Altair Hypercam 269c Camera set up INDI

[dean7828]

hello peeps, wandering if someone can point in the right direction here, so i have the above camera - Altair Hypercam 269c one shot colour, I have been useing theis with and Starwave  115 F7 ED and until now been fumbling around with default settings.

dose anybody know good settings in terms of offset and gain for polluted sky's with a CLS filter. ??

Im trying to understand the dual gain settings - HCG and LCG Gain ratios, im also looking into ofset settings which I believe is the black point or Gamma setting??

is anybody else using this camera? and if so what is the sweet spot, i know i need to do some research but its hard finding documentation. im useing Kstars Ecos and Indi.

any help would be greatly appreciated.

Dean.

 

[rickwayne]

Sorry, I know nothing about the camera per se. But I can at least offer you some guidance on the concepts.

The tradeoff between high and low gain is between shorter exposures to achieve a given SNR, and "top-end" range. If you want color in stars and other bright areas of the image (e.g. a galaxy core or the Trapezium in M42), your exposures have to be short enough not to max out those values. High gain is rarely needed for one-shot color cameras; you can always make up the low end with more subs to yield more integration time.

From Altair's documentation, it looks as if HCG is just an extra multiplier that can be applied to gain values; how you set it in the application you're using may vary.

Although higher gains paradoxically yield lower read noise, the effect is small compared to the loss of highlight detail; many people use "unity" gain so that one electron on the sensor means incrementing the output pixel value by one. That appears to be LCG and 200 gain for the 269, but I could be wrong.

Offset is a means of protecting the low end from various kinds of noise. Since the sensor can't read anything less than zero electrons, and noise can affect the signal in either direction, in some cases a non-zero input plus the noise "clips" to a zero value, since negative ones aren't possible. So an offset adds a "cushion" to every pixel, below which signal+noise should always be > 0. Of course, you lose a bit of range this way too. I suppose you could call it the black point but it's really an entirely different concept; it has the effect of setting the black point below zero.

[rickwayne]

BTW the 269 does not appear on this list of their cameras that do HCG, so maybe it's moot?

[dean7828]

Thanks Rick, this is very useful, I need some time to digest this.....