Weather
warm, calm, fairly humid. Low temp ~80-85F seeing is fair to good (~2.0 arccsec) humidity around 75%. Around 2:00am some fast-moving high clouds passed overhead. 2:45am – increasing number of thin clouds all around both targets – but still 90% clear even there.
UPDATE: Clouded over completely before I could get the final object (Beta Aqr) for the WR stars.
Rig #1: WR134, 135, & 137
This is about the tenth night dedicated to obtaining spectra of three WR stars for Tony Moffat. Tonight everything is running well. The newly-refurbished Astro-Physics 1200 mount is tracking VERY nicely! But there is so much story behind getting that mount working.
AP1200GTO CP3 mount
The mount now used for rig #1 was purchased used of off Astromart back in February. It was not until about April that I had assembled the additional pieces necessary to install the new mount in the observatory. But as soon as did get things working I immediately noticed tracking and goto problems with the mount. The problems began as soon as I tried the first polar alignment. It appeared the mount was tracking in RA a bit too fast. Posts to the AP Goto site were of little help as folks there tried to tell me it was because the tracking is intentionally slightly fast to compensate for refraction. Well, I wasn’t buying it. I noticed that the gotos were off by a fair bit too, even after getting the mount very nicely aligned using drift alignment. The mount would also runaway and stall when set to slew at 1200x. I began measuring how far it was off and discovered it was over-shooting every goto by about 1 part in 50 of whatever distance it had to move in RA. That, together with the stalls, initiated a long series of emails back and forth with George and Howard at Astro-Physics. I finally got them to let me send the RA motor assembly. When they received it they found the motor and encoder were bad and so replaced both. As it was not under warranty the fix cost around $475. I received the motor assembly and re-assembled it to the mount, only to find almost the exact same problems. Many more emails and phone calls were exchanged as the guys at AP tried to figure out what was wrong. Finally, late in May, I decided to see if I could actually just bring the entire mount to them as I was planning to visit my dad in western Michigan. The agreed to meet me on Thursday before Memorial Day. I arrived at AP around noon and they checked the mount in and went to work on it. By the time I made the trip I had carefully documented exactly everything I saw that was wrong. The most acerbic test was timing the rotation of the worm which was 1 part in 46 too fast. I also measured how far off the gotos were and again found them to be over-shooting by about 1 part in 50. The AP guys (George, Howard, and Wally) took the entire afternoon working on the mount to figure out what was going on. Ultimately it was the motor and encoder again – it appears that the new motor and encoder had the same problem as the 10-year old motor I’d previously sent them. They’d never seen anything fail like that – but the did give me a free motor and encoder and I was on my way back to Kalamazoo, and finally back to Baltimore. In late May I re-installed the mount, got it polar aligned, and the next possible clear night I ran through a few gotos – they were spot on! I’d also measured the timing of the worm cycle and found that it, too, was (within my ability to measure) spot on. The mount has worked very well since. After doing a 15-star pointing calibration the mount has never failed to put the object I’m slewing to on the spectrograph’s small (around 3.5 arc-min) chip! Guiding has been very good as well, typically a few tenths of an arc-second or better.
Still one problem, however
There still seems to be one problem – the mount keeps turning itself off for brief intervals, just a second or so. I’ve tried the obvious things of making sure the power cable is making good contact with the center pin on the CP3 controller box, checked wiring connections back to the power supply, but still have not found what the problem is.
Update – August 10, 2013
The declination motor and encoder failed as well. Clearly the electronics of this mount were on their “last legs”. We’ll see if the new motor and encoder have any effect on the power-off episodes.
Update – July 19th, 2014
The constant turning on-and-off of the hand controller turned out to be dirty contacts inside the hand control unit. I simply opened it up and cleaned the pins where each of the four main ribbon cables connect with rubbing alcohol and all is fine!
Rig #2: J19150199+071747
A new CV (in Aquila?) which was bright enough that I used the V filter early in the run but is now so faint that 90-second integrations through the clear filter are only yielding S/N of around 35-40. So my time observing this object may be nearing it’s end, especially with the moon now moving back towards fullness. Tonight is about the seventh night of coverage for this object.
The CGE mount seems to be working fairly well right now, but a few weeks ago began having “no response 16” and “no response 17” issues. I’m not sure it was really the problem, but opening the RA motor cover and re-seating a couple of the connectors seemed to help – no troubles since.
Problem flipping after meridian crossing
Seems like there is a problem as the did not want to flip after meridian crossing. One thing I noticed was that the “german” box was not checked in the “telescope setup” window in MaxPoint. I’d seen that before but had set it with a checkmark. Looks like that does not stick – may need to check it at the beginning of the night. Why it did not get saved?
