SharpCap Forums

High res image here https://www.astrobin.com/370493/C/?nc=user

100 lights, 26 darks, 50 flats, 50 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.

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=6.6
Black Level=50
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=2018-10-07T02:57:11.7824463Z
SharpCapVersion=3.2.5762.0

Absolutely phenomenal, Dave! Excellent focus, too.

(I still think you could benefit from more darks. At 15s each, 50 darks cost you 12 minutes. Be sure to capture them before lights. You've got hints of raining noise happening.)

Brian

Thanks Brian. Bahtinov mask used for focus, best twenty quid I ever spent. viewtopic.php?f=18&t=1151, I stumbled upon this by accident - apply a mini histogram stretch plus a zoom in and the diffraction spikes are easy to see.

I started the imaging session at 20:00 on the Saturday evening, the Orion shots were around 04:00 Sunday morning. I don't think I could have managed a bias frame let alone a bunch of darks. The Orion was almost a throwaway attempt before I packed up (lucky imaging?). I think gain=400 certainly warrants more investigation.

Dave

Gain 100 is great for star clusters of all types. I would also consider it for faint nebulae and galaxies having bright stars in the foreground that you can't crop out.

Gain 400 is unity gain for you and me. I get a paltry 4,000 electrons at unity gain. High-end CMOS cameras and especially CCDs will give you much deeper wells at unity gain. Then you're talking big bucks but also great images.

Brian

This has turned out be a 'good example' of a 'bad example'. Looking at the Image Statistics for the stack I have the less than desirable min/max of 0/65535. So I could do better with faint data. Next time an investigation with 100x15s using gain=100 and gain=200. A last gasp capture at 04:00 without checking a single frame in FITS Liberator.