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  1. #1
    Skyhawk727's Avatar
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    Default Son of: I'll show you mine...PemPro Graphs



    I struggled figuring out PemPro to refine my polar alignment, but think I have it figured out. When I initially ran it, the program told me my alignment for azimuth was off by 10.9 arcminutes and elevation off by 5.6. I got there using CCD drift alignment.

    Using Pempro I locked down my mount at a 2.1 arcminute azimuth error and 1.2 arcminute elevation error. Would love to get it closer, but my Meade Superwedge is really difficult to adjust in such small increments.

    I started the thread about PHD graphs in this forum which I found to be very helpful, thanks to all those who contributed. My question in this thread really is: " How good is good?" On a practical note, my polar alignment seems good enough to do 10 minute guided exposures, which is better than my skies can handle, but I would like to know if folks are able to do better my errors detailed above..

    My setup is: Meade 10" LX200GPS on Meade Superwedge using a DSI III pro for imaging. Guiding is through a TelVue Pronto and DSI IIC piggybacked on the Meade using Losmandy dovetail bar and rings. Counterweight is Meade 5000 adjustable with 6 lbs of weight.

    So to start, have posted my PemPro altitude graph and hope to see others. Forgot to do a screen shot of azimuth, will do another and post.

    If you want to try PemPro, you can download a 60 day trial, you might like it. With practice you could be aligned in fairly short order.

    Posted here instead of under mounts as I think this relates more to imaging than anything else.

    Dave
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    LX200ACF 10" in observatory, TeleVue Pronto, Astro Tech AT65EDQ, ZWO ASI120MC, SBIG 8300M, SBIG FW5 filter wheel, Baader LRGB and 7nm Ha filter.
    Other hobbies: flying, history and woodworking,

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  3. #2
    Skyhawk727's Avatar
    Skyhawk727 is offline SUPER GIANT
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    Default More data

    Hi,

    Went out last night and with my new found experiance went through PemPro's polar alignment procedures again and tried to make some small changes. This time I managed to do a screen shot of the graphs for both azimuth and elevation. I had the program show me movements in arcsceonds and I got azimuth a bit closer than when I started, but elevation ended up a little less good.

    As I mentioned, the Meade superwedge is not very precise and you can drive yourself nuts trying to make these small adjustments.

    Once I got things locked down I tried a 10 minute unguided exposure just for giggles. What I got was a lot of drift. I made the error of not letting the scope settle enough after a significant slew before starting an exposure. It was 30 degrees and I wanted to close up and go to bed. After looking at the 10 minute frame of C30 I could tell that most of the drift in the unguided frame came during the first 2 minutes.

    In the future, I'll remember to let things settle out better. Have also seen that when setting up PHD, results are better if I allow the scope to settle a couple minutes before calibrating and then allow the guider to work a few minutes before starting an exposure.

    Have you fount this to be true? The LX200 backlash seems a bit sloppy, has anyone had success trying to get rid of backlash? Heven't tried that yet.

    Also tried PemPro for PEC and I think it helped. I'll run a few more iterations before saying more.

    I do not respond well to cold (probably should move out of Northern Illinois) so my winter plan is to network and try to do as much form the house as I can, only going to the observatory for the essential open/shut/move the dome.

    Burrrrr, already I can feel the pain.

    So, I did a 5 minute C30 after all this and went to bed.

    Dave
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    LX200ACF 10" in observatory, TeleVue Pronto, Astro Tech AT65EDQ, ZWO ASI120MC, SBIG 8300M, SBIG FW5 filter wheel, Baader LRGB and 7nm Ha filter.
    Other hobbies: flying, history and woodworking,

  4. #3
    ghswen's Avatar
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    Default

    As with all mounts there is 'gear lash'. Any time you make a correction to the mount by using the slew keys you should give the mount a bit of time to "settle in". One of the big mistakes is trying to make adjustments before letting the "settle in" happen. This just compounds the errors.

    Not sure of the ability to remove backlash in the LX200 but my assumption would be that you can't really "eliminate it".

    I still have not done PEC training as I occasionally have a problem with the mount powering down on it's own. Haven't figured it out yet so don't want to put in the time to do the PEC training until I have that issue resolved.
    Gordon
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  5. #4
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    Default

    PemPro has a prgram to improve the DEC backlash. You may want to try it. As for the PEC correction via PemPro, I got my LX200 error down to 3.75 from an intial 40+. Obviously I'm very pleased.

    Jim
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  6. #5
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    Default Pempro

    Hi,

    Wow thats great to hear of a 400% improvement in PEC. I'm just getting going with PEC so I'll see how it goes.

    Have been corresponding with the program's author who says that good polar alignment is 2 arcminutes or less error. I'm now there. will see how PEC goes.

    Thanks for your input.

    Dave
    LX200ACF 10" in observatory, TeleVue Pronto, Astro Tech AT65EDQ, ZWO ASI120MC, SBIG 8300M, SBIG FW5 filter wheel, Baader LRGB and 7nm Ha filter.
    Other hobbies: flying, history and woodworking,

 

 

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