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Good point Fred. So QE is the senior consideration then using OAG's.
I tried using my ST402 on a Vixen 96LMC and immediately had troube finding guide stars. And it has very high QE.
The SG4 KAI340 has only 55% QE.
I need a 2nd autoguider anyway as I am about to start imaging with 12 setups (CDK17 on a PME and TEC180 or AP140 on the NJP). So MMOAG with the CDK and a guide scope with the APOs.
Having something that is totally automatic sounds good in one way but a bit worrisome in another. What if it freaks out about something at 2am?
I imagine SBIG have it so it is bulletproof and reliable.
I had trouble at one point not being able to callibrate the ST402 due to hot pixels. I solved that by using subframing so I had a single bright star in the subframed image and nothing else to confuse the software.
I usually use 1x1 binning with the 402 and 1 second exposures but I sometime use .5 or even .25 second exposures if the seeing is good and there is a slight improvement in tracking. It handles it fine.
Greg.
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