Sensor Analysis setup for QHY168C

Somewhere to ask questions about the best way to use SharpCap
Forum rules


If you have a problem or question, please check the FAQ to see if it already has an answer : https://www.sharpcap.co.uk/sharpcap-faqs
Post Reply
rockenrock
Posts: 68
Joined: Tue May 03, 2022 12:53 am

Sensor Analysis setup for QHY168C

#1

Post by rockenrock »

Hi Robin,
I successfully got the sensor analysis to complete, but took about 10times trying different capture areas (the red box) and brightness. After I did get it to run, I found it very compelling and powerful that you (anybody) can create the programming to go through the myriad of camera adjustments and measurements. Then add to it 50+ different cameras models/brands it can work with. Wow! Only John Murphy's NSG script has given me that feeling before.
-- Does it matter if Debayer preview is On or Off?
-- Does setting the Resolution in Capture Format and Area have any affect? Smaller areas let the camera get more FPS. I left it at my cameras max resolution, but maybe smaller would be better.
-- The adjustable red framing window on the sensor analysis screen is what I adjusted to finally get the analysis to complete. Is there any way to know the framing size in X - Y pixels so I can go back to it easily in the future?
-- My Camera Controls area shows R, G and B gains. SharpCap takes over these during sensor analysis, so my setting them does not matter. Does the separate Image Control Gain have any affect on sensor analysis? I set it to minimum.
-- My camera also has an offset. SharpCap takes over that during sensor analysis. Is the Smart Histogram going to tell me the recommended offset?
-- My sensor analysis results were pretty close to the QHY spec sheet. Good to know. In SharpCap's sensor analysis output chart the first column is called Gain. Is this actually my camera's Gain Setting, and is it the R, G and B adjustable gain setting in Camera Controls?
-- I doubt my, or any, color camera has equal sensitivity (efficiency) in R, G and B. If my light source was not white, but tinted or even predominantly in one color will that affect the sensor analysis? Haha, I should just run it again with different color films on top my light panel. But please comment.
Many thanks, and I will be upgrading to Pro soon.

Roger
User avatar
admin
Site Admin
Posts: 13177
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: Sensor Analysis setup for QHY168C

#2

Post by admin »

Hi Roger,

let's run through those questions...

Debayer preview should be on - that way the analysis knows about the pixel pattern of the sensor and will in fact only use green pixels for the analysis (to make sure that the different brightness of the different pixel colours doesn't cause issues).

Reducing the resolution is fine to increase frame rate and will not cause any problems.

The separate gain is a 'digital gain' which just makes the image brighter by multiplying up all the pixel values by some number (bigger than 1 if you turn it up from minimum). Setting it to minimum is the right thing to do.

Yes, SharpCap measures how the offset control affects the background brightness of the image, so it can work out what offset is needed to cleanly separate the histogram from the left hand side and avoid zero pixel value clipping.

The first column corresponds to the number that you set the R/G/B gain sliders to (or for other cameras with a single gain, that you set that slider to). Different manufacturers have different ideas about what values to use for this gain number, from tenths of a decibel (ZWO, some others) to 100 for minimum, 200 for twices as bright, etc (Altair), to a random mix of different things including just numbers depending on model (QHY sadly).

The analysis data will not vary for the different colour channels, since it is measuring the electronic performance of the sensor (read noise, full well depth, e/ADU etc), not the efficiency at converting photons into electrons, which is the thing that varies with colour channels. Now, when you come to do the smart histogram measurement, you will have different image background brightnesses for the different colour channels, and you can choose to calculate the optimum for a given channel or the darkest channel. The darkest channel is usually blue and often gives a very long exposure. In many situations you can ignore this though, if your target has not much blue faint stuff then you may not need to care about the blue channel much.

Hope this helps,

Robin
rockenrock
Posts: 68
Joined: Tue May 03, 2022 12:53 am

Re: Sensor Analysis setup for QHY168C

#3

Post by rockenrock »

Hi Robin,
Thanks for your answers. It helps me understand better and do things correctly.
Roger
Miesilmannimea
Posts: 10
Joined: Tue May 24, 2022 2:35 am

Re: Sensor Analysis setup for QHY168C

#4

Post by Miesilmannimea »

admin wrote: Mon May 30, 2022 7:48 pm Debayer preview should be on

With dslr via ASCOMDSLR (EOS 1100D) too?

M.
User avatar
admin
Site Admin
Posts: 13177
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: Sensor Analysis setup for QHY168C

#5

Post by admin »

Hi,

yes, that applies for any colour sensor.

cheers,

Robin
Post Reply