spectro-aras.com

Hi all
I have just bought a new camera to go on my LHIRES. I was using a SBIG ST8XME with 9um pixels and it has worked very well. I use a 35um slit mostly. It has just started to become a little unreliable so I purchased a ASI294MM. The QE is very good which is why I bought the new camera. It has a Sony IMX294 with 14 bit ADC. They achieve this by binning 2x2 in the camera. The end result is pixels that are 4.63um.
This is about 1/2 the size of what I was using with the ST8.
I know that binning CMOS cameras doesn't achieve any real noise reduction but it does result in much lower file size. Unbinned each file is 22meg and ISIS turns them into 45meg files when processed. This is compared to 1.5meg files with the ST8. I will fill the hard drive of my observatory computer pretty quickly.
Is there any advantage to using the CMOS camera at it's full resolution?

cheers
Terry

Binning or not binning with a CMOS camera ?

It's a difficult choice...

First with a CMOS you have "telegraph noise" and you need a special process. See the Christian Buil's page here :

http://www.astrosurf.com/buil/UVEX_soft/

Sorry this page is in French only.

Bin 1x1 is recommanded, but some time with very faint target it's necessary to work in bin 2x2 or 3x3 with this king of CMOS camera, but another problem come with binning. This is the dark current.

With a IMX 294 CMOS you have this curve depending of the temperature of the sensor



For exemple il you cool your camera at -20°C, you have a dark current about 0,00244 e-/s/pixel.
With a time exposure of 900s, you have for one pixel, 1,29 e- of noise, in binning 2x2 : 5,16, in binning 3x3 : 11,61

And some time is not possible to cool the camera at -20°C (during summer for exemple)

I am currently testing an ASI294MM. The results are coming in no time...

Christian