Colin does the SC3 feature a 0.7x reducer like the FW8G does? and can you confirm that the SC3 can be binned 4x4. The only reference to its binning abilities I can see is in the screenshot of the DL utility in the manual thanks Martin
Supplemental question: When I bin the SC3 4x4 the DLImaging AO Control windows shows the following: SNR ~60 Total Counts - fluctuates around 200 counts. When I bin 3x3 I get: SNR ~80 Total Counts - fluctuates around 370 When I bin 2x2 I get: SNR ~ 80 Total Counts - fluctuates around 600 and finally, when I go unbinned I get: SNR ~50 Total Counts - fluctuates around 1500 counts. although, unbinned the star does fill the 32x32 guide box. Unless I am confused, this does not make sense. Surely the ADU count should be higher when the binning increases. as should the SNR right? Martin
There is no focal reducer in the SC3. It has a CMOS APS with 4.8um pixels. The STX Guider and remote guide heads used a CCD with a 0.7x reducer, as the CCD had 7.4um pixels. (netting about 5.2um). So they are nearly equivalent in effective pixel size. The APS devices don't bin like CCDs. The SC3's sensor has hardware binning of 2x2; this binning is like averaging the voltage of the 4 active pixels. It's not like combining the charge of electron wells in the CCD, but it does give you a larger effective pixel size. For higher binning, it does a combination of hardware and software. I've sent a request to @Adam Robichaud for a bit of clarification. The SNR in the AO is a "fast estimated SNR" - it is not a mathematically rigourous signal-to-noise ratio - the calculation needs to be performed quickly for speed, not for precision. What's the scope optics eg aperture/focal length you have?
Ok: the sc3 does support 4x4 binning by doing software combining of 4 super-pixels binned 2x2 in hardware.
FYI most CMOS sensors cannot do analog binning. Some of the SONY sensors can analog bin 1x2. In our experience, some CMOS sensors that do have on-chip digital binning are actually noisier when they bin!
yes, at 4x4 binning the image is very noisy so I am trying to stick with 3x3 binning when using the AO. However, I cannot achieve automation under CCDAutopilot because initialization fails. I have spoken to John Smith several times about it and he is unable to fix the problem. So the next question I have is with the SC3/AOX combination, how do I now turn off AOX and use the SC3 as a regular guider? Colin….this is a CDK24 - almost 4m focal length.
To turn off AO-X, just change the Camera 2, Setup - DL Imaging setting for AO from Sensor 1 to Disabled.
Gents.....I can advise that after several weeks of use now, there is no advantage to using the SC3 in bin 3x3 or bin 4x4, which is very disappointing as it hinders AO use I believe. I get a larger value ADU when binned 2x2, so that is where I am. But the sensor is so small and rather 'insensitive' that I can rarely find guide stars now for AO use. It is only really usable now as a regular guider with 3-5 second exposures. Anyway, is there any way to increase the gain on this sensor? I looked at the DL Config, but dont want to change anything in there without checking with you. thanks Martin
I don't have any advice on adjusting the sensor settings, as I haven't experimented with them. We are currently working on a new generation of StarChaser. It has a different sensor, which is very slightly smaller but has better sensitivity and lower noise.
