Thor’s Helmet

Ever have one of those nights when things just don’t  seem to start well? Turns out that this was one of those nights. A friend and I  went to our club’s dark sky site to capture a couple of images, I was trying for Thor’s Helmet while my friend was imaging the Cone Nebula. It was nice to set up our scopes without needing gloves, but soon the temperature started to drop and that’s when things started to go wrong.

First thing that failed was the switches used to find the home position on the mount. Some moisture froze and the RA switch stuck forcing manual home positioning. Next up I had an issue with the RA guiding. Seems that I didn’t do a great job in balancing the RA axis and my guiding produced odd double stars. The solution was simple, rebalance and adjust some of the PHD settings, but it cost me 30 minutes of adjustment and realignment. Since it was a work day in the morning this meant a shorter than intended exposure for the evening. After focusing again and starting the exposure I noticed the battery was failing in my trusty intervolometer. Fortunately it lasted through the session and the imaging finally got underway.

The Saint Croix Observatory is a wonderful facility owned and operated by the Halifax Centre of the RASC. The facility has a much appreciated warm room that we made good use of for the rest of the evening while the cameras and scopes did all the work to collect data for our images. By the time we packed up I had collected 112 minutes of data on Thor’s Helmet, an emission nebula surrounding a Wolf-Rayet star. The image was calibrated with flats, flat darks and bias frames. Darks were not used as my 60Da has built in dark suppression that does a great job of removing the dark current from the system. I simply shot three one minute darks to average and use as a hot pixel map and processed the data in Images Plus. After a little post processing the image turned out reasonably well for the shorter than intended exposure.


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