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Attention all Star Max 90 Owners

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#26 CollinofAlabama



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Posted 15 July 2013 - 02:18 AM

Googled "dovetail saddle for vixen Ploaris" and found this ...

ADM adapter

Found my post on this matter from 2007 here.

Looks like what you need. Call UA or ADM and ask. Oh, you'll need a vixen dovetail for your C80ED. Of course, the Orion Maks all come with one already attached, so you won't even need tube rings to attach one of them to your mount if you had a saddle installed.

I'm back in the saddle again. Out where a friend is a friend.

#27 spencerj



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Posted 15 July 2013 - 10:15 AM

Problem is, like other folded catadioptric designs, the MCT uses fast mirrors to achieve a system focal ratio of f/13. Collimation criticality depends on the speed of the mirrors, not the final system in such a scope. These MCTs are every bit as dependent on perfect collimation for best results as an SCT I suspect (most of which have f/2(!) primaries; collimating an SCT is akin to collimating an f/2 Newtonian).



I agree with Jim. I have owned a number of MCT's over the years: 90mm Apex, 127mm Apex, M503, MK66, M703. They ranged from F10 to F13 and the sweet-spot for collimation is a lot smaller than a half inch.

That is a huge target and if true, these scope would never be that far out. In my experience, very small collimation changes (1/8 turn of a screw) in these scopes make a big difference at the eyepiece. In a properly collimation MCT the images are very sharp, in a slightly miscollimatied scope, the images are soft.

I have had to collimate every one of my MCT's. Usually once set, it holds very well but it cannot be ignored. Collimation is not that difficult, but it needs to be done from time to time.

#28 pdxmoon



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Posted 15 July 2013 - 10:16 AM

Thank you Collin!

#29 jrbarnett


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Posted 15 July 2013 - 04:53 PM

Google for images of an SCT or MCT on the Vixen Porta II. What do you find? Not much.

Why? Ergonomics.

The Vixen is a uni-directional alt-az mount. The front of your scope *must* face in the opposite direction of the sweep of the fork arm.

Depending on where the dovetail is mounted relative to the orientation of the focuser knob, it can put the focuser in awkward places, such as pinched between the side of the diagonal and jaws of the mount saddle or above the diagonal at 12 o'clock such that the eyepiece gets in the way of focusing.

I've seen some folks rig L-brackets to allow the SCT/MCT to be mounted dovetail-down to preserve ergonomics, but that means more bits and pieces and more tinkering.

Another alternative if you end up with bad focuser placement would be to move the dovetail 90 degrees in one direction, assuming there are tappings that allow that or you don't mind drilling new tappings into your baby.

If you can rig it ergonomically though, the Port II should be able to carry that OTA.




#30 orion61


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Posted 15 July 2013 - 05:15 PM

I had one for 3 years never had to touch it.
I have an ETX Astro that I have had since they came out.
I finally sold the Orion 90. The ETX was a tad better,
The Starmax lacked a bit of contrast compaired.
But you can drop them off a Mountain, and unlike Hank Williams Jr. have no need to align them. I'm sorry Hank....

#31 rocketsteve


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Posted 21 July 2013 - 11:42 AM

I've owned a StarMax 90 since 2004 and have never needed to collimate it. I even brought my mak to the Grand Canyon when I took my family on vacation in 2005. It was one of my carry-on items, so it went through TSA scanning and inspection, jostling in and out of the overhead compartments, and it was perfectly fine after returning home. Even though the scope is small, it's quite robust in it's construction. It's my primary telescope when doing planetary observing.

Dropping the telescope, onto a hard surface, is probably the only thing that would wreck your collimation...

Hey Steve, what mount do you have your 90 on?

Sorry it took so long to reply...

It's your standard, run-of-the-mill EQ-1 mount with an EQ-1M tracking motor attached to it. I replaced the slow-motion control cables with radio tuning knobs that I bought from Radio Shack. They work really well and don't get hung up on the mount when the telescope rotates to the zenith. Instead of using the battery pack, that came with the tracking motor, I set it up so I could use a 6-volt, 12 amp-hour, SLA battery. The battery provides enough power to run the drive for at least two nights of observing, which comes in handy at weekend-long star parties. Also, the battery has some weight to it, so vibrations are dampened.

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