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2005.03.11 Both of us found ourselves with time Friday night and no option for work on Saturday, so we went out to the star party at El Rito. The main purpose of the star party was to insert the new alignment pins on the 16" LX200 scope in the dome and hopefully fix the tracking issues it was having. However, this happened to be the best weekend day this year for a Messier Marathon so Bob and I decided to engage in this as well. We arrived at 6:10pm, just after sunset and long before dark, and got Bob's 14" scope set up in Alt-Az for some rapid-fire Messier GOTO action. While waiting for the sky to darken, the other club members arrived and we went to work on the alignment pins. The process of putting the pins on includes taking the OTA off of the fork mount by removing four bolts, then screwing the two alignment pins into place, then replacing the OTA. The OTA required four people to lift and two more people did the bolt work while we were supporting the tube. A six-man job, but it went quickly. Once it was all back together, the OTA was obviously much more flush with the fork than it had been. Bob and I returned to his scope and let the rest of the club do the checkout on the new alignment. The time was 6:59pm and we began our Messier Marathon. I will include a detailed account of what we found when and in what order below. While we were working, however, the guys in the dome came out to indicate that the scope still couldn't track and that they were stumped. The images drifted out of the field of view within 15 or 20 seconds and it was a pain to use. This was very disheartening. When we had exhausted the available Messier objects in the sky at 8:10pm, Bob and I went into the dome to see what we could discover about the problem. They were looking at Saturn at the time. After hooking up the reticle eyepiece to the scope to do a drift measurement, I was struck by the fact that aligning the reticle with the E-W movement on the hand controller left the eyepiece at a strange cockeyed angle with respect to the optical assembly. I checked to make sure that the computer thought it was in an equatorial mount and was shocked to discover that it was listed as Alt-Az. There was no reason why anyone would have changed it, but apparently when they sent the telescope in for service back in 1998, they replaced the computer and it must have reverted to a default setting of Alt-Az. No one around since the scope came back had ever checked it. So we fixed that setting and instantly the scope was much more behaved. The alignment was not perfect but was quite good. Images would stay in the field of view for 10 or 20 minutes before needing adjustment. This was perfect for visual work, though imperfect for photography. I did a drift alignment that indicated there were errors in both elevation and azimuth on the pier. My hope is that the evident elevation error was just a result of a significant azimuth problem, as the pier is a welded-bend pipe and is not adjustable except for shimming the scope - something I don't want to resort to. Adjusting the azimuth of the pier is possible, it just requires a crowd of people to man-handle the whole thing over. The next time we get together we will probably get the club to participate in a large azimuth-correcting party that will take several hours but should result in something very good. My hope is that correcting the azimuth should make the elevation error disappear - the pipe was custom made for the exact coordinates of the dome, and the pier base was supposedly leveled very well. Even with the present drift, the scope would work quite well for photography. There would be some amount of frame rotation, but not a lot. Exposures that weren't too long would be quite feasible. I am very excited about using this platform for photography. Roger was also looking forward to this opportunity. However, the camera mount and counterweight system is currently unacceptable for real astrophotography. I discussed our options with Roger and he said he would try talk Drew, the overseer of the observatory for the College, into coming up with $1000 for a full Losmandy kit. Two dovetail rails, a camera mount, and a counterweight set. I can't wait!
Details of the Messier MarathonThe real point of a Messier Marathon is a test of your star-hopping and finding abilities. With a manual pointing scope, doing a marathon can take the entire night except for a two hour break towards the end waiting for objects to rise. We found that in Alt-Az mode, Bob's telescope computer was extremely accurate and the GOTOs were right on. We were able to average about one object a minute until we ran out of objects to look at. This is obviously a mockery of an actual Messier Marathon, which is why we didn't put a lot of dedication into actually finishing it. It would be interesting to make an expanded catalog specifically for GOTO contests. But to fill up a whole night would require hundreds of objects. Macholtz indicates that he once saw ~600 deep sky objects in one night. 6:59: Found 45 and 42 with naked eye. Tried 77, 74, and 33 with no luck. Sky still too bright. Found 31, but skipped 32 and 110 because the sky was bright and they were still high up. Proceeded with 76 and 34. 7:06: Went back to the beginning and found 77 but failed to find 74 and 33. Continued on list with 52, 103, 79, 41, and 93, then went back and found 33.
7:16: Continued on with 43, 78, 1, 35, 37, 36, and 38. Went back and finally found 74, just before it set. 7:23: Continued on list with 50, 47, 46, 48, 67, 44, 95, and 96. Went back and found 32 and 110 which were now very easy with the improved darkness. 7:34: Worked through a large portion of the list in order: 105, 65, 66, 81, 82, 97, 108, 109, 40, 106, 101, 102, 94, 63, 51, 3, 53, and 64. Failed to find 98, 99, and 100. 7:56: Continued on with 85, 84, 86, 87, 89, 90, 88, 91, 58, 59, 60, and 49. 8:05: At this point, all of the following items on the list had not yet risen, so we went back to fill in the 98, 99, 100 hole and failed to find any of the three. Found Caldwell 1, then took a break from 8:10 to 10:10 to fix the dome telescope and allow objects to rise. 10:10: Returned and found 98, 99, and 100. Continued on with 61, 104, and 68. Failed to find 83. 10:17: Continued with 5, 13, and 92. Once again, the next objects had not risen yet (57, 56, 29, etc.). Took another break from 10:20 to 10:57 to talk with security guard. 10:57: Came back and found 83. Still, no new objects had risen yet and were not due for some time. We started going through the Caldwell catalog in numerical order for lack of anything better to do. Some of them hadn't risen and a couple we couldn't find, but we did managed to locate 2, 3, 6, 7, 8, 10, 13, and 14. 11:30: With the prospect of only a few objects appearing every half hour or so, we quit with 70 Messier objects and 9 Caldwell objects located. |