Anza Trip August 2013 Part 2
I was able to make it out to Anza again and that completed my back to back weekends for the month or August. The new moon fell on a Tuesday this month which made the trips possible. I was looking at the moon chart for September and it appears it will be possible for another back to back in about 3 weeks. Good stuff!
I did not want to change my imaging setup for this trip because I am getting comfortable with the new mount, electric focuser, and new guide scope setup. So, I was looking for a target that would cover my 2 x 1.5 degree field of view and I chose Vdb149, Vdb150, and LDN1235. Vdb 149 and Vdb 150 are reflection nebula and appear blue in the image while LDN1235 is a large dark nebula cloud that fits nicely between Vdb149/150. My plan was to get three nights of data or roughly 21 hours on this object.
I arrived Thursday night and all went well with setup, polar alignment, etc. I moved the telescope to my target and set up 20 minute RGB exposures and let it rip. I was tired that night so I went to sleep by 11pm but before doing so I set my alarm for 2am to do a meridian flip. The meridian flip went quickly and I was back to sleep in no time. I woke up and checked the exposures and everything looked great at first. What I mean by this is the objects were framed nicely, the focus was fine, and I didn’t lose any images. However, on closer examination I noticed the stars in all four corners had semi-circle elongated stars. Never experiencing this before, I thought maybe I forgot to tighten the camera and it rotated slowly during the night but this was not the case. I brought this up to a couple of the guys and they both thought that my guide scope wasn’t aligned properly with the imaging scope. I explained that I didn’t change anything since last week and all images looked great from that trip. They explained that my imaging target last week was near the celestial equator and the guide scope error was not showing up in this part of the sky. However, my target this week was near the North Pole and the guide scope error was more pronounced in this part of the sky. It made sense to me so I had a choice, align the scope at night or choose another target in a part of the sky that won’t reflect the error. I chose another target because I did not have any shims or washers to align the guide scope.
Friday night I decided to image the Helix Nebula. However, I had about a 1.5 hour wait until my target was high enough in the sky. Not one to let prime imaging time go to waste I decided to image some globular clusters so I chose M9 and M19. I usually take very short exposures of clusters so I went with 60 seconds in RGB. I was surprised by the huge dust cloud near M9. I may revisit this target and go after some long exposures to see if I can bring out that dust cloud. By the time I was finished with the globular clusters the Helix Nebula was in a good location so I set up for 15 minute exposures in LRGB and let it rip. All went well that night and I was happy with the images when I examined them Saturday morning. No Field rotation! I am surprised that the guide scope alignment error has such a great effect close to the North Pole. I mean, it is not like the alignment error is that great. I can see the target star in the guide scope field of view when the same star is centered in the imaging scope. I learn something new each time out.
On Saturday night I wanted more data on the Helix Nebula but I had another 1.5 hour wait. I decided to do two more globular clusters, M22 and M28. I used 60 second exposures in RGB and everything worked well with these targets. M28 is right in the belt of the Milky way and the star field is really stunning. The Helix Nebula was well placed right after I finished with the globular clusters and again I went with 15 minute exposures in LRGB. I quickly inspected each exposure Sunday morning before packing up and all looked fine. After that I packed up and hit the road for home.
The data from Thursday night was a complete loss but I learned a valuable lesson about the orthogonality of all imaging items. I can fix this easily once I set up at the house. Friday and Saturday went well so the weekend was a success for the most part. Besides, any time away from the city is always relaxing! See you next month.