I just came in from a night of testing and practicing with the Sirius mount carrying the Tak 102. Attached were the Canon T3i and the QHY5L-II autoguider on a Stellarvue 50mm guide/finderscope.
The whole mess was balanced by two 11 lb weights. One weight was approx. 1/3 of the way from the top and the other weight was about 2/3 of the way down.
The Stellarvue 50 has a helical focuser and the QHY5L focuses fine without the need for an extender or a diagonal. The QHY5L does stick out a lot and the tension screw bites the end of the camera.
One drawback of the helical focuser is that there's no way to lock it down. So, inevitably when slewing from one target to another the tension on the USB or autoguider cable causes focus issues.
I was surprised by how much the focus goes out of whack between slews. I taped the helical focuser to stay in one position, but I found it still changed focus when slewing to a different part of the sky.
The big issue for the evening was PHD2. After polar alignment with the polar scope, I slewed
to Orion and started PHD2. Everything worked well and I made my way up to 10 minutes autoguided with round stars. The temperature from Backyard EOS reported pretty high
temps (like 25-35 C) from the camera. I don't know what was up.
The stars were a little bigger than I'd hoped. But I found this is just the nature of the TV .8 flattener and reducer.
After Orion, I slewed to M82 and decided to autoguide again. No love. I turned the autoguider off,
reset everything, turned it back on and tried to calibrate PHD. But I kept getting an error:
Star did not move enough.
It was really odd. I searched online and tried changing settings in PHD2. I increased calibration step duration from the default of 750ms to 2000. It didn't do much if anything. I kept getting the error. I tried pushing the arrow buttons on the handset controller for the mount. Nothing. After a
frustrating hour of re-attaching cables, I tried jiggling the USB cable connecting the camera to the latptop, and lo and behold it started to calibrate "West" like it should have. I also moved the focuser controller from the area of the USB. There may be a chance that "noise" is interfering with the cable that connects the laptop to the autoguider.
I noticed that you can hear the autoguide corrections as a periodic high pitched hum corresponding to some directional info on the bottom the PHD2 window.
But even with a successful calibration, the mount wouldn't guide for more than 60 seconds before there would be a blinking red screen and PHD2 acted like it couldn't guide correctly. Frustrating.
I was getting trailed stars in 60 second exposures.
I tried polar aligning again using the DSLR technique. It looked like I already had pretty good polar alignment. I rebalanced the scope/camera gear and tried PHD2 again. This time it worked.
I set the calibration duration to 1200ms. I got round stars in a 12 min. test exposure.
One obvious thing I learned was that PHD2 calibration should be done locally. That is, it should be done AFTER slewing to your target. If you rely upon the PHD2 calibration from a previous object, it will try to make massive corrections and eventually, it will fail the autoguide.
[Update: The mount made unusual cyclical motor noises when the scope was WEST heavy. This may have contributed to the calibration issues. The fix was straight forward -- moving the weights to balance everything or making the setup slightly EAST heavy.]
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