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Is it stupid to image RGB stars during full moon nights?

Acquisition One-Shot Color RGB Light Pollution
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kuechlew avatar
kuechlew avatar

Hi all! I recently started to augment my narrowband images with RGB stars taken with a one shot camera. So far I collected the RGB data during new moon or after moon set. However, I wonder if I’m only interested in the stars whether this is really necessary. Since the stars usually are fairly bright and moon light is full spectrum it shouldn’t disturb too much. I may lose some magnitude 10+ stars but this wouldn’t bother me. Am I overlooking something?

Addendum: I’m usually operating under bortle 5-6 skies

Clear skies

Wolfgang

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Wim van Berlo avatar
Wim van Berlo avatar

As long as you’re not imaging near the full moon, you should be ok. Living in northern Europe, I have to use any opportunity I get, and imaging rgb during a (nearly) full moon is certainly doable. Imaging deep sky objects (galaxies, nebulae) is another matter, of course.

Cs,

Wim

kuechlew avatar
kuechlew avatar

Thank you for your response Wim. I live in northern europe too and suffer from the same sparsity of clear nights. Of course I’ll try to stay away from the moon as far as possible. There are a lot of nights where the moon is up part of the night and it would help me a lot to use this time for the rgb stars and then once the moon has set use the precious moonless time for nebulae, OIII/SII and the like. Will give it a try.

Clear skies

Wolfgang

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Tony Gondola avatar
Tony Gondola avatar

Yes, you certainly can and should, just keep the sub exposure length short. I generally use 15 sec. This keeps you from over-saturating and loosing color and keeps the stars small by limiting star bloat. 30 min. of data should be enough in most cases.

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kuechlew avatar
kuechlew avatar

Thank you Tony! Currently due to physical limitations I’m imaging with a lightweight rig based on Samyang 135 mm f2 lens, stepped down to f 2.8 for better star shape in the corners. So maybe I even have to go down to shorter exposures.

Clear skies

Wolfgang

Tony Gondola avatar
Tony Gondola avatar

You might stop down a bit too. Just beware that because you’re shooting with a camera lens that your bright stars will not be round but multi-sided because of the iris in the lens.

Wim van Berlo avatar
Wim van Berlo avatar

Tony Gondola · Oct 4, 2025, 07:28 PM

bright stars will not be round but multi-sided because of the iris in the lens.

The use of step down (filter) rings should solve that. Never tried it myself though.

kuechlew avatar
kuechlew avatar

Thank you Wim, thank you Tony, indeed the effect of the iris can be seen when looking at the full size image of M45: https://app.astrobin.com/u/kuechlew?collection=14461&i=lhfcjm#gallery.

As with the diffraction spikes of Newtonians it’s a matter of taste whether you like it or not. I will have to collect some experience over time.

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Bill McLaughlin avatar
Bill McLaughlin avatar

Wim van Berlo · Oct 4, 2025, 07:49 PM

The use of step down (filter) rings should solve that. Never tried it myself though.

Yes, although I have found a better way is to make an aperture mask either by 3D printing or by drilling or machining a hole in a screw-on lens cap. That will give you a very precise f ratio of your choosing.

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kuechlew avatar
kuechlew avatar

Thank you Bill!