Guide CGE

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gjmccormick
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Joined: Thu Jul 31, 2008 10:10 pm

Guide CGE

Post by gjmccormick » Tue Sep 29, 2009 1:25 pm

Hello Doug,
I have been using the GPUSB adapter ever since I purchased my CGE about 14 months ago. Every thing was great until about 4 months ago. I dont think my problem has anything to do with the GPUSB adapter, but I need help, and I have not been able to find it with any one else. Here is my problem.
For 8 months I could take 30 minute subs with round stars. Then I went out one night to start taking subs, and I started getting image shift no matter how low my subs were. I have spent the last 4 months doing every thing some one suggested. I have spent many many hours and money and I have done all I know to do. I made sure there is NO flexure, My drift alignment is as good as humanly posible. Like last night, i just tracked a star for 45 minutes on a cross hair on the screen with maybe a half of pixel movement. But soon as I do my config, and start guiding, I get movement. After each sub counts down, and loads, the image shifts. If I do 5 minute subs, I get 1 and a half pixel shift. If I do 10 minute subs, I get 3 pixel shift for each sub. The stars are football shape. No matter what length of sub I take, as long as I am guiding, I get pixel shift. I get it if I use PHD or MaximDL. But, if I stop guiding, and just track a star, no pixel shift. Do you know if there is any firmware inside the CGE that could have gotten corrupted? I have deleted NexRemote, deleted PHD, reloaded them and still the same thing. I dont know enough about how the guide interface works with the mount to say if there is something between the interface and the Guide port on the CGE could be the problem. I ask you because, I bet you know more than most about the guide proceedure. Please Help Me before I go crazy.

Thank You.

dpanderson
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Re: Guide CGE

Post by dpanderson » Tue Sep 29, 2009 2:30 pm

First, let me go on record to say that I am not the leading expert on autoguiding, but thanks for the complement.

From the exhaustive list of things you have tried, it seems like you have tried everything except trying a different guide imager. If you can borrow one from somebody else, this might be worth a try.

I don't know about the CGE mount, but even if there were a bug there, I would expect the autoguide system to be able to compensate for it. The autoguide system is attempting to keep the star in the same position on the guide image. So, for example if the mount tried to move too far, the system should bring it back to get the star properly located on the guide imager.

Another thing you might try as an experiment is swapping the guide and main imagers so that the guide imager is now looking through a different telescope.

I'll keep thinking this over, and if I come up with something else to try, I'll let you know.
Doug Anderson
Shoestring Astronomy
http://www.ShoestringAstronomy.com

gjmccormick
Posts: 23
Joined: Thu Jul 31, 2008 10:10 pm

Re: Guide CGE

Post by gjmccormick » Tue Sep 29, 2009 10:41 pm

Thank You Doug for responding,
I guide with a Meade DSI Pro. I purchased a second DSI Pro off of Astromart to see if that was my problem. I had the same results. What I don't understand is, when the guide camera takes a image, it goes through the computer and the guide software the computer sends a signal to your adapter(GPUSB), a signal is sent from your adapter(GPUSB) to the guide port, then the guide port signals the motors to move according to the movment the camera saw. Is this right? If this is right, could the guide port on the mount be sending corrupted signals to the motors? I downloaded the motor control firmware to the motors today just to see if that would make a differance, it did not. It was the version of motor control firmware already in the mount, but no differance. I took the cable that goes to the GPUSB and mount today and switched ends to see if that made a differance and it did not. Have you ever heard of Maxim causeing anything like this? When this went crazy, I had purchased a Orion SSII monochrome camera and downloaded MaximDL. I just can't remember if this started the day I did this, or a week later. Could MaximDL cause this? I have deleted MaximDL and tried it with out it, but it made no differance. . The only thing I have not done, is reformat my harddrive and start from scratch. Boy, I hate doing this, but I would if I knew it would solve my problem. I purchased a new cable form you today that goes from the GPUSB to the mount just to rule this out. I had already purchased a new GPUSB adapter a couple of months ago from you, but I did not buy the cable. I tried the new GPUSB when I got it, but it did not make a differance. SO, I ruled your adapter out a long time ago. But I will try this cable when I get it because I know cables can cause crazy things. Just trying to rule out everything. One last question. If I purchased the Orion guide camera, would going straight from the camera to the mount make a differance. I AM not going to hold you to this if it does'nt, but you know a whole lot more than I do.

I an sorry Doug for going on so much, I just need help. Thank You

dpanderson
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Joined: Fri Apr 28, 2006 1:34 pm
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Re: Guide CGE

Post by dpanderson » Wed Sep 30, 2009 7:11 am

Your understanding of how an autoguide system is correct. This document discusses it in more depth:
http://store.shoestringastronomy.com/Es ... uiding.pdf

Even if the motors drove too far on one correction, the system should try to drive it back the other direction on the next correction. It seems to me that the issue is in the guide imager or in differential flexure between the guide scope and imaging scope.

Since you had the same results with PHD Guiding, I don't think the problem is with MaximDL.

What happens if you rotate the guide imager by 90 degrees in the guide scope? Does the tracking error (elongation of stars) rotate by the same amount? If so, then I would say it is some kind of bug in the Meade DSI Pro.
Doug Anderson
Shoestring Astronomy
http://www.ShoestringAstronomy.com

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