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OAG and Explorer 130P-DS

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I'm trying to get OAG working for my Explorer 130P-DS.  I'm using the TS Off-Axis-Guider here https://www.firstlightoptics.com/off-axis-guiders-oag/ts-off-axis-guider-tsoag9-length-only-9-mm.html with a Canon 550D and a ZWO ASI 120MC-S USB 3.0 Colour Camera as a guide scope.

It all goes together OK and I can bring a satellite dish to focus in the Canon successfully.  Using Astroberry, I can get a live view from
the ZWO and, with the lense it comes with, I can see with it happily with exposures about 0.005s.  What I can't do is bring it to focus when directly attached to the OAG (without its lense).

I've checked the OAG prism is the right way (ie flat side towards the telescope) and I can see up the bit the camera attaches to and out of the telescope ok (well the spider at any rate) but all I can see on the ZWO's live view is varying tones of grey through the OAG as I change the focuser or move the prism up and down in the OAG.

Should this work?  Or do I need stars?  Or some sort of attachment for the guide camera?  Any help appreciated...



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Ok after some more investigations I think my ZWO can't move in far enough to focus.  It's got a nosepiece that came with it which screws onto it then gets inserted into https://www.firstlightoptics.com/adapters/baader-click-lock-125-inch-eyepiece-adapter-with-t-2-thread.html which then attaches to the OAG and it looks like it's all too long.  I can bring it to focus if I screw the ZWO directly to the OAG and move the focuser about but with that there's no way to adjust the relative distance between the DSLR and the ZWO.

The DSLR comes to focus when the draw tube extends about 11mm and the ZWO about 8mm so is there some attachment which would add an adjustable length of around 3mm which would join the ZWO to the OAG?

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Have you got any m42 extension rings, but I do believe they're a slightly different thread pitch to t2?, Micro adjustments can also be made on the zwo by taking the nosepiece off and screwing the extension rings directly onto the camera body.

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In the end I just bought a set of T2 spacer rings and a set of T2 extension tubes and spent some time trying to focus on chimney pots and satellite dishes with various combinations.  I was hoping there was something which could be adjusted on the fly like a smaller version of the baader click lock but I guess you only need to do this once. 

Just need a clear night to see if I've got the focus good enough for guiding....


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