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Equipment Discussions >> Mounts

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orlyandico
Post Laureate
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Reged: 08/10/09

Loc: Singapore
Re: Servo vs Stepper new [Re: freestar8n]
      #5451355 - 10/02/12 05:19 AM

Ah ok wrong terminology on my part. When I said "tracking" I really meant.. guided tracking, since I had assumed this is what all normal folks with normal mounts do

And you're right, the contribution of non-orthogonality would be tiny.


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Stew57
Carpal Tunnel
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Reged: 05/03/09

Loc: Silsbee Texas
Re: Servo vs Stepper new [Re: orlyandico]
      #5452277 - 10/02/12 04:56 PM

Drift alignment takes care of the tracking issue. Does the 4 calibration stars (well actually one as they are averaged) compnstae enough to take care of pointing accuracy enough for ASPA to be accurate? Perhaps that (orthogonality) is a variable in the wide discrepancy in user reported success when using ASPA.

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jaddbd
professor emeritus


Reged: 05/18/05

Loc: Woodbine, MD
Re: Servo vs Stepper new [Re: photodady]
      #5452564 - 10/02/12 08:02 PM

If you use a DRIFT alignment method (computer assisted or otherwise), you should be able to achieve accurate enough polar alignment regardless of orthogonality. The goal of DRIFT is to get the RA plane of the MOUNT perpendicular to the pole. Since you adjust the MOUNT to bring the DEC drift back to parallel when shooting East and at then at the meridian South, it seems to me that any angle of error on the RA plane would be irrelevant (since it is parallel to the plane you are trying to achieve) and any angle created by shooting a little high or low off the DEC plane would have to be very large to be of any measurable relevance.

That being said, I have 3 different scopes which I use (one at a time) on my permanent (drift aligned) set up, which all point slightly different when mounted, but all “track” and “guide” the same.

Also (responding to some banter earlier in the thread), my experience in thinking that you can just point and shoot a high end mount “unguided” is a bit of a misnomer. Even if you have excellent polar alignment, and very little periodic error, you still have to account for the fact that objects in different parts of the sky move at different rates due to refraction, and that rate may change position of the said object changes. There are software tools provided to adjust for this, but it is way easier and more accurate just to guide IMHO.

John D
Maryland


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rmollise
Postmaster
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Reged: 07/06/07

Re: Servo vs Stepper new [Re: photodady]
      #5453566 - 10/03/12 01:46 PM

Quote:

If the users in this group can't, or refuse to, acknowledge the effects RA-DEC orthogonality has on the ability to polar align and ultimately its effects on tracking then I'm definitely in the wrong place.




It doesn't and won't. But stick around and you'll learn the basics before taking the bit in your teeth again...


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EFT
Vendor - Deep Space Products
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Reged: 05/07/07

Loc: Phoenix, AZ
Re: Servo vs Stepper new [Re: EFT]
      #5454375 - 10/03/12 11:48 PM

I took a look at the possibility of putting the Atlas system into the CGEM. While maybe not impossible, it would not be easy. The first issue would be the motor mounts. I would be necessary to reposition the mounting holes on the Atlas steppers to fit the CGEM locations. That could probably be done and there is probably enough space for the motors.

The biggest challenge would be the motor board. The Atlas motor board is longer than the CGEM board but not as tall. Getting the board in the hole and attached to a face plate might be challenging. Worse yet, the Atlas motor cables attach to the board on end creating a further space issue. If it can all be fit, then a custom face plate would need to be made to attach the motor board to.

Perhaps not impossible, but definitely difficult. Considering the cost of a Synscan conversion kit (if you can find one anymore), it's hard to say whether or not it would be worth the effort.


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orlyandico
Post Laureate
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Reged: 08/10/09

Loc: Singapore
Re: Servo vs Stepper new [Re: EFT]
      #5454590 - 10/04/12 05:42 AM

Thanks Ed. I suspected as much regarding the motor board.

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andysea
Pooh-Bah
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Reged: 09/03/10

Loc: Seattle, WA
Re: Servo vs Stepper new [Re: jaddbd]
      #5507487 - 11/06/12 08:19 PM

Quote:

Also (responding to some banter earlier in the thread), my experience in thinking that you can just point and shoot a high end mount “unguided” is a bit of a misnomer. Even if you have excellent polar alignment, and very little periodic error, you still have to account for the fact that objects in different parts of the sky move at different rates due to refraction, and that rate may change position of the said object changes. There are software tools provided to adjust for this, but it is way easier and more accurate just to guide IMHO.

John D
Maryland




I fully agree with you John!
Guiding seems to be the best way to achieve good tracking even with excellent mounts; and guiding with an OAG in my opinion is the way to go.
As long as the mount as a smooth and repeatable periodic error it will be easily guided out along with any drift generated by not perfect polar alignment.

Andy


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