Questions about using the Edge HD 8"

[Grierson]

I am hoping to use the 'scope above at some future date and I would welcome any comment on the following from any existing users.

I would like to mount as much as possible on the tube in a similar way to my current set on the SW80 ED as in the picture.

However something tells me that using my existing SW 9X50 finder 'scope with a likely fl of 180mm and the ZWO ASI120mm may not be a good guiding combination for the Edge which has a native focal length of 2032mm. I wonder if any Edge imagers are using this combination successfully at the moment or is an OAG likely to be a better answer.

Looking at the manual the finder 'scope bracket appears to screw to the rear rim of the tube. Could someone tell me if the rim will be able to carry the extra weight of a dual finder shoe to which will accommodate the ASIAIR. Is anyone using such an approach and if so could you point to a suitable duel shoe? Do you use the finder which I believe comes with the 'scope or something else?

Thank you for reading. Any comment would be appreciated. - John  

 

Edited May 2, 2020 by Grierson

[ollypenrice]

Any reflector is best guided via OAG because the mirror can always move. The term 'mirror flop' is a mighty exaggeration but a tiny movement will harm your results in high resolution imaging. Also, at high resolution, an increase in guider resolution is to be preferred. My foray into catadioptric imaging involved an OAG and, once set up, it worked fine.

Olly

[knobby]

+1 for OAG, never got anywhere near round stars with a finder guider on mine (reduced to 1400mm) definite improvement with OAG but my AVX wasn't really up to it.

Edited May 2, 2020 by knobby
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[Grierson]

Thanks chaps for the responses. It has been suggested elsewhere that with the OAG and given the focal length of c. 1400mm (with the reducer) that finding and retaining a suitable guide star is difficult. Would you care to comment further?

Edited May 4, 2020 by Grierson

[cvucki]

what is oag ?

[Merlin66]

OAG = Off axis guider

[Merlin66]

Grierson,

A couple of things...the HD design I believe has mirror lock to minimise any slop/ flop.

I've been using a OAG (well, an on axis guider - a reflective slit plate) of my spectroscope/ C11 combo for over ten years and never had any issues finding or guiding. I use a Lodestar guider @ f10.