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Equipment Discussions >> Mounts

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Phil Sherman
Pooh-Bah


Reged: 12/07/10

Loc: Cleveland, Ohio
Re: EQMOD Polar Alignment vs Celestron ASPA precision new [Re: cn register 5]
      #6054307 - 08/30/13 12:09 PM

Quote:

Quote:

Quote:

Please give us a detailed technical explanation of what you are saying.



Sorry, that's only on a need-to-know basis



So just your usual wind and *BLEEP*, I thought so.

Chris




EQMOD's pointing model is very easy to explain. Every time you do a sync on an object, EQMOD records the mount's altitude, azimuth, and the motor encoder values. This allows an exact repositioning to that point in the sky, which never changes as long as you don't move your mount or release the clutches. Once you have a number of sync points defined, all goto operations are computed using one of two methods.

If the target is contained within a triangle formed by three sync points, then the three points are used, with the equation of time, to compute the encoder values for the target. The mount is then instructed to move to that position. If the target lies outside of a triangle of sync points, the closest sync point is used by itself. In this case, the equation of time and the target's RA and DEC are again converted to an altitude and azimuth but a displacement from the closest sync point is used instead of a surrounding triangle of sync points.

One interesting effect of this is that you can sync on the same star multiple times during an evening. Each sync will give a new altitude, azimuth, encoder value which is stored in a sync point table. The table can be saved and restored which is ideal for a mount on a fixed pier. There's also a recovery routine that can resync the scope to the sky model if you've had a power failure, which causes loss of the motor encoder values. This can also be used for a multi night portable session to bring the mount back into sync with the saved sky model.

EQMOD also runs the mount using the ASCOM platform, which allows multiple programs to concurrently control the mount. The mounts that EQMOD controls also support pulse guide, which means that any camera that PhD will control can be used as a guide camera, without requiring a connection to the ST4 guide port. One less wire and one less piece of hardware to carry and have fail in the field.

Phil


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rmollise
Postmaster
*****

Reged: 07/06/07

Re: EQMOD Polar Alignment vs Celestron ASPA precision new [Re: Phil Sherman]
      #6054453 - 08/30/13 01:22 PM

Actually, none of the mounts supported by EQMOD have encoders except for the new alt-az EQ6, and EQMOD doesn't use them.

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Moromete
professor emeritus


Reged: 02/15/12

Loc: Romania
Re: EQMOD Polar Alignment vs Celestron ASPA precision new [Re: rmollise]
      #6054466 - 08/30/13 01:31 PM

I propose that all EQMOD users should ask kindly the EQMOD developer to create an ASPA routine based on his N-Star alignment. This routine should give better accuracy than Celestron's. I can't believe such opportunity has been missed.

What do you say guys?


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rmollise
Postmaster
*****

Reged: 07/06/07

Re: EQMOD Polar Alignment vs Celestron ASPA precision new [Re: Moromete]
      #6054473 - 08/30/13 01:38 PM

As I said earlier, there were plans for one, and there is some preliminary code for it in some of the earlier releases. But not much was done thereafter. It doesn't hurt to go over to the Yahoogroup and ask Chris about it, though, I suppose. It's something that hasn't been mentioned in a long time.

Edited by rmollise (08/30/13 01:38 PM)


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Alph
Carpal Tunnel


Reged: 11/23/06

Loc: Melmac
Re: EQMOD Polar Alignment vs Celestron ASPA precision new [Re: Moromete]
      #6054687 - 08/30/13 04:08 PM

Quote:

I propose that all EQMOD users should ask kindly the EQMOD developer to create an ASPA routine based on his N-Star alignment. This routine should give better accuracy than Celestron's. I can't believe such opportunity has been missed.

What do you say guys?



As I said, not doable. They tried and failed for the reasons mentioned earlier. The EQMOD does not model the geometrical mount errors/terms.


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