Astrophotography on a Budget by Martin Cohen

Many years ago, before digital photography revolutionized the medium, taking a beautiful shot of the Andromeda Galaxy (M31), or even a detailed image of the moon, showing its many craters, rilles and mountains would only be possible if you had a large wallet and access to highly specialized equipment and techniques. For the average amateur astronomer it was entirely out of reach. With high-end telescopes now being mass produced, new optical designs and most importantly, the digital camera in combination with brilliant new software solutions that dramatically increase the quality of the images, the popularity of astrophotography has increased exponentially over the past two decades. What was virtually impossible twenty years ago is now available to anybody with a passionate interest and willingness to spend long hours perfecting the art of celestial imaging. Polarex (Unitron) 50mm Achromatic RefractorI was thirteen when I received my first telescope, a Polarex (Unitron) 50mm achromatic refractor. It was a present from my maternal grandmother and I remember clearly how impressed I was with its beauty and quality. Both my parents were supportive of my new hobby, but whereas my dad would take a quick look at Saturn and continue whatever he was in the midst of, I could not get enough of it – I spent hours and hours behind my little telescope, never tiring of the ever changing views that the moon would offer, the rings of Saturn and the four largest moons of Jupiter. DSLR Eyepiece ProjectionI soon began taking pictures through my scope, first by simply holding my camera behind the eyepiece, and later with an inexpensive Russian reflex camera (Zenith B), using a special adapter for eyepiece projection (see photo). This technique uses the same eyepiece you look through to project an image on the film or sensor of your camera. It is a great way to shoot the moon and the planets. By that time, I had also built my first darkroom and I started to experiment with specialty film developers (like Acufine and Diafine) to push my Kodak Tri-X film to ISO 1600. The results were actually quite decent (see samples), considering the fact that it was only a 50mm refractor without motor drive or anything. I exposed the film by opening the camera shutter and then moving a black piece of cardboard in front of the telescope, briefly uncovering the lens, so vibrations from shutter and mirror would be minimized. I cherish that little telescope to this day and last year completely refinished its beautiful wooden case (which over half a lifetime was pretty badly beaten up). Fast forward to 2011. I have moved from my native Amsterdam, Holland, to the west coast of the United States, where I make a living as a photographer. My passion for the stars was lying dormant for a long time. Then, about two years ago, the itch to take some new photos of the moon (37 years after those romantic days of Tri-X developed in Acufine!) got ignited when I won a bid on Ebay for a Meade 90mm GoTo refractor at a great price. Very quickly, I discovered that my Photoshop skills were a real asset in getting the maximum out of this modest telescope. After a few efforts, using the same eyepiece projection techniques that I used as a kid in Amsterdam, I was able to come up with very sharp images that looked as good as some of the shots I had seen by the “big boys” in the early seventies– shot with a scope I had bought for less than $100! (click here for samples) In March of last year, I bought a large Dobsonian (10-inch mirror, f/5), brand new on Ebay, again for very little money. I was curious to see what the larger aperture would do for my moon shots and indeed, without any tracking, using a wireless remote for the shutter and flipping up the mirror of my Nikon (to minimize vibrations), I got some very detailed images. There are several myths regarding equipment for astrophotography that are still going around:

MYTH #1: in order to take sharp photographs of the moon, you need an expensive scope with motor drive, to track the motion of the moon along the night sky.

Not so. At an exposure of 1/30 sec, the movement of the moon along the sky is less than 0.5 arc second, well below the resolution of most amateur instruments. Shooting at ISO 400 to ISO 800, which I consider the best range for the moon, there is enough leeway to extend your focal length all the way to f/45; if your lens or mirror has a 10cm (4”) diameter, the effective focal length can be as long as 4.5 meter (15 feet). It is best to shoot when the moon is high in the sky, otherwise turbulence increases and clarity suffers. Here are some rough exposure guidelines for the moon:
Crescent Moon f/32 ISO 800 1/30 sec
First and Last Quarter f/45 ISO 400 1/30 sec
Full Moon f/45 ISO 400 1/125 sec
  Moon 04/19/2010 by Martin CohenPersonally, I like to use eyepiece projection, but a good Barlow works just as well, especially with telescopes that already have a long focal length. The pixels in the sensor of your DSLR (= digital single lens reflex camera) will not be able to register the finest detail of your telescope if you shoot prime focus, particularly with the shorter and faster type Newtonian telescopes. Of course, you cannot frame the whole moon using those long focal lengths, so if your goal is to show the full disc, you have to piece them together from the detail shots in Photoshop, like I did with the photograph to the left (click on photograph to see more detailed samples, shot with a 10-inch Dobsonian).     In summary, taking photographs of the moon is relatively easy. All you need is:
  • a simple telescope with a mount that provides good support
  • a digital camera, preferably a DSLR (a used Canon EOS is fine)
  • an eyepiece projection adapter to attach your camera to the telescope
  • a so-called T-ring that is specific to your camera
  • a wireless remote to trigger your camera shutter
Look around for the best deals on telescopes- here is a fantastic one at Optics Planet: Celestron Powerseeker 80 EQ. The T-rings are around $15, like this one for a Canon EOS: Celestron T-Ring for Canon EOS Camera. And here is a very nice wireless remote, available for a multitude of cameras (here for the EOS): Wireless Remote Switch. This one is compatible with Canon 1D/1DS, EOS 5D/5D Mark II, 50D, 40D, 30D, 20D, 10D, 7D, and D60. Also, here is a super inexpensive one that only works for selector models that have an IR receiver built in: IR Wireless Remote Control. Let's cover the process step-by-step: first, you place your eyepiece in the camera adapter (best to start with a 20 or 25 mm eyepiece since it gives you a wider field) and then attach it to the camera and the telescope. Set the camera to ISO 400 or 500 for half moon - which shows the most craters. If the moon is almost full, ISO 100 or 200 is plenty and for a small crescent, ISO 800 works well. Now focus your telescope as precisely as you can through the viewfinder of, even better, using LiveView on the display screen. In order to avoid a blurry image caused by the shock of the mirror, it is advisable to lock the mirror before taking the shot. You can experiment with exposures between 1/15 and 1/60 of a second in manual mode. I don't recommend using automatic exposure, but sometimes it works quite well. Using a wireless remote will help keep everything steady, since touching the camera can cause vibrations. If preferred, you can shoot in prime focus or with a Barlow lens by connecting the front part of the adapter directly to your camera (using the T-ring). So you leave the part with the eyepiece out altogether. That way, the exposures will be even shorter and you can easily capture the whole moon instead of a partial disc. It takes practice to get great results but you will be surprised how many craters will show even in your very first attempts.

Deep Sky Photography

With my newly reawakened interest for the night sky, it was only logical that I wanted to extend my efforts to Deep Sky objects as well as the planets. But how on earth was I going to do that with my very limited equipment? By now, I had seen gorgeous photos of nebulas and star clusters, taken by experienced amateurs with apochromatic refractors and high-end Newtonians or Schmidt-Cassegrain systems (the difference between these telescopes will be explained later in the article). They always used sturdy equatorial mounts with precise motor drives to track the night sky and achieve pinpoint stars. I was fairly convinced that I would need to invest some serious money in order to produce similar results.

MYTH #2: in order to photograph nebulas, star clusters and other Deep Sky objects, you need an equatorial mount, with motor drive and a guide scope, to allow for sufficiently long exposures.

I need to be perfectly clear: if you can afford a good equatorial mount with precise tracking capability, there is no question that your images will benefit from the more sophisticated equipment. However, these days it has become entirely possible to create powerful images of our amazing universe with fairly basic means, like a simple GoTo Alt-Az mount. Here is my list of imperatives to reach good results without the big bucks:
  • A dark site, far away from city lights
  • A fast lens or telescope (f/5.6 or faster)
  • A tracking mechanism, Alt-Az is fine, equatorial is better
  • Deep Sky Stacking software
  • Basic knowledge of Photoshop
  • A good DSLR, allowing settings from ISO 400 to ISO 3200
  • Patience and the willingness to spend many hours in the dark

The Dark Site

Most of us live either in or close to the city and with a few exceptions (notably the moon and planets), there is really not that much to see, let alone to photograph. On a clear night, we may catch a glimpse of the brightest Deep Sky objects like the large Orion nebula (M42) or the Andromeda Galaxy (M31); M13 in Hercules may offer a pleasant view, same with the Pleiades (M45). But compared to the wealth of objects that are visible once we get away from the big cities (even with a simple pair of binoculars), the skies above our living quarters usually offer remarkably little. For Deep Sky photography, you will be much better off with a small telescope at a truly dark site than a fancy 10-inch Schmidt-Cassegrain in the middle of a large city. Many expensive telescopes sit and gather dust for exactly that reason: their well-to-do owners never really took the time and effort to get the maximum out of their instrument. A dark sky will allow for longer exposures and render images with higher contrast and much better detail. If you are in a big city, just try pointing your digital camera at the night sky (on a tripod) and open the shutter for a minute or so at f/4. Even at a moderate ISO 400, chances are that what looks like a fairly dark sky to your eye ends up being completely washed out in the photograph. Under those circumstances, there is no way to get a good image of your targeted fuzzies. Investing in a good quality Light Pollution Filter helps overcoming the problem a bit, but nothing beats the splendor of a truly dark site.

The Equipment

MYTH #3: you get what you pay for.

This is common wisdom, and when it comes to telescopes, it is entirely flawed. I know people who spent a small fortune on a telescope that they never really understood and were unable to work with. Years later, they’d be lucky if they could sell it on Ebay for a quarter of what they paid. It’s entirely possible to get good results from inexpensive equipment. More money does not always mean a better telescope. Often, it means a heavier and more complex instrument, so serious research is strongly recommended when buying one. What makes all the difference is knowledge and experience: knowing the constellations, understanding the differences between refractors, Newtonians and Schmidt-Cassegrain systems, spending lots of time studying the night sky… The truth is that a modest instrument in the hands of an expert will yield far better photographic results than a very advanced telescope in the hands of a novice. Here is a list of the most basic equipment you will need:
  • A small telescope with a short focal ratio (I used an inexpensive 80mm f/5 short-tube refractor for most of my Deep Sky images, you can often find them on Ebay for well under $100)
  • A mount with a motor drive to track the stars (preferably equatorial, but up to 20 second exposures can be done with an Alt-Az mount)
  • A DSLR camera (I like the new 24MP Nikon 3200 and the Canon EOS series; for $700 or less you are in business, $300 if you buy used )
  • A T-adapter (prime focus) to connect the camera to the telescope ($25 or less)
  • A T-ring specific to your camera ($15 or less)
  • A wireless remote to trigger your camera shutter (keep vibrations to a minimum for $20 or so)
  • A computer with stacking software (Deep Sky Stacker, downloads for free on the Internet) and Photoshop, any version is really OK
Most smaller telescopes are sold with a mount – for a novice, the GoTo capabilities on the inexpensive Alt-Az mounts will make finding the objects in the sky a lot easier. I highly recommend Cloudy Nights classifieds for used astro-equipment. Ebay is another great source.

The Shooting Process

I always prefer to set up my gear before sunset, when there is still a fair amount of light to see what I am doing. If you are lucky to live under dark skies, then you can shoot from your own backyard, but most of us will need to drive out for at least 20 to 30 minutes to be away from city lights. An open parking lot or campground, preferably with picnic tables is ideal. Make sure to bring some flashlights with red foil or gel over the front (red light does not affect your night vision, whereas white light does). Set everything up in the most organized way, so you will not have to look for things later. If you are using an equatorial mount, you need to align it to the North Star (Polaris) to make sure the polar axis (also called right ascension) is parallel to the rotation axis of the Earth, see diagram. Equatorial Mount A compass is very helpful in finding your general orientation before it is dark enough to see the stars. For most GoTo systems, you will also need a compass to point your telescope north at the start of your alignment. It is a good idea to know in advance which celestial objects you are going to photograph that night. Studying the night sky beforehand is essential and I highly recommend using planetarium software like Stellarium (free download). There are also many great books available, like Night Sky Atlas by Robin Scagell, for only $10 to $15 plus shipping on While it is still light, you attach the camera to the telescope, using the T-adapter for shooting in prime focus. You can use a faraway mountain or something near the horizon to focus on. If the moon is visible, that's even better. If your camera has LiveView, you can zoom in on the display, that makes precise focusing much easier. Once you are in perfect focus, you lock the focuser with the lock screw. (In case your telescope does not allow locking the focuser, all you can do is tighten the mechanism so it feels pretty stiff and will not move by itself). We will be needing so-called flat frames in the final processing of our images and this is a great time to shoot them. No optical system is perfect and especially with cheaper telescopes, the corners of your image are less bright than the center. A flat can be an image of an empty part of the sky, that shows nothing except the difference in brightness. Point your scope up well before any stars appear and take a few shots on automatic, ten is more than enough. The stacking software we use later will be using these images to subtract from the actual photographs, thereby correcting the differences in brightness. You can also put a white T-shirt over the front lens and shine a light though it, but I prefer this method. Once it is dark enough to start shooting (usually about an hour or so after sunset), we need to find the Deep Sky objects on our shooting list. Locating those faint nebulas in the sky that look so rich and detailed in photographs is not easy at all, especially in the beginning. A good pair of wide-angle binoculars (7x50 or 7x35) is a fantastic tool to bring them a little closer and get a better idea of their position. Once you found them, it will not be too hard to center them in your telescope, using a good finder scope. You will definitely need a motorized tracking mechanism to keep them centered. Of course, if you are using a GoTo mount, it will find the object for you. It certainly makes life a lot easier, but it also creates a dependency; I am a strong advocate of learning the night sky and finding objects based on the position of the stars. For Deep Sky objects, I usually set my camera to ISO 1600. You can go higher, but it adds more noise to the image. I like to shoot in RAW-mode, but setting your camera to hi-res JPEG files will work just fine.You will need to take a lot of exposures of the same image, at least ten or fifteen, which will all be stacked later in the Deep Sky Stacker software. The more exposures you take, the less noise will appear in the final processed image, which makes it possible to get more detail. If you use an Alt-Az GoTo mount, the maximum you can expose for is about 20 seconds before the stars will begin to show trails. With a simple (unguided but motor driven) equatorial mount you can go up to 30 sec or even one minute, especially if you are using your camera with a telephoto lens. The longer the focal length, the more difficult it will be to get pinpoint stars. Precise polar alignment makes a real difference. At the beginning and end of each sequence of exposures (individual exposures are called subs), you need to shoot the so-called dark frames. Deep Sky Stacker will use these files to correct the inherent flaws of your camera sensor (the dark signal), which also depends on the outside temperature. A dark file is shot with exactly the same exposure as your subs, only with the lens covered. Usually 6 dark frames at the beginning and six at the end is plenty; if you need to move fast then three or four will do. So by the end of our shooting session we will have a dozen flat frames (shot early in the evening), all our picture files (or subs), and a series of dark frames for each object we photographed. Finally, we need to create the bias frames by shooting ten or twelve shots at the very shortest exposure our camera allows (same ISO setting as the picture files), again with the lens covered. Take good notes about which frames are which, since you can't tell much from a black image! All these files will be combined in Deep Sky Stacker to produce our final shots. Images taken with 80mm f/5 short-tube refractor, focal length 400mm These photographs were taken with my 80mm Rokinon short tube on my Meade Alt-Az mount, 12 to 15 subs at ISO 1600, exposed at 15 or 20 seconds, stacked in Deep Sky Stacker. Click on image to see larger version:   Images taken with Nikon D300 with 180mm ED lens on an EQ-1 mount with motor drive For these shots, the subs were taken at 30 sec each at ISO 1600, usually about 15 to 20 exposures per photo. Stacked in Deep Sky Stacker, further processing in Adobe Photoshop CS3. Click on image to see larger version:


Deep Sky Stacker can be downloaded for free at After loading the images complete with flat frames, dark frames and bias frames, we simply let the software do its amazing job. The image file we end up with will have most of the noise removed and probably show more detail than the single frames we started with. However, the image is far from done. It is only in the final processing that an image truly comes to life. To achieve that, we need a velvety black background, pinpoint stars (at least the small ones), rich color and plenty of detail in the nebulosity. I am amazed at the amount of online images that could be so much better if the techniques I am about to describe would have been applied to them!! Here is an example of a very nice shot of the Horsehead and Flame nebulas, posted by an experienced astro-photographer who used Nebulosity 2 and Photoshop 4 to process the image: Horsehead and Flame Nebula Notice the wonderful detail (shot with a Astro-Tech 65mm f/6.5 wide-field apochromatic refractor and a $2000 S-BIG CCD camera, a beautiful set-up, with a total exposure of almost ten hours in five-minute increments). However, the photo lacks a bit of contrast, the sky is not really black and the H-alpha clouds are pink instead of red. Also, in several places the gas clouds look yellowish and muddy. Additional processing and sharpening in Photoshop reveals a stunning image: Horsehead and Flame Nebula After Of course, it’s never perfect: some of the faintest nebulosity got lost here, so I could probably start again from scratch and try to keep all the thin filaments. The main point is that the final processing in Photoshop can make all the difference between a good photograph and a great one. Personal taste is an important factor, too: many astro-photographers prefer their skies dark but not quite black. So which are the basic Photoshop techniques to bring out the best detail and color in your astro-photographs? Let's start with an example of my own Deep Sky images, the Orion star field. Using an f/2.8 telephoto lens with a 180mm focal length on my Nikon D300, taking about 25 exposures of 30 seconds each at ISO 1600 (total exposure 12.5 minutes) gave me the following file after stacking the images in Deep Sky Stacker: Deep Sky Stacker Processing Nothing too exciting: we barely see the Flame nebula and the Horsehead nebula is completely absent. The background is a bit muddy and has a reddish brown cast. More than anything, it does not seem to show very much! One would almost discard the photograph as a failed attempt. This is typical of a stacked but unprocessed image. It holds much more information than you can see. The first thing to do is to increase the contrast and improve the color. You can play with the Levels (Ctrl-L) and the Curves (Ctrl-M), but personally, I like to start with Brightness/Contrast (Image-Adjustments-Brightness/Contrast – top of the menu). I just keep sliding the cursors to the right until the hidden details start showing. If your version of Photoshop has Shadows/Highlights built in (also under Image-Adjustments), then moving those cursors can give you a good idea of the information in the file. The trick is to keep making the image brighter and then darkening the background by adding contrast. Another helpful way of doing this, while at the same time removing a color cast, is using Color Balance (Ctrl-B, also under Image-Adjustments). At the bottom of the color balance window, where it says Tone Balance, click on Shadows. It will light up in blue. Then you choose the color you need to remove, in this case mostly red. By moving the red cursor to the left (adding cyan), not only do you fix the color cast, but at the same time the background becomes darker and more contrasty. I also moved the yellow cursor a little bit to the right (adding blue). It needs to be done subtly, but it greatly improves the overall appearance. Finally, I go to Hue/Saturation (Ctrl-U, also under Image-Adjustments) and move the saturation cursor to the right, adding depth and color. Again, don't overdo it; go as far as you can before it starts looking a bit artificial. Photoshop Processing The new image is much better: color and contrast have improved and there is lots of nebulosity showing where before there was nothing. Even the Horsehead nebula is starting to show. A lot of people would stop here and many times I have done so myself. Yet, we can push the envelope even further. One of my secret Photoshop weapons comes into play here: the Lasso tool. I always use it with a feathered edge, which you can set at the top of the menu in a little window to the left where it says Feather (after you click on the lasso tool). Depending on the size of the area you want to affect and the size of your original file you can set the feather anywhere from 3 px (for a tiny area) to 250 px (for a very large area). Usually, it will be anywhere from 10 to 50 pixels. There is no way a regular DSLR could show a detailed Horsehead Nebula with these kind of short exposures (30sec x 25). So it's time to get creative. In order to bring out the faint detail we have to isolate the nebula and work locally. It helps to look at a great shot of the object done with more advanced equipment, so we get a good feeling where to draw the lasso. Once we have defined the area with a nice feathered edge, we can accentuate the nebulosity by going to Levels (Ctrl-L) and moving the central cursor to the left, opening up the shadows. If the effect gets too muddy, we go to Brightness/Contrast and add contrast to darken the background. Now we can also play with the color: go to Color Balance (Ctrl-B) and add some red, maybe even a hint of magenta. We can further intensify the color by adding saturation (Ctrl-U) until it looks just right. Again, don't push it too far! Applying this technique locally for the Flame Nebula as well as the Great Orion Nebula to the right has brought out details that were completely invisible in the first stage. I used a little sharpening and increased the overall contrast a hair more to reveal the final image:
Orion Star Field Final
Click on the photograph to see the hi-res version
Two factors could significantly improve this photograph: 1. Using a modified DSLR with a much higher sensitivity in the H-alpha region would make the nebulas stand out even more clearly (more info at Hap Griffin's website) 2. Using longer exposures (3 to 5 minutes each) would show a richness of detail that is impossible to get in thirty seconds. To further improve contrast at long exposures, a Light Pollution Suppression (LPS) filter is highly recommendable under less than perfectly dark skies. Of course, we would be leaving the low-budget area here and move into a more sophisticated field of astrophotography. Longer exposures require a very sturdy equatorial mount with precise tracking and a high quality auto-guider. That will be my next stage of exploration.

Fun and Easy First Steps

If you are new to astro-photography, there are so many easy ways to begin. With a simple digital camera on a tripod, it is possible to take some very nice photographs of the stars. You need a camera that allows manual settings so you can use time exposures and keep the shutter open for at least thirty seconds. First set the focus of the camera to infinity. Then open the aperture all the way (usually to f2.8 or f3.5 – the smaller the number the wider the aperture). Point the camera in wide-angle mode to a bright part of the sky with lots of stars. Of course, you want to be far away from city lights, otherwise the results will be disappointing. Set your sensitivity to ISO 400. If you go too much higher (ISO 800 and up) the image may be noisy, especially on the less expensive cameras. Now just open the shutter for 10 seconds, 20 seconds and 30 seconds. You can see how long you can expose before the stars become small trails instead of points. The rotation of the Earth causes the stars to move, so with a static tripod the exposure can't be very long. However, if you point the camera North and leave the shutter open for an hour or more (you need a very dark site to do that, otherwise the image blows out completely), the star trails will form beautiful concentric circles. Keep the ISO settings fairly low (ISO 200 or less) and you can even stop down a bit (to f5.6 or f8), so the background remains dark. It is surprising how much light a simple digital camera can gather in a few minutes. If you own a DSLR with a fast lens (f/2 or faster), you can really get some good results without any tracking. All you need is a dark site and a sturdy tripod. With relatively short exposures you can photograph the constellations and even see some of the brightest nebulae and star clusters. If you use a wide-angle lens, pointed at the Milky Way in summer, you can expose up to 20 seconds before the stars show any trails. At ISO 1600, you can gather a wealth of information, especially if you take ten or more exposures and use Deep Sky Stacker to process the images. Even ISO 3200 can be used, because the stacking software will considerably reduce the noise. The following images were taken very recently with a Nikon D300 at ISO 1600, using my 85mm f/1.8 lens (shooting full open). I exposed for only 4 seconds, taking about a dozen exposures stacked in Deep Sky Stacker, then further processed in Photoshop CS5. I was pleasantly surprised to see how many stars are visible of the Double Cluster in Perseus, as well as the Pleiades (M45), and how well the Andromeda Galaxy (M31) and the Great Orion Nebula (M42) are coming through. Even the Flame Nebula in Orion's belt is showing (barely, but still!). The shot of Orion was composed of three images since my 85mm lens is not wide enough to show the full constellation. No tracking here, just a sturdy tripod! Click on image to see larger version:         

Piggy-back Photography with a Telescope

If you have a small telescope, especially one that has a tracking mechanism, you can mount your camera to the telescope and use the scope to track the stars while the shutter of the camera is open. This way, you can expose a lot longer before seeing star trails, especially with an equatorial mount. Because the axis of an equatorial mount is parallel to the axis of the Earth, it completely compensates for its rotation once your tracking and polar alignment are precise.

Overview of telescopes

There are many different kind of designs for telescopes, but most amateur telescopes fall into one of three categories:
  • Refractors
  • Reflectors
  • Catadioptric systems
Refractor Refractor Telescope A refractor is a simple tube with a lens (the objective) in the front and another lens (the eyepiece) in the back. Usually the front lens consist of two pieces of glass, each with a different breaking index to control false color (chromatic aberration). Those are called achromatic objectives. The best corrected and most expensive refractors are called apochromatic: they often have an objective that consists of three and sometimes even four elements. For astrophotography they are ideal, but again, they aren't cheap.
Reflector A reflector uses a concave primary mirror instead of a front lens: Reflector Telescope A smaller secondary mirror under a 45 degree angle reflects the light outside the tube where an eyepiece can catch the focus point. This design is called the Newtonian telescope, invented by Sir Isaac Newton. A variety is the Dobsonian telescope, which is exactly the same design on a very simple and inexpensive mount. Because of the relatively simple construction and the large mirror size, these are great instruments for exploring Deep Sky Objects such as nebulas and distant galaxies, since they gather a lot of light.
Catadioptric Finally, the catadioptric systems, such as the Schmidt-Cassegrain telescopes or the Schmidt-Newtonian telescopes, use a glass corrector plate in the front of the tube. These are complex optical systems that have become affordable since they were mass produced by companies like Celestron, Meade and Orion. Their short build and large light-gathering capabilities make them ideal for observations of the moon and planets, as well as Deep Sky Objects. Since their effective focal length is rather long, they would not be my first choice for photographing faint nebulas and galaxies, but for imaging the moon and planets they are absolutely wonderful.
Martin Cohen with New Telescope!Martin Cohen is a professional photographer and amateur astronomer in Santa Monica, California. Martin Cohen's Astrophotography Website Martin Cohen Photography Photos of the Moon Photos of Havana, Cuba See Martin's tutorial on AstroPhotography Tonight: Creating Seamless Mosaics in Photoshop.      
Recommended websites: Stellarium Stellarium is planetarium software that shows exactly what you see when you look up at the stars. It's easy to use, and free to download. A great way to learn about the stars and prepare for nightly observations. Cloudy Nights Cloudy Nights is a wonderful site with great forums, articles, equipment reviews and classified ads for new and used equipment. It is free, all you need to do is sign up online for membership. Deep Sky Stacker Deep Sky Stacker is a revolutionary free software for serious astro-photographers, that will enable you to stack and align many exposures of a nebula or galaxy, to maximize the signal to noise ratio. Try it out!! George Kolb Astrophotos George Kolb is one of the many experienced astro-photographers in the USA whose gorgeous images show you what is possible with lots of dedication and high-end equipment.


  1. Gary Phillips

    Hi Martin, I found your great website while doing a search for… I don’t have a tracking mount, can you tell me if DSS is expected to work when using a stationary tripod? I can’t get it to stack my 17 minutes worth of stars that are trailing in my photos. I even minimized the trails to 6sec exposures. Is that expected or do I have DSS setting wrong. It does recognize stars, but won’t stack.

    1. Hi Gary,

      I am surprised to hear that, since I used DSS to stack some short exposure subs (4 sec each) that I also took with a stationary tripod and it worked fine.

      All I can suggest is to keep the exposures short enough for the stars to still be round. DSS is an amazing software and I hope you’ll find a way to make it work!



  2. Amazing website full of useful info!
    Many thanks for the time and effort these articles took, and for giving those on a budget hope for producing our own images in the future . 🙂

  3. Hi martin,
    Thanks for the info,
    I have a celestron c90 spotting scope and Nikon d3200 if I put that on a goto tripod would I be able to get some good photos like yours on your 80mm short refractor.


  4. Great site, I am a complete noob in the field of astrophotography. Got a skywatcher 130 for my bday last year, but living in Liverpool, England dont get the best vewing conditions but what I’ve seen so far has blown me away. Anyhoo, like most amateur astronomers we want the next fix, and mine was to start clicking away, so got me a Nikon D3200 and the various accoutrements from Amazon to enable me to photograph the The Moon etc…….Pfff, I was underwhelmed to say the least, so after trawling the many forums found your site and I thankyou. Highly informative and instructional.

  5. Mersim Gjonbalic

    Hi Martin,
    First off, wow am I happy that I happened to find this site. The information is amazing. I started taking some star field photos with a Canon EOS T5 and a simple tripod pod. After learning a bit on DSS I think I’m hooked on taking photos of the night sky. I need your help because I’ve come to a fork in the road. Should I get a refractor on a GoTo mount, a Maks-Cas or Schmidt or just get a really good lens and buy the iOptron Skytracker (I’ve read some great stuff about it). My main goals are to get some really nice shots of the moon and possibly some big things like Andromeda and Orion Nebula. Your input is very appreciated.

    P.S: If it helps I have a budget of about $700 I can work with for this.

    Thanks again.

    1. Hi Mersim,
      For $700 you can get a decent set-up to start with. You already have a DSLR, do you have a 2″ T-adapter and T-ring? You will need those to attach your camera to the telescope. My advice would be to get a GoTo equatorial mount and a small ED refractor. The mount is the most important part. Check Ebay, Cloudy Nights and Astromart for good deals. Here is one on Ebay:
      Figure about $500 for a used Equatorial GoTo mount, that only leaves $200 for the scope. You will have to be a bit lucky to get a great refractor for that price, you may consider a 6″ f/5 Newtonian as well. They are often inexpensive and deliver great quality, only problem is you need to collimate them (= properly align the mirrors). Here is a small refractor on Cloudy Nights that is very decent:

      And more info on that scope:

      If you want to start with an iOptron SkyTracker, they are great, too – for wide field shots of the night sky. Good luck, feel free to ask me more!



      P.S. If you prefer to buy new, the Celestron Omni XLT 150 is a surprisingly good scope for the money. It is not a GoTo but you can get a dual axis motor drive for it (just over $100) so tracking is possible for the Andromeda and Orion Nebulae. You will have to learn where they are in the sky. Also a polar scope (about $40) to get precise polar alignment is recommended. Here is a link to the scope:
      And here are photos taken with it (will take some time to get to that level):

  6. Hi Martin,

    Thank god I found your site! Lots of really good information.
    I’m trying to get started in astrophotography. Have taken some pictures of the milky way using just a simple tripod and DSLR, but I want to advance a bit more by taking pictures of some nebula.
    From what I read online these few days it seems like at the minimum a $500+ motorized equatorial mount is required. Which is a lot of money to just get started… But after reading your article and seeing the pictures you’ve taken, I’m excited to see what can be achieved with less budget (aka my budget).
    Are there any particular good mounts you recommend that is under $300? Doesn’t have to be new. I don’t plan to get a telescope yet, just want to see what can be done with a mount that can track + a DSLR w/ regular lens.

    Thanks in advance!

    1. Hi Chen,

      As long as you don’t intend to take detailed pictures of the moon and the planets (for which you need a long focal length) there is an amazing small and inexpensive mount that will enable you to take beautiful tracked shots of the night sky with lenses up to 200mm: the Ioptron SkyTracker. Price is exactly $299, but sometimes they show up used on Astromart or Cloudy Nights for even less. Here is a link:

      An absolutely GREAT way into astrophotography. Good luck!


      1. Thank you for replying Martin.
        I actually found a used iOptron Skytracker and CG4 mount on CloudyNights. They are about same price range (though slightly above my budget). Besides portability, do you think the CG4 is better or worse than the skytracker for astrophotography purposes?

        Thanks again.

  7. They are very different mounts: the SkyTracker is made for a DSLR with lens up to 200mm, has great Polar alignment and is easy to transport. The CG4 is much more sturdy and will hold a telescope up to 15 lbs, you need a special motor drive and a polar scope, neither of which I believe come with the mount when you buy it new. You may also consider the iOptron Smart EQ Pro, which has GoTo. If you are only going to use it for a DLSR with a lens on it, I’d get the SkyTracker. If you plan to mount a telescope as well, then a CG4 or a Smart EQ Pro would be a better choice.

  8. Hello Martin,

    I recently bought the Nikon D3200 for astrophotography based on a review within one if the astrophotography sites. I have an Meade LX200gps on an equitorial.
    My challenge is finding a specific answer to the D3200 settings in prime mode. I believe I’m close but still getting the question mark and object too dim. Can you please help list the Specific D3200 settings? Thank you very much, Dan

  9. Hi Dan,

    First of all, you need to set the camera to MANUAL. You can start playing around with 1 minute exposures at ISO 1600 or 3200. Your telescope is probably F/10, so not very fast plus it has a long focal length. It will be much easier to start with a small F/4 Newtonian or a small ED refractor. However, for the moon (and planets) your scope is great. Try it on a clear night, use live view focus and zoom in on your screen (10x). Focus precisely and expose using the guidelines in my article. You should get some good results!
    Clear skies,

  10. hi, Im really glad I found your site, Actually I have a DSLR (nikon D3300), a Scope, ( Celestron 130EQ) and the t adapter and T-ring for my camera, I was wondering if I get a dual axis drive for my scope I can get a little long exposures (just for get decent photos of nebulaes, etc), I know the mount of the 130eq is not a great one, but I dont have a lot of money right now, and a motor drive could be just like 50 bucks, I can afford that, but no more.

    1. Hi Roberto,
      You can definitely start playing with the gear you already own. Question for you: can you achieve focus at infinity with your DSLR connected to the scope? That would be the first requirement. If not, then you can still take shots of moon and planets through an eyepiece but Deep Sky with long exposures will not be possible. The D3300 is a great camera and will get you really nice images IF you can achieve focus and your mount is well polar aligned. As far as I know, there is no dual axis motor drive for the 130EQ, but they sell a little single axis drive for under $30 ( If you keep your exposures short (20 or 30 sec max) at ISO 1600 or 3200 you can photograph the Orion Nebula, the Andromeda Galaxy and other brighter Deep Sky Objects. Pick a clear night under dark skies with hardly any wind. Use the live view to focus. Are you good at building things? Because it’s possible to move the primary mirror forward in the tube so the focal plane falls further back (in case you won’t reach focus, which would not surprise me since these scopes are primarily made for visual observation). Collimation needs to be right on, you know about that? Steep learning curve but it will be fun!

      Clear skies,


      1. Hi Martin, thanks for your quick answer, I think focus will not be a problem, I’ve already taken some photos of the moon, using a barlow between the camera and the scope, and focus is fine, also, I think my scope is well collimated, I’ve read that if you unfocus a star with a well collimated scope, you will se a circle around the star first, and that is my situation, Im ordering the drive you sugest from amazon, since Im in guatemala, I hope to get it by next weekend, and again, thanks for your help!

  11. P.S. The 130EQ has a special piggy back mount – you can get very nice images once you installed the tracking motor if you attach your camera with a regular or telephoto lens.

    1. roberto Trujillo

      yup, I have seen the piggy mount, but have never used it, Cant wait to get the drive

  12. Hey Martin!

    I just have to say – thank-you ever so much for taking the time to make this ‘tutorial’. We’ve just bought our first telescope (meade lxd75 6″ newtonian reflector), and are enjoying it thoroughly. I’m at the research stages of looking at how to start at astrophotography, and this page has answered so many questions I had!

    Thank-you again!

    Groetjes uit NL!

  13. Josep Ashley

    Hi Martin, Excellent site. Don’t know how I’ve missed it over the years.

    I’ve used a Celestron 4SE mount(on its wedge in the equatorial mode) and a SkyWatcher SynScan AZ GOTO telescope mount for years to photograph deep space objects using a DSLR with a Celestron C6S (150mm SCT), Meade 2045 (102mm SCT), or an Orion ST80A. short tube f/5 refractor. The two SCTs were at f/6.3. While the SkyWatcher mount will not compete with a German equatorial mount, it can produce decent images using short exposures, stacking with Deep Sky Stacker, and processing with photoshop.

    For thoes folks who seem to insist that you can’t do astrophotography with an azimuth mount; yes you can….see my flickr site for examples. All the images were made at my home in the Athens Greece urban area with its significant light pollution:

  14. Hi – any ideas on a photo stacking software available to run on a Mac (preferably without switching to a windows shell)?

    Great site! Thanks.

  15. Hi James,
    Of course, if you switch to a Windows shell then you can use Deep Sky Stacker – and I believe that is exactly what many Mac owners do. I use Windows myself and I agree it’s a bit unfair to the many Mac owners that there is no platform for DSS. You may want to consider using Nebulosity created by Stark Labs: it is great software, compatible with Mac, but unfortunately it’s not free. Hope that helps a bit.


  16. Patrick Lloyd

    Thanks for sharing so much of your knowledge with us greenhorns … that’s very kind!

    Do you know if … … is a reputable place for me to purchase a telescope? They are selling a new Stellarvue SVR102T refractor for $1,437 which makes me nervous given that all other sites list the same scope for around $2,200. Also, they are located in Jacarta. I don’t know whether run or roll with it?! Virtually all of their prices undercut the other sites by this same relative percentage. They have a great looking site and a lot of products listed … their site “presents” well in every other way.

    Have you ever heard of them?
    Though it’s of course ultimately my responsibility, I would value your opinion on this!

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