Moon + skyglow spectrum?

[SteveL]

Can anyone tell me what the spectrum of the moon (and associated skyglow from the moon) looks like? Am trying to determine why Ha imaging during full moon nights works, whereas OIII aparantly doesnt. Am assuming there is more blue/green in it than the dark red of Ha, but would like to see the spectrum anyway, just for curiosity's sake

[Psychobilly]

This any good for starters

http://www.ichmt.org/upcoming-meetings/ELS-X-07/Extended%20Abstracts/Grynko.pdf

Peter...

[TheThing]

Ken (Merlin66) is the chap to ask about spectrums. He undoubtedly knows more than anyone else!

[SteveL]

ooo good point, wish i`d thought of that first. I hope he spots the "spectrum" in the subject title and joins in to share his knowledge.

[TheThing]

I'd subtley PM him with a link to this thread!

[sgazer]

good question, I briefly thought about this before as well. The moon is reflecting sun light, so I would have thought that the glow would be all parts of the spectrum, unless it doesn't reflect the red end very well.

[riklaunim]

Moon has the same spectrum as the Sun, as it reflects sunlight with nearly no absorption. Narrowband filters can work good when moon is glowing as they limit his glow greatly, and do not limit nebula emission - "extreme" boost of contrast.

Green O-III should perform as well, however green is more refracted by the atmospehere and slight ammount of light pollution can go through the filter (emission line between O-III lines). Also does O-III has the same band length as H-a filter?

[Psychobilly]

Shall I google it for you...

http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1269.pdf

[Merlin66]

Guys,

Look's like you got the answer without me!

Yes it's just reflected sunlight so a very even Planck curve energy distribution.

The bandwidth of the various filters and the sensitive of the CCD will have some impact.

[SteveL]

Thanks all, I think thats kind of answered my question...

[brianb]

Yes it's just reflected sunlight so a very even Planck curve energy distribution.

The bandwidth of the various filters and the sensitive of the CCD will have some impact.

Yes but don't forget for DSO imaging is the spectrum of the scattered skylight that is of interest, not the spectrum of the Moon. That's Rayleigh scattering, amount proportional to the inverse square of the wavelength ... so there's much less at extreme red / near IR (say 800 nm) than there is at extreme blue / near UV (say 400 nm) even if the input energy spectrum is completely flat.

As for OIII, it's in the green i.e. short wavelength relative to Ha, and at the peak of the solar / lunar spectrum whereas the intensity in Ha is falling off.

That's why you get much less interference from moon glow in Ha.

Incidentally you can use the same principle to image the Moon or planets in broad daylight - a deep red (Wratten #29) or IR pass filter will darken the blue sky background enough to make the object stand out ... in fact e.g. the Astronomik Planet Pro 742 actually works even better than a DSO Ha filter for this purpose. Not so good for DSOs because it will not transmit the Ha which you probably do want to record.

[SteveL]

That makes even more sense, especially the Ha vs OIII differences... thank you!