What to shoot when the Moon is out

[smr]

Hi all,

Is it okay to image star clusters when the Moon is out? 

I think I've read that you can do so, but is imaging them in moonlight affected by the moonlight as opposed to no Moon ?

[symmetal]

The moonlight increases the level of the sky background, so can be considered as light pollution, though over pretty much the full light spectrum, as opposed to urban light pollution which is generally concentrated in narrower width peaks.

Any imaging object which is fainter than the sky background at that light wavelength will not be visible as the sky background will swamp it. The recogizable stars that form star clusters will, on the whole, still be brighter than the sky background so can be imaged successfully. Fainter stars may not show however. Moonlight can give rise to noticeable gradients, though these are easier to correct on images which just contain stars.

The spectrum of moonlight, which follows fairly closely the light spectrum of the Sun exhibits a dip at the wavelength of Ha (656nm), which is why narrowband Ha imaging can be performed in moonlight with good results. Narrowband OIII at 501nm and SII at 672nm don't have similar dips so are more affected by moonlight.

Alan

Edited October 16, 2019 by symmetal

[smr]

Thanks Alan. 

Was looking for a star cluster which will look sufficiently big to image in my fov but M13 isn't that big, probably not worth imaging with 430mm.

[symmetal]

Some open star clusters as opposed to globular clusters can be quite large so may be more suitable to image. 

Alan

[alacant]

45 minutes ago, smr said:

star clusters when the Moon is out?

Hi

Yes, sure you can. Choose something as far away from the moon as possible.

9 minutes ago, smr said:

sufficiently big to image

For tonight, how about m39? With your eos, take the ISO down to 400 and see how 90 second frames look, but beware; 430mm over aps-c is gonna give you a sizable moon gradient to have to wipe away.

Cheers and HTH.

Edited October 16, 2019 by alacant

[alan potts]

I imaged the other night with analmost full moon and below 20 degrees. Not brilliant I grant you but far from rubbish.

 

Alan

[DaveS]

When there is the moon up I only bother with hydrogen narrow band, even oxygen and sulphur are badly affected, and I wouldn't even think of RGB.

[kirkster501]

Ha - especIally 3nm - and even then as far away from the moon in the sky as possible. I got some RGB on the heart nebula on Sunday and had to trash it the gradients were so bad.

Or image the moon 😀👍 you can spend a lifetime doing that alone if you image in detail different features.

Edited October 17, 2019 by kirkster501

[don4l]

I imaged M34 and M39 last week, and I was very pleasantly surprised with the results.  I'm not sure that I would have done any better on a "perfect" night.

[don4l]

This is 6:6:6 min of RGB M34, shot on 9th of this month.  I haven't imaged many open clusters, but I was very pleased with it.