Thursday, June 1, 2017

A Foggy Start to Winter

Last night I didn't manage to get out to Kumeu until around 9 pm, not long after I arrived Auckland Astronomical Society member Alan Kane turned up and set up his big Dobsonian telescope to continue his current visual observing challenge of ticking off all the Catalogue of Principal Galaxies (PGC) objects that he can see through his telescope, he's already ticked off all the NGC objects! so he's onto fainter more challenging targets now.

Before Alan had turned up I had opened up the dome, pointed the telescope to near the zenith and started to attempt to gain a good focus using the auto-focus function in MaxIm DL but I couldn't manage to get anything better than a FWHM of 2.3 arc seconds per pixel, I had already wasted around half an hour trying to get a better focus but I was kind of in a rush because I really wanted to go after a Star Cluster that Grant Christie and Tim Natusch have been currently studying over at Stardome Observatory, the time constraint was because the Star Cluster is in the Constellation of Carina and at this time of the year Carina quickly goes behind the trees so it's hidden from our view for most of the night as seen from the Kumeu Observatory dome.

So in the end I had to just settle for a less than perfect focus, finding the Star Cluster which is named "Westerlund 2" was fairly uncomplicated because all I had to do was enter the RA and DEC coordinates into the My Chart Elements feature of the Sky X, then centered the target and slewed to the object and it almost dead center on the first try, I then proceeded to image the cluster until it went behind the trees I managed to grab around 58 images, unfortunately these images couldn't be correctly reduced as we still haven't taken any sky flats for the "Wratten filter" which is the filter we should be using for all our scientific work from now on, I did fire off a couple of the images for Grant to take a look at for comparison purposes, I can now really appreciate how much work is needed to try get the "Nustrini" C14 as optimised as the 16' Meade LX200ACF that Grant and Tim use over at Stardome.

The Star Cluster Westerlund 2 in the constellation of Carina, this cluster contains some very interesting Wolf–Rayet stars. ^

One piece of news that I'm really happy to announce is that our frosting issues seem to be over for now. I think the desiccant obviously just need more time to remove moisture out of the imaging system, last night was a really good test as well because the weather station was recording the humidity at 91%!

While I was imaging the Westerlund 2 Star Cluster I was thinking about why I couldn't gain as good a focus as the last time I was out at the observatory, one thought was that maybe the collimation may have slipped out but it then dawned on me that I had made a rookie mistake, last time I was out at the observatory I had the dew strap cranked up to full and I had forgotten to turn it off, a quick trip up to the dome confirmed my suspicions, so I turned off the dew strap and waited for a few minutes while it cooled off before I again pointed the telescope to near the zenith to try gain a good focus, this time I managed to measure a magnitude 8 star at a FWHM of 1.4 arc seconds per pixel, so I think it must have been the dew strap that was mucking up my focus attempts earlier on in the night, so it has to be part of our shut down procedure from now on that you turn off the dew strap when closing up for the night.

I should note that about twenty minutes after getting a good focus I had to turn the dew strap back on as the corrector plate was starting to fog up, I had to wait for five minutes or so for the corrector to clear again but thankfully the focuser was tracking the temperature correctly so I didn't lose my sharp focus.

<- Two frame mosaic of the Cats Paw Nebula in Scorpius.

With all that behind me I set about imaging the Cats Paw Nebula I wanted to try making a mosaic of the entire nebula but only managed to grab two fields of view using 25 x 1 exposures each with the Optolong Red filter before the stars all started to fade, thinking that corrector plate had fogged up again I raced up to the dome but no the corrector plate was clear, I then ventured outside to see some of the thickest fog I have ever seen! In fact the fog was so impressive it even made this evenings News report. It was so thick you could barely even see any stars with the naked eye anymore, seeing that this was going to end my nights activities I closed up the dome and headed home around 4:30 am.

Posted by Jonathan Green

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