Aligning the scope with the mount

Using SharpCap's Polar Alignment feature
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JayThree
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Joined: Mon Mar 13, 2017 4:45 am

Aligning the scope with the mount

Post by JayThree » Tue Jan 02, 2018 6:24 pm

Hi,
I have used the PA routine in SharpCap a couple of times and have gotten good and excellent results at the end of the routine. I start with my Meade LX90 in polar home position with the scope pointed toward the NCP (using an equatorial wedge). After polar Aligning, when I return the scope to polar home position to begin the two star alignment process, I Find that the scope is pointing to a place a couple of degrees off of the NCP. I have ignored that and gone ahead with the two star alignment process but the GOTOs are bad and the tracking is poor. Is it possible that although the mount is aligned well with the NCP,the scope is not aligned well with the mount and should I slew to the NCP with the hand controls before beginning the two star alignment process? Thanks!

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Re: Aligning the scope with the mount

Post by admin » Tue Jan 02, 2018 8:49 pm

I'm afraid I'm not familiar with Meade mounts, but with Skywatcher mounts it is possible to end up with the home position mis-set if the setting circles move - could this be possibly part of the problem. I have a feeling that the setup is described in this video (or one of the others in the sequence) https://www.youtube.com/watch?v=4fO6hyYtPwM.

Another thing that can throw off goto movements is cone error - three star align should correct for that, but two star cannot. There's a 'ConeSharp' program on the SharpCap web site that helps measure and correct cone error.

cheers,

Robin

JayThree
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Re: Aligning the scope with the mount

Post by JayThree » Thu Jan 04, 2018 5:06 am

Hi Robin,
With the LX90, I can do 1 and 2 star alignments; a 3 star is not an option. The mount has a GPS; perhaps this is why they don't have a 3 star routine. Also, it is mounted on an equatorial wedge -- will Cone Sharp work with this set-up?
Thanks!
Jerry

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Re: Aligning the scope with the mount

Post by admin » Thu Jan 04, 2018 8:06 am

Hi Jay,

it should do. You need adjustment bolts on your telescope mounting plate to be able to make the required adjustments of the front or back of the scope in/out though.

Robin

JayThree
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Re: Aligning the scope with the mount

Post by JayThree » Sun Jan 28, 2018 5:23 am

Hi Robin,
There are no threaded holes in the plate of the equatorial wedge to screw a bolt into, so I'm not sure I can run ConeSharp.
I'm wondering if my OTA was not aligned parallel with the SCT's fork arms during my initial home position set-up (as a result of a setting an incorrect angle for the wedge). Would this cause a "cone-error-like" problem?
Thanks!
Jerry

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Re: Aligning the scope with the mount

Post by admin » Sun Jan 28, 2018 10:39 am

Hi Jerry,

I think that if you mean the altitude on the Alt/Az mount wasn't quiet straight 'up' then that shouldn't give cone error - that's equivalent to having your scope slightly off in DEC and that is a simple offset that gets fixed by even a 1 star align.

Basically an offset in the direction that the altitude axis moves is not a problem. An offset at right angles to that (ie the scope points a bit towards either one fork or the other) would give you cone error I think.

cheers,

Robin

JayThree
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Re: Aligning the scope with the mount

Post by JayThree » Mon Jan 29, 2018 5:25 am

I believe it was primarily, maybe exclusively, an error in declination (altitude). I'll try to get a better look when the weather is better. If there is a discrepancy, I'll slew such that the NCP is aligned with the reticle, try to measure the Azi and Dec amounts of error and then try a 2-star alignment. Anything else?
Thanks Robin.
Jerry

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