Monday, January 25, 2016

Slewing Problem Resolved

I rang Grant Christie today to let him know about the unhealthy noise the mount has been making when slewing, he let me know that the problem was probably due to me having to home the scope during the T - Point calibration run, apparently doing so changes two of the parameters of the pointing model and can cause problems, so I went out to Kumeu tonight to clear the pointing model to see if this would fix the slewing problem and I'm very happy to report that the slewing of the mount is now back to sounding healthy again, I also finally figured out how to connect the CCD to the Sky X, the reason I was getting error messages was that you can't have the camera connected to Maxim DL and the Sky X at the same time, up until now the first thing I used to do when I arrived at the observatory was to connect the camera to Maxim DL so I can turn on the camera's coolers as it takes a while for the camera to cool down, I know now this was the reason why I was getting no response from the camera when attempting to connect to it through the Sky X, I'm feeling a little bit sheepish that it took me so long to figure this out but I guess it's all part of the learning process to have a bit of trial and error.

Unfortunately the sky was pretty cloudy out at Kumeu tonight, I did take a few images using the Sky X to control the CCD but I failed to astrometrically solve the images, this was probably due to the images being affected by clouds, hopefully the next time it's clear I will be able to do a new pointing model using an automated calibration run, I plan to take two to three hundred samples of the sky so we will end up with a very robust pointing model, I stayed out at Kumeu until 10:30 but the sky seemed to be getting worse and with the internet not working ( another problem that needs to be addressed soon ) I had no way to know if it was worth waiting around to see if it would clear up, so heading home a bit frustrated that I couldn't get more done tonight I had to console myself that at least when the next opportunity presents itself the telescope and mount are ready for action again.

Posted by Jonathan Green

Sunday, January 24, 2016

New T - Point and Slewing Problem with the Paramount

On Friday night I spent the entire night working on making a new pointing model, I scrapped the last one after reading the T - Point user manual and finding out that it was not advisable to take samples down near the horizon due to atmospheric refraction that causes offsets between the actual position of an object and it's observed position, I started collecting samples around 9:30 and only stopped collecting samples early in the morning due to the mount making an inexplicably unhealthy noise when it was slewing, I couldn't see any obvious reason why the mount was suddenly making the noise ( sounds like a rattle with clicking or cracking type noises ) so I just put the mount back in the home position and called it a night, by the time this had happened I had collected 82 sample points, the new model showed that we are only off by 2 arc-minutes in azimuth while the altitude was still excellent and we don't need any more adjustments in that area.

After attending the Auckland Astronomical Society council meeting at Andrew's house on Saturday, I thought I'd head out to Kumeu and see if the Slewing was still making that same noise and to also test the new pointing model, The first ten or so slews sounded healthy but then again inexplicably the unhealthy noise started up again, so again I just put the mount back into the home position and called it a night, I've talked to Steve about the problem and he is at a loss to explain it as well so we might need Grant Christie or Tim Natusch to come out and take a look at it, hopefully it's nothing too serious, before this happened I was quite happy with the accuracy of the new pointing model, objects were always just a few arc-seconds from the center of the frame although I didn't get a chance to slew all over the sky so some areas may be worse than others, I still had the same problem with the mount in the area of sky to the South East that I had the first time I attempted a pointing model so I couldn't take samples around Centaurus, Crux or Carina, below is an example image of the Galaxy NGC 1532, the image was a 100 sec long exposure and I was quite happy with how close the galaxy was to the center of the frame, the image exhibits some pretty bad vignetting but I think this was due to the Moon being almost full and very bright.

Posted by Jonathan Green

Wednesday, January 20, 2016

T - Point

Last night the waxing gibbous Moon was up and more than a few clouds were about as well but seeing that there were plenty of large gaps in the clouds I thought it would be a perfect night to get the new pointing model done using T - Point, when I arrived at the observatory I noticed that the computer was off and the temperature compensating focuser was flashing, I'm guessing that there was a power cut during the storm we had earlier on in the week, I booted up the computer and connected to both the telescope and camera without issue but when I tried to connect to the focuser it would not connect and came back with an error message from both Maxim DL and the Sky X, after ringing steve for help I switched the focuser back to manual mode and manually set the focuser back to the last known good focus, this worked well enough for me to be able to do the pointing model, the next issue was aligning the finder scope again which must have been knocked fairly far out of alignment at some point, this took me a while to get right but once I was happy that the finder scope and the field of view of the CCD were aligned again I got started on the pointing model, at first I had wanted to do an automatic calibration run but unfortunately the Sky X would not connect to the camera and I got error messages, I also noticed that it will be quite hard to keep up with an automated calibration due to the dome being fairly slow, not wanting to waste a good opportunity to get a pointing model done, I set about doing a manual pointing model using stars that I knew and that I could confirm through the finder scope, by the time the clouds really rolled in at 2:30 am, I had captured 57 samples, one problem I noticed when I was capturing the samples was that I couldn't take any samples from around Carina and Crux any attempt to jog the telescope in this area of the sky caused the mount to become confused and try to point the telescope at the floor, each time this happened I had to re-home the telescope before it would accurately point and track again.

The new pointing model confirmed that the altitude of the mount is correct but that the azimuth still needed to be adjusted ( by about 3 arc minutes ), I then enabled the Pro Track so that the new pointing model can make minor adjustments to improve the sidereal tracking rate of the Paramount GT - 1100S, at this stage the clouds had become so thick that trying to test the new pointing model's accuracy was pointless, so at 3:30 am I closed up the dome and called it a night, I'm looking forward to the next clear night when we can test out the adjusted tracking rate and also the accuracy of the new pointing model.

Posted by Jonathan Green

Tuesday, January 19, 2016

Polar Alignment Refined & Observations of Arp 123 & Arp 279

Last week we had a one good clear night and few nights with sporadic clouds, Thuesday night was the one clear night and on that night I took images of two pairs of galaxies that are in the catalog of interacting galaxies of Dr. Halton C Arp, one pair was NGC 1253 & NGC 1253A, collectively known as ARP 279 they are located in the constellation Eridanus and are thought to be lie around 75 million light years away, the other pair is NGC 1888 & NGC 1889 which are collectively known as Arp 123, they can be found in the constellation Lepus, after doing some research I've found that NGC 1888 is thought to lie 33.5 megaparsecs away which is over 109 million light years! for now this is the most distant object I have ever imaged, I'm looking forward to breaking that record soon hopefully, the image below is of Arp 123, image data was captured by Jonathan Green and then processed by Amit Kamble.

On the Thursday I also collected more image data on Arp 279 but not long after the Moon set clouds started to roll in, there were still gaps in the clouds so I attempted to image a couple of comets, I imaged both 81P/Wild and 203P/Linear but finding them took some effort, I realised after finding the 1st comet that our pointing model was off by about 13 arc minutes, this was due to our refinement of the polar alignment on a previous night.

On the Friday night the sky looked nice and clear and the satellite image data also looked promising so I rang Steve to see if he was free to head out to Kumeu to work on the Polar alignment and to create a new pointing model with T-Point, we also had a couple of Auckland Astronomical Society members show up with their Dobsonian telescopes looking to take advantage of the clear skies, unfortunately the clear skies did not last long so the nights observing was a bit of a bust, fortunately we could still detect stars through the cloud so we ended up spending the night until 2 am in the morning refining the polar alignment again, now all we need is some clear skies to do a new pointing model.

Posted by Jonathan Green

Saturday, January 2, 2016

Rain, rain and more rain....

After some wonderful days and nights between Christmas and New Year, (when, of course I was away from Auckland!), the rain has been falling pretty much non-stop - not to great for observing, but a perfect opportunity to get a few things done that have been on the list for a while. First order of business was getting the USB interface board for the dome rotation system. This has up to now been screwed to the wall inside the dome, but with the issue being unprotcted and that its location was right below the dome home position.  Whilst we've been working, a number of times we've opened the dome and has mosture drip perilously close to the board.  Installing the plastic enclosure took a little longer than expected, but the board should now be protected from and water or moisture from above and be a little more immune to spiders and dust. 
 With that complete, next step was to install the new red LED strip lighting around the dome.  The old dome lighting was too dim with the red bulbs in when working in the dome, and inconvenient to adjust brightness or turn on/off (as the switch is downstairs).  We switched out the bulbs for white bulbs making it easier when we are working (not imaging!) but also bought some red LED lighting with an RF remote to adjust brightness and/or turn on and off. The new lighting is much more controllable and convenient, and hopefully makes life much easier whilst imaging in the dome.  
The final job for the day was re-wiring the dew heater to the new power supply.  At the same time, i added in a PWM controller to control the temperature, ironically one actually designed to dim LED lighting strips.    A good productive day, even though the rain continued relentlessly. The only challenge at this point seems to be that Azimuth sensor for the dome rotation doesn't seem to be functional  (before and after the board was remounted, so not the loose wire I was hoping for) this could be a configuration issue rather than a hardware fault (the dome home sensor is working fine proving the interface inputs are working) but this will need more work

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