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Equipment Discussions >> Mounts

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George P Dunham
super member


Reged: 06/24/12

Loc: Pinecliffe,CO USA
CGE PRO 2 star alignment question.
      #5414116 - 09/10/12 09:13 PM

When I do a 2 star alignment on my CGE PRO, I find that at the start of alignment the 2 stars are always placed about 1/8th a finder field away from center and seem to be placed in the same relative position. After alignment the sync stars are dead on and once completed, the goto is near perfect. What I am wondering about is this initial error normal and since it seems pretty consistent, can it be corrected? My polar alignment is pretty good and time and location are very precise. Another way of asking this might be is this a physical misalignment of the OTA or some part of the mount or is it in the software? If it is a physical thing, can I measure it and correct it and is it worth it?

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dwitek
sage
*****

Reged: 07/03/08

Loc: White Lake, Michigan
Re: CGE PRO 2 star alignment question. new [Re: George P Dunham]
      #5414171 - 09/10/12 09:37 PM

Once you start doing the calibration portion of the alignment the cone error of the mount is corrected. Cone error is the misalignment of the scope with the mount. You can try adjusting the telescope on the mount but if your gotos and tracking are good only you can determine if it's worth it to you to work on the alignment of the OTA on the mount.

Here's a link to an article on CN about this issue. I have not read through the whole thing:

http://www.cloudynights.com/item.php?item_id=2524


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George P Dunham
super member


Reged: 06/24/12

Loc: Pinecliffe,CO USA
Re: CGE PRO 2 star alignment question. new [Re: dwitek]
      #5415164 - 09/11/12 12:48 PM

Makes sense. Will the cone error information tell me anything that will help me correct it? or is it more about what a drift adjustment tells me. If I have a persistent 1/10 degree-ish error on my initial star alignment and then proceed with a 4 star synch, is the "all star polar alignment" only as good as my initial alignment or will the synching correct everything and make a subsequent all star polar alignment more accurate. I hope this makes sense

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freestar8n
Post Laureate
*****

Reged: 10/12/07

Re: CGE PRO 2 star alignment question. new [Re: George P Dunham]
      #5415475 - 09/11/12 03:02 PM

If the mount has been calibrated previously with a 2+4 alignment then the mount "knows" the cone error and will use it to find the first star. If it is off in RA then you need to run the "RA Calibration" routine - in the section on mount calibration I think. Most people ignore it - but it applies to the accuracy of pointing to the first stars.

If you can do a 2+4 alignment and the GoTo is accurate, then cone isn't a problem because it "knows" what it is.

In order for the mount to point to the first star accurately, it needs to be well polar aligned and level - and you need to have done the RA calibration routine when it was well polar aligned and level.

Frank


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