· Get a Cloudy Nights T-Shirt · Submit a Review / Article Click here if you are having trouble logging into the forums Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User You are not logged in. [Login] Entrance · Main Index · Search · New user · Who's Online FAQ · Calendar Equipment Discussions >> Mounts Previous   Index   Next   Threaded   Pages: 1 orlyandico Carpal Tunnel Reged: 08/10/09 Loc: Singapore PHD Problem with Guiding       #4389854 - 02/16/11 09:22 AM Edit   Reply   Quote Quick Reply   What does this mean? Look at the DEC error. It drifts off scale, then eventually corrects. Later on, it stayed pretty much in the middle. My polar alignment isn't perfect, but it isn't terribly shoddy either (drift alignment 30 seconds via CCD method). Post Extras:       adamsp123 scholastic sledgehammer Reged: 11/20/08 Loc: welshpool mid wales UK Re: PHD Problem with Guiding [Re: orlyandico]       #4389953 - 02/16/11 10:10 AM Edit   Reply   Quote Quick Reply   cable snag? wind? Post Extras:       Peter in Reno Post Laureate Reged: 07/15/08 Loc: Reno, NV Re: PHD Problem with Guiding [Re: adamsp123]       #4389969 - 02/16/11 10:20 AM Edit   Reply   Quote Quick Reply   What mount do you have? Excessive Dec backlash? Maybe needs mesh adjustment at Dec axis? Looks like you have a sensitive guide camera. I can easily tell you are guiding M42. What kind of guide camera? Peter Post Extras:       orlyandico Carpal Tunnel Reged: 08/10/09 Loc: Singapore Re: PHD Problem with Guiding [Re: Peter in Reno]       #4390132 - 02/16/11 11:34 AM Edit   Reply   Quote Quick Reply   it's an old Meade DSI Pro I.. Vixen GP with DD-1 stepper drives and GPUSB-AH. i think it was cable snag.. because after i left the laptop (which I literally had in my lap..) to wash dishes, the DEC flattened out. need to work on my brain settings though.. Post Extras:       dale c member Reged: 03/30/09 Loc: Sedro-Woolley, Wa. Re: PHD Problem with Guiding [Re: orlyandico]       #4390200 - 02/16/11 12:02 PM Edit   Reply   Quote Quick Reply   In addition to the DEC track, the RA track looks like there is a problem also. I notice you have the min motion setting set to 0.03 I don't know how PHD handles such a small number but I would think with a qhy5 camera and about a 600mm guide scope a 0.3 min motion setting is more realistic. Dale I see I adamsp123 guide scope info but the image scale looks about the same. Dale Edited by dale c (02/16/11 12:07 PM) Post Extras:       orlyandico Carpal Tunnel Reged: 08/10/09 Loc: Singapore Re: PHD Problem with Guiding [Re: dale c]       #4390240 - 02/16/11 12:18 PM Edit   Reply   Quote Quick Reply   dale, yup someone in my local club told me to up that number. the RA was not a problem, over 40 minutes (4+ worm periods) it behaved, average PE was 20 arcseconds. Except for a huge spike every worm period! i copied the 0.03 settings from some forum blindly.. obviously not such a good idea..! Post Extras:       dale c member Reged: 03/30/09 Loc: Sedro-Woolley, Wa. Re: PHD Problem with Guiding [Re: orlyandico]       #4390279 - 02/16/11 12:32 PM Edit   Reply   Quote Quick Reply   Looks like you may have some binding or rough spots in your RA worm bearings. I had some surface rust in mine not too long ago (thanks to the pacific northwest humidity) which was giving me a problem in RA. Sounds like you are getting things under control. Dale Post Extras:       Falcon- Post Laureate Reged: 09/11/09 Loc: Gambier Island, BC, Canada Re: PHD Problem with Guiding [Re: dale c]       #4390332 - 02/16/11 12:54 PM Edit   Reply   Quote Quick Reply   The DEC problem you see there looks like taking up backlash to me. I know with my CG-5 when I first start guiding it DEC often runs away like that until backlash is taken up, then after that the graph flattens out (just as you described). Yours seems to have taken quite a long time to flatten out, but that may be a difference in your DEC motor's guide rate. Post Extras:       adamsp123 scholastic sledgehammer Reged: 11/20/08 Loc: welshpool mid wales UK Re: PHD Problem with Guiding [Re: Falcon-]       #4390432 - 02/16/11 01:50 PM Edit   Reply   Quote Quick Reply   That would seem to be one hell of large backlash to account for that graph especially considering the 2000ms DEC setting I stick will cable drag or similar. I also agree set the min motion up, I use a 50mm finderscope and set that to about 0.5, I don't want to chase the seeing or keep sending large amounts of correction data which I believe increases the chance of unecessary oscillations in the guiding Post Extras:       jmasin Carpal Tunnel Reged: 12/22/08 Loc: Murphy, TX (DFW) Re: PHD Problem with Guiding [Re: adamsp123]       #4390668 - 02/16/11 03:04 PM Edit   Reply   Quote Quick Reply   I would agree that's some crazy backlash if that's it... but I don't know the mount. Definitely the 0.03 px min move # is too small. Regardless of what you say about the RA not being a problem, you PHD graph says otherwise and I think you can approve. That oscillation in RA is due to too much adjustment and bouncing back and forth, likely due to the aggressive min move and 100% setting. IMHO you are making PHD do too much. I guide at 5"/px and image at 1"/px, so I've set min move to 0.15, which is just under a 1px move for the main imaging scope scale. I set RA aggressiveness to 0.95 (or 0.9 if seeing is bad) and do 3 to 5 min exposures. This has served me fairly well and never resulted in runaway adjustments. YMMV. One other thing I'd add, I don't know if this makes a difference, but I always try to select a guide star without any nebulosity around it if possible. This can be hard with the M42 region. I do this so the light is starlight only, and not some misshapen source that may cause an inaccurate calculation of the centroid. Again, I have no idea if this matters, but it's been my practice and served me well. Edited by jmasin (02/16/11 03:06 PM) Post Extras:       Pages: 1 Previous   Index   Next   Threaded   Extra information 20 registered and 32 anonymous users are browsing this forum. 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