Wednesday, April 20, 2016

Initial Tracking and Slewing Tests

Last night I headed out to Kumeu Observatory even though the sky was fairly cloudy, I figured there were enough gaps around so I couldn't resist testing out the repaired Paramount GT-1100s, I'm very happy to report that the slewing and tracking sounds very smooth now, in fact I've never heard it sound this good before! I did manage to take some images although I had trouble with the focus, predictably the focus was out after having the OTA off the mount, so I manually got the focus close again, I then attempted to do an auto focus with Maxim DL but it failed as it wanted to go past 7000 which is the maximum amount of steps the TCF can go to, I'm not sure why this was the case perhaps we don't have enough back focus or the primary mirror might need to have the shipping bolts loosened.

Seeing more dense clouds coming in I decided to make use of the sucker holes while they were still there and took some exposures testing the tracking in different areas of the sky, I'd say the results were very promising with the tracking being even better than before the repair, I took 100 sec and 200 second exposures without any noticeable movement in the stars, although I didn't get to test all parts of the sky due to the clouds so I may have just been in "sweet" spots, we could never get 200 second exposures without star drift before the repair so this is all looking very hopeful, once we get the auto guider working we should be able to get up to 500 seconds without too much issue.

I've included some images from last night but note that after the failed auto focus runs I just manually got the focus back to being close so it definitely wasn't anywhere near perfect focus, also there was significant vignetting due to the gibbous Moon being up and the image calibration doesn't really work anymore due to the camera being taken off the OTA during repairs so no doubt we will need to re-do all our calibration files again, one thing I did notice was that the SBIG-ST10 CCD was still unable to reach -20, it did seem like a hot night but it's a bit of a concern that it still can't get down to -20 at this stage of the year.

100 second exposure tracking test ^

200 second exposure tracking test ^

Posted by Jonathan Green

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