East Veil Nebula (NGC6992) and Equipment Tuning

As a result of our recent guiding discussions, there were several guiding changes that I wanted to try out, and I wanted to check drift after I readjusted the worm blocks the other day. And finally, I wanted to try some new meridian flip settings. After doing that, I collected some data on Eastern Veil Nebula, which will be part of a project to capture 10 hours each on the Eastern and Western Veil will be part of a two-panel mosaic of The Cygnus Loop. I plan to reserve this target for the back yard, so I will select other targets if I get to a dark sky site.

It was a warm night. I was in shorts and a t-shirt until about 2am, at which time I put on a light jacket. I also correctly read the air temp, dew point, and relative humidity forecast to determine that dew would start forming at around 2am. I think that dew is much less of a mystery for me now that I have been watching more carefully.

I put the NP101/ASI6200 on the G11. Set up, power up, and start up all went very well. I had no major issues with anything. I was pleased to note that I was able to start using Polemaster at 2110 – ten minutes earlier than the last time I was out!!

Guiding was interesting. I wish that I had written down some numbers, but I remember enough about the settings that I tried that I can write a coherent story about it.

I started off by doing a PoleMaster alignment, a calibration, and a drift alignment. Calibration completed without throwing a reliability warning, and the graph looked much better. Still a slight wiggle in the Dec leg. I was getting about the same guiding RMS that I always get – something around 1.10” total. I then did a drift alignment and repeated the calibration, and got an even better looking graph. The guiding RMS dropped to around 1.00”. I then did a guiding assistant run, and found a 1.9’ polar alignment error, and the backlash test completed without failing. It reported a 1350ms error, which is not unreasonable. A few weeks ago I was estimating 3000 to 4000ms just by watching how long the drift continued after I nudged the mount after changing directions on the Ra axis. The backlash graph looked much better too. The last one that I had looked like the one that we saw on your mount, where the downward 45 degree leg was almost horizontal. This time the plots moved slightly past the ideal path, and then paralleled it the rest of the way down.

I moved on to shooting Eastern Veil in RGB at 50 x 45s. The data looked reasonable coming in, but at one point I noticed that the guiding RMS had crept up to 2.30”. Looking more critically at my graph, I noticed that PHD was guiding on just one star, so I went looking and found that multi-star guiding had been turned off. I must have done this sometime in the past. I turned it on an guiding dropped down to 0.90”. Looking at the main guiding graph more carefully now, I was seeing sub-.30” guiding on the Dec axis, and it was getting hardly any guiding impulses! Even though Ra RMS was at round .70”, it was getting lots guiding impulses, and over all looked awful compared to the Dec axis. 

Recalling that I did not balance the mount east-heavy, I tried that, and Ra RMS improved and the graph looked better. I do not remember what the RMS number was.

The meridian flip worked, but it was kinda wonky. I am not ready to rely on that yet. I’ll play with that as time permits, but maybe someday I’ll have it working, but today ain’t that day.

I have two to-do items. First, I want to readjust the worm blocks. Last time I jammed them all the way in, and made sure that they were all the way in by checking that they were binding. I then turned the adjustment screw a smidge and checked that they weren’t binding. I want to redo this with about ½ a smidge of adjustment. I was getting an error in NINA after most dither adjustments, which I had set to every second frame. PHD2 – Timed out waiting for guider to settle. I had the settle time at 15s and have never had this error before. I adjusted it upward a couple of times ultimately leaving it at 30s. I was getting the error only occasionally after that, but I could never seem to make it go away. There are other dither-related settings, but I want to read about them before I make any more adjustments.

I am going to modify my polar alignment workflow. Presently I do a Polemaster alignment to correct for settling when the mount hasn’t been moved. I am pretty sure that I can see stars with the guide camera earlier than I can with the Polemaster camera, so I will go straight to drift alignment if I am just correcting for tripod settle. If I have a fresh set up at a dark site, then I’ll do Polemaster first.

East Veil Nebula - 2022-07-19 - Star Reduced
East Veil Nebula

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