M45 Pleiades with Altair 183C

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turfpit
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M45 Pleiades with Altair 183C

Post by turfpit » Sun Oct 07, 2018 2:59 pm

_M45-60x60s-g400-bl50.jpg
_M45-60x60s-g400-bl50.jpg (118.1 KiB) Viewed 362 times
Full image here https://www.astrobin.com/370439/

60 lights, 30 darks, 100 flats, 100 bias.
Altair Astro 66ED refractor, Altair 183C V2 camera, AVX mount, Planostar 0.8x flattener/reducer.
Capture software SharpCap v3.2 beta.
Focus with Bahtinov Mask, unguided.
Bias frame checked with FITS Liberator to ensure balanced histogram, used to decide black level setting.
Stack produced using Siril plus colour calibration, SCNR & colour saturation. Stack finalised with GIMP 2.10. About 1 hour for calibration and processing.
Looking at the histogram, I will reprocess the stack as some work needed on colour balancing.

Dave

[ALTAIRH183C]
Debayer Preview=On
Output Format=FITS files (*.fits)
Capture Area=5440x3648
Binning=1x1
Pan=0
Tilt=0
Colour Space=RAW12
Fan=Slow
Temperature=6.5
Black Level=50
USB Speed=2
Auto Exp Target=120
Frame Rate Limit=Maximum
Analogue Gain=400
Exposure=60000
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=2018-10-07T01:04:23.0750588Z
SharpCapVersion=3.2.5762.0

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turfpit
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Re: M45 Pleiades with Altair 183C

Post by turfpit » Sun Oct 07, 2018 3:01 pm

bias-frame-used-to-set-black-level.PNG
bias-frame-used-to-set-black-level.PNG (177.82 KiB) Viewed 361 times
This was the bias frame used to establish the black level setting.

Dave

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oopfan
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Re: M45 Pleiades with Altair 183C

Post by oopfan » Sun Oct 07, 2018 4:28 pm

Dave,

Great work!

You need to flip around the vertical axis.

I compared it to several online photos. The Merope Nebula does in fact turn reddish the farther from the star's center!

Try pulling back on the saturation level.

Maybe my eyes are playing tricks on me but is that a diffraction spike on Merope?

Brian

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turfpit
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Re: M45 Pleiades with Altair 183C

Post by turfpit » Sun Oct 07, 2018 4:43 pm

Thanks Brian.

I will reprocess the stack once I have slept. I was wondering where the red had come from.

The bias frame method worked a treat - it took a couple of goes to get the histogram balanced (2 x 0.26ms).

Dave

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turfpit
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Re: M45 Pleiades with Altair 183C

Post by turfpit » Sun Oct 07, 2018 10:38 pm

_M45-rev1.jpg
_M45-rev1.jpg (83.61 KiB) Viewed 342 times
Suggestions implemented - thanks Brian. I don't know how the diffraction spike arrived.

Dave

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turfpit
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Re: M45 Pleiades with Altair 183C

Post by turfpit » Mon Oct 08, 2018 7:11 am

I have been considering how to get a better image of this object i.e. acquire more of the blue nebulosity. I found this from Gary Palmer

https://www.facebook.com/astrophotophot ... 75/?type=3

Gary's is 20x180s, mine is 60x60s. Both 60 minutes integration time - looks like the longer exposures win out. Next time out, I will try 120s exposures, I think the mount will manage that without guiding.

Dave

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oopfan
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Re: M45 Pleiades with Altair 183C

Post by oopfan » Mon Oct 08, 2018 12:09 pm

Definitely try 120s. Though it could be that Gary was at a much darker site.

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turfpit
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Re: M45 Pleiades with Altair 183C

Post by turfpit » Tue Oct 09, 2018 12:43 pm

I did better with this capture. Image statistics for the stack have min/max at 48/59677, so no clipping. To get at the nebulosity, more data needs to be acquired => increasing the exposure length.
M45-image-statistics.PNG
M45-image-statistics.PNG (124.64 KiB) Viewed 313 times

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