October so far has been a month of frustration, with no end of problems both equipment and software related to wade through. I think there is a light at the end of the tunnel now, and most issues seem to have found a fix. Lets rewind to the start of the month however, and the next clear night after my triangulum image.
It had been my hope that after two nights of testing and work that I might finally have had all of my various issues with guiding sorted out, and so I went out thinking that this night would be an error free night of excellent imaging. Almost immediately however my carefully tested guiding software threw a tantrum and started giving very poor results on nearly every image, odd shaped stars and nasty drifts all over the place. This was not good, the problem appears to be in the declination axis and guidedog didn’t seem to be handling it.
This triggered another night of testing and adjusting, including another session with WCS to get the alignment as perfect as possible, I think I will have to register that software. I ran through every free autoguiding software solution I could locate.
- PHD Guiding – So much promise but it hates modified webcams even at 5fps.
- Guidedog – Lovely software, easy to use, but it doesn’t appear to handle dec backlash.
- Proguider – Looks good, but I couldn’t work it out, needs better documentation.
- Guidemaster – Bingo!
I eventually tried out Guidemaster, and found software that not only does some excellent calibration routines to work out declination backlash, movement speeds and over useful information, but also manages such useful things as automatic aggression adjustment and automatic setting of single direction declination adjust. That last one is great, declination will normally only drift off one way, so if it only corrects one way then it will always be loaded on the gear and backlash won’t be an issue.
Unlike PHD, Guidemaster has no problems with dropped frames from the SC modified webcam, a real issue with PHD to me. I also liked the calibration routine and the ability to adjust the calibration movement time on both RA and Dec individually, really handy if you are suffering from a lot of backlash.
Once calibrated I ran several five minute test exposures and was massively impressed with the result, it appeared to be guiding far more accurately that I had managed with the other programs, I have to say that it gets my recommendations hands down. It did also however, highlight the issue with the declination axis that had caused Guidedog so many problems. Over 5.5 seconds of backlash and the calibration routine needed 9 seconds of declination travel before it was able to register the movement.
Over the weekend I found the cause, when setting up for an image the declination axis stopped moving entirely. This was a major concern and I immediately stripped the mount down hoping that it wasn’t anything major. It turns out that it was the worm gear assembly, which sits in a captive bolt which is adjusted to restrict the linear movement of the gear whilst allowing it to rotate. For some reason the captive bolt had seized onto the worm shaft, now everytime the declination axis was rotated it was slowly screwing the bolt further into the assembly and eventually clamping itself so tight it could no longer move. Luckily no damage was done, I was able to release the captive bolt assembly and took the time to clean and re-grease it.
Unfortunately that was the end of clear skies for now, I’m really hoping that it was the end of my problems as well, time will tell.
