should I have used my HA filter when the moon is full
If you're really close to the moon you'll always get skyglow so it doesn't matter what filter you are using. It will always be a challenge to extract details very close or above the sky count. That's where calibration and good flat fielding will make a world of difference.
You'll find that debayering to red only will minimize skyglow. Also flat fielding will reveal noise on the edges of the field (vignetting) that will show as white when you calibrate so you might mistake that for inverted vignetting. The solution is to push your subs longer and also push your flat duration 25% longer so they're brighter. That will get rid of the 'glow' you get in the corners and outside the field. You'll have to test different values depending on your scope but in my experience double the ADU value of the center part of your flat for Ha based on the value you normally aim for with no filter on and that works for you.
Last edited by multiweb; 25-10-2010 at 09:59 PM.
Reason: clarification
should I have used my HA filter when the moon is full
Yes but as Marc said, the Horse Head is quite close to the moon at the moment. Perhaps some moonlight was shining directly on to the front of your scope? I can't wait to have a go at the HH myself this year.
James
Trevor, I'll post a couple of shots from the past week that I've been collecting photons from, M20 and 2070. All shot from first Quarter to nearly full moon. Each sub either 600 sec or 900 sec respectively. About 4 hours of each so far. I'm fairly happy with them. Mind you there was really only one day when the moon was anywhere near M20.
I didn't do the whole lot Trevor, just the first night. 150 min (10x15min, 16/10 1 night past 1st quarter) NGC2070 and 80 min (8X10min) M20. The rest don't appear any different to the first night
No fancy processing just levels and curves for viewing.
Yes I am shooting from a dark site, but the moon is just as bright. Also 2070 is only about 15 deg to the SE when I started, which is directly into the Bris skyglow direction.
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