Light pollution vs. Moonlight

[skiddieleet]

I wasn't thinking tonight and drove out a ways to a location I remembered seeing a lot of stars at when leaving a wedding.  I got out there, and realized the moon was very bright.  I thought I would get better views of things I had seen from my house, but they looked basically the same and I wasn't able to coax out any more detail.

Does moonlight have the same effect as city lights, or should I have been able to see things better even with the moon shining so bright?

[tingting44]

moon light has the same effect as day light lol you wont see a fraction of what you would normally with no moon showing, head out next time when the moon is not about and see the difference! you will be gob smacked, not bad you done it this way as you will appreciate the difference next time, ive just come in from inside now trying to spot the ISS over head ar 5:55am but couldnt spot it, dam its cold tho

[glappkaeft]

I sometimes estimate the limiting magnitude and have found that locally

Does moonlight have the same effect as city lights, or should I have been able to see things better even with the moon shining so bright?

Light pollution is light pollution no matter if it is natural or man made. The moon is actually harder to handle (can't filter it) and there are no moon free dark sites we can go to (except into space).

[Minimalist__]

I remember I found a great wee site about 45 mins from me that I could see the Milky Way quite well etc. I headed there again on my third outing in this hobby, didn't consider looking at the moon's phase or where it was in the sky. Got there and was astounded at the fact that the whole field was lit up, and I was casting a large shadow along the ground. Couldn't see much at all.

Needless to say, I always check where the moon will be to see if it's worth going out when it's bright. Unless I want to look at the moon of course!

[ronin]

The moon was shining well last night. It washed out quite a lot of nice easy beginners bits owing to where it was sat as well.

Equally the moon itself was a good target.

Moonlight will have a similar effect to light pollution, however I suppose there is some "technical" degree of diffence.

[SW130p]

I viewed last night from my garden which it is quite light polluted together with the bright moon yet still got the clearest view of Jupiter. Can't imagine how it will look under completely dark skies. all I couldn't see was Andromeda as was close too the moonshine Which is only going to get brighter as the nights go on.

[RikM]

I viewed last night from my garden which it is quite light polluted together with the bright moon yet still got the clearest view of Jupiter. Can't imagine how it will look under completely dark skies. all I couldn't see was Andromeda as was close too the moonshine Which is only going to get brighter as the nights go on.

Jupiter will look pretty much exactly the same, maybe worse from a dark site.

Planets are bright enough to cut through light pollution and moonlight (they even look good through a bit of haze). Oddly, with the moon in the sky, your eye don't open up so wide, so just like stopping down a lens, you can sometimes see sharper detail and better contrast in planetary detail.

If you have been observing for the planet for a bit, take a quick peek at the moon ad then go back to the planet, you might be surprised at the extra detail that can pop out.

[ollypenrice]

The moon is far more invasive than street lighting because it is almost full solar spectrum. On the other hand it's much nicer becaue it's natural. Living at a dark site means that astronomy stops, full stop. The near-full or full moon casts shadows and allows you to function quite normally outside. If I go out for firewood, or to the car, or whatever, I've no need of further light. You can see in limited colour, too, though I personally couldn't read by it. I suspect that there are people who could.

There's another factor, transparency. In a very dry, transparent sky, a little low, crescent moonlight doesn't kill the astronomy. If it is hazy, though, the moonlight is scattered all around the sky.

Olly

[SW130p]

Cheers I did notice that when switch between the moon and back

Sent from my iPhone using Tapatalk

[Special K]

The moon was wreaking havoc last night and though it looked clear there was a lot of moisture in the air. I couldn't make out much even after the moon had set. However I had a good look at the moon in the bins to beat it at its own game! Severely bright at first glance but lots of easy detail.

I wwanted Andromeda too but there's no chance at the moment.

[bingevader]

I know it's not everyone's cup of tea, but the moon is rather magnificent itself if it precludes your observations of other objects.

I had a lovely night last night. First clear (ish) sky in weeks, so had hoped for a bit of DSO observing, but there was the stunning moon instead.

Started off at Plato and the Vallis Alpes, then round to the Apennine Mountains. Then Copernicus and the Hortensius Domes! All in good relief and spectacular detail.

Cheers

[AlexB67]

a UHC filter can help a bit under moonlight for deep sky targets, only to a point of course and when there is not too much of it.  I've noticed a noticeable improvement on nebulae with a bit of moon around for example, the UHC filter did a good job in boosting to object against the background the few times I tried that.  Example M46 and PN NGC 2438 recently showed up quite nicely.  When I got the filter the first night I observed M27 in my smaller 5 inch Dob, it did a good job of enhancing it against a nearby moon too. 

That said on near full or very bright moon, just accept the moon, observe it instead

Another you can try under brighter moon light is to pick a very bright DSO like the Orion nebula, you may actually pick a bit of extra colour when you don't dark adapt properly.

[jetstream]

From my dark site and the moon "half full" the sky brightness was 19.2 mag....with no moon the site is typically 21.5-21.7.That is well over a 2 magnitude difference.......lots.Still a few DSO were viewable and I did get a new one...ngc 2392,the Eskimo nebula,with my OIII.With a full moon the sky mag on the SQM will go down into the 18's,worse now in winter with all the snow as well

[Moonshane]

whilst I would not generally travel to a dark site to view Jupiter/Moon etc, the lack of chimney pots etc would make the seeing a lot steadier than average so it's possibly still worth traveling even 'just' for solar system objects and double stars.

[jetstream]

Travelling to a dark slie for lunar/planetary is not worth it unless there is better seeing conditions,etc as Moonshane rightfully indicated.I have been checking the skies under different conditions,inluding the effect of the bright moon and snow on the SQM readings.Baselining the darks sites,for reference.The other night,on the lake ice,my VX10 took a very long time to stabilze,without the fan while setting up,then with the fan on ( typically stabilzes faster,with the same temps)Even after settling in the seeing was not the best,partly because of sky conditions.However,and I'm not positve yet...viewing from the ice may have caused me a bit of trouble with tube currents or thermals entering the tube.I thought the ice would be a thermally stable place to view from,but not so sure yet-the water is 40 deg under the ice.Maybe a warmer area just above ice compared to the temp above it...(?)The investigation continues... I find moonlight harder to view through than LP of the same mag,just my opinion though.

[acey]

I never observe under strong moonlight - it drowns out all but the brightest DSOs. It's only worth going to a dark site if there will be sufficient time with the moon below horizon. I'll sometimes start a session before moonset, beginning with bright targets on the opposite side of the sky from the low moon, and switch to fainter targets once the moon is down.

At a light-polluted urban site the effect of moonlight is far less obvious because the sky is already so bad - the moon is just another streetlight.

In theory you can cut some moonlight using a polarising filter, but you have to aim at the right part of the sky (ninety degrees from the moon) and the filter will cut at least half of incoming light, so in practice it's not really worth it. Viewing emission nebulae with a UHC filter is a better option.

[Moonshane]

surely though if you are only interested in solar system objects and double stars light pollution is largely irrelevant and seeing most important. in my garden, local seeing creates big problems sometimes. I stress I am not describing myself but the benefits of steadier air are often not appreciated at sites with no/fewer houses by newer observers.

[acey]

surely though if you are only interested in solar system objects and double stars light pollution is largely irrelevant and seeing most important. in my garden, local seeing creates big problems sometimes. I stress I am not describing myself but the benefits of steadier air are often not appreciated at sites with no/fewer houses by newer observers.

I agree - those are the only things worth looking at in moonlight (apart from the moon itself). And there's no point going to a dark site to observe them. I only observe DSOs (and always at a dark site) so if there's strong moonlight then I don't observe.

[cantab]

Personally I feel that we get few enough clear nights that I have to take them, Moon or no Moon. Of course for me there's still loads of DSOs I've not yet looked for and will see just fine even with the Moon up.

[johncneal]

I'm with you cantab, give me the Moon over light pollution anytime. At least if the Moon is that bright you can do some useful observing of it - even on a good night my local streetlights kill everything fainter than about mag 3.5 naked eye. Thankfully, 15mins drive puts me at a reasonably dark site. I'm relatively new to this but what really bought home to me how much light pollution impacts observing, was a trip to darkest Lincolnshire over Christmas - completely flat countryside for miles in any direction, clear sky and the most amazing view of the Milky Way I've ever had. If it hadn't been absolutely freezing and blowing a gale I could have stared at it for hours!!

john

[Qualia]

if you are only interested in solar system objects and double stars light pollution is largely irrelevant and seeing most important.

Aye, Moonshane has summed this aspect of astronomy well. LP really makes little difference when it comes to viewing doubles, Jupiter, Saturn or the Moon.

Been out tonight, city roof top, 96% full Moon, good amount of LP and have had one of the most stunning sessions with Jupiter and the Moon in many, many weeks. Spent most of the night viewing at 250x, wonderful Io shadow transit, clear colour to many of Jupiter's most ready features, and it could have been just an optical illusion, or a bit of wishful thinking on my behalf, but swear I saw a tinge of orange to Ganymede. The quality of the atmosphere, the seeing, is everything. 

If possible, I generally divide my evening sessions in two categories: dark site, DSOs; LP site, brighter objects.

[colesmat]

Excellent thread and thank you. Answered alot of questions I had myself. Planned on having a trip to galloway if the weather changed (not that it has) but I'll leave it 2 weeks now. Typical, the first week I bring my binos away to work and it's a full moon.

Matt.