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I want to take some astrophotography shots of objects in the sky while not keeping the moon in the shot. I have read in a few places that you need essentially a moonless sky to do so. Does that mean that I have to wait for a new moon phase or for the moon to set? Or does it mean that I just don't want the moon in my frame? I'm traveling to an area with very little light pollution, so I would like to take some star trail shots, but am unsure what I can do since the moon will be at around 1/2 phase.

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  • \$\begingroup\$ I would have thought the advice is more to do with the ambient light reflected by the moon, meaning you do not get a true-black night sky, which you would want for astrophotography, no? So not just about it being in-shot, but your blacks won't appear as black if there is a bright moon (even elsewhere from where your camera is pointed). \$\endgroup\$
    – Mike
    Mar 15, 2012 at 19:49
  • \$\begingroup\$ @Mike - I am pretty much as unsure as you are. If the concern is the moons presence anywhere in the sky, would using a lens hood help? I'm just not sure. \$\endgroup\$
    – dpollitt
    Mar 15, 2012 at 19:58
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    \$\begingroup\$ A lens hood would not help. Just think about the night sky when there is a moon. Wherever you look, it's not truly dark. You'd want a night with no moon, and be away from any light pollution, so as to ensure as dark a sky as possible. \$\endgroup\$
    – Mike
    Mar 15, 2012 at 20:00
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    \$\begingroup\$ What?!? Is the moon no longer a celestial body? ;) \$\endgroup\$
    – Joanne C
    Mar 15, 2012 at 23:30
  • \$\begingroup\$ Try looking at a Moon Phases Calendar: dso-browser.com/solar-system/moon-year/2018 it shows which nights are dark in your area. That site includes some Calculators useful for Astrophotography. There are 1000's of similar websites that can provide you a simulation of what your resulting photo or video will look like, so you can practice before you go. \$\endgroup\$
    – Rob
    Feb 4, 2018 at 19:52

2 Answers 2

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It will actually depend on your humidity! As the air gets more humid there is more water vapor in the air and this helps scatter the bright moon light, brightening the dark black sky.

However, to answer your question, if you wait until the moon is well set you should be fine. You may find it easier to wake up early rather than stay up late.

Dew can be a real problem. You are pointing a piece of glass at the sky as the temperature drops. A homemade cardboard dew shield is quite effective. Just wrap a cylinder around the lens. The height of the cylinder should be about the width of the lens. Of course, if you are shooting wide angle then this could block parts of the image. But if you dew up, well, all the image will be blocked.

Keep the lens pointing down at the ground when you take a break. Once you dew up it is difficult to remove it. A portable hairdryer in the car's lighter can do it, but preventing it is much easier.

A cable release would be awesome.

A practice BEFORE you go to your dark site.

Oh, and wear warm clothing.

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    \$\begingroup\$ Oh god, waking up early is not easier for me than staying up late :) To clarify, you are saying high humidity is bad for astrophotography? \$\endgroup\$
    – dpollitt
    Mar 15, 2012 at 20:27
  • \$\begingroup\$ Sorry I am so unfamiliar with this I would like a bit more clarity. You note to "wait till the moon is well set". So I am wondering, if I am shooting on a night when the moon isn't set during the hours I am shooting, will my results be poor? \$\endgroup\$
    – dpollitt
    Mar 15, 2012 at 23:27
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    \$\begingroup\$ yes, the higher the humidity the more the moon's light will reflect. As for doing it before it sets, it will be worse with the moon up, will it be poor? Dunno. Where are you going? (State/country is fine) and when? I'll look it up on my astronomy software and let you know what I know. \$\endgroup\$
    – Paul Cezanne
    Mar 15, 2012 at 23:46
  • \$\begingroup\$ The moon is at half phase twice in the monthly cycle, once when waxing and once when waning. If "wait until the moon sets" doesn't work, then try "shoot before the moon rises" instead. The former works when the moon is rising and then setting roughly 6 hours before the sun (waning), the latter works when the moon is rising and setting 6 hours after the sun (waxing). \$\endgroup\$
    – Michael C
    Apr 15, 2014 at 16:08
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Well, it depends on how much desperate you are :-). This picture http://www.astrobin.com/253803/ has been taken with a moon approaching being full, and, by the way, it is muuuuch better than taking frames without the moon but with a poor sky (I wrote it in the comments too)

I had no other options, since were I live the clear sky nights are few (strange, but true, I live in Italy!), if you add family, work, wind ... you end up taking picture when it is possible.

Moon was at approx 100 degs far from the subject

In your case, watch out that the moon may introduce a background gradient which is difficult to remove in post processing, in my case the field of view was tiny so I had no problem of gradients

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