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Part 3: Astro-Photo Anatomy

Know your Target

So you have your equipment and you're under clear/cloudless night skies. You've read my Breaking Down Astro posts and now it's finally time to catch yourself a target. Always mind the moon phase, as a full moon adds way more light than you'd expect. (long exposures under a full moon will result in photos that look almost like daytime) I prefer to do my wide nightscapes while the moon is about halfway illuminated or less.

Milky Way Galaxy Nightscapes

In the northern hemisphere, you'll want to face south and look for the constellation Scorpius. (a summer constellation) It will rise from the southeast and set in the southwest, all along with the Milky Way galaxy. As long as there's minimal light pollution, your eyes may just notice a silvery cloud stretching across the sky from the horizon. Set your camera's manual settings, and watch how much better a camera can 'see' it in the night.

If the moon is high in the sky and full, you'll probably have a really hard time getting the nightscape photo you're after. Always triple check the weather and moon phase before heading out.

The Moon Phase Schedule:

  • New Moon (no illumination)

  • Waxing Crescent

  • 1st Quarter (half illuminated)

  • Waxing Gibbous (almost full)

  • Full Moon (fully illuminated)

  • Waning Gibbous

  • 3rd Quarter (half dark)

  • Waning Crescent

  • (Repeat)

Note - 'stacking' together multiple photos into one will help with the overall quality of the final product. Many software programs exist that do this for you (such as a free program called 'Sequator') There are generally a few different files/frames for the astro stacking process, which I'll cover in more detail below.


Startrails are a ton of fun. Simply find your celestial pole (Look for the North star in the northern hemisphere for example) then frame your camera on it from your desired angle. Set it to take a series of photos in interval (done with external or built-in intervalometer) Once you've gotten at least a couple hundred shots over the course of an hour or so, just merge the photos in a software such as StarStax.

Deep Space Galaxies and Nebulae

The more light/signal you can gather from your target, the better your final product will be. Here's one photo of the Orion nebula, VS ten stacked together.

Firstly, you want to level your tripod, place your mount and telescope on, then balance the telescope on both rotating axes. Now, after focusing everything, make sure to polar align it (per its own instructions) and pick your target from within the built-in 'Go-To' database. Once it's taken you to target, make sure your autoguider has stabilized with steady corrections. You'll need to capture as much signal/light from it as possible. The more signal, the better your final product will be later. These photos are referred to as 'light frames.'

Now let's say it's 2am. You've captured 50 light frames/files and you're ready to pack up. Well, do not forget to take additional photos called 'flat frames' before leaving. Flats will identify imperfections (such as dust/hair/specs) on your glass so that they can be removed in processing later. Lastly, unless you've saved yourself a catalog of 'Dark frames' and 'bias frames', you'll need to capture these as well. What's great about these frames is that they can be taken anywhere and anytime, as long as you can cool the sensor to the same temperature that it was when taking the light frames.

Light frames - the more photos the better, monitor your cameras histogram and keep it peaking around the left third.

Recommended Minimum - 20

Flat frames - cover telescope face with soft, evenly balanced light. Some use a white shirt (attached with rubber bands) and use their headlamp for white glow. Some use an artists tracer board but this usually requires an additional power source. The very short exposure length will be determined by your cameras Aperture Priority mode or Flat frame mode, based on histogram/intensity of white light. Again, the purpose of these is to catch uninvited visitors hanging out on your lens, so you can save ruined photos.

Recommended Minimum - 20 (acquired very quickly)

Dark frames - these frames can be taken at home during the day, and cataloged for recycled use. These photos are completely dark (taken with the telescope cover still on) but have to match the exposure time and temperature of your light frames. These frames identify noise in your light frames to cancel out in processing.

Recommended Minimum - 20 (takes same amount of time as light frames)

Bias frames - good news! these frames, just like dark frames, can be taken at home and catalogued for recycled use. These have all the same requirements as dark frames, except the exposure time needs to be the quickest/shortest Shutter Speed that your camera is capable of. These frames will identify sensor pattern noise for canceling later.

Recommended Minimum - 100 (acquired very quickly since exposure times are fractions of a second)

After you have all these frames caught and consolidated, you can merge them in computer programs such as DeepSkyStacker (free and simple) or PixInsight (paid and advanced). Once all raw files/frames are merged into a master file, take that master raw file into an editing software such as Adobe Lightroom, tune and export as shareable JPG files, or per your project demands.


Once you've managed to pull all this off once or twice, it really does become second-nature. You reeeally don't want to get home and begin processing your photos, just to immediately find out they're all ruined and can't be salvaged.

Clear skies!


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