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jmiele
Patron Saint?
Reged: 12/04/10
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Re: AP900 Question
[Re: RodShea]
#4480468 - 03/28/11 07:28 PM
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Actually after doing some more reading on the subject I think I've got it wrong. The error I found in Dec is not a problem. I problem in this case would be "cone error". That is to say the optical tube not being aligned with the dovetail yes. but not as I did it with the scope in the west level to the ground. This would be the difference or distance of the scope from the dovetail as it sits on the rings (each ring) front and back must be the same. That distance not being equal creates a cone shape (in or out) when the scope moves in RA and the optics are pointed to the pole. This is where the shims come into play. To your point about the error being greater at the pole, thats a good place to check for it. So looks like my tak tube holder is to blame because when looking for this a can visually identify they are not equal. The space between my optical tube and the dovetail are NOT the same in the front and the back of the dovetail plate.
I will test this tonight and prepare to shim it next time out. BTW, anyone out there mounting a TOA-150B with other than the tak tube rings?
Joe
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David Pavlich
Transmographied
Reged: 05/18/05
Loc: Mandeville, LA USA
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Re: AP900 Question
[Re: drksky]
#4480803 - 03/28/11 09:51 PM
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Quote:
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This is the reason I really like the Mount section.  Gotta' love mechanical things even when they frustrate the bejeebers out of you. I was thinking while reading this, a fork mount on a wedge or a purpose built mount like Mathis Instruments' fork mount solves the flip problem. HOWEVER, once committed to a fork, you have very limited options when it comes to scopes. You have the scope in the fork and perhaps a piggybacked refractor.
I've always liked the old Meade RX400s and thought that a 12" version would be a pretty terrific imaging scope if the electronics stayed healthy. But then, you're committing to a wedge. No flip, but that's your scope. Perplexing problems we have.
David
Not to derail the topic even more, but why not build a fork mount that has a dovetail platform in the center instead of have it mount to a scope directly? Then you can have your fork and eat it too...or something.
You wouldn't necessarily be limited by what scope you could mount, although you would certainly be limited by the instrument length.
I'm going to take a wild guess and say that the encoders in the fork assume that the scope is in a specific spot. Considering that, depending on the size of the fork, were a Losmandy dovetail be rigged to be in the middle, if you put, say a 12" SC in there and decided you wanted to do some widefield stuff with an FSQ106, the centerline of the 106 would be drastically different from the SC. Something would be out of whack I would think.
David
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RodShea
member
Reged: 11/01/09
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Re: AP900 Question
[Re: jmiele]
#4481031 - 03/28/11 11:39 PM
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,Quote:
So looks like my tak tube holder is to blame because when looking for this a can visually identify they are not equal. The space between my optical tube and the dovetail are NOT the same in the front and the back of the dovetail plate.
Joe,
That seems very strange. You are saying the OTA is visibly not parallel to the dovetail plate? I've never actually seen a TOA 150, but the scopes I was working with are both Taks, and that just does not sound right. I'd guess there is a trick, you are missing a part, have a wrong part, or something like that. I'd probably post this to the Uncensored TakGroup (can I say that here?) and/or call Art Ciampi or Fred Garcia at Texas Nautical Repair/TakahashiAmerica.
Rod
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jmiele
Patron Saint?
Reged: 12/04/10
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Re: AP900 Question
[Re: RodShea]
#4481067 - 03/28/11 11:52 PM
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Problem solved! A couple od thin shims and I was pointing all sky in the field of a 13 Ethos in the TOA-150 all night.
Rod, I have a pretty good eye for that. It was only out a couple of mills. Don't ask me how I can see that but I did/can. I also saw the dove and scope where were out of level by a 1/32 from each other.
All I know is it pointed great tonight and PEMPro showed my PE curve as 3.93 arc sec peak to peak with no PEC running. They make a great product!
Thanks to all who posted suggestions. 
Joe <----Happy
Oh and last..... took a couple of pics of Saturn and all I can say is those guys in the Solar System AP forum should be Knighted! How do they do it?
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RodShea
member
Reged: 11/01/09
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Re: AP900 Question
[Re: jmiele]
#4481270 - 03/29/11 02:06 AM
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Great to hear it worked1
Rod
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skybsd
Post Laureate
Reged: 02/01/08
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Re: AP900 Question
[Re: jmiele]
#4481327 - 03/29/11 03:41 AM
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Hi,
Glad to hear you found the root cause
Good eye! 
Regards,
skybsd
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