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Equipment Discussions >> Mounts

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Footbag
Postmaster
*****

Reged: 04/13/09

Loc: Scranton, PA
Re: CG5 seems to drift, not steady tracking at all new [Re: jrcrilly]
      #5772465 - 04/02/13 09:57 AM

I always powered down after ASPA and then re calibrated on the stars. I think it says to in the manual. This was with a wedge mounted CPC, but I dont see the gems being different.

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WadeH237
Pooh-Bah


Reged: 02/24/07

Loc: Snohomish, WA
Re: CG5 seems to drift, not steady tracking at all new [Re: Footbag]
      #5772509 - 04/02/13 10:17 AM

On my CGE and CG5s, the ASPA with recent versions of the NexStar firmware do not require you to redo the 2+4 alignment. I vaguely seem to remember that when ASPA first appeared in the firmware, you may have needed to do this.

Some people still redo the 2+4 anyway. I've tried it both ways, and get good results either way. Since it's easier to not re-align, and there is no improvement in results, I don't.

-Wade

PS: If you choose to power down and redo the goto alignment, you only need to do the 2 star alignment. There is no need to redo the 4 star calibration unless you have removed/reinstalled/changed the OTA.


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dickbill
scholastic sledgehammer


Reged: 09/30/08

Re: CG5 seems to drift, not steady tracking at all new [Re: DaveJ]
      #5772552 - 04/02/13 10:37 AM

Quote:

Quote:

Align on Kochab, almost 26 degres away from Polaris! and still get good GOTOs....wow.




Well, actually Kochab is 16.6° away from Polaris and 15.8° away from the NCP.




Hmm? isn't it just Dec(Polaris)-Dec(Kochab)=~ 90-74 degres?


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rmollise
Postmaster
*****

Reged: 07/06/07

Re: CG5 seems to drift, not steady tracking at all new [Re: bunyon]
      #5772578 - 04/02/13 10:50 AM

Quote:

Quote:

Quote:

That is, do mounts that use Nexstar track by turning about the RA axis or do they try to compensate in Dec as well? If the former, what does it matter (for tracking) how accurate the goto model is?




Tracking is only in RA and is dependent on polar alignment. ASPA is dependent on the accuracy of the goto model. That's why the goto model is critical for tracking.




Okay, I get that. But why would you need to do a remodel AFTER ASPA? I think it was answered above but I want to be sure. If ASPA gets the axis lined up, that should be it.




Why? Because during polar alignment you physically moved the mount (by adjusting the altitude and azimuth of the RA axis).


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jrcrillyAdministrator
Refractor wienie no more
*****

Reged: 04/30/03

Loc: NE Ohio
Re: CG5 seems to drift, not steady tracking at all new [Re: rmollise]
      #5772636 - 04/02/13 11:16 AM

Quote:

Quote:

But why would you need to do a remodel AFTER ASPA? I think it was answered above but I want to be sure. If ASPA gets the axis lined up, that should be it.




Why? Because during polar alignment you physically moved the mount (by adjusting the altitude and azimuth of the RA axis).




Hi, Rod.

It's certainly true that you walk up to an aligned mount and, unknown to the controller, adjust it in azimuth and/or elevation you will have disrupted the alignment. With ASPA, though, you are moving the mount as directed by the controller. The controller knows just what you did - in fact, it is relying on that to preserve the star alignment. Any requirement for realignment after that implies an error somewhere in the process; either inaccurate alignment star centering, inaccurate ASPA star centering, firmware errors, or mechanical slop in the system.


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rmollise
Postmaster
*****

Reged: 07/06/07

Re: CG5 seems to drift, not steady tracking at all new [Re: jrcrilly]
      #5773038 - 04/02/13 02:09 PM

That's what some folks say, and I certainly believe you've not had to realign. Celestron doesn't seem awful sure, though... (they say "try it, and if go-tos are off, replace stars") given what's in their instructions regarding AllStar. I've had varying success in not having to do/not having to do another go-to alignment after an AllStar. On my to-do list is doing more experimenting with AllStar this spring. I am lazy and usually just use Celestron's earlier Polaris alignment procedure (in NexRemote).

Edited by rmollise (04/02/13 02:10 PM)


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jrcrillyAdministrator
Refractor wienie no more
*****

Reged: 04/30/03

Loc: NE Ohio
Re: CG5 seems to drift, not steady tracking at all new [Re: rmollise]
      #5773055 - 04/02/13 02:16 PM

Quote:

That's what some folks say, and I certainly believe you've not had to realign. Celestron doesn't seem awful sure, though... (they say "try it, and if go-tos are off, replace stars") given what's in their instructions regarding AllStar. I've had varying success in not having to do/not having to do another go-to alignment after an AllStar. On my to-do list is doing more experimenting with AllStar this spring. I am lazy and usually just use Celestron's earlier Polaris alignment procedure (in NexRemote).




The ASPA works quite well on the CGE and no realignment was necessary on the ones I've owned, or on others with which I am familiar locally. It may just be that the Chinese mounts are less precise and permit positioning errors to creep in. I know people with CGEMs; I'll have to ask how it works for them.


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DaveJ
Carpal Tunnel
*****

Reged: 01/07/05

Loc: NE Ohio
Re: CG5 seems to drift, not steady tracking at all new [Re: dickbill]
      #5773149 - 04/02/13 03:31 PM

Quote:

Quote:

Quote:

Align on Kochab, almost 26 degres away from Polaris! and still get good GOTOs....wow.




Well, actually Kochab is 16.6° away from Polaris and 15.8° away from the NCP.




Hmm? isn't it just Dec(Polaris)-Dec(Kochab)=~ 90-74 degres?




Ah, exactly. 90 - 74 = 16 NOT 26! (although, the 74° isn't exactly correct, it's actually 74.16° so we have:
90° - 74.16° = 15.84° or rounded to 15.8° as I mentioned in my post above.


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dickbill
scholastic sledgehammer


Reged: 09/30/08

Re: CG5 seems to drift, not steady tracking at all new [Re: DaveJ]
      #5773740 - 04/02/13 07:12 PM

dumb me! mentally i substracted to 100, not 90.


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