A problem with drift - Any ideas?

[Robby]

Main problem with OAG's (especially on SCT's) is the difficulty finding a bright enough guide star with the webcams low-ish light sensitivity.
But if you can do it, then yes, it's much better than a guidescope. I started out with an OAG, but got so frustrated with it, that it was a no brainer moving to a seperate guide scope.
Cheers

[[1ponders] (Paul)]

Painfully frustrating Scott, really painful. I've perservered with the Meade OAG for a while and as Robby says its hard to find a bright enough star off axis to use the Toucam to guide with. I won't pitch it out the window yet, but it does make a great paper weight. I might give it another go further on down the track. I'll wait and see how the gudiescope goes. Especially if I can get a "Side by Side" adapter built.

[tornado33]

With the Meade OAG, does it allow you to search radially?, that is to move in or out from the center a ways to locate a guide star. With my Newtonian OAG setup I can move in or out about the field of a low power eyepiece to find a star, as well as rotate through a full 360 degrees. While in a few cases Ive had to settle for a fairly faint guide star, in most cases I come up with one thats not too bad. Also as the pick off prisim is built in to the focusser assembly but outside the focusser tube, I get unfiltered light from the guidestar
http://www.users.on.net/~josiah/focuser/IMG_9935.jpg
The pick off prisim is above the inlet to the focusser itself and is on the edge of the light cone and doesnt in any way intrude into the images.
The screw on bottom right of image allows me to move the arm in or out, tilting the prisim so I can search radially, and the whole thing can rotate through 360 deg.
Scott

[[1ponders] (Paul)]

I can rotate it 360 deg by loosening the SCT threaed collar, but the whole unit includeing the camera then rotates which means I then need to loosen the small screws in the "T"-Mount Adapter to rotate the camera back to the best position. Unfortunately the Meade OAG doesn't allow for radial movement of the pick off prism.

[tornado33]

Bummer re the no radial adjustment,
This Lumicon OAG may be better
http://www.lumicon.com/eg7.htm
Cannot say for sure but they do claim it has radial adjustment too.
List of dealers here http://www.lumicon.com/2dealer.htm
Scott

[[1ponders] (Paul)]

I've thought about the Lumicon, Scott. I'm a bit gun shy of getting another OAG after the frustration of my existing one and I've been in contact with a number of people over the net who have had one and have ended up going for guidescopes.

I'm currently tossing up between getting the Losmandy guiderings and mounting rail, which I've heard nothing but praise for, or get just the rings and get a "side by side" mounting plate made. I'm definately swinging towards the "side by side" though. The idea of keeping the center of gravity as close to the mount head as possible is very appealling to me. I was quite amazed at how much addition weight I had to add to the counterweight arm to balance the setup with the Orion mounted on the top of the Meade. Lowering the amount of counterweight and keeping everything as close to the mounthead as possible has got to be a benefit imaging.

The one thing that does sort of swing me to the OAG is the complete removal of all the additional weight of guidescope, rings, rail etc and the corresponding reduction of "lever Torque" (don't know the proper name for it, but that's how I think of it )

Hmmm....OAG, less weight, more hair pulling finding a guidestar........Over/Under guidescope and imaging scope, easier to find a guidestar, more flexure and "lever torque" and more counterweight......"Side by Side" guidescope/imaging scope, easy to find guidestar, less flexure than Over/Under, less "lever torque" less counterweight, maybe more total weight to the mount due to increased amount of material required to construct as compared to Over/under rail........

OAG winds hands down for weight........but I think the "Side by Side" wins when looking at the overall picture. That's how I see it anyway. Would love to hear some comments on my beliefs and deductions. would love to hear of some alternatives. I've even thought of the Tau Ceti XY finder http://www.sciencecenter.net/hutech/gd-acc/xyfinder/ so I can use normal mounting rings and do away with the need for a guiding OTA balanced on screws. Decisions, decisions. If this keeps up how am I ever going to afford the buy the Argo Narvis I want

[gbeal]

Paul,
the Lumicon does offer a sort of radial adjustment, but I still believe the frustration factor is way up there.
In my case the difference between weight away from the pivot (separate guidescope on top) is similar to the side by side, as the side by side is HEAVY. Maybe I could skinny it down a tad, but not that much. I did have a picture of a Tak accessory, and this made an effective side by side system, with what appeared to be WAY less weight than my homebrew system.

[[1ponders] (Paul)]

My thinking Gary was that with the guidescope in a side by side position the amount of leverage, say with the mount in a horizontal position which would be the worst case scenario, would be much less than with the guidescope in the over and under situation. Like carrying a heavy weight with outstretched arms or tucked in close to the body. The amount of mount flexure and sensitivity to vibration must surely be less. Plus I believe it would be much easier to balance, especially if the side by side was on a sliding dovetail that could slide "sideways" to balance the disparate weights of the scopes over the mount head.