setting Gain/offset & Sensor Analyst resut

[tiziano]

Goodmorning everyone

Excuse for my two beginner questions,

(1) I have the QHY183C camera, connected to Sharpstar 61-dph, does anyone know how to correctly set the GAIN and OFFSET in Sharpcap,
(2) about the 'Sensor Analyst' tool
how should I interpret the final result

Thank you

[admin]

Hi,

for setting the gain there is no single correct value - it depends on what you are doing. Planetary imaging requires high gain, as do quick images for focus or alignment. Deep sky may require lower gain if your mount can cope with long exposures. If not then medium gains may be best.

Setting the offset is easier - once you have your gain and exposure chosen, cover the telescope and expose some dark frames with the selected gain/exposure. Adjust the offset to make sure that the peak in the image histogram is clearly separated from the left hand side of the graph.

There is a section in the user manual that gives more information about what the numbers in the sensor analysis results mean : http://docs.sharpcap.co.uk/3.2/#Sensor% ... %20Results

cheers,

Robin

[tiziano]

Hi Robin
thank you very much, as soon as there is clear sky I will do some tests
Tiziano

[archer1960]

Waking this topic back up, so I don't need to start a new thresd...

Can the sensor analysis results give me an indication of what offset value to use, or do I pretty much have to use the dark frame method? I have been using 15 on my QHY-600, but I have seen others recommend values as high as 30 to 50.

[admin]

Hi,

the sensor analysis does measure the brightness of bias frames at different gains, so that is the required data, but it's not shown in the graphs, so you can't use it directly.

If you use the 'Smart Histogram' functionality (specifically the 'brain' button), that will measure the sky background brightness for you and recommend a gain, minimum exposure and offset level that should properly meet the usual requirements.

Otherwise, adjust the histogram for short exposure dark frames at the gain you want to use. Full exposure dark frames will be a bit brighter due to thermal noise, but for modern cameras that is a pretty small difference (not so small with older CCDs).

cheers,

Robin

[archer1960]

Thanks!