NGC7000 with Ha filter

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turfpit
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NGC7000 with Ha filter

Post by turfpit » Mon Sep 24, 2018 9:42 pm

_NGC7000_Ha-60x90s-g1000-bl150-reduced.jpg
_NGC7000_Ha-60x90s-g1000-bl150-reduced.jpg (165.07 KiB) Viewed 669 times

Altair 66-ED refractor, Planostar 0.8x reducer/flattener, Altair 183M camera, Ha 7nm narrowband filter.
SharpCap 3.2 + FITS Liberator + Siril + GIMP 2.10

60 lights, 50 darks, 100 bias, 100 flats
exposure=90s, gain=1000, black level=150 [unguided]

I had to set the gain much higher than I am used to (100) in order to get a decent histogram. The other surprise was with taking flats, normally to get a reasonable histogram I use an exposure of 250ms but with the filter in use I had to use 15s. I also had to push the mount tracking capability by upping the exposure to 90s but it looks like the AVX held up here.

This was my first experience with a narrowband filter - some interesting challenges with settings . Quite pleased with the image but have noticed some horizontal banding that I will need to go away and investigate further.


Dave

Lights
[ALTAIRH183M]
Output Format=FITS files (*.fits)
Capture Area=5440x3648
Binning=1x1
Pan=0
Tilt=0
Colour Space=MONO12
Fan=Slow
Temperature=8.8
Black Level=150
USB Speed=2
Auto Exp Target=120
Frame Rate Limit=Maximum
Analogue Gain=1000
Exposure=90000
Timestamp Frames=Off
Apply Flat=None
Subtract Dark=None
#Black Point
Display Black Point=0
#MidTone Point
Display MidTone Point=0.5
#White Point
Display White Point=1
TimeStamp=2018-09-23T19:58:58.1949246Z
SharpCapVersion=3.2.5762.0

Flats
[ALTAIRH183M]
Output Format=FITS files (*.fits)
Capture Area=5440x3648
Binning=1x1
Pan=0
Tilt=0
Colour Space=MONO12
Fan=Slow
Temperature=8
Black Level=149
USB Speed=2
Auto Exp Target=120
Frame Rate Limit=Maximum
Analogue Gain=400
Exposure=15000
Timestamp Frames=Off
Apply Flat=None
Subtract Dark=None
#Black Point
Display Black Point=0
#MidTone Point
Display MidTone Point=0.5
#White Point
Display White Point=1
TimeStamp=2018-09-23T23:02:59.5309235Z
SharpCapVersion=3.2.5762.0

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turfpit
Posts: 869
Joined: Mon Feb 13, 2017 8:13 pm
Location: UK
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Re: NGC7000 with Ha filter

Post by turfpit » Tue Sep 25, 2018 12:02 pm

NGC7000-comparison.pdf
(158.87 KiB) Downloaded 48 times

Last night I ran the same object, NGC7000, kept the 90s exposure, dropped gain to 100, no Ha filter. 50 each of light, dark, bias and flat frames. Both images processed to same stage in Siril (histogram transformation). No evidence of horizontal bands. This indicates everything ok with hardware, cabling, power, 90s exposure and processing workflow.

Next step - I have some single images from this morning with the Ha filter in place which progressively increase the exposure but using gain of 100. These have yet to be evaluated. Note - Alnitek dead centre is a very interesting area in a 5000x3000 frame using Ha - I will revisit that.

Dave

mAnKiNd
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Location: Long Island, NY
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Re: NGC7000 with Ha filter

Post by mAnKiNd » Fri Sep 28, 2018 11:20 pm

nice one here too! Did you figure out what was causing you the banding? 50Hz?

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turfpit
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Location: UK
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Re: NGC7000 with Ha filter

Post by turfpit » Fri Sep 28, 2018 11:58 pm

Thanks Minos.

I made 2 changes that night. Ha filter and exposure up to 90s (from 60s). Investigations are underway. I will report back.

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