Using an ST-8 as an autoguider.

I would like to get in contact with someone who is familiar with using an St-8 in the "Autoguider" mode. I am using it on a piggyback refractor. I haven't been able to determine if the corrections are actually being sent to the mount.

 

My setup is a 26", f/4.8 Newt, HD fork mount (permanent...accurately polar-aligned), home brew. I am currently attempting to use a piggyback 4.5", f/5 Vixen refractor as a guide instrument, while the imaging CCD is used on the main instrument at a fl=125". I think the autoguider may actually be working, but the guide image keeps drifting off the guide chip area. I'm not sure just how to get the settings correct...I'm using CCDOPS Ver. 3.5 to control the camera. Weather-permitting, I will try what you suggest this evening and get back to you. Thank you for responding to my inquiry.

 

I wasn't able to observe last night due to overcast skies. It's looking like Tuesday may be my next opportunity. I don't currently have Internet service at the observatory, but I will try to set up a Hot Spot to download the Upgrade 5.66 if it has some features that you would think helpful. I also plan to eventually get it set up on Maxim DL.

Home brew?...I fabricated the optics and designed and built most of the mount. I farmed out the welding and machine work on the heavy sections. I attached an image.

 

Thanks! I tried this for a pulse of 10s, or so...I could hear the relay faintly click, but I couldn't really tell if the drive motor actually activated and moved the telescope. I'll try using a longer pulse...long enough to see if the telescope actually changes position a little? And yes, good idea to test all 4 directions.

I didn't mention before...the telescope control system I am using is PC-TCS...developed by Dave Harvey of Comsoft, Inc. of Tucson, AZ. He originally developed it to control the 90" Bok Telescope on Kitt Peak, for Steward Observatory. He then made it available for sale generally. He developed stepper-motor and servo motor versions. I purchased the stepper version in order to cut back on the costs...it's open loop, so the telescope can occasionally get lost if anything slips in the system. I've been pretty lucky, though, because that's only happened a few times in the last 20 years. The software is actually DOS-based, but will operate under Windows. Unfortunately, Dave Harvey passed away a few years back...a VERY talented guy!

 

I have attempted using the Move Telescope command several times over the past few days. It’s been too cloudy to get actual images, but I have watched the telescope position readouts on the computer, as well as watch the actual stepper motors to see if any motion is taking place. Using moves as long as 30s, there is no apparent motion of the telescope in DEC, or R.A. I can hear faint clicking inside the SBIG Relay Adapter box, but that signal is apparently not making it to the stepper motor Com-Box. I cleaned all the connections, etc. The Relay box is connected via a 15-pin cable to the com-box. I purchased the relay box and associated cables from SBIG back when I purchased the ST-8 camera…and, as mentioned before the self-guide operation worked just fine back then. Do those Relay boxes ever develop problems…is there a way to test the performance of that box?



Thanks--Ron

 

The cable from the SBIG Relay Adapter box to my mount has 15-pin connectors on both ends. Do you happen to know if this cable is wired straight-through…or is some special wiring required? If it is straight-through, I should be able to try a different 15-pin cable without damaging anything. I can attempt to do a continuity test on my cable, but that’s a pretty tricky procedure with those small connectors and pins. If special wiring is required I could sure use a diagram with the pin assignments, etc.



Thanks--Ron

 

Thank you...these may be helpful...I will let you know.

Thanks--Ron

 

Doug--Sorry I didn't let you know sooner, but I finally did get the ST-8 working via CCD OPS. As you mentioned, the main issue turned out to be bad cable connections. I am now able to use it as an autoguider, but still haven't got the settings refined in order to make the corrections often enough to completely nail the tracking. It seems that the tracking error grows too large before the adjustments are made....and the last time I used it, the declination corrections became locked in a cycle wherin the dec corrections just bounced back an forth...over-correcting and forming a strange double image. I was wondering if "stiction" in the declination drive could create that kind of image?

P.S.---I am also now attempting to get the camera working with MaxIm DL. I had it working a couple years ago, but for some reason no camera is found when I attempt to connect. I don't know which port address to use, but I tried them all with no success. The Device Manager indicates that the ports are working properly. As mentioned previously, the camera connects fine using CCDOPS. I am using Win XP Pro. Comments welcome...
Thanks,
Ron Dyvig

 

I got lucky this morning! I successfully got the ST-8 connected and operating via MaxIm DL! I hope the clouds clear so I can give it a try tonight. I attached a DSLR image illustrating the alleged "Stiction" issue for your inspection.

Cheers--RonD

 

Yes, that was about a 10m exposure, while guiding was taking place. The guider was continually cycling back and forth in declination, forming those strange double images.