Monday, May 16, 2016

Day and Night at Kumeu Observatory.

On Saturday the 14th of May myself,Tony Burns and Steve Hennerley met up at Kumeu Observatory to see if the dome slave issues could be resolved, I'm happy to report that with Tony's expertise the dome now stops at home and can be parked again, so now it should just be a matter of refining the parameters to get the dome slaved to the telescope properly, Tony did mention that he wasn't really that happy with the setup and is already making plans on how to best improve the dome slave situation, Steve also managed to find the problem with the dew strap it was just a wire that was loose so that's all fixed now so dew shouldn't be a problem anymore, while we were testing the dome rotation a new problem with the dome motor became apparent it was really making some jerking movements that none of us had seen before, after some inspection Steve discovered that one of the bolts had worked it's way loose, so he jacked the dome up a bit so we could take the motor out and repair it which Steve did without much issue, this was really lucky that this had happened while Steve and Tony were there as no doubt if it had happened at night when I was there by myself it would have sent me home early and been a waste of a good night.

Tony Burns working on the dome control board. ^

Steve Hennerley fixing the loose bolt on the dome motor. ^

One thing that happened while we were trying to refine the parameters of the dome was that when Steve was driving the telescope around with the Sky X it kept on trying to point at the ground, we couldn't figure out why it was doing this at the time, at this stage it was getting late in the day and Steve's daughters who had been very well behaved all day were starting to become a little bit restless so we called it a day and all headed home, after making myself something to eat I headed back out to Kumeu by 7 pm, after setting up I discovered that the Sky X no longer knew where it was pointing in the sky, when the mount was in the home position the Sky X thought it was pointing up near the zenith, so no doubt this was the reason why the telescope had been trying to point at the ground earlier, after ringing Steve to discuss the problem I set about doing a resynchcronisation, the 1st problem I ran into was the finder scope was not even closely aligned anymore as we had taken it off the OTA a while back, trying to center a star without the finder scope aligned is like trying to find a needle in a haystack! So after further discussion with Steve he suggested I align the finder scope on the Moon, but even with the lowest exposure I couldn't see any detail on the Moon, I was a little bit exasperated as I was thinking that I might have to go home and grab my diagonal and eyepiece and have to take off the CCD to just get the finder scope aligned, thankfully I got lucky as some thick clouds rolled in, they acted like a Moon filter and allowed me to see detail on the Moon so I found a large crater and managed to align the finder scope on it, I think this must be the very first time that I was actually happy to see the clouds come rolling in.

Moon image captured with heavy clouds acting as a filter that allowed me to see surface detail and align the finder scope. ^

Now that the finder scope was aligned I set about synchronising the Sky X on some bright stars, through gaps in the clouds I managed to synch to nine bright stars before the rain arrived, this seemed to do the trick as now the Sky X knew where it was, I have left the finder scope on the OTA just in case Grant or Steve thinks we might need to do more star synchronisation than the nine I managed to get, in fact I was thinking that perhaps the problem with our slewing in the zone of death may be due to never having done any synchronisation in that part of the sky before, the rain was quite heavy at this stage ( 10 pm ) so after packing up I headed home to relax, by midnight things had cleared up again, after consulting some satellite images I figured I had maybe a 3-4 hour window of clear skies to work with so I headed back to Kumeu and got back to work, the sky was fairly clear when I arrived so I set about capturing a new pointing model, I managed to capture 230 samples before I ran into the zone of death as sample points must have drifted into this area, so I finished and saved the pointing model before re-homing the telescope, I then turned the pointing model into a super model and found that it just dropped the last sample just like last time so I had 229 good samples to work with, I noticed that the RMS wasn't quite as good as the last model I captured but I think this may have been due to the sky conditions not being as good as last time, the astronomical "seeing" wasn't as good and I did have to image through thin passing clouds from time to time, even though the Sky X had no trouble solving all the images I suspect this may still have had an adverse effect.

After converting my pointing model into a super model and turning on the Pro-Track function so the model could make adjustments to the Paramount's tracking, I set about testing the accuracy of the new pointing model, again I was very impressed with the accuracy of the model with objects either directly on the crosshairs or just a couple of arc seconds off from it, I'm going to have to monitor the tightness of the shipping bolts on the C14 as any movement in the primary mirror will of course cause the pointing accuracy to deteriorate over time, if this is the case and we do discover that the primary mirror is indeed displaying signs of movement then I'm hopeful that adding locking nuts should resolve the issue, after doing quite a few pointing tests I noticed that the clouds had rolled back in, so I closed up the dome just in time before another heavy rain shower came rolling in, it was 3:40 am by this stage so I just packed up and headed home to catch up on some sleep.

Pointing test of Comet 116/P Wild with a 100 second exposure at 2x2 binning. ^

Pointing test of NGC 5643 the image is a median stack of 4 x 200 second exposures at 2x2 binning. ^

Posted by Jonathan Green

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

Wednesday, May 4, 2016

A Perfect Night

Got out to Kumeu Observatory last night and was happy to see the conditions were much improved from the Monday night, I measured my focus star with a full width half maximum of 2.1! this is the best focus I've ever recorded with the C14 so it must have been pretty decent astronomical "seeing", hopefully after we refine the collimation we will be able to get even sharper images, with the conditions being so good I set about capturing a new pointing model and this time I isolated the south east portion of the sky thanks to advice from Grant Christie who dubbed this region the "zone of death", I was ecstatic to see all the pointing samples solve without issue, I had almost completed the entire model when I got my 1st fail it was up near the zenith in the east, the point was probably just a little too close to the dreaded "zone of death" so I aborted the slew and saved my model which at this stage was up to 209 pointing samples, I then converted the standard model into a "super" model and was pleased to see it only dropped one sample, it was the sample captured just before the fail, I was really happy to see that as when I attempted to turn the previous night's model into a "super" model it dropped 130 odd samples! so feeling like I've finally got over the hump in regards to capturing a robust pointing model I set about testing the new model.

I imaged targets in all areas of the sky including the "zone of death" and was really pleased to see that targets were either on the crosshairs or just a few arc seconds to either side of it, so I'm thinking we finally have a really decent pointing model to work with now, I'm also feeling much more confident about the whole T-Point process so if I need to capture a new model in the future it shouldn't be a problem, I've enabled the pro-track feature and it seems like the tracking has improved some what, in some parts of the sky you can easily get 200 second exposures without any noticeable drift.

All we need to do now is concentrate on getting the auto-guider working but this should just be a simple matter of sourcing the correct cable, we also need to replace all the filters in the SBIG as when we had the camera off when the mount was being repaired we noticed mold growing on them, thankfully there was no mold on the CCD sensor itself, the dome slave issues need to be resolved and the collimation of the C14 needs to be refined, after all this has been taken care of we should be ready to do some research grade astronomy.

Below are a couple images from the night, note that the calibration is not really effective anymore as all calibration files date back to Summer so I'll need to replace them with new calibration files soon ( I'm just waiting on the new filters to arrive )

Pointing and tracking test of the Sombrero Galaxy, the image is a 200 second exposure and is un-calibrated, weird stuff near the edges might be from the mold? I'm not sure. ^

Pointing test of the Southern Pinwheel Galaxy, this image is a median stack of 11 x 100 second exposures, the image was also calibrated. ^

Posted by Jonathan Green

Tuesday, May 3, 2016

Fog and Dew.

Last night was the best night in ages so after taking care of some commitments for the Auckland Astronomical Society I headed out to Kumeu Observatory, I was a bit discouraged when I arrived in Kumeu to see that the fog was really thick, I could barely see a few meters in front of my car even with the fog lights on! Thinking that I would show some perseverance I set about setting up, the fog was well above even the tallest trees and so thick that with the naked eye I could only see the brightest stars so after taking some test images I realized I would have to wait for the fog to thin out a bit.

The state of the Fog when I arrived at Kumeu Observatroy ^

As the temperature started to drop around midnight the fog finally started to settle down, it was still really thick in the east so I decided to start my pointing model in the west, I opted to make a really dense pointing model as I had no idea how long it would take for the fog to lift in the east, everything was going really well and I had astrometrically solved over 150 odd samples without issue until all of sudden the images would no longer solve, what turned out to be the problem was that the correcter plate on the C14 had become "fogged" up due to the dew, earlier on in the night I realized this might be an issue so I had turned on the dew strap to full power as a test to see if it would keep the dew off all night, but to my hand the strap still felt cold after hours so maybe it was never re-connected when we put the OTA back on the mount, at any rate it was not keeping the dew off at all.

Dew on the corrector plate ^

I didn't want to give up but I was also now in a part of the sky where the star density was low, so I lowered the detection threshold in T-Point and increased my exposures to 10 seconds, I then stepped to a higher up part of the sky where the effects of the fog were the least, this seem to do the trick as I managed to get up to 182 sample points, it was 3 am by this stage so after getting almost all the western side of the sky I turned the telescope towards the east, the fog had finally started to settle down a bit so I figured I might be able to continue on until dawn but as soon as I took my 1st image in the east I got hit by an error message saying that "The mount is at a minimum or maximum position limit and cannot be slewed. This error may be the result of improper synchronization near the meridan. When syncing near the meridian, be sure the optical tube assembly and the synchronization star are on opposite sides of the meridian. ".

Error message ^

I tried to continue the pointing model but the mount had become confused and attempted to point the telescope at the ground so I aborted the slew and finished and saved the pointing model before "homing" the telescope,
even though I was annoyed that I couldn't finished the pointing model I was happy with how many samples I had captured, so hopefully next time I'll get the entire sky, I tested the pointing model and found it was extremely accurate in the western side of the sky as you'd expect with every target being right in the middle of the crosshairs, the eastern side targets did not fall in the center of the frame though so a new pointing model will have to be done of course, the images at this point were pretty bad due to the dew and with no way to de-fog the corrector plate I closed up the dome and headed home around 4 am.

Pointing test of Omega Centauri ^

Pointing test of NGC 4945, image quality had really deteriorated by this stage ^

The fog had settled down a bit by early morning but as you can see it was still very foggy conditions. ^

Posted by Jonathan Green

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