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CPC Backlash settings?

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#1 Doug Culbertson

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Posted 11 October 2013 - 10:24 AM

I have had my new CPC 800 for a few weeks now, but have only had time to get it out a total of three nights. Overall it's a great scope with optics that seem to be very good.

Mechanically I think that my previous NS11GPS was better, but maybe I just need to learn the quirks of this CPC. Anyway, on to my question...

The nights that I have had it out, I keep playing with the backlash settings in azimuth because of an extreme lag when pressing the right/left buttons when centering an object. I have the Goto Approach at factory settings (Az/Pos, Alt/Neg? maybe the other way around...). When centering an object in alt, the motors are fine at all speeds, and there is an immediate movement in the eyepiece. Azimuth is another story though. With the motor speed at 6 and higher, it's fine, but at higher powers that causes the object to scoot out of the fov pretty quickly. When in speeds 5 and slower, there is a lag of several seconds before any movement is seen at all, though I can hear the motors speeding up.

According to the manual, the typical backlash setting is between 20 and 50. I have tried anywhere from 0 to 50 with no noticeable difference. FWIW, both axes are locked tightly. Last night was kind of strange because when I was in the area around M57 and M13, there was noticeable lag, whereas when I was in the area around Perseus and Andromeda, it wasn't nearly as bad.

Anyway, my question is, do most folks use a backlash setting higher than 50, or do I have a potential problem on my hands?

#2 FXDX

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Posted 15 October 2013 - 12:14 PM

hello doug,

positive and negative settings should have the SAME values! did you consider that?

holger

#3 SporQ

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Posted 15 October 2013 - 12:51 PM

I could never get my backlash settings to help my azimuth axis until I reset the tension on the main pivot nut. It uses a very coarse thread and it is very easy to have it too tight (like they did at the factory).

I also replaced my bearings with metal balls. Not saying you have to do this, but I am sure glad I did it. I learned how on this forum.

Mine works pretty well now, with much less backlash (did not get rid of all of it), better GoTo's and tracking.

#4 NorthernSoul man

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Posted 15 October 2013 - 02:14 PM

Hi Doug, I'm sorry to hear your having problems, I have the 1100, not sure if you have a bubble level in the tripod, not sure where you set up - is it the same location - or do you set up in different areas. I tend to set up in the same location where possible, making sure to level the tripod and balance the OTA - also I usually set up on concrete, once I set up on grass and found that the AZ movement was like you say??? but on concrete - much better.

You say that pointing the scope to a different part of the sky helps - so this may point to a balance/level problem?

As said above - the bearing mod may help - but I read somewhere that the newer CPC's had half metal and half synthetic bearings.

Also you could try to tighten the AZ clutch just enough so that it bites with less tension - this may help. I think it may be a little trial and error, also, as mentioned, checking the worm tension on the gear.

Hope you get it sorted, but try these - if you slacken the AZ clutch off - and it helps, then maybe check the worm tension against the gear, but all this comes into play, Balance, level and what terra firma you use.

Paul.

#5 Doug Culbertson

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Posted 15 October 2013 - 04:41 PM

Hi folks, I really appreciate the tips. I did realize that positive and negative settings needed to be the same, so I have been playing with both settings with mixed results.

Since I am using a 2" SCT diagonal, along with 2" eyepieces and a focal reducer/corrector, I would have expected to have more issues in alt rather than az, but alt is just fine.

As to the bearings, I passed over a good deal on a used CPC in favor of a new one because I had read that the bearings had been improved the last year or so. Is that true? Be that as it may, I would appreciate it if someone could point me to directions on how to adjust the tension on the azimuth bearing.

Paul, thanks for the tip on a little less tension, I will try that next night out. BTW, I set up on a level concrete pad, so that shouldn't be the problem.

#6 Doug Culbertson

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Posted 15 October 2013 - 05:16 PM

Ok, I just went out and checked my Goto approach settings, and it was set o negative ALT and positive AZM. I believe that it should be the other way around? At any rate, I changed it, and await to see if that helps.

#7 Doug Culbertson

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Posted 24 October 2013 - 05:42 AM

Finally had a clear night to check things out and the proper goto approach settings did the trick.






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