Friday, May 13, 2016

Windy Night at Kumeu

Got out to Kumeu Observatory last night to find the conditions were atrocious, strong winds and fast moving clouds had me heading home without opening the dome, I figured it might calm down after the Moon had set so I set my alarm and took a nap, I must have been quite tired as I slept through my alarm, luckily I woke up early in the morning, conditions looked better from my house so I headed back out to Kumeu, when I arrived conditions were only marginally better the wind was still really strong but at least there wasn't as many clouds about, up at the gate the wind was gale force but down the hill were the observatory is located I felt it was sheltered enough to risk opening up the dome.

There must have been a power cut out at Kumeu since the last time I was out there as the computer was off, after booting up the computer and cooling down the CCD I set about doing an auto focus run, but found that the focus was way off, it must have been due to the power cut knocking out the temperature compensating focuser, after putting the focus back to the last known focus point, I attempted to do an auto focus run, but I couldn't get a v- curve as the auto focus was trying to step past 1 which it can't do to complete the curve, knowing that the only way to fix this was to put the temperature compensating focuser back to the half way point of 3500 and manually focus the C14 back to a close focus point, I was really loath to do this as this meant I had to undo the shipping bolts to move the primary mirror and doing that would no doubt ruin my last pointing models accuracy but seeing no other option I ended up having to do just that, having got the C14 back into near focus I then went to an 8th magnitude star and finally got an auto focus v-curve to work, now the focus is sitting around the four thousand mark so hopefully I won't run into this problem again, I also noticed when I was undoing the shipping bolts that one was kind of loose, I had only done them up finger tight before and to be honest I was really gentle about it as well, so this time when I tightened up the shipping bolts I made sure they were really robust and as tight as I could get them by hand so hopefully they will stay tight or else we might need to source some locking nuts to keep the shipping bolts in place.

After all that was completed I turned my attention to seeing how badly my pointing models accuracy was affected by moving the primary mirror and just as I predicted it has had an adverse effect, now objects are around five arc minutes away from center, so next clear night I'll have to do a new pointing model, I spent the rest of the night testing out the tracking of the Paramount GT-1100S and I've got to say I'm really impressed with how well the mount tracks unguided, I could get 200 second exposures in most places in the sky so this is looking good, no doubt with auto-guiding we will easily be able to extend our exposure times, at astronomical dawn the winds really started to pick up again so I closed and clamped the dome and headed home around 6am.

NGC6000 a galaxy in Scorpius the image was a tracking test and is a stack of 11 x 200 second exposures, calibration files are out of date and the "seeing" was bad on the night so image quality is not the best. ^

Pointing test of Comet 116/P Wild, all objects are roughly in the same spot as this comet being around 5 arc minutes left of center, the image is a single 200 sec exposure, the streak through the center is from a passing satellite. ^

Posted by Jonathan Green

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