Piggybacking to a Skywatcher 180mm Maksutov Cassegrain

[RPW]

Hi,

I have a Skywatcher Mak 180 and want to attach a small refractor (like a SW80 or similar once I decide) to it for auto-guiding. The dovetail bar for the Mak comes screwed into the OTA so I imagine tube rings might be difficult to attach.

Is there a simple solution to this problem and/or has anybody got a similar set-up that I can emulate?

[mldee]

From ADM in upstate NY, I have two, they're good.
http://www.admaccessories.com/V_Series_Dovetail_Adapter.htm

[RPW]

Hi Mike,

Thanks for the info - I was previously not aware of this website.

Can you please however describe how to use these products in my case? Are you suggesting the side-by-side mounting system?

Rod

[mldee]

I was presuming you had a Skywatcher (Synta/vixen) dovetail bolted to the top of your OTA. I'm beginning to think you may have been referring to the bottom OTA mounting vixen-style dovetail though.

For what it's worth, I'm not a familiar with the Skywatcher Mak OTA. I have a Celestron C8 that has the bottom dovetail bolted to the tube, so also cannot fit tube rings. I was able to bolt a normal vixen dovetail to the top of the OTA (The celestron had some ~6mm mounting holes there) and then the ADM adaptors will grip onto that dovetail, and can slide along to adjust ring-to-ring spacing.

The hole you can see in the ADM adaptor photo is where you would bolt the tube guide ring to. On the ADM website you can see other gadgets they sell to do exactly that.

I have attached some pics of my C8 taken when I was making the upper dovetail mounts, so it's just perched there in the photo. The bottom shows the ADM Losmandy-style dovetals and the Side by side (a Skywatcher BD ED100 is on the RHS mount.) I love toys.....

I'd be happy to send you some more detaild photos tomorrow if you wish to pursue this further.

[RPW]

Thanks Mike - terrific photo's - I know now what you mean.

Yes - you are correct - the dovetail bar is bolted into the bottom of the OTA. There are no holes on top where I could otherwise simulate your solution to the problem. This brings me back to square #1 unless you (or anybody else) has another option in their bag of tricks.

Perhaps the side-by-side mounting system is my only option???

Rod

[mldee]

Coming up with a bracket solution using two tube rings, or clamping a top dovetail, would be simpler and probably much cheaper than a side by side just for a guide scope. (I used a small SW 70x500 refractor). The side by side would also be slightly tougher to align, My SBS C8 & SW ED100 don't see quite eye to eye, although not enough to worry me.

I had earlier tried some 8" rings around my C8 with some rubber packing to fill the gap. Wasn't very successful, and left some really ugly rubber marks on the OTA as you can see:mad2:

Since it was an inexpensive 2nd hand C8 and I don't intend to sell it any time soon, no big deal. I wonder what dissolves rubber marks but won't damage paint? :P

Good luck.

[RPW]

Thanks again Mike - will have to put on the thinking cap for this problem.

You might try eucalyptus oil on the rubber marks - just a very small amount lightly applied for a start just to make sure no damage otherwise.

Hope you were out tonight - terrific views of Jupiter.

Rod

[mldee]

Thanks for the eucalyptus oil tip, I'll try it.

Not much chance of seeing Jupiter here last night, rained until 11.30pm.

Cheers