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alt az for 8" f/5 reflector?

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#1 pmckeogh

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Posted 10 January 2013 - 11:18 AM

I have an Antares 200mm f/5 reflector which I love but the eq-5 it came with is not my favorite. The mount itself works well and is very stable but I hate how the eyepiece always ends up in an awkward position.

Can anyone recomend a stable alt az mount for this size of telescope that is just as stable, and maybe slow motion controls? I'm considering the unistar but was wondering if anyone had experience with other mounts. No motorized mounts please, I dont want to deal with them freezing in cold weather.

Thanks for the help.

#2 314Sprout

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Posted 10 January 2013 - 10:17 PM

I use a Desert Sky Astro DSV-1 atop an Oberwerk wooden surveyor tripod to mount my 150MM F/5 Newt and an AT-72 or C90 at the same time. It is very solid set up and I couldn't be happier. Raul Medina (owner / builder) has a very solid reputation here in these fora as well. There is another discussion active in this forum 'Ordered my new Alt / Az mounts" (yes plural) discussing the merits of the entire line.

#3 pmckeogh

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Posted 12 January 2013 - 11:08 AM

I contacted Desert sky but Raul said he does not recomend the dsv-2 for an 8" but the DSV-3 would do the job. Problem is DSV-3 is too expensive right now so I'm looking for something else.

Thanks

#4 Pat at home

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Posted 13 January 2013 - 11:27 AM

The Duo-T (same as Skywatcher SkyTee-II) is not cheap at $300 without a tripod but you do get a lot of mount for the money. It holds my 8 inch newtonian without any problems. I found it easier to reach the slow motion knobs with the ep oriented to the inside. The suitability is of course dependant on the rigidity if the tripod.

Another option is the venerable DIY dobson mount.

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#5 Eric63

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Posted 13 January 2013 - 04:38 PM

This is just a thought. Can the EQ5 not be converted to alt-az mode? This is what I did with my EQ3 and 150mm f5 newt.

Eric

#6 Gray

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Posted 13 January 2013 - 09:44 PM

You could make some Wilcox rotating rings for cheaper. Heres a link....
http://www.andysshot...ting_rings.html

#7 Cotts

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Posted 13 January 2013 - 09:55 PM

Discmount DM6. Holds C11's, TEC 180 refractor nicely. Pro tip. Avoid their wooden tripod. Get a Losmandy Hd on the used market - much more stable.

Dave

#8 Jon Isaacs

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Posted 13 January 2013 - 10:26 PM

The obvious solution is a Dob mount...

This was discussed in a duplicate thread in the reflectors forum.

Alt-Az mount for an 8 inch F/5

The scope is a little short for an Dob mount but the base can be easily raised.

I have an 8 inch F/5, I tried it on my Stellar-Vue MG-2, it was OK but it was awkward reaching around the tube to use the slow-motion controls.

Jon

#9 opticsguy

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Posted 13 January 2013 - 11:51 PM

Sorry guys but I am not familiar with these secret codes;
Duo-T
EQ5
DM6
Help please??

#10 izar187

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Posted 14 January 2013 - 12:58 AM

The obvious solution is a Dob mount...

This was discussed in a duplicate thread in the reflectors forum.

Alt-Az mount for an 8 inch F/5

The scope is a little short for an Dob mount but the base can be easily raised.

I have an 8 inch F/5, I tried it on my Stellar-Vue MG-2, it was OK but it was awkward reaching around the tube to use the slow-motion controls.

Jon



A dob mounting that is raised via legs or a taller rocker box is a darn good solution.
But not if someone wants slow motion controls. Or does not want the rocker box mount.
All possible options are a set of compromises.

#11 izar187

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Posted 14 January 2013 - 01:01 AM

Sorry guys but I am not familiar with these secret codes;
Duo-T
EQ5
DM6
Help please??


I often google the codes that I don't grok. : D

#12 Jon Isaacs

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Posted 14 January 2013 - 06:48 AM

A dob mounting that is raised via legs or a taller rocker box is a darn good solution.
But not if someone wants slow motion controls. Or does not want the rocker box mount.
All possible options are a set of compromises.



All true.

In my experience, using my 8 inch F/5 on StellarVue MG-2, because of the short tube, I had to stand on the side away from the mount and reaching the slow motion controls was awkward, I had to reach around the tube. It is certainly easier to make a rocker box mount stable than a tripod and balance is easier, no one sided mountings.

I have often wondered how one would go about designing slow motion controls for a Dob.

My thinking:

Any alt-az mount that is sufficiently stable to handle an 8 inch F/5 Newtonian at higher magnifications will cost more than an entire 8 inch F/6 Dob. Just buy the Dob and be done with it.

Jon

#13 Cotts

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Posted 14 January 2013 - 07:11 AM

With respect to the DM6, check here.

A bit pricey but it is the best one out there.

Dave

#14 izar187

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Posted 14 January 2013 - 11:10 AM

A dob mounting that is raised via legs or a taller rocker box is a darn good solution.
But not if someone wants slow motion controls. Or does not want the rocker box mount.
All possible options are a set of compromises.



All true.

In my experience, using my 8 inch F/5 on StellarVue MG-2, because of the short tube, I had to stand on the side away from the mount and reaching the slow motion controls was awkward, I had to reach around the tube. It is certainly easier to make a rocker box mount stable than a tripod and balance is easier, no one sided mountings.

I have often wondered how one would go about designing slow motion controls for a Dob.

My thinking:

Any alt-az mount that is sufficiently stable to handle an 8 inch F/5 Newtonian at higher magnifications will cost more than an entire 8 inch F/6 Dob. Just buy the Dob and be done with it.

Jon



Well, no.
Just built a dob mount instead, without the goofy oversized base board.
If one is willing to pass on the slow mo controls, and already has an ota.
But better still, build a pipe mount. Then you get to use it under more than one scope.

#15 Phillip Creed

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Posted 14 January 2013 - 11:30 AM

I have an Orion 8" f/4.9 OTA I put on a Unistar mount with a Universal Astronomics Heavy-Duty Wooden Surveyor's Tripod. Works like a charm. Very easy to set-up, stable well beyond 200X, reasonably priced, and very easy on the back with the right observing chair.

I have a 12"-dob I now rarely use. The 8" f/4.9 combo is simply a joy to use. I can leave the set-up fully assembled in the garage and carry it out by hand for casual observing. Once the set-up is assembled at an observing site, it's easy to move it if you're trying to find an object that's skirting the tree-line.

It's like a "grab n' go", only one with some serious bite under dark skies. The fact it's an 8" f/5 vs. an 8" f/6 means it maintains some of the wide-angle capabilities reserved for fast 6" achros (you can easily get a 2-1/2 deg FOV out of an 8" f/5 with the right eyepiece), only with none of the false color.

Clear Skies,
Phil

#16 Kfrank

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Posted 14 January 2013 - 11:40 AM

"But better still, build a pipe mount. Then you get to use it under more than one scope. "

The problem with a pipe mount it that it's getting harder and harder to find pipe that does not have tapered threads. I 've tried a couple of pipe mounts with poor results. The tapered threads make it very difficult to get the tension properly adjusted and severely limit the range of motion.

Even with a very light scope (ST80), I found that either the ALT motion was so loose that the scope wouldn't hold position or that it was too tight for smooth operation. The AZ motion was severely limited by the tapered threads as well.

If you could find the straight cut pipe, you might create a decent mount, but even then, an 8" reflector, 40 inches long is a substantial scope and I doubt you'd be happy with it's operation, even on a decent pipe mount.

#17 izar187

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Posted 14 January 2013 - 01:31 PM

"But better still, build a pipe mount. Then you get to use it under more than one scope. "

The problem with a pipe mount it that it's getting harder and harder to find pipe that does not have tapered threads. I 've tried a couple of pipe mounts with poor results. The tapered threads make it very difficult to get the tension properly adjusted and severely limit the range of motion.

Even with a very light scope (ST80), I found that either the ALT motion was so loose that the scope wouldn't hold position or that it was too tight for smooth operation. The AZ motion was severely limited by the tapered threads as well.

If you could find the straight cut pipe, you might create a decent mount, but even then, an 8" reflector, 40 inches long is a substantial scope and I doubt you'd be happy with it's operation, even on a decent pipe mount.


This has not been my experience at all, with three successively larger ones that I've made over time. The last for my 20 lb 8" f/5.
All with tapered threads that were matched for smooth togetherness in the plumbing aisle before I left the store.
I use teflon tape on the threads rather then lapping and oil, and attach the the ota via their tube rings directly to the flange in the top of the mount.
No mounting board or bar. Threaded knobs, chair or table feet allow mounting the tube rings to the flange with no tools assembly.
Tightening or loosening the altitude movements are done by quarter turns on those tapered pipe threads, and/or adding a wrap of the telfon tape.
My choice has been one 90 degree inny/outty elbow only on top. Rather then a tee with counter weight opposite the ota. No 45 degree elbows down below.

#18 Patrick

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Posted 14 January 2013 - 04:38 PM

Duo-T looks nice. I wouldn't mind having something like that for my ES Comet Hunter Mak Newt.

Patrick

#19 Jon Isaacs

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Posted 14 January 2013 - 08:00 PM

Duo-T looks nice. I wouldn't mind having something like that for my ES Comet Hunter Mak Newt.

Patrick


For the Comet Hunter, that just might be the perfect mount. The Duo-T is very similar to the Stellar-Vue MG-2. I would guess both are/were built by the same manufacturer. The MG-2 is a good mount for my NP-101, awkward for the 8 inch F/5, adequate but not as solid as a Dob mount. My solution is to use the 8 inch F/5 on it's CG-5 and if I want an Alt-Az mount I use a Dobsonian...

Jon

#20 pmckeogh

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Posted 18 January 2013 - 06:56 AM

Thanks for the responces.

First, I won't be buying a dob as many suggested, my first scope was an 8" skywatcher dob and it was awful trying to follow anything at high mag. If the the new dobs out there are super smooth and I can try one out a couple nights before buying then maybe... I also lucked out with the scope I have, views thru it are great. I've had it out next to 10" SCT at RASC meeting and my scope offers much cleaner views, better contrast, sharper, I'm reluctant to give it up.

Phil, I'm glad to read the unistar works well, I'm leaning towards it but the DUO-T throws a wrench in that plan.

PAT AT HOME how much do the counterweigths weigh on the duo-t when using the 8"?

#21 Pat at home

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Posted 19 January 2013 - 10:42 AM

PAT AT HOME how much do the counterweigths weigh on the duo-t when using the 8"?


22 lbs in the photo. I tried it with 11 lbs placed at the end of the bar and it did ok. The Duo-T is not super critical of exact balancing in Azimuth.






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