Meade lx90 12 inch screws and guiding queries

[Nightingale]

This might be a silly question.. but the two screws marked in black lines at the back of this OTA; has it got anything to do with the primary mirror or are they just accessory screws for me to mount brackets etc.?

second question.. so I purchased this 60mm guidescope (as you can see in the pic) and attached it to my OTA hoping to guide it when my ZWO Asiair pro and ZWO Asi120mm mini arrives.. After further online reading, the question I have is if this scope will actually guide the 12inch lx90 at all? should I just not bother and go for an OAG instead? if so, what would be your recommendation?

[Merlin66 (Ken)]

I've used the Lx200 series Meade SCT's in all sizes from 8" to 12".
I can't honestly remember seeing any instrument that had those two holes/ screws in the rear of the cell, definitely non-standard. They could have been added to support a focus motor or similar.


Re guiding - worth trying your finder guider....but if you really want to get serious imaging the 12" ( remember you have a very long focal length) you would probably also end up with a x0.6 reducer and an OAG.


This is an image of my 12" Lx200 in the original TSO observatory.

[Nightingale]

Thanks for your thought.. I might try the guidescope first.. I have a 0.75X astro-physics telephoto reducer.. does the job well with a canon APS-C sensor.. I suspect the 0.6 reducers would cause some vignetting…
if the two screws are not standard, I might use them to mount a dovetail bracket for the Asiair pro..

[RodW (Rod Watkins)]

The two screws at the rear are for mounting the #909 Accessory Port Module.

It's a expansion module for the LX90 only, not for the 200.

I have one almost new in box that I'm wanting to sell.

(ps, I might have originally bought it off Merlin, can remember, long time ago.)