Jump to content


Photo

T-Rex Heavy Duty Alt / Az Mount

  • Please log in to reply
20 replies to this topic

#1 Olivier Biot

Olivier Biot

    Amused

  • *****
  • Posts: 24946
  • Joined: 25 Apr 2005
  • Loc: 51°N (Belgium)

Posted 14 February 2011 - 05:33 PM

T-Rex Heavy Duty Alt / Az Mount

By Peter J Hexter.

#2 skybsd

skybsd

    Skylab

  • *****
  • Posts: 4281
  • Joined: 01 Feb 2008

Posted 14 February 2011 - 06:45 PM

Nice article, Peter..,

Reads like a good old fashioned, honest impression of the gear.

I like the fact that you took the time and opportunity to have it side-by-side with a DM6 - much appreciated!

Regards,

skybsd

#3 7331Peg

7331Peg

    Sirius Observer

  • *****
  • Posts: 1930
  • Joined: 31 Aug 2008
  • Loc: North coast of Oregon

Posted 14 February 2011 - 07:25 PM

Great review, Peter.

I have two of these things now, so you can pretty much guess what I think of the T-Rex.

I've had both a Meade AR-6 and a Meade AR-5 on the mount at different times (each with a 60mm scope attached to it), a C9.25, several smaller scopes, and even a 60mm f16.7 by itself. My favorite combination of scopes on it is an Antares 105mm f14.3 with a 60mm f16.7 riding on the back of it. Moving around the sky with a well-balanced long refractor tube on one of these mounts is a real pleasure.

I've got one of the T-Rex mounts on a Stellarvue wooden tripod that used to carry their M7 mount, and the other is on a Losmandy G11 heavy duty tripod with two pier extensions attached for use with the long Antares scope. Both setups are as solid as a rock.

The ultimate compliment any mount can be paid is to say it gets out the way while you're observing because you simply forget about it -- and that's exactly what happens with this one.


John :refractor:

#4 Doug Reilly

Doug Reilly

    Viking 1

  • *****
  • Posts: 670
  • Joined: 29 Jul 2008

Posted 14 February 2011 - 09:43 PM

With the larger OTAs like the newt or the SCT, did the tube width restrict altitude motion, could they all reach zenith?

#5 Waxing Gibbous

Waxing Gibbous

    Viking 1

  • -----
  • Posts: 541
  • Joined: 19 Nov 2010
  • Loc: Victoria, Australia

Posted 14 February 2011 - 10:55 PM

With the larger OTAs like the newt or the SCT, did the tube width restrict altitude motion, could they all reach zenith?


The SCT reached zenith with no trouble.
The 8" f5 Newt fully loaded (w 72mm WO, 31mm Nagler and SV60 finder), needed to be shuffled a bit and the tripod legs bought in a little.
Fortunately there are a fair number of extension piers that fit the mount (its basically a Synta/Orion base) that will allow complete clearance of a longer, thicker OTA.
Despite not having a terribly big scope, I've ordered one anyway as I find the mass of the (lowered) tripod very useful in balancing a heavy tube - especially with the wind here!
Clear Skies,
Peter

#6 7331Peg

7331Peg

    Sirius Observer

  • *****
  • Posts: 1930
  • Joined: 31 Aug 2008
  • Loc: North coast of Oregon

Posted 15 February 2011 - 12:05 AM

Yep, my experience, too, with the C9.25. There's nothing about the construction of the mount that will limit viewing at the zenith. Of course, your tripod might (although not likely with an SCT), but the extension or a pier type of tripod will cure that.

I had a DM-6 and loved it. But I used to really struggle with that thing when viewing directly overhead. It works for that kind of viewing, but it can be kind of a wrestling match at times, especially with a short-tubed scope like an SCT. It's much, much easier to do that kind of viewing with the T-Rex.

........ although it can still leave you with a pain in the neck.


John :refractor:

#7 mike174

mike174

    Viking 1

  • -----
  • Posts: 794
  • Joined: 04 Jan 2005
  • Loc: Central, NJ

Posted 18 February 2011 - 08:47 PM

How will it handle a Mewlon 250?

Mike

#8 Waxing Gibbous

Waxing Gibbous

    Viking 1

  • -----
  • Posts: 541
  • Joined: 19 Nov 2010
  • Loc: Victoria, Australia

Posted 18 February 2011 - 10:03 PM

How will it handle a Mewlon 250?

Mike


Hmmmn?
Good question Mike.
It handled an M210 like it wasn't there, but that's not a particularly heavy scope.
I used the standard, back-heavy configuration to mount it which seemed to have no adverse effect.
I would think that it would handle an M250 well. If memory serves they have a counterweight system that can be adjusted to balance the tube?
At around 13kgs the 250 is well whithin the ballpark weight limit so I think if you can adjust the scopes centre of gravity (or moment or whatever its called this year)
it would be fine.
Just as a BTW, and because I was bored, I filled an 8" ID / 30' long bit of aggy pipe with 20kg of sand, mounted it and was able to move it about with little difficulty.
I had to tighten up the tension levers to almost full, and I couldn't push/pull steadily, but the slo-mo controls worked just fine.
Hope that helps!
Peter

#9 Tamiji Homma

Tamiji Homma

    Gemini

  • *****
  • Posts: 3115
  • Joined: 24 Feb 2007
  • Loc: California, USA

Posted 19 February 2011 - 07:18 PM

How will it handle a Mewlon 250?

Mike


Hi Mike,

I've use Vixen VMC260L on T-REX. I think other people use C11 on it. So I think Mewlon 250 should be OK.
Posted Image

I use Intes-Micro MN-86 (8" f/6 MakNewt) on T-REX. The scope setup is about 40lb. With good tripod, it is indeed rock solid.
Posted Image

As you can see, the flexible cable is too short for MN-86.
Barry@Kokusai Kohki is working on longer slow motion control flexible cable.

PS: Peter, nice review :)

Tammy

#10 SteveLD

SteveLD

    Lift Off

  • -----
  • Posts: 9
  • Joined: 31 Jul 2008

Posted 19 March 2011 - 08:03 AM

I have a TEC-140 that I want to use with the mount. I also own a Planewave 12.5" which weighs around 48 pounds that ideally I would also like to use with the mount. I know, that exceeds the recommended carrying capacity. Does anyone know have a sense whether T Rex or DM6 would support this load better?

#11 SteveLD

SteveLD

    Lift Off

  • -----
  • Posts: 9
  • Joined: 31 Jul 2008

Posted 22 March 2011 - 06:09 PM

As I understand it there is a counterweight option with the DM6 that makes it possible for people to use this mount with a C-14 or a Planewave 12.5. Does any such option exist for the T-Rex or can it handle scopes such as these without counterweights?

#12 Waxing Gibbous

Waxing Gibbous

    Viking 1

  • -----
  • Posts: 541
  • Joined: 19 Nov 2010
  • Loc: Victoria, Australia

Posted 23 March 2011 - 12:04 AM

Steve,
I think a Planewave would be a bit beyond its capacity.
I've had 20kgs (about 4lbs less than your Planewave) on it, but 'free' movement was definately affected as I had to tension the bolts to nearly full lock.
There is, AFAIK, no counterweight system for the T-Rex and I'm not sure if the c-w system on the DM6 actually increases carrying capacity or just helps balance a heavy load.
Pete

#13 SteveLD

SteveLD

    Lift Off

  • -----
  • Posts: 9
  • Joined: 31 Jul 2008

Posted 23 March 2011 - 11:12 AM

Pete,

Thanks for the information about your experience with your 20 kg scope and the T Rex. Tammy Homma's comments about his 44 lb MN 86 scope and the T Rex suggests that that combination is "rock solid" though no two scopes have the same geometry. The Planewave weighs 2-3 pounds more, but does not require as much mounting hardware (no rings needed) so the weight has to be fairly close. Also, the tube length of the Planewave is only 31" vs. 46" for the MN86 which may make it easier to handle in that respect. The only thing I can thing of going against the Planewave vs the MN86 is the larger diameter optical tube which puts it's center of gravity 2-3 inches further away from the center of the tripod.

Supposedly, there are folks who use C-14's with the DM6 + counterweights. As I understand it, the weights not only help balance the load across the tripod, but in doing this, weight gets distributed more evenly across the bearings which makes them more functional with higher loads. Of course, the fact that some people do this doesn't say anything about how well it works in practice.

The only option I can think of that is specifically designed for heavy loads like a Planewave 12.5 and more is APM's maxload alt ax mount. Unfortunately, they do not appear to offer a DSC option. I suppose there might be some way to install encoders. Anyway, thanks for the feedback.

Steve

#14 SteveLD

SteveLD

    Lift Off

  • -----
  • Posts: 9
  • Joined: 31 Jul 2008

Posted 24 March 2011 - 10:33 PM

I emailed Barry Gooley regading his recommendations concerning using C14/Planewave 12.5 class scopes with the T Rex. He corroborated what some of you have already said in that he would not recommend it. He said C-11 is the limit. He said some folks will say "no problem" when it comes to mounting such big scopes on the T Rex, but added that he doesn't agree. He also included photos showing examples of people loading huge scopes on the T Rex including people who have added counterweights and shafts to help do this. I would post these here if I knew how. My impression is a counterweight system or other options for heavier scopes may be in T Rex's future as Barry gets lots of inquiries like this.

I also contacted Tom Peters at DM6 who said there is a counterweight option for that mount, but he does not publicize this on his web site because he does not want people to think that it is needed it for scopes up to C-11 or TEC-180 size. He said there are a few C-14 owners who use them. The counterweights are supposed to make the DM6 serviceable with this kind of load as it evens weight distribtuion across the bearings.

The heavyweight king among portable alt az mounts appears to be the APM Maxload which is supposedly capable of handling loads of 120 pounds without difficulty.

#15 fredjone

fredjone

    Lift Off

  • -----
  • Posts: 2
  • Joined: 19 Nov 2010

Posted 05 April 2011 - 07:30 PM

I've had the T-Rex for a couple of months now and my impression of it was very good until last weekend when I took it out to a dark site where the conditions presented 25mph gusts of wind. In this scenario the image was flopping all over the place to the point where I finally packed it up. Has anybody else had this experience in windy conditions? Additional info: I'm using this with Stellarvue's TSL7M Pier Tripod and a Takahashi TSA-120.

I've fine-tuned the gears a couple of times because initially when I got the mount, when utilizing the slo-mo controls they were too tight causing stiction, which in turn caused the scope to vibrate with every little minute adjustment of the controls. After adjusting the gears I was able to eliminate the stiction so everything moved nicely, but this was at the cost of creating slight back-lash on the azimuth which is where I think the movement is coming from in windy conditions. I suppose it may come from the Stellarvue tripod, as such I may have to try it on another tripod to rule out that variable. Does anybody else have slight azimuth back-lash that doesn't cause them problems in windy conditions? If so, maybe I need to rule that out as the problem. I'm just trying to figure out where the weak link is and if I can fix it.

#16 Waxing Gibbous

Waxing Gibbous

    Viking 1

  • -----
  • Posts: 541
  • Joined: 19 Nov 2010
  • Loc: Victoria, Australia

Posted 05 April 2011 - 10:31 PM

Hi Fredjone,
The only time I get vibration is when I've mis-balanced the tube. I am using the EQ6/Atlas Tripod and its very solid and effectively wind-proof. As a result I've been able to view succesfully in winds up to 35mph. Trying a heavier tpod might indeed work.
What I have noticed is that the mount responds more easily with a heavier scope. It will move my TOA130 with all the trimmings much more smoothly than it does my AT106.
However it is not as "stictiony" (I can't call it [i]stiff[/i} exactly :) )as when I first got it. I'm not very good at fiddling with things, so I've left mine stock, but I suspect some fine tuning might just ease it up.
Peter

#17 7331Peg

7331Peg

    Sirius Observer

  • *****
  • Posts: 1930
  • Joined: 31 Aug 2008
  • Loc: North coast of Oregon

Posted 05 April 2011 - 11:48 PM

I have a T-Rex mounted on the same Stellarvue tripod you've got. I normally use a Meade AR-5 on it, which has a 13 inch long Losmandy style dovetail, a Moonlite focuser, and a 60/800 refractor added to it - so there is plenty of weight on it. Mine is just as smooth as can be in azimuth, and provided the balance is reasonably close, also smooth on the vertical axis. And it's very stable in 20 to 30mph gusts of wind.

So the tripod is not the issue (shouldn't be, anyway), and you should have more than enough weight with the TSA-120 on it.

There are two things that you might check. The first one is to make sure the T-Rex mount head is very tightly in place on the tripod pier. When I put the mount on the pier, at the point where the head stops turning on the stud, I loosen it a bit, and then give it a good, strong twist to make sure it's really tightly in place. Grab hold of the bottom half of the mount head (the part that doesn't turn when the azimuth clutch is loose) when you do that. And I check that periodically, too, to make sure it hasn't become loose.

The other is to check your azimuth clutch and make sure it's locked down tight when the wind is blowing. I normally leave mine loose and move the scope in azimuth by hand. But if it's windy, I'll get a lot of motion also unless I lock the clutch down tight. There are instructions with the mount on adjusting the tension of the clutches, so you might check that, too.

Hope one of those two things helps.


John :refractor:

#18 fredjone

fredjone

    Lift Off

  • -----
  • Posts: 2
  • Joined: 19 Nov 2010

Posted 07 April 2011 - 01:03 AM

Thanks for the replies. 7331Peg, next time I'll definitely try your advice on locking down the clutch. I, like you normally leave them loose enough (not overly loose) to slew the scope around for big movements. Do either of you have any back-lash in your gears? I only ask, because maybe I over loosened them.

#19 7331Peg

7331Peg

    Sirius Observer

  • *****
  • Posts: 1930
  • Joined: 31 Aug 2008
  • Loc: North coast of Oregon

Posted 07 April 2011 - 12:44 PM

Fred,
There is just a bit of backlash in the vertical movement of one of the two T-Rex mounts I've got - none in the horizontal movement on either mount, though.

Might try sending a message to Barry at T-Rex, also. He's very responsive, and since he designed the mount, he knows it better than anyone else.


John :refractor:

#20 APM M.Ludes

APM M.Ludes

    Vendor (APM Telescopes)

  • *****
  • Vendors
  • Posts: 1410
  • Joined: 01 May 2003
  • Loc: Germany

Posted 26 April 2011 - 03:45 PM

I am a new proud owner of the T-Rex for my own use and its a pleasure to be a member of the club of owners of the T-Rex.
A friend of mine have had the idea to install a Synscan Goto and after Barry gave me all details we checked what we need and it seems to be not difficult.Is this something other owners would be interested too ? If a few kids could be made, it may cut down a bit the cost

enjoy your T-Rex

#21 Stellarfire

Stellarfire

    Apollo

  • -----
  • Posts: 1303
  • Joined: 10 Jul 2011
  • Loc: Switzerland

Posted 31 October 2011 - 10:46 AM

The T-Rex is an outstanding and beautifully made alt/az mount. A larger version would be great and I e-mailed Barry Gooley to think about a larger T-Rex II, supporting load capacities in the 20kg+ / 45lbs+ range.

Stephan






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics