the moon--L or LRGB filters

[iwols]

hi with the moon out,decided i will try the moon instead of the dso objects,dont want to alter my imaging train so i was wondering what would you use to image the moon filter wise,just Lum or lum and rgb cheers

[ollypenrice]

If you want a monochrome image it might be worth trying the red filter. The longer wavelength of red will reduce the effects of the seeing and may give you a sharper image than any other filter. Obviously, if you want a coloured moon image then you'll need RGB but you could still use the sharper red layer as luminance over that. 

Olly

[symmetal]

I image the moon using an UV/IR cut (L) filter as well as an IR Pass filter to get seeing improvements as Olly says on the longer wavelengths. However the IR pass image is always softer than the L image using the same 10mS exposure and stacking 30s videos. I just use higher gain on the IR pass. I focus on a nearby star with a Bahtinov mask and have to change the focus between the two filters as you'd expect. Perhaps bahtinov mask focusing with an IR pass filter doesn't give the correct result but I can;t see why. Using the scope with a 2x powermate and working at f12 I wouldn't have thought the moon distance compared to infinity would have a more noticeable effect at IR wavelengths compared to visible.

Alan

[symmetal]

Thinking further, the scope I used (FLT-98) is optimised to bring wavelengths passed by the L filter (300nm bandpass) to the same focal point. The IR pass filter from 685 to beyond 850nm, (runs off end of spectrum plot). The APO visible optimising could be creating havoc at different IR wavelengths with the focal point being all over the place. This would lead to softer IR pass images. If this is the case why is the IR pass regarded as the 'secret tool' of planetary/moon imaging. Maybe it performs better on an SCT or newt that it does on an APO frac.  I think in this case a red filter would be better for me (and iwols) than an IR pass filter. Any thoughts?

Here's a crop of two images of the same area taken a few minutes apart, both 10mS exposure and 30s videos, stacked in Autostakkert but no sharpening or other enhancements applied. The L is sharper.

Alan