Hi,
I’m a little confused and hope that someone might be able to enlighten me.
I recently bought an ASI294MM-Pro camera, of which it is said, that it runs in two different modes 1x1 and 2x2 binning. According to several different sources, hardware binning for CMOS camreas doesn’t actually happen, so one is supposed to do the binning in the processing software.
But and this is where I get confused, I’ve recorded data with 1x1 and 2x2 binning in SGP and to me it does look like some sort of binning takes place. I’ve plate solved two images and gotten the following results:
1x1 Binning: Pixelsize: 2.31 um, 8288 x 5644 pixels and 96MByte file size
2x2 Binning: Pixelsize: 4.63 um, 4144 x 2822 pixels and 23MByte file size
So, to me it looks like SGP is indeed binning the pixels or am I making some logical error here and I’m actually losing data by using the 2x2 mode? Should I be using the 1x1 binning mode?
I found with my QHY cameras that the binning setting in the ASCOM driver combines with that in SGP, so that I accidentally got 4x4 binning.
Binning a CMOS camera is not as beneficial to read noise as with a CCD. I bin AF and plate-solving for speed but decided to not bother with binning lights. I can still improve SNR by same amount by binning in the image processing software. There are a few particular CMOS sensors that do specialist internal binning, like the IMX294, which does bring unique benefits. Best to check out the datasheets.
The results you have are correct but SGP is not software binning the pixels in bin2x2.
Bin 1x1 and bin 2x2 expose the IMX492 (aka 294MM) in two different modes. Bin 2x2 uses Sony’s quad pixel architecture to effectively hardware bin 2x2 giving you a 14bit ADC instead of 12bit ADC and a much larger full well capacity. Bin 1x1 let’s you use the cameras native tiny pixels for a massive resolution increase that I’m finding fairly spectacular to use but with the drawback of a small FWC and less dynamic range.
Only binning 3x3 and 4x4 with this camera actually result in any software binning taking place.
@mos - are you certain about the combined binning effect. If I am operating the camera in 11MP mode, binning 2x2 in SGP gives me a smaller image still. The binning setting in SGP pre-dates the camera modes on the 294 and I am not sure SGP binning is changing the camera mode. When the camera changes from 11 to 47MP mode, it operates entirely differently.
For the ZWO yes. I believe for the QHY version they handle things slightly differently and haven’t utilized the binning options to control the locked and unlocked readout modes of their camera. As you mentioned this is simply switched in the Ascom driver. Not by changing binning. So I imagine you’d always want to leave the binning as 1x1 in SGP for your QHY camera. Anything else will just result in straight software binning of whatever readout mode you have enabled?