scope for $256.45? Not only is that 5 percent off our normal price, but you get free shipping as well. To that, you could add a ZWO ASI120MM-S guide camera for $225.10, which is 5 percent off as well. Mixing ZWO and QHY stuff? Shock, horror! Well, it is Black Friday! At the other end of the spectrum, you need to keep an eye on the weather, so we've got multi-function tabletop weather stations for $19.95 - that's 67 percent off! If you want to save big, you can save $1300 on a Sky-Watcher EQ8 mount with tripod! But hurry, all this silliness ends at midnight on Monday night! https://www.opticscentral.com.au/black-friday-sale

10.01.2022 Over the last few weeks I've posted about a few star clusters. These are groups of stars you can see using an inexpensive telescope from the suburbs while you're under lockdown. Here's another one. This cluster was named after its (supposed) discoverer, the ancient Greek astronomer Ptolemy. It's in all sorts of catalogues, including Messier's catalogue as M7 and the New General Catalogue as NGC 6475. You don't actually need a telescope to see this one. A pair of binoculars wi...ll do, because not only is it made up of nice bright stars, it's also quite large. In fact, if you're in a dark sky area, you might see it with your naked eye. The cluster itself is just outside Scorpio. This is a very recognisable constellation that's rising in the East in the evening at this time of year (July). I always think that it looks like a gigantic backwards question mark. I've attached a screenshot from Stellarium, but of course you can use your own: there are lots of similar programs available. The results will be the same, because the stars are the same. Notice the end of the scorpion's tail? There's a line of stars. These are Lesath, Shaula, Mula and Girtab. You'll see them in the screenshot. There's another star outside the question mark in the map, called Fuyue. This slightly yellow star is your signpost. Looking through your scope, start from a spot between Girtab and Mule, and find your way to Fuyue. Then, make the same hop again, and you will find yourself at Ptolemy's Cluster. I've marked your hops with green arrows. I've also attached a photo, along with circles that show roughly what you'll see using 10mm and 25mm eyepieces using 650mm and 910mm telescopes. Just for fun, I have also included my photo taken from my back yard in Kew. the camera picks up more than the human eye can see, and the background of Ptolemy's cluster is a nice chunk of the Milky Way. If you want to see this with your eye, you'll need an 8" or 10" Dobsonian and a dark sky - but it's worth it!

10.01.2022 What's that madman doing this time? A few nights ago I was out in my back yard taking photos of planets. Using a monochrome camera and filters, I got a couple of images. They're not great, but that's another story. While I was out there, I noticed a problem. Jupiter had a big dark blob in front of it. The blob was about the same size as the planet, and roughly circular. Because Jupiter was a smallish image on the sensor, I was able to move my mount so that the blob didn't int...erfere with the image, but I suspected I had dust on one of my filters. Next morning, I looked at the filters and the camera. Try as I might, I wasn't able to see anything. Dust is a frustrating problem, especially for planetary photographers. With photos that use the whole frame, you can compensate for dust, but for tiny planets you can't do this. I decided to find it using the camera itself, by getting a "flat frame". This is a photo of what should be a blank featureless field. Because there's no background, dust shows up as round or donut shaped blobs. It also highlights vignetting, where the centre of the frame is brighter than the edges. To do this I went and got a white tee-shirt and put it over the lens. I stretched it so the weave was consistent - it wasn't tight on one side and loose on the other. I went outside and pointed the scope at some clouds to get an unfocused, consistently illuminated field. I exposed the photo so none of my pixels were black, but none were white either. The image was boring - just a grey box. But when I fiddled round with the levels tool in Photoshop, the vignetting and two dust shadows emerged. They were on the luminance filter, one above and one below the line of the sensor's long side. Now that I knew where the dust was, I was able to have a closer look, and I was able remove them using a blower brush. Once I took a second flat frame, and processed it similarly, you can see that it's more or less clear of dust. Back to work!

09.01.2022 I’m sure you heard about NEOWISE, the comet that dazzled viewers in the Northern Hemisphere. I received several amazing photos from my friends in the US. Sadly, by the time it got to the Southern Hemisphere it had dimmed off considerably. Yes, it was visible from Melbourne but how visible is visible? What's worse, Melbourne was in lockdown for the Coronavirus, so people like me couldn't get out from under the dome of light pollution. The whole thing was a bit of a bust, r...eally. Comets are unpredictable. They regularly brighten when far distant, something that gets astronomers jumping up and down. But just as often they fizzle out or even break up before getting close. Once (well, in my memory at least) a comet even crashed into Jupiter. Let’s call that a bad day. The photo I've attached is NASA's daily pick from back in July. What's going on here? Why does the comet have two tails? Nearly all comets develop a twin tail. It's because they leave behind two types of particles as they are warmed by the sun. The broad white tail you see on the right is mostly made up of plain dust, blown away from the nucleus by the solar wind. Because dust particles are relatively heavy, they start slowly, gently accelerating as they are blown by the solar wind. Incidentally, in the photo, the comet is travelling from right to left. The curve in the dust tail is a result of this motion. The ripples are a matter of debate, but might be due to the nucleus spinning. But the comet is also shedding ions, individual molecules that have directly collided with a particle from the sun. These are much lighter particles than dust, so when they enter the solar wind, they match its speed almost instantly. As a result, the ion tail is much straighter. Think of it as a blue motor cycle and a white semi trailer waiting at the traffic lights. On green, the light motor cycle speeds away, leaving the heavy semi trailer lumbering along behind. https://apod.nasa.gov/apod/ap200722.html

08.01.2022 A little while ago I posted about how you can improve your single photos of the Moon by using video instead. You set your phone or DSLR to take a video, and then process that in a succession of free software (PIPP, Registax and GIMP). The idea is similar to image stacking. Multiple images contain more information and less noise than a single one. The combined image can then be manipulated far more. In my example, I set my DSLR to take video frames of the Moon. We ended up wit...h a photo that looked better than any of the original frames (such as the one with the passing aeroplane). But we can improve it again. Standard video frames are only 1920x1080 pixels, which means we don't have a huge number of pixels to play with. The Moon itself was only about 400 pixels across. But my DSLR has a sensor of 6016x4000 pixels, so we can get more resolution using stills. Again, I set my camera up. (Incidentally, you can tell from the Moon's phase that I did this a day after my first video was taken.) After framing and focusing as before, I used a timer to take 100 individual photos. I downloaded these to my computer. The Moon was about 900 pixels wide on these frames. That was more than double the size of the video images. My workflow was very similar to before. I opened all 100 files in PIPP, had it detect the Moon, centre it, crop some of the black off and keep the best 25 frames. I also had it convert to monochrome. It's the Moon - there's not much difference. I took the 25 TIF files to Registax. I set align points, aligned and stacked using default values. Then I sharpened using the first two wavelets, and finished in GIMP. Because we had so many more pixels to play with, the image is larger, so I've zoomed in on Mare Imbrium. Compare details with the originals - the video with the plane and the one out of the still camera. As in all these things, there are details I haven't talked about. That's for you to research. You've got the basics, go and shoot the Moon!

07.01.2022 Merry Christmas everybody! Just a quick one this morning: my composite photo from Sunday evening. I'd borrowed a saxon 1021 Hyperion refractor from work, which I'd set up on my NEQ6 mount on the roof of a neighbour a couple of doors down (I can't see the western horizon from the front of my own place due to a street tree).... So in front of several spectators, I took eight video captures using my Pentax K3-II DSLR. Each capture was around 3000 images, set to different exposures, and I chose the best four for this composite. Jupiter is very bright, so the capture with the shortest exposures was for that. The second shortest was for Saturn, and the two moons you can see (Io to the left and Ganymede to the right, I think) were the longest exposures. I processed each video in AutoStakkert, and then blended the results in Photoshop (but you could use the free GIMP software). I do have to reiterate that this was a composite, meaning the images you're seeing were from four different exposures using different processing. I've also included one of the processed video captures. You can see that Jupiter is overexposed in this one, and you can't see much of the moons at all. This is the one I used for Saturn in the final composite. Finally, I've attached a single image, which shows the atmospheric distortion that was happening at the time. You can see that Saturn and Jupiter were quite badly distorted. Astrophotographers are rarely happy with their work, and I think I could do better - Jupiter could be brighter, and possibly Saturn, just a little, too. I know that there's a third moon in the darkness there as well. If anyone wants to know more details about how I processed these images, just yell out.

07.01.2022 It's planet season! Jupiter is blazing away in the evening, pretty much unmissable high in the East just after dinner, and Saturn isn't far behind it. If you're up much later you'll see Mars approaching opposition. I had a good look the other night using a saxon 909AZ3 and Mars is about the same apparent size as Saturn without its rings. My mate Paul just got this shot of Neptune, which is difficult, but a beautiful blue. There are plenty of bright clusters like 47 Tuc, and d...immer objects like the Helix Nebula. or the Sculptor Galaxy. Far into the North, the Ring Nebula will challenge you. Here’s the list of springtime objects. It spans 12 to 20 hours in RA, and is biased to the southern objects. Because we're locked down in Melbourne, it won't be easy for you to see the dimmer objects. The list is ordered by the time targets pass the meridian that is, their highest point of the night. The Omega Nebula is past the zenith before 7pm, so go for that one first. Also, depending where you live, some of these targets are circumpolar, meaning they don’t set at all. To this list you can start to add some summer objects. The Pleiades is up in the mornings now, and if you're keen, that makes a beautiful sight in a small telescope. Diffuse nebula: M 17 - Omega Nebula (06:45 PM) Globular cluster: M 22 - Sagittarius Cluster (07:00 PM) Open cluster: M 11 - Wild Duck Cluster (07:15 PM) Planetary Nebula: M 57 - Ring Nebula (07:15 PM) Globular cluster: NGC 6723 - Chandelier Cluster (07:20 PM) Open cluster: Cr 399 - Brocchi's Cluster (07:50 PM) Double star: HIP 95947 - Albireo (07:58 PM) Galaxy: NGC 6822 - Barnard's Galaxy (08:10 PM) Globular cluster: M 15 - Pegasus Cluster (09:55 PM) Planetary nebula: NGC 7293 - Helix Nebula (10:55 PM) Globular cluster: NGC 104 - 47 Tucanae (12:50 AM) Galaxy: M 31 - Andromeda Galaxy (01:10 AM) Galaxy: NGC 253 - Sculptor Galaxy (01:15 AM) Galaxy: NGC 292 - Small Magellanic Cloud (01:20 AM) Double star: Rho Eridani - Cat's Eyes (02:05 AM)

07.01.2022 This is what you can do with a small star tracking device. Steve from Tassie recently got himself a Sky-Watcher Star Adventurer, which is like a small equatorial mount designed to carry a camera and normal lens. Steve used his Lumix G9, a micro four-thirds camera with a 200mm f/2.8 lens. This gave him the equivalent of 400mm focal length for a full frame. Using ISO 1250, he took 12 30 second exposures, which he stacked using Affinity. Final touches he did in Apple photos. As ...to the photo, it’s one of my favourite areas in the sky, the end of the Rho Ophiuchi dust trail. There’s so much there. The bright yellow star is Antares, the eye of the Scorpion. Above and to the left is the globular cluster M4, but between them is the smaller cluster NGC 6144. Continuing anti-clockwise, Alniyat is next, and then the smaller star HIP 80079 to the left of the shot. Below this is (for me, at least) the star of the show, Rho Ophiuchi, the star that gives the whole area its name. Faintly seen around Rho is its nebula, which shines blue in reflected light. Finally, back towards Antares is the star HIP 80815. The whole area throughout the shot is dusted with nebulosity, visible in reflection and emission. Apart from the blue around Rho Ophiuchi, there’s yellow reflected from Antares and red from ionised hydrogen around Alniyat. These are contrasted by the Great Nothingness of the dark dust lanes running from the bottom of the shot. Not far from the Galactic Core, this is one of the most colourful areas in the sky. With his setup Steve has a field that most telescopes just can’t reach, it's way more than what I can get! For polar alignment, Steve used a phone app and compass. He’s clearly done a good job those stars at the edges are good and round. You know, you can also add a small refractor to the Star Adventurer. Officially, it’s rated for 5kg of payload, although I think it’d probably struggle with balance if you loaded it up that much. Great work, Steve!

06.01.2022 We’ve been selling the new Celestron StarSense Explorer telescopes for a few months now. The StarSense Explorer is a nifty new development in the world of beginner to intermediate telescope mounts. It uses the camera on your mobile phone to determine which way the scope is pointed by looking at the stars and consulting a database. It then guides you to whatever you want to look at. Very clever. Of course, our stock sold out before we were able to grab one to use as a display ...model, so I still have yet to play with one. But that’s not the point of this post. The point is the strange Barlow lens that comes with the StarSense Explorers. A Barlow is inserted into the converging rays of the telescope, making them converge less. Put simply, this pushes the focal point (where the light actually converges) further back from the objective lens, increasing the focal length (magnification) of the telescope (see my ray diagram). You also have to move the eyepiece back. We had a series of queries from customers who had had trouble using the Barlow lens that was supplied with the telescopes. Try as they might, users simply couldn’t get anything in focus with this Barlow. Eventually we got one back, and tested it on a scope. Nothing. We could focus on a tree just outside the window a few metres away, but nothing further. Clearly there was something wrong. We contacted Celestron and described the problem. After some thought, they identified what the issue was and told us what to do. This particular Barlow has to be inserted directly into the focuser prior to attaching the right angle and the eyepiece. I’ve shown this in one of the photos. We had set it up like other Celestron Barlows, going focuser right angle Barlow eyepiece (see the other photo). Once we set the train up in that way, we were able to find focus in distant objects, although the magnification was greater than expected. Celestron is in the process of updating their telescope instructions.

06.01.2022 I'd been waiting to get a photo of "the object formally known as the asteroid Ceres", for weeks. I'd written about it previously, and my research had piqued my curiosity. Finally I got a decent night. Ceres isn't exactly dazzling. After all, it's less than 1000km across (about the distance between Melbourne and Mildura) and it's orbiting between Mars and Jupiter. On the night, a three quarter moon was pretty close. What's more, Melbourne's light pollution was ... still there.... This was a challenge. I wasn't going to know if it worked until after I processed the image. I was confident, though. Ceres is magnitude 7.7, and I've taken a photo of Oberon (one of Uranus' moons) before, and that's magnitude 14 or so. The way to take photos of tiny planets is to get several over time and see if one of the dots moves. I wasn't after colours or anything sophisticated, so I used my monochrome sensor with nothing but a luminance filter - plain glass, really. Because I wasn't after the dim light from nebulas (or light pollution) I used a series of 30 second exposures that would leave the background dark, revealing just the stars. And, I hoped, Ceres. I set my scope up in the back yard and watched it work for five hours. It paused only to focus every hour, as well as do a meridian flip as Ceres passed overhead. All up, it took 378 exposures. When I started processing the next morning, I was worried to discover that all of the images looked the same. However, when I compared the first one and the last one, one dot had shifted. I breathed again. There it was. I used Deep Sky Stacker to align the shots precisely, and crop so the movement was noticeable. Then I used Photoshop to open each one, brighten them and save them as files I could use in a video. Finally, I opened these in my video editing software, Shotcut, and made the video. Finally, I watched Ceres drifting lonely through the darkness. There's a good chance that I was the only human watching it at the time.

06.01.2022 Something is coming up that you'll probably want to know about. Jupiter and Saturn are going to meet just before Christmas. Will it be the end of the world? A planetary conjunction is when two planets appear very close to each other in the sky (from the Earth's point of view). They're not particularly uncommon, mainly because planets don't stray far from the Ecliptic, which is a little like the Sun's equator. However, this one's going to be pretty special. On 21 December, jus...t after sunset, Jupiter and Saturn will appear in the sky only one tenth of a degree apart. If you've got - meh - fairly dodgy eyesight like I do, you may not be able to tell they're separate. They'll be very close to the horizon in the South West. I've added a few screenshots from the free planetary software program, Stellarium, to show you what it's going to be like. The wide field, showing the various constellations as well as the horizon will give you an idea what it'll look like with the naked eye. You can see from the labels that the two planets are right on top of each other. The view through a telescope shows that the planets will appear closer to each other than some of their own moons. By the way, this is the view you'd get through a basic telescope, the saxon 909 with a 10mm eyepiece. For the photographers amongst us, I've also added a view as taken through a Celestron 8" Cassegrain with a planetary camera, in this case a QHY5III 462C. It'll be a devilishly hard photo to take: the planets are low and different brightnesses, the atmosphere will be awful, you'll need the whole frame... and in my case I'll have to demolish my own house to see it! Of course, the planets won't suddenly appear where they are, they will have been edging towards each other for ages. Even now, several weeks before, they're quite close. Also, knowing the media, there'll be lots of stories about it, and not all of them totally factual. Shall we make bets as to the most breathless of clickbait headlines?

02.01.2022 "I can't see anything". I was chatting with an astronomer who had just got a camera onto to his scope. All he could see was a black screen. It was focus.... Out of focus stars look black. My photos here are a series taken as I approached focus. They're all correctly exposed and pointed the right way - it's just that the stars are so diffuse you can hardly tell they're there. There are three main variables you're playing with to get a nice image: exposure time, camera gain and focus. All of them are critical - if one of them is wrong, all you're going to see is black. So here's my strategy for focusing stars. Exposure time is the easy bit. Set it to three seconds. This is going to give you enough time to see stars if they're there, while being quick enough for you to move at a reasonable speed through the range. Gain is what you're going to play with to get a usable image. You don't know where your focus is, so you're going to have to work your way through the whole range. Suck it up. So... with your three second exposure looping onto the computer screen, start at one end of the focus range. Now adjust your gain. What you're after is an image that is charcoal grey in colour. If it's black, you're underexposing and you'll never see any stars that pop into focus. If it's too light, like a light grey, you might not see the stars due to poor contrast. Now, time for the slog to start. Move your focus a little. How much is another guess. Too little and you'll be there all night. Too much and you might miss the focus entirely. Then wait for at least two exposures. If you're focusing manually touching the scope will have shaken it so the stars won't be visible. Inspect the screen. What you're looking for are fuzzy blobs that only just stand out from the background. If you don't see any, adjust the focus again. Once you find those stars you're on your way. Be patient, and remember to measure the point where your focus is. You don't want to be doing this all again!

01.01.2022 For the past several weeks now - it feels like an eternity - Melbourne has been in what authorities call "Stage 4 lockdown". We are allowed out for one hour per day for exercise, and can go shopping at the local supermarket, but only one at a time. One thing that's not permitted is travelling to a bird watching area and strolling around with camera or binoculars. That's not considered "exercise" and neither is it on the way to the shop. Legally, the only birding I can do is a...t home. My garden is mostly native, meaning it does attract a number of birds. Numerically, however, visitors are largely Common Mynas and Spotted Dove. At least the Dove is a native. So for something to do during lockdown, I rigged a feeding table in a White Cedar we have. The White Cedar is beautiful, and has grown very large in the decade we've had it. The disadvantage is that it's severely impinging on my view of the sky, and I can't see to the south-west any longer for astrophotography. The feeder base is a flat bit of wood with beading around it. This way, I can put a square ceramic plate on it to contain the seeds, and then wash that plate in the dishwasher to prevent the spread of any diseases. Beak and feather disease is, shall we say, unpleasant. We use the "wild bird" seed from the supermarket. After some discussion on Birding-Aus, Lorikeets get limited quantities of the smallest seeds. Larger birds such as Cockatoos get larger seeds, mostly sunflower seeds. We have a pair of Rainbow Lorikeets who we call Thomas and Geraldine, as well as a regular Sulphur Crested Cockatoo named Shirley. We have also had visits from a King-Parrot, a Raven and Pied Currawongs. The dominance equations are quite complex. Shirley sees off everyone. Tom and Gerry together can see off the Doves and Mynas. One alone can too, but the effort keeps them from feeding. A group of Doves can keep Mynas at bay, but a pair of Mynas can see off a Dove. Having the feeder has helped us stave off lockdown fever.