Guiding and periodic error

[Dark knight 101]

Hi everyone, I bought the enhanced dual axis motor drive for eq3-2 mount, I have it guiding but have bad guiding most of the time due to what I believe is the periodic error of the mount, the image settles for a minute or to and then goes off on one for about four minutes till it returns to starting position. Any how my question is this, can I use an eq mod cable to connect mount via ascom? I am aware that there would be much functionality as the motors are dc rather than stepper, but I was hoping that I could use pecprep to try and sort my guiding problem. Has anyone any experience with this please as phd cant guide my mount very well at the minute. 

Thanks everyone in advance 

Gary

 

[ollypenrice]

Welcome. Here's an astrophoto to go with your avatar! 

The problem you describe may well not be due to the mount's PE. This kind of behaviour isn't unknown and can arise from a number of things:

- Cable snagging.

- Loss of guidestar due to cloud or bad connection.

- Incorrect calibration. Are you guiding at 0.5x sidereal? If not I'd try that first. Once the basic calibration routine has run its course have you tried running PHD's Guiding Assistant? It's very good. Just apply the recommendations it makes.

- Backlash. If there is backlash in the gears and the mount is in perfect balance the guider may get into a vicious circle of opposite corrections causing the mount to oscillate across the free play. The usual fix, apart from adjusting the mesh, is to run the mount with the east side a little heavy so the payload/resistance will rest against one side of the gears. This works for backlash in RA but it isn't so easy to cure the problem in Dec. For this reason, and others, it's a good idea to post your guide trace, plus an image taken, and to know which axis is RA on your image and which is Dec.

Basically ST4 guiding does work. Some prefer the extra features of EQ Mod but I'd be surprised if it would cure an inherent fault. I don't use it but others will come along and help on that.

Best of luck,

Olly

[Dark knight 101]

I am loving that photo olly, as soon as I work out how to load it in it will be there

Sorry I should have been more Clear, I have watched the mounts behaviour with out guiding, checked for snags, tried balancing and mount fails to calibrate if go to east heavy. One thing that does repeatedly appear is no east movement detected and no south movement detected during calibration. ????????

I was just wondering if eqmod could be used with my enhanced dc motor drive to analyse and improve the mounts behaviour to eliminate that as the cause of my bad guiding.

I see that there is a st4 to usb cable that can be got, and that the option is there to use it in phd2.    st4usb (ascom).  Wondering if the method will even work for my cheap mount, and if so is it an improvement over oncamera method I am currently using with mixed results. 

 

Strong possibility I have much to learn about phd2. Aswell lol.  Just dont want to buy the £34 cable if it doesn't work on my mount.

Thanks to olly and thanks to anyone else who might be interested in my nightmare lol.

I have attached a log that I saved that was the best guiding in ra I have achieved had to turn dec guiding off. Would that be considered acceptable for the eq3-2 mount? I think I would be happy with that if I could consistently get my graph that nice!!! I will attach a log of typical bad guiding, the guiding I normally have to deal with, it just doesn't work most of the time I'll go hoke a bad log out here.

Clear skies

 

 

 

[kens]

Please attach the log file rather than a screen shot.