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Photometric data during the full moon

PVEA's picture
PVEA
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Joined: 2011-07-15

I am curious whether some practical rules about submitting photometric data obtained during the full moon exist. I have seen recently lots of submitted photometric data in that time.

Can we trust to such observations? I personally stop photometric observations for about 7-8 days. Am I right or I am worrying unnecessarily?

Velimir

Hi Velimir Take a look at
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jji
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Joined: 2010-07-24

Hi Velimir

Take a look at your data.  Is the error starting to get larger than you would like it to be?  If not, then you should be ok.  If it is getting excessive, you might want to stop imaging that target for awhile.  What's excessive...well if you are involved in a precision photometry project 0.02 might be excessive.  If you are taking a time series of a CV, then 0.07 might be acceptable.

But don't stop observing.  Have some "full moon" targets (brighter, futher away from the moon, different type of target....) that you can switch to.

My motto is all night, every night.

Jim Jones, JJI

 

 

Photometric data during the full moon
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I also take data all month long regardless of moon size.  The key it to avoid shooting variables too close to the moon when it more than 65% lite.  Between waxing and wanning gibbous, I usually shoot variables no closer than 15 degrees away.  From my Urban location, (Bortle scale 9) the moon doesn't add that much to a sky that's 15-20x brighter than Bortle scale 3-4 skies that I travel 100 miles away to take my "pretty" astroimages.

James

full moon
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HQA
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As another data point, APASS takes data on every clear night, regardless of moon phase.  We do plan only bright star exposures for the 5 days centered on full moon, but otherwise, we just avoid the moon as others have mentioned.  A dry mountaintop helps with scattered light, as I know the sky gets pretty milky white with almost any visible moon from my personal observatory in New Hampshire!

So I agree with other posts:  if you want to optimize your observing, perhaps you can create separate target lists, based on clear/cirrus, moon/nomoon, good/bad seeing, etc.  I usually had a base set of targets that were ok under almost any condition, and then a few add-on targets to take advantage of the specific night.  But if it is relatively clear, it seems a shame to have anything keep you from collecting photons!

Arne

Photometric data during the full moon
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PVEA
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Thank you Jim, James and Arne,

You gave me a new point of view. Since I do not want to feel ashamed, I will continue with the observations in every clear night... wink

Velimir

Spectra Observations during Full Moon
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WGR
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What I am told by Professional Astronomers who have done it, Full moon time and cloud time is often used for spectral observations at professional observatories.

 

Gary

Photometric data during the full moon
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PVEA
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Joined: 2011-07-15

Hi Gary,

You’re right and I know that so I asked my question. Our remote controlled systems are built in the territory of a professional astronomical observatory. Normally on a moonless period the professionals perform CCD photometric tasks but during the full moon they use Coude-spectrographs for spectral studies.

As I understood from previous explanations, obtaining photometric data during the full moon is permissible for certain objects but the data must be checked carefully.

Velimir

full moon
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HQA
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As Gary mentions professionals often do spectroscopy during full moon.  If you are working on bright stars at high spectral resolution, there is essentially no sky background, and what little there is can be easily subtracted out.  The other professional activity during full moon is NIR/IR imaging.  Here the sky scatters very little light (I've worked within 3 degrees of the full moon) and you often can't tell that the moon is up at all.

The Bright Star Monitor, which typically works in the range 2<V<9mag, is always photon limited and never sky limited.  I can do as well from the roof of HQ in the midst of Boston as I do in a more rural environment, as long as I stay clear of local lighting.  The only concern is scattered light into the telescope, so you have a zone of avoidance around the moon, which grows as it heads towards full moon.  Note that there is a sharp peak in brightness within a couple days of full, which is why APASS switches programs for the 5 days centered on full moon.

The moon is horrible for faint object photometry or for extended objects, as there you are background dominated, and any change in the background directly impacts the signal/noise.  Gradiants in your image from the moon scattered light look bad, but don't affect the photometry of moderate-brightness targets that much since you are taking sky in a small region surrounding your target.  However, in most cases, you just need to be a bit more careful with a bright moon in the sky.

Arne

Moon is just another source of light pollution!
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lmk
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FJQ wrote:

From my Urban location, (Bortle scale 9) the moon doesn't add that much to a sky that's 15-20x brighter than Bortle scale 3-4 skies that I travel 100 miles away to take my "pretty" astroimages.

James, Your the man! Anyone who suceeds in observing from the LA basin is a champion in my book ;) I used to live right down in that "muck" for many a year, too...before I got back active in astronomy.

Mike LMK

 

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