Shooting for the Moon: A Perspective on Prime Focus Astrophotography


You look a little funny…Oh! You’re infected with full Moon fever. Fire up your camera and get ready to photograph a celestial body. Does that sound sexy? Do craters turn you on? When you’re ready to stop blushing, please read this Moon photography guide, because protection is important, and no one likes an overexposed Moon. Trust me.


It’s Never Polite to Overexpose


Don’t get it twisted—the full Moon is pretty damn bright, and that’s all you need to know. A more sophisticated explanation involves comparing astronomical apparent magnitudes, but we’ll go ahead and skip all of that technical shit. The Moon has a -12.6 apparent magnitude, or it’s pretty damn bright. Take your pick.

An astute observer realizes that the Moon goes through distinct phases each month, and each phase shows a varying degree of sunlit lunar surface. The Moon’s brightness is not a fixed attribute, so the camera settings need to be accurately adjusted, or something bad may happen.

Stop. Hold on.

This guide details a particular viewpoint which is centered on a specific way of photographing the Moon—prime focus.


** Astronomical Prime Focus Requirements **

  • DSLR camera (manual settings)
  • Telescope
  • T-adapter

Camera attached to telescope (prime focus)

The photographic exposure settings expressed in this guide will not be appropriate for standard camera lenses. Sorry.

A specialized T-adapter allows you to attach a DSLR to a telescope, however, each brand utilizes their own adapter. Do yourself a favor and avoid cheap T-adapters, or you’ll discover how easy it can be to break a steel ring.

Great! Now that we got all that fun stuff out of the way, let’s discuss the details.


** Technical Details **

  • Telescope: Orion 4” catadioptric (Maksutov-Cassegrain)
  • Focal Ratio: 12.7
  • Focal Length: 1300mm
  • Camera: Canon Rebel XSi
  • ISO: 100
1/25sec = Overexposed!

The first Moon photograph is overexposing itself…and it’s not very pretty! The subtle details are washed out and the image was saturated with too much light. 1/25sec proved to be too long of an photographic exposure. The lack of contrast is also appalling. Yuck.

1/50sec = Overexposed!

The second Moon photograph is a little better, right? The contrast between the lunar seas and highlands is much better. Copernicus and Tycho crater are also more apparent, as well as the impact rays which surround the craters. 1/50sec was still too slow, though.

1/100 = Exposed!

Look at that! A properly exposed Moon. Gorgeous. Tiny changes to exposure settings drastically affects how the photograph looks, so depending on your telescope’s focal ratio, you may need to adjust the camera exposure settings.


1/30sec = Exposed!

Hey! Do you remember reading about the Moon going through phases each month? The image above this sentence was taken during the Moon’s waxing crescent phase, and if you thought the Moon’s surface was less bright during certain phases, go ahead and pat yourself on the back—you’re a damn genius! The exposure setting were much slower compared to the full Moon photograph.


1 second = Exposed!

Certain conditions also affect the Moon’s brightness, like lunar eclipses, for example. 1/100sec simply wouldn’t cut it—the Moon would have been drastically underexposed, and, of course, no one likes an underexposed Moon. My telescope’s relatively slow focal ratio (12.7) couldn’t allow for quick exposures, and the Moon’s unnatural darkness certainly didn’t help.

A telescope’s focal ratio is a numerical value which correlates to its overall ‘speed’: slower telescopes, which have larger focal ratio numbers, require more time to collect light. Telescopes with shorter focal ratios are able to produce faster exposure times, but optical defects are more apparent (coma, aberrations…).

Shorter focal ratios are typically desired, especially for prime focus astrophotography. Long focal ratios can be used to photograph the night sky, but you would need to take longer exposures (which require sophisticated tracking systems).


Telescope Focal Ratio Equation

Divide focal length by telescope’s aperture

Example: 1300 ÷ 102 = f/12.7

(Numbers should be in millimeters)


Focus Pocus


If you want your images to be sharper than a samurai’s katana, then you’ll need to adhere to certain practices, or your images will be a little soft…and nobody likes that.

If your camera allows you to ‘live-view’ the photographic subject through the LED screen, then follow these easy-peasy directions.


  1. Focus.

  2. Magnify 5x. Focus.

  3. Magnify 10x. Focus.


The weather ultimately determines a photograph’s sharpness and clarity.

You can do everything correctly and it’s quite possible that your images will turnout to be astronomical duds. The rough and tumble nature of Earth’s atmosphere does not guarantee any promises, my friend.


Tycho Crater: 102mm Orion Maksutov-Cassegrain (prime focus)

If you’re not stacking hundreds of photographic frames to create a single master image, then it’s important to pay attention to the weather, that way you can maximize a single frame’s potential. Thunderstorms flush pollutants from Earth’s atmospheric nasal cavity…you know…volcano puke…car vomit…factory snot…aerosol spit—all the lovely stuff we inhale. Pick the right time to photograph the Moon and the image quality will be noticeably sharper. Pick the wrong time time to photograph the Moon and the image quality will be softer than a chinchilla.


** Sharpen Your Unguided Lunar Images **


  • Wait for calm nights, mornings, or evenings

  • Magnify the image, and then focus!

  • Don’t under or overexpose the Moon

  • Use the camera’s automatic timer, or remotely control the camera (reduces vibrations)


If you own a telescope and DSLR, you are so damn close to being able to photograph the Moon. Seriously. You’re pretty close. There are a variety of DSLR brands, but I’ll provide two links where you can purchase a T-adapter.

Click here to purchase Nikon T-adapter

Click here to purchase Canon T-adapter


(All links are unaffiliated)


Orion Telescopes & Binoculars sell decent T-adapters, however, avoid cheap adapters, or you may end up purchasing more than one adapter, which will end up costing you more cash. Amazon sells a variety of cheaper T-adapters. Buy at your own risk.

The telescope featured in this article: Orion Apex 102mm Maksutov-Cassegrain

There’s no silver bullet which can be fired at every scenario. Lunar photography is a vague topic, and a ‘one-size-fits-all’ tactic doesn’t exist. This article was just a sliver of a perspective. There’s plenty of slivers. And plenty of perspectives. Remember that.


Questions? Comments? Send me a message:




…Hey! Do you need a meteorite photograph?

!!** Click Here & Download a high-resolution meteorite photograph **!!

Signup for a Shutterstock account

!!** Click Here & Download Photographs **!!

(Referral link: if you signup using the provided link, I earn a commission.)



PrettyDamnGraphick, LLC



…Are you still here?

!!** Free eBooks **!!

About FlyTrapMan (264 Articles)
I have no idea what I'm doing.

9 Comments on Shooting for the Moon: A Perspective on Prime Focus Astrophotography

  1. Proper stuff…Love it…your photo of that crater is tops. You put stars into my eyes.

    Liked by 1 person

  2. What a gorgeous post! Your breadth of knowledge regarding photographing the moon is impressive. My brain is ready to erupt!! That’s quite a lovely and sturdy looking telescope. How much does something like that cost? It’s cool how the camera fits up against the telescope like that.

    Liked by 2 people

  3. Very informative guide Fly…and again you made me wanna do it myself..but i have always been stuggling following technical instruction.

    Liked by 2 people

Say something. Come on. You know you want to.

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: