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astrovienna
super member
Reged: 12/04/06
Posts: 131
Loc: Vienna, VA
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I thought I had identified a problem in my dec axis, but yesterday I went to the dealer and spent a couple hours testing two other CPC1100s, and got the same result. So I'm thinking this behavior is normal.
Here's a summary of what I've reported before. The dec axis of my CPC1100 usually won't respond to short move comands at rate 1 or 2. I can press the button dozens of times, and as long as the button presses are short, the target doesn't move. (And the Get RA/Dec function confirms there is no movement in dec.) I hear the motor engage, but the scope doesn't move. It does respond to long presses, and will respond to short presses at rate 3 or above. This is NOT a backlash issue, because this happens when all the presses are in the same direction. After a direction change (which kicks in my anti-backlash settings), a slew, or a long button press, Get RA/Dec shows the mount will respond to short move commands for about ten seconds, although I don't really think it is - I think this part actually IS just backlash being taken up. When the dec clutch is disengaged, Get RA-Dec reports that the mount will again respond to short button presses (which just means the encoder wheel on the dec motor is now moving freely, since the motor isn't under any load.) This happens in both directions, and the scope is very well balanced.
I figured this meant my dec axis was binding in some way, but the other two CPC1100s responded in exactly the same way. So it looks like this is normal.
I figure what is happening is that once the dec axis stops moving, stiction is just too strong for short move commands to be executed. Only when the mount gets a big move command does it actually respond. This seems like it would make autoguiding a challenge, because short moves are what guiding is all about. What do you guys think? If you can test out your mounts for this (this can be done in daytime using Get RA/Dec) I would be very interested in the results.
Kevin
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The Hole in the Trees Skybox
CPC1100 on a Milburn wedge
C8 Phoenix (1985 Super C8+ remounted on a Nexstar GPS fork)
Meade DSI II Pro
DMK 21AU04.AS
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rboe
Reged: 03/16/02
Posts: 45411
Loc: Phx, AZ
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Under 1 or 2 I think you'd have be using pretty high power with maybe a cross hair to see movement. That is pretty slow. Then if you are any where near zenith movement is very hard to detect. 
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Ron
NS11GPS
Pronto
16" dob
15X70 Obies
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astrovienna
super member
Reged: 12/04/06
Posts: 131
Loc: Vienna, VA
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I can see the lack of movement when I'm imaging Jupiter at f/18 in my webcam. When I put a grid overlay on the screen it's easy to see when the planet is and isn't moving.
Has anyone had a chance to try this out? If you're on a wedge, you can use the Get RA/Dec function. Alt-Az, you can use Utilities>Get Axis Position.
Kevin
--------------------
The Hole in the Trees Skybox
CPC1100 on a Milburn wedge
C8 Phoenix (1985 Super C8+ remounted on a Nexstar GPS fork)
Meade DSI II Pro
DMK 21AU04.AS
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