Jump to content


Photo

Slews are off after alignment?

  • Please log in to reply
10 replies to this topic

#1 James Cunningham

James Cunningham

    Gemini

  • *****
  • Posts: 3241
  • Joined: 07 Aug 2010
  • Loc: Maryland

Posted 09 July 2013 - 12:27 AM

I own an 11 inch Celestron SCT on an alt/az mount. Up until about 3 months ago, my slews were near perfect. Then, all of a sudden, the slews were off. The scope is balanced and I use Nexremote. After I get a good alignment, I always check it by going back to my first star and it is always near the crosshair. However, when I slew to an object or another star, that object or star is iusually n my FOV but is always way off center. and sometimes it is out of the FOV. I am using Nexremote 4.21. I have tried 4.18 and get the same results. I have even tried it using the handset but the results are still the same. What could be the problem? Would a factory reset of the handset fix the problem or are my encoders going bad? I need to fix this problem. Thank you.
Jim

#2 RTLR 12

RTLR 12

    Aurora

  • *****
  • Posts: 4559
  • Joined: 04 Dec 2008
  • Loc: The Great Pacific NorthWest

Posted 09 July 2013 - 06:34 AM

Do a 'Factory Settings' and you should be fine.

Stan

#3 KerryR

KerryR

    Gemini

  • *****
  • Posts: 3068
  • Joined: 05 Dec 2007
  • Loc: SW Michigan

Posted 09 July 2013 - 09:15 AM

When this happens to me with my CPC11, it's usually because I don't have the clutches tight enough. I've found this usually means "scary tight". So, check that possibility out if you didn't already.

If that's not the problem, did you train the drives recently? Worth a try.

#4 James Cunningham

James Cunningham

    Gemini

  • *****
  • Posts: 3241
  • Joined: 07 Aug 2010
  • Loc: Maryland

Posted 09 July 2013 - 10:27 AM

I have never seen anything in the Celestron manual about training the drives. It is on my Meade mount.
Jim

#5 KerryR

KerryR

    Gemini

  • *****
  • Posts: 3068
  • Joined: 05 Dec 2007
  • Loc: SW Michigan

Posted 09 July 2013 - 11:07 AM

It's actually "Calibrate Goto" in Utilities. While the manual doesn't state explicitly that it's intent is to help with goto accuracy, it's is something that MAY have helped my CPC11 in the past when goto's were missed, particularly when the balance of the ota changed.

When my CPC misses goto's after aligning: I "Calibrate Goto" before turning the power off, power down, power up, then manually point the scope to the first alignment star (loose clutches), then throughly tighten the clutches (scary tight, unfortunately), power up and align. Always solved the problem.

While I can't be sure, the above process SEEMS to have yielded better accuracy than skipping the "Calibrate Goto" step.

#6 James Cunningham

James Cunningham

    Gemini

  • *****
  • Posts: 3241
  • Joined: 07 Aug 2010
  • Loc: Maryland

Posted 09 July 2013 - 11:29 AM

Why do you turn off the power after the calibrate goto? Don't you have to redo the alignment all over again and then you lose your calibrate goto?
Jim

#7 KerryR

KerryR

    Gemini

  • *****
  • Posts: 3068
  • Joined: 05 Dec 2007
  • Loc: SW Michigan

Posted 09 July 2013 - 12:11 PM

Depowering is the only way I'm aware of to get to the full alignment menu. It does not loose the calibration (for the balance used at calibration time), just like it doesn't loose backlash settings or user objects.

I haven't had much luck with using 'align' and 'replace' under conditions of clutch slip (or whatever is the culprit). It's possible there's a way to get to the full align menu of which I'm unaware-- particularly with Nexremote with which I'm unfamiliar.

I just do what I do because it always works, so far, anyway, when slews get off after alignment.

Be sure to share any solution and/or shortcuts you find.

#8 James Cunningham

James Cunningham

    Gemini

  • *****
  • Posts: 3241
  • Joined: 07 Aug 2010
  • Loc: Maryland

Posted 09 July 2013 - 12:17 PM

I really don't understand. Whenever I turn off my handset and turn it on again, it wants to start the alignment process all over again. Perhaps I misunderstood what you meant by "de-powering"?
Jim

#9 KerryR

KerryR

    Gemini

  • *****
  • Posts: 3068
  • Joined: 05 Dec 2007
  • Loc: SW Michigan

Posted 09 July 2013 - 12:38 PM

De-powering: Turn the switch on the CPC base to the off position, wait a few seconds, then back on again. You'll need to re-do the alignment process from scratch, which is the point of turning off the power; to get to the full alignment menu. Is there a way to get there without doing so? I may have missed that option. This is the only fix I've found in cases where clutch slipping is the suspected culprit for missed slews. As I've mentioned, the clutches on my CPC seem to need to be much tighter than seems sufficient.

#10 mclewis1

mclewis1

    Thread Killer

  • ****-
  • Posts: 10892
  • Joined: 25 Feb 2006
  • Loc: New Brunswick, Canada

Posted 09 July 2013 - 12:54 PM

Calibrate goto is a routine that teaches the HC how the mount reacts to a slew. When you change the weights of the scopes etc. calibrate goto is useful to help compensate for that change.

The routine stores information in the HC (there is a small non volatile storage area ... that's where your location, DST and other settings are also stored) so powering off doesn't remove it.

#11 Cellofan

Cellofan

    Sputnik

  • -----
  • Posts: 39
  • Joined: 21 Jun 2007
  • Loc: Venice - Italy

Posted 30 July 2013 - 08:06 AM

Another check, your LST is correct for your location?






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics