Help I have an issue with an STi guide CCD. I first posted this issue to the Astrophysics GOTO forum and they suggested I disconnect the CCT from the guide interface port on the mount and the issue went away, hence I believe the issue is with the CCD. The issue: With the STi connected to the guide port on my AP1200 the mount tracks significantly (~2x) faster than sidereal rate and if slewed N or S the pointing moves west of true north or west true south for either a north or a south slew. E or W slews proceed in a true to command direction. This occurs if the STi is powered or non powered. I can get and download images from the STi therefor the imaging seems to be OK. I performed this test using CCDOPS to operate the STi. If I physically disconnect the guiding cable from the STi at either the mount or the CCD the mount behaves nominally, ie it tracks at sidereal, and all slews proceed true to direction commanded. If I connect the guide cable to my STF 8300 the mount also behaves nominally. My setup is: Sky version 5. 00.108. AP 1200 GTO CP3. ASCOM V2 driver 5.06.05. Firmware version E. Operating system is Windows XP Professional 2002 version SP-3. CCDOPS is version 5.57 build 3-NT. The STi is SN 11578. Thoughts as to how to fix this issue would be greatly appreciated. Conrad
We had a batch of bad cables; sounds like you got one of those. Please send your mailing address to Bill Lynch <bill@sbig.com> and he will mail you a replacement. Throw out the bad one!
Doug, thanks for your reply. When I connect the STF 8300 to the guiding port, (with the same cable I use to connect the STi) the mount works nominally, ie like it should, it tracks at sidereal rate, and the slews are all in the correct direction. I have gone back and forth connecting the mount to the STi and the STF 8300 and the behavior repeats. OK when hooked to the 8300, not OK when hooked to the STi. I did that because I thought it would diagnose a cable issue, and to me, that eliminated the cable.
Okay if the cable is built backwards, it tends to permanently short the South input to ground, and connects the West input to the auxiliary line (which can be nothing, GND, or +12V in SBIG cameras depending on jumper setting - default is nothing). In your case, it kinda sounds like West is permanently actuated? That sounds like a possible short circuit on the West output. You may have to send it to Bill.
Thanks for your reply. OK I think I understand now. The camera internals may not be identical, so working nominally with one, may not be true with another camera. Is there any test I can perform at home with an ohm meter to check the cable?
