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Old 25-10-2010, 08:32 PM
TrevorW
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When too use HA

I spent last night until 2am capturing data on HH

6min 10 and 15min subs with the 80ED and QHY8 OSC

all washed out due to the moon

should I have used my HA filter when the moon is full
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Old 25-10-2010, 08:34 PM
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[1ponders] (Paul)
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definitely Trevor. Gotta love Ha in the moonlight.
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Old 25-10-2010, 08:40 PM
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multiweb (Marc)
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Quote:
Originally Posted by TrevorW View Post
I spent last night until 2am capturing data on HH

6min 10 and 15min subs with the 80ED and QHY8 OSC

all washed out due to the moon

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
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Old 25-10-2010, 10:16 PM
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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
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Old 25-10-2010, 10:25 PM
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Best RGB under dark skies, best NB under dark skies - end off!!
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Old 25-10-2010, 11:40 PM
TrevorW
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Yes Doug words of wisdom, all hail Dougie
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Old 26-10-2010, 07:52 AM
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Yes Doug words of wisdom, all hail Dougie
A last my genius is recognized - thanks Trevor

ps... in vino veritas!!
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Old 26-10-2010, 08:28 AM
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too much wine I think
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Old 26-10-2010, 10:26 AM
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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.
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Old 26-10-2010, 07:03 PM
TrevorW
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Ok, thanks Paul, will check out
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Old 26-10-2010, 07:30 PM
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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.
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Old 30-10-2010, 02:51 AM
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Paul are you shooting from a dark site as I'm in the burbs

Last edited by TrevorW; 30-10-2010 at 10:59 AM.
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Old 30-10-2010, 07:50 AM
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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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Old 30-10-2010, 10:58 AM
TrevorW
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Thanks
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