Nov 14 2009 – My first real try at using the internal guider in my SBIG ST-2000xcm camera.
For some reason it’s been hard for me to get up the nerve to set up and use the internal guide chip of my SBIG camera. Up to this point I’ve always used Craig Stark’s wonderful PHD program along with a separate guide scope and camera. PHD is a pleasure to use and takes a lot of the guesswork out of the guiding process. However, using the internal chip in the camera has substantial benefit in simplifying the equipment setup and eliminating flexure as a potential problem.
Recently, I’ve been working on improving my ability to work with my more portable mounts, a GM-8 and a CG-5. These mounts can’t handle much weight, and I figure the only way I’d be able to image at longer focal lengths would be to keep the weight down (to keep friction in the mount at a minimum) and minimize flexure. Using the internal chip helps meet both those goals.
First off, there is a great page on the Starizona website ( HERE ) which helps get you started on the process and settings. I read it twice and still needed to refer back to it.
I first tried guiding with CCDOps, and got it working fairly well…. but I hit some snags alnog the way (I’ll describe in a minute) and I decided to try CCDSoft v5. I found that CCDSoft picked up the settings I had input in CCDOps so I hadn’t lost any ground, and with a few more tweaks I had it guiding pretty well. I was trucking along guiding at about +/- 1 px (which equated to about 1.5 arcsec at the 1200mm FL). Not too shabby.
So here are the snags, gotchas, and ah-ha’s:
I found that the Starizona instructions were really good. Using them as a starting point gets you 90% there. A few tweaks after you should be getting real close to good guiding. One problem I had was that one direction wouldn’t calibrate. I checked all four axis before the calibration run, but after calibration (which reported itself successful) one of the Y directions would have become “unchecked”. I found the problem was that I selected a star that was too close to the edge of the frame and the calibration steps took it out of bounds. Chosing a star near the center of the frame fixed it.
The other issue I had was that CCDOps doesn’t seem to have an easy way to get guiding going separately, and then letting you start taking a series of images (like doing “autograb”). If there is a way, it’s well hidden in the docs. I didnt’ find it. This is why I jusmped over to CCDSoft after I got guiding working in CCDOps.
I got things going pretty quickly in CCDSoft as it’s routines are similar to CCDOps. One small thing I don’t like is there isn’t a nice graph of the tracking like in CCDOps. However, it does have a numerical readout, so you can still get a good feel for how you’re doing.
I found that I had to set the aggressivness down to about 5 to keep the guiding to smooth out, higher values would make it overshoot.
These were the settings I used in CCDSoft for calibration. While guiding I had the aggressiveness around 5 and the guide exposures at 3 secs.
Here’s a graph of the guiding log. I’d say not too bad for the first time with it, and I’m pretty sure it can be tweaked some more.