Narrowband imaging and the moon.

[swag72]

...... I always thought that narrowband imaging when the moon was about was fine. I knew that RGB was pretty much a no no due to the moon just washing everything out. 2 nights ago I tried to capture some SII to add to my Ha in my latest narrowband target. in the morning when I checked the subs, I was surprised to see that I could see nothing in the image at all with regards nebulosity. I stacked th 2.5 hours worth of subs and again, there was nothing to see. I know that there is some SII around as I have looked on the net.

I am a very unscientific person, but looked at some SII subs when taken when the moon wasn't up and compared them to the moonlit subs from last night. I used Maxim and looked at the pixel ADU for the background of each sub and also the pixel ADU in the nebulosity area of the no moonlit sub. The two subs are not from the same target, so it's really not hugely scientific, but gives me some ideas.

SII - No moon light ---> Background ADU of 512 and the nebulosity was showing an ADU of from 650-820ADU

SII - Moonlight ---> Background ADU of 3226

This suggests to me that there was no way any SII signal was going to break through that and also suggests to my unscientific mind that any signal will have to have an ADU figure of approx 3400 before it will even show in the image.

Is that about right? So have I learnt that imaging in moonlight, even for narrowband is a total waste of time?

I know that this would be more scientific if I had 2 x SII subs of the same target (I may do that tonight), but am I generally correct in my assumptions?

[Earl]

If I recall Olly saying something Ha is ok in the moon but the others do suffer. I could be wrong mind you

[Spikey]

I think it can depend on how 'narrow' the wavelength of your narrow band filter is and also the peak transmittance comes into play.

[Spikey]

Just found this http://www.astrodon.com/Orphan/astrodonfaqnarrowband/

A bit of light reading for you Sara !

[Ant]

I thought that same... Ha is OK - especially the narrower of the two bandwidths, but OIII and SII is a no no...

Cheers

Ant

[swag72]

Good link there Simon, thank you.

I was always under the impression that SII and OIII could be done with moonlight - Now I know!!