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rdegoutier
super member


Reged: 02/18/08
Posts: 123
Loc: White Rock, BC, Canada
Re: 3 Star Alignment issues with Atlas EQ-GOTO new [Re: jmasin]
      #3119054 - 05/21/09 03:11 PM

The only thing is that you won't be able to see Polaris when the scope is in the Home position. There is a shaft inside the mount with a hole in it, and the scope has to be horizontal for the hole to line up with the Polar Scope. So change step 1 to:

1. Start with the mount facing north in HORIZONTAL position. Once polar aligned, swing the scope vertical to Home position, put the caps on the Polar Scope, turn the mount on and start star alignment.

--------------------
Sometimes I sits and thinks; sometimes I just sits.



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Skylook123
Postmaster


Reged: 04/30/05
Posts: 7171
Loc: Tucson, AZ
Re: 3 Star Alignment issues with Atlas EQ-GOTO new [Re: chitown]
      #3119252 - 05/21/09 05:14 PM

Quote:

Please correct me if I am wrong.

This is what I have understood from all the help above:

Steps:
1. Start with the mount facing north in Home position
2. Home position is weight end down, scopes facing north straight
3. All levers locked (RA and Dec)
4. By looking at either the polarfinder software or the clock value on the HC, match the polaris on the BIG cirlce of the polar scope. Ignoring the pictures on it and the polaris small circle
5. Adjust the position of my ENTIRE rig to match polaris on the big circle. WITHOUT touching the RA.
6. Once its in the right position, turn on mount. And start with 1 Star alingment. And select Polaris as GOTO
7. Adjust again if necessary
8. Begin with the rest of the 3 Star Alignment

Please correct me if I am wrong in the most simplest words.

Thanks




<big grin> OK, I'll cut down the rambling. Sort of correct, except 6 and 7 go ahead of 4 and 5; it's that iteration that will bring Polaris into the polar scope field of view. Then you can put Polaris on the big circle in the right place.

But, as pointed out above, if the mount is in the usual delivered condition, the polar scope opening will be blocked when the OTA is pointing north so first, loosen the three allen screws and make the scope point north when the hole is open. I did mine three years ago and forgot that part.

If you get your routine down, if you are level, and get Polaris onto the big circle where it belongs, and your OTA is square with the mount RA axis, you might only need a 1-star alignment. The point of the 3-star on Synta mounts is to correct for cone error (OTA and RA axis slightly off from each other). If you're "good", a 3-star can make GOTOs less accurate because the hand controller is trying to fix a problem you don't have. If your NCP pointing (polar alignment)is good, and you do a good 1-star, the 1-star provides information for alignment in both axes and that's all you need (but you must be leveled for this to be true). A 2-star will adjust for slight errors in polar alignment and off-level. Three star alignments can give disappointing results for the EQ6/Atlas EQ-G mounts if your mount setup does not have a little cone error.

This is due to the SynScan algorithm; in general, the more stars the better but SynScan tries to fix cone error, so a 3 star might not give you the results you're after. Be very rigorous in your setup (level, polar aligned, good home position), and try a 1-star, then 2-star, then 3-star and see how the GOTOs do. You might be surprised that a 1-star ain't bad when the mount is level and polar aligned.

--------------------
Jim
South Rim Coordinator
Grand Canyon Star Party
gcsp[at]tucsonastronomy.org

“Equipped with his five senses, man explores the
universe around him and calls the adventure
Science” - Edwin Hubble


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David PavlichAdministrator
Transmographied


Reged: 05/18/05
Posts: 21117
Loc: Mandeville, LA USA
Re: 3 Star Alignment issues with Atlas EQ-GOTO new [Re: chitown]
      #3119745 - 05/21/09 09:40 PM

Quote:

Quote:


Step 3: Return the scope to HOME position.




But if i do this, then polaris will escape the reticle circle of the polar axis scope?




Yes, it does, but that's ok. The exercise to rotate the RA axis to match the sky then putting Polaris in the circle is to polar align the mount and that's it. So unless you move the mount's legs or loosen the Alt or Az bolts, you'll be fairly close to a polar alignment. It will aid in your gotos to be a bit more accurate.

David

--------------------
Money can't buy happiness, but it sure makes misery easier to live with.



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Charlie HeinAdministrator
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Reged: 11/02/03
Posts: 11211
Loc: 26.06.08N, +80.23.08W
Re: 3 Star Alignment issues with Atlas EQ-GOTO new [Re: David Pavlich]
      #3121786 - 05/22/09 09:38 PM

chitown: stick with Skylook123 for a bit and let's see if you can get this down - everyone is trying so very hard to be helpful but it seems you may be getting confused at all the input... I think that you're just about there!

--------------------
Weston CSC:


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John Miele
Carpal Tunnel


Reged: 05/29/05
Posts: 1588
Loc: North Alabama
Re: 3 Star Alignment issues with Atlas EQ-GOTO new [Re: Skylook123]
      #3122892 - 05/23/09 01:53 PM

Quote:

...try a 1-star, then 2-star, then 3-star and see how the GOTOs do. You might be surprised that a 1-star ain't bad when the mount is level and polar aligned.




I can attest to the accuracy of the 1 star alignment. I was lazy one night and started doing a 1 star alignment instead of 3. I have had the best pointing accuracy yet using just the 1 star! Now I level my mount and I do a good polar alignment. And I also use a reticle EP to center my alignment stars. The other night, I was imaging with a DSI II at a focal length of about 700mm. Every target landed on the chip. 1 star aligning is now all I ever use.

John

--------------------
G11-GI w/ Ovision Worm
Edge 8 SCT
ST-402ME
QHY5-II/ST-80


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Skylook123
Postmaster


Reged: 04/30/05
Posts: 7171
Loc: Tucson, AZ
Re: 3 Star Alignment issues with Atlas EQ-GOTO new [Re: John Miele]
      #3123381 - 05/23/09 07:09 PM

John, those are my strongest points of advice as well. I never have alignment troubles with the DSCs on my dobs, but this mount drove me nuts for a while.

1. Level and quality polar align really helps. So does a good starting home position. Then the first star in the alignment is close, and frustration relaxes.

2. A reticle eyepiece saved my sanity. The hand controller firmware will warp the dickens out of the sky with just a bit of imperfection in centering. You'll be surprised how much your nose will cause parallax in the eyepiece. If 1. above is true, then you won't bee too far off with a 1-star alignment. But if 1 star warps space, 2 stars with the same centering defect will turn space into a fun house mirror if you let it. Throw in a 3-star alignment when no cone error exists, and the software is correcting it out, whooee. In my case the gift of a reticle eyepiece (8mm, nice and high powered) has made this a 1-star alignment performer when level and polar aligned.

--------------------
Jim
South Rim Coordinator
Grand Canyon Star Party
gcsp[at]tucsonastronomy.org

“Equipped with his five senses, man explores the
universe around him and calls the adventure
Science” - Edwin Hubble


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