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Mounting Piggyback Scopes

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#1 DMR

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Posted 09 May 2011 - 08:59 PM

I have what is likely a basic question, but I'm a little bogged down in the specifics. I am currently using a CG5 mount with my AT72ED scope as a beginner imaging setup. I'm considering adding my 6" Newt to the setup as a guidescope, but I'm unclear as to what kinds of adapters and things I would need to get everything attached to the mount. The Newt currently has two rings with screw holes used to attach my my other mount, but these rings will not work on the CG5. Could someone help me figure out what I would need to get it all attached?

In addition would I need to modify the Newt to use as a guidescope as I would to image with it. I do not currently want to modify it for photography purposes, so I'm hoping this would not be needed.

I've attached a shot of what the scope connection points look like.

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#2 darkman

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Posted 09 May 2011 - 09:25 PM

Dave,

I have an AT72ED that I use for wide-field imaging: what I did was install a dovetail shoe from Scopestuff, P/N RDPZ and then used a surplus 9 x 50 finderscope with an adapter from Precise Parts to accept an Orion Starshoot Autoguider. It ends up being a very light-weight set-up that works well, but you may want to add an ATFF field flattener depending upon what camera you choose to use.

The other option if you really want to use the Newt is to contact Anthony at ADM and get an MDS dovetail bar and guidescope rings.

#3 Geo.

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Posted 10 May 2011 - 08:34 AM

For the rings to the mount you need a Vixen format dovetail bar. I'd recommend Scopestuff's - #EQD6 - 8.25" Solid Aluminum Dovetail Bar 0.590" Thick $39.00 http://www.scopestuff.com/ss_eqdb.htm

The L bracket on the WO may or may not be configured in the Vixen format. I can't tell. To piggy back it and not us it as a guider a simple length of 3/8th" by 2" aluminum bar with holes in the proper locations will work fine. Some slotting will let you align it. If you want to guide with it Scopestuff's - #RSBK - Ring and Accessory Mounting Bar with Hardware Kit $44.00 and #CR30 - 3" or #CR35 - 3.5" Cradle Rings set $36.00 plus $15 for the - #CR99 Three-Point Centering Option will be needed.

You can see how a mill pays for itself pretty fast!

#4 Dmitri F

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Posted 10 May 2011 - 09:14 AM

From my experience with piggybacking, I discovered the following:

1. The scope that is on the top is so far from the center of the mount that it requires a lot of counterweights and puts a load on the mount that is disproportional to it's weight. I have a 2.5lb WO piggybacked on top of a 40lb CAT, and I'm seriously considering switching to a side-by-side setup. ADM has a side-by-side saddle setup that looks nice.
I am not saying that SBS is always better than piggyback - I don't have enough experience with both to make such claims. But definitely something worth considering.

2. I find the 3-point mounting rings awkward to use. Each time I setup, I need to slide both rings on the mounting bar, unscrew three bolts on each ring all the way out (because the focuser on one side of the scope and dew shield on the other require extra clearance), put the scope in, and then tighten the bolts and try to keep them more or less even while holding the scope with another hand. Awkward and time consuming, and the scopes come out misaligned which requires yet more time. I have ADM rail and rings that are very nicely made so the problem is with the concept, not with the specific hardware.

The alternative would be to use the clamp-on rings lined with felt. The problem with them is that there is no way to align the two scopes. The solution is once again provided by ADM - he has a double saddle that has built-in adjustments just for that. I think that this would be a better setup than the three-point rings, at least for me.

Finally, you can use the L-bracket that is in your picture instead of the clamp-on rings. It can be attached to a vixen-style bar with two hex bolts.

#5 biomedchad

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Posted 10 May 2011 - 02:19 PM

im with you dmitri but that adm saddle is like $400!!!

#6 Dmitri F

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Posted 10 May 2011 - 08:11 PM

Now I remember why I never got it! That's a little steep, considering that the adjustments are likely to be needed once. I had a chance to hold it at NEAF. Nice piece of equipment, as anything else made by Anthony.

Let's look at the bright side - the SBS saddle looks like a bargain now.






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