Help with Sensor Analysis and results from imaging

[mjd6191]

Hello all,
I have a rather basic question and hopefully someone on this forum can help me. A quick rundown of equipment: Orion Skyview Pro 8" reflector, ASI120mm guide camera, SVBONY SVB160 guide scope, SVBony 605C imaging camera, PHD2 for guiding, sky is Bortle 4/5. I ran a sensor analysis for the camera for both 8 and 14 bit (they call it 16 bit).
When I use the Smart histogram, it is telling (trying to image M1) me to go to 3.1 seconds with a gain of 130. If I lower the noise level in the smart histogram the time lengthens but the gain only changes marginally. The results (when I am not fighting wind or clouds), have been very noisy images. I was actually getting BETTER results BEFORE I did the sensor analysis and just used trial and error to get a better result.
Did I screw up the sensor analysis, do I need to just shoot more frames?
I am attaching the results of the analysis and some photos, M1 was shot last light with the recommended settings, the Orion Nebula was shot about a week ago with me estimating the imaging. Last night was 450 subs at 3.1 seconds, the Orion nebula was 52 sub at 180 seconds. I did use flats and darks made specifically for each image.

Orion_605.jpg (222.04 KiB) Viewed 1839 times

m1 copy.jpg (745.69 KiB) Viewed 1839 times

16 bit sensor 01_09_2023.txt

(1.34 KiB) Downloaded 41 times

[jolo]

I have checked the sensor analysis you attached and it looks like there is a unity gain point around gain 130, which is why the smart histogram probably "likes" this value.
I would leave the gain at 130-150 so the read noise is low and the quantization error as well and I would play with exposure times. Longer sub exposures will always give a better result, but at some point, the benefit starts to be invisible.

It may also happen that calibration frames are somehow wrong, so you may check it and stack only light frames for comparison.

[admin]

Hi,

the SV605CC camera switches mode at a gain value of around 100, moving into HCG mode for higher gains which leads to a significantly lower read noise. This reduction in read noise is usually enough for SharpCap to prefer suggesting gains in the 120-130 region, compared to zero gain.

As long as you are using exposures that are as long as recommended (longer is fine - just not so long that your guiding/tracking becomes an issue) then the noise level of the final image is determined by the total amount of time that you image for. That is, you should get the same results if you use 120 x 15s frames as if you use 15 x 120s frames (total time of 30 minutes in each case).

As Jolo pointed out, taking more light frames will not help you if you are using darks/flats and you didn't take enough of those, meaning that the dark and/or flat is noisy. That noise from the dark/flat will be the same in every stacked frame, so will not vanish as you add more frames.

cheers,

Robin

[mjd6191]

Thank you Jolo and Robin. I will try your suggestions, especially with regards to the calibration frames and see what results I get

[mjd6191]

Hi Folks, Thank you for the input. I did another imaging session, and I got somewhat better results, but still have a long way to go. I did create new darks/flats and bias frames through Sharpcap Pro. I also used the smart histogram and shot 350 lights at 11.5 seconds, 10 darks, 20 flats.
A few thing I noticed, and need to know if this is normal, in order to get the histogram a little more stretched , I needed to move the RGB slider over to the right, (400, 366, 398), or else the histrogram was VERY tight at the left, barely out of the amber area into the green.
Next was the lack of color. Is this due to the color bars/white point not being correct?
Lastly, I used the FWHM Multi-Star for focus. I tried using my Bhatinov mask but even though I got very low numbers with it, I did not feel the focus was very good, I think my mask was not seated properly, so I went with the FWHM Multi-star. The lowest number I achieved was 4.110, which is the attached photo. It was all green bars, but I still feel it was a bit off, any thoughts? And is the number relative to the stars, because I could never get any closer to zero than the measurement listed. Attached is the result of my efforts

All post processing was done in Pix Insight followed by a little cleanup and files size reduction in Photoshop, which I am just learning so I followed along in a tutorial

m1_v5 copy.jpg (171.45 KiB) Viewed 1726 times

.

[admin]

Hi,

I would recommend leaving the colour sliders at their default settings of 128 - they don't do you any favours when you adjust them, since they simply multiply pixel values by some number. It is better to leave them at default and fix colour issues after stacking.

If the image is too dark to view nicely, it's better to turn up the gain to brighten all 3 channels by the same amount - this is an analogue gain, so much less of an issue than the digital brightness manipulation of the colour balance sliders. You can also use the stretching function of the mini histogram on the right to brighten the image on screen (without affecting what is saved) - see https://docs.sharpcap.co.uk/4.0/#!2!Min ... %20Stretch

I don't know quite what is going on with your colours - I was imaging with the 605C over the weekend and had no problems with colours...

Stack_168frames_1816s_WithDisplayStretch.jpg (592.5 KiB) Viewed 1725 times

The settings used to take this were 168 frames of 10.8s at gain 150, all colour settings set to 128, cooler at 0C - details below.

It would be worth checking your settings in case you have set an odd value for some control (contrast or gamma or something) and forgotten about it.

cheers,

Robin

Code: Select all

[SVBONY SV605CC]
FrameType=Light
Debayer Preview=On
Output Format=PNG files (*.png)(Auto)
Colour Space=RAW16
Binning=1
Capture Area=3008x3008
Pan=0
Tilt=0
Black Level=5
USB Speed=1
Frame Rate Limit=Maximum
Gain=150
Exposure=10.808s
Timestamp Frames=Off
White Bal (B)=128
White Bal (G)=128
White Bal (R)=128
Sharpness=0
Gamma=1
Contrast=50
Cooler Power=7
Temperature=0.1
Target Temperature=0
Cooler=On
Trail Width=2.5
Minimum Trail Length=100
Trail Detection Sensitivity=13
Mask over exposed pixels=Off
Flip (after dark/flat)=None
Remove Satellite Trails=Remove
Background Subtraction=Off
Planet/Disk Stabilization=Off
Banding Threshold=10
Banding Suppression=0
Apply Flat=None
Hot Pixel Sensitivity=5
Subtract Dark=None
NegativeDisplay=0
Display Black Point=0.001953125
Display MidTone Point=0.18190844536439493
Display White Point=0.998046875
Notes=
ZWO Focuser (1)=4113
Focuser Temperature=10.1899995803833
EQMOD ASCOM HEQ5/6=RA=05:36:31,Dec=-05:26:10 (JNOW)
TimeStamp=2023-01-18T22:23:53.2254658Z
SharpCapVersion=4.1.10037.0

[mjd6191]

Thanks Robin, your replies always help! I am attaching my camera settings just as a comparison. Tonight it wi

M1_00001.CameraSettings.txt

(1.09 KiB) Downloaded 40 times

ll be stormy here in Florida, but tomorrow night will be clear and calm so I will be out using your suggestions and will see what new results I get!.