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How does Side by Side Mounting Work???

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#1 NightRyder


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Posted 11 March 2010 - 11:22 PM

I am interested in setting up a Side by Side rig for an imaging scope and a 80mm guide scope. However, I have noticed in most pictures of these setups, that the dovetail rail across the bottom of the Side by Side Mount ends up pointing the scopes perpindicular to the Scope Mounts dovetail slot. In otherwords, if you were to align the "Index Marks" on the mount, the scopes would be pointing to the west/east, not towards the NCP...

How does this work?

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#2 NightRyder


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Posted 11 March 2010 - 11:23 PM

Closer View...

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#3 Terrance


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Posted 12 March 2010 - 01:32 AM

For Goto or using DSC's I suspect it does not work at all.
It seems to me the computer would assume the scope is inside the dovetail shoe and pointed in the same direction as the dovetail shoe on the top of the mount. With a dual scope setup, the 2 scopes are pointed at right angles to the direction the computer expects. I do not think goto would work at all. I think a GEM could still track, but not find anything.

Maybe somebody has actually tried this and can chime in. I hope I am wrong because I might like to try a dual scope setup, but would like to be able to use computer assisted finding as well, and suspect that I would not be able to.

#4 scout72



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Posted 12 March 2010 - 01:58 AM

You have shown two different mounts there- an Atlas and a Cg-5/ASGT one.

I can't remember on the Atlas, but on the CG-5 the mount doesn't "know" where you are pointing the scope- that is why there are alignment marks- you just make sure the scopes are polar aligned when you start and then start with your star alignments...

On the CGE, which does have a "home" position that the scope knows, there is a function you access through the setup function to tell the scope it is sideways mounted.

Hope this helps

#5 NightRyder


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Posted 12 March 2010 - 02:40 AM

What if I were make a new index mark exactly 1/4 of the way around the declination axis so the mount would then think it was on index when in fact the scopes are pointed towards the NCP???

#6 Chris Rowland

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Posted 12 March 2010 - 03:31 AM

The recent Celestron HC software has an OTA Orientation option. You can set this to East or West and use the normal align marks with the scopes starting pointing East or West.

It works very well.


#7 mclewis1


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Posted 12 March 2010 - 10:15 AM

The CG-5, CGEM and the Atlas/EQ-6 have no idea where they are initially pointed, there is no physical "index point" for the computer. The computer assumes that the starting point is where the mount is pointed to when it's powered up, this starting point is assumed to be the ota(s) pointing either directly north or south.

The physical index marks on the mounts are there for convenience, they give you a consistent starting point so the mount can point relatively accurately to the initial alignment objects. You can move the index marks to where ever you like to start from to compensate for where the otas are actually pointed. The position of the marks have absolutely no effect on goto accuracy once the initial alignment is done.

A side by side setup also has absolutely no affect on the goto accuracy of these scopes. When you install a SbS configuration you have a few options. Rotate the otas 90° and then start the initial alignment, you can remove and reinstall the index marks so they reflect the 90° offset so you can continue to simply line them up and then start the initial alignment. What I'm not certain about is whether the mount will let you do an initial alignment when you have to move a large amount (like more than 90°) or whether you'll get an "alignment failed" message.

The other option for Celestron scopes is what Chris described, use the OTA Orientation routine in the HC.

If you have a CGE or CGEPro (which have switches for a hardware derived initial index or starting point) then you must use the OTA Orientation routine (or modify the mount to re orient the SbS mounted otas back to the original orientation).

#8 JAT Observatory

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Posted 14 March 2010 - 08:45 AM

Since my mount is indexed I modified my side x side plate so I could mount it without turning my Ra axis 90 degrees.

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