269c HCG and LCG

[MillHeyAstro]

I have just run the sensor analysis on my Alatair 269c camera using ShapCap4.0.8185.0. From the read noise graph (attached), it would appear that the switchover from LCG to HCG is occurring at a gain of 2000. I thought that the switchover was supposed to happen arounfd a gain of 200. Is there anyway to manually set the camera to the HCG mode?

[admin]

Hi,

on a lot of cameras the switch happens at as low a gain as possible (this varies from model to model, 200, 300, 900). On the 269, SharpCap switches as late as possible (ie keeps LCG up to the maximum normal gain value). This was a decision from when we first tested the camera - there were some artifacts on the image in HCG at low gain (I think it was banding noise) that were not present in LCG. On this camera the read noise reduction of HCG is smaller than on a lot of other cameras, so I decided to keep SharpCap in LCG as long as possible to give the best overall experience.

It occurs to me now that maybe we had a pre-production sample of the 269 to test with, so it could be that the artifacts are gone in production models.

Anyway, if you want to do your own experiments on HCG/LCG you can do so by using the Altair ASCOM driver which lets you either switch manually or have the same sort of auto switch mode as SharpCap has.

cheers,

Robin

[MillHeyAstro]

Hi Robin,

Thanks for the reply: that makes things clear. I will start off using the Sharpcap default. Once I have used that for a while, I may experiment as you suggest. I will let you know the reults when I do.

Cheers,
Chris