Rob
I'm not guiding. This is a 6"newt on the mount with a toucam at prime focus. Nothing else. The mount is levelled, balanced and ccd drift aligned until no movement over a two minute period either straight up or just above the western horizon. No matter what I do it will not keep up with the western movement of the stars. It always has a -18.5 arcsec/minute r/a drift which effectively means the stars drift west by 18.5arcsec/minute and seems to be excessive to me. I'm not sure if guiding would even be possible given the drift rate. During a one or two second guiding exposure the stars would drift about 0.7arcsec and I don't know if that's too much for guiding. Is it? So I'm trying to determine if it is excessive and/or where problem lies. Is the right ascension motor/electronics in the mount faulty? I know it is usually the user at fault but assuming it's the mount, how do I prove it? That's the rub and what I'm trying to do. Hence the attempt to find out
1/ r/a rate in arcsec/min (to compare with current measurements)
2/ lunar rate in arcsec/min (to compare with current measurements)
3/ Does eqmod constantly send pulses to the mount during normal sidereal rate tracking and I'm losing some due to my long cabling.
4/can I play with the custom rate and if so how?
Basically any data that would allow me to determine the nature of the fault (if there is one).
Thanks for the replies
Stephen
Quote:
Originally Posted by RobF
Hi Stephen
When I read back through your original post, I think you're fundamentally concerned your guiding isn't right and want to compare with other people?
PE is nice to sort out, but if you're relatively new to this game its probably better that the conversation focuses on what guiding software you're using and what sort of performance it shows on the tracking graph it shows. FWIW, your PEC looks about average for an EQ mount I would say. You may be able to improve it with PEC or mechanical tweaking, but would suggest you look at other things first, specifically:
- what camera and scope combination (main and guiding) are you using?
- critically look for flexure (e.g. guidescope focuser and mounting)
- are you using a guidescope or off axis guider (or 2nd chip)
- how good is your balance in every dimension?
- guiding parameters (you can get a lot of improvement by changing the guide interval, max/min movement, etc)
All this stuff really needs to be systematically tweaked over many months (or years  ) of careful monitoring.
Getting back to your last post, its relatively unlikey the sidearal rate of your mount is a major issue. Its good that you've eliminated power as a problem. Depending on your guiding and main OTA setup, next goal I would suggest is to try and get your guiding error down under a few arcsecs max variation during an extended exposure (>5mins). Do you have any images from your last guiding session? |