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Equipment Discussions >> Mounts

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user8881
member


Reged: 06/27/07

Can you attach a dobsonian newt ota to a gem?
      #4482337 - 03/29/11 02:09 PM

For example, could I put my Orion XT10 classic on a Meade LX75 or equivelant mount? I don't see why not, it meets the weight requirement, but I don't know if there is something different in how a newt is constructed when it's made for a dob mount or a gem that would make incompatable. I really enjoy mt XT10 but I can help but wish for tracking.

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Doug76
Long Achro Junkie
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Reged: 12/05/07

Loc: Refractor Heaven
Re: Can you attach a dobsonian newt ota to a gem? new [Re: user8881]
      #4482379 - 03/29/11 02:28 PM

You can indeed, but that particular scope is too much for that mount to handle.
IMO you'd need at least an Atlas/CGEM sized mount to do that scope justice.
It isn't all about weight rating, the length of the scope plays into it too.


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JadeSmith
scholastic sledgehammer
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Reged: 07/15/08

Loc: SE Michigan
Re: Can you attach a dobsonian newt ota to a gem? new [Re: Doug76]
      #4482572 - 03/29/11 03:36 PM

I wouldn't put my Z10 on my CGEM. No way.
It might be able to handle it, but still...


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Magellan
Pooh-Bah


Reged: 01/26/06

Loc: Enfield, NS Canada
Re: Can you attach a dobsonian newt ota to a gem? new [Re: JadeSmith]
      #4482786 - 03/29/11 05:08 PM

Yeah thats a heavy scope, I wouldn't put it on my CGEM either.

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Eddgie
Postmaster
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Reged: 02/01/06

Re: Can you attach a dobsonian newt ota to a gem? new [Re: user8881]
      #4483117 - 03/29/11 07:39 PM

Remember that you also need to incude the weight of the tube rings and the dovetail.

A agree with everyone else that it is a lot of weight for an LXD-75.

The other issue is that when GEM mounted, the eyepiece of a Newtonian can get in some odd positions. To counteract this, you should get some kind of rotating system for the tube. You can buy rotating rings (very expensive, but work beautifully) or you can modify the tube with rollers so that it can move in regular rings.

The advantage of tracking is very real, and if that is what you are after, I encourage you to persue it, but I recommend a beefier mount.

If you ONLY need tracking (and not go-to or setting circles), you can use a Poncet table. Expensive to buy, but people build their own too.


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Mirzam
Post Laureate
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Reged: 04/01/08

Loc: Lovettsville, VA
Re: Can you attach a dobsonian newt ota to a gem? new [Re: Eddgie]
      #4483134 - 03/29/11 07:49 PM

The other important consideration is the mirror cell. In all likelihood the XT10 uses a mirror cell with clips to hold the mirror at any orientation. However, many dobs use slings to support the mirror in which case the supports only work for altitude movements in a single plane (i.e. straight up and down). You could not mount such an OTA on a GEm without modification.

JimC


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mclewis1
Thread Killer
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Reged: 02/25/06

Loc: New Brunswick, Canada
Re: Can you attach a dobsonian newt ota to a gem? new [Re: Mirzam]
      #4483322 - 03/29/11 09:38 PM

If you look back (20+ years) to when vendors regularly put big newtonians on gems you'll notice a few things ...

1) They were just about always on piers not tripods. The piers usually had wheels and leveling bolts.

2) The gems used were generally quite a bit heavier than the mounts like LXD75s or CGEMs, even the "lightweight" models had 1" shafts. Most regular weight gems for 8" and larger scopes had 1.25-1.5" shafts, this is CGE to CGEPro class of mount.


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Arbacia
Pooh-Bah
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Reged: 04/18/07

Loc: Madrid, Spain
Re: Can you attach a dobsonian newt ota to a gem? new [Re: mclewis1]
      #4483332 - 03/29/11 09:44 PM

A friend is using a 12" Newtonian on a EQ6. He is very proud.

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KWB
Postmaster
*****

Reged: 09/30/06

Loc: Westminster,Co Elev.5400 feet
Re: Can you attach a dobsonian newt ota to a gem? new [Re: user8881]
      #4483360 - 03/29/11 10:05 PM

Quote:

For example, could I put my Orion XT10 classic on a Meade LX75 or equivelant mount? I don't see why not, it meets the weight requirement, but I don't know if there is something different in how a newt is constructed when it's made for a dob mount or a gem that would make incompatable. I really enjoy mt XT10 but I can help but wish for tracking.



Hi

The XT10 OTA combined with this Meade mount will flunk your test in short order and will not pass muster. If you want a tracking Dob,other possibilities/tracking platforms exist other than using a mammoth sized GEM,and that is what you need if using a GEM.

Choose wisely.


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Doug76
Long Achro Junkie
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Reged: 12/05/07

Loc: Refractor Heaven
Re: Can you attach a dobsonian newt ota to a gem? new [Re: Arbacia]
      #4483378 - 03/29/11 10:14 PM

Quote:

A friend is using a 12" Newtonian on a EQ6. He is very proud.




I bet he is!

It's doable, but I bet it's shaky. With a 12" it's not only the weight but the length taxing an EQ6.
With a 10", you are within the weight limit of an EQ6/Atlas/CGEM class mount, but the length will give you fits.


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avarakin
Carpal Tunnel
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Reged: 07/13/09

Loc: Parsippany NJ, USA
Re: Can you attach a dobsonian newt ota to a gem? new [Re: Doug76]
      #4483603 - 03/30/11 12:40 AM

At some point I mounted my Antares 40lb 10" dob OTA on LXD75 and it worked without much trouble. The reasons why I am not using this configuration anymore:
1. the whole setup is very heavy, there is no way to pick it up and carry few feet as possible with the dob
2. I have to stand while observing, where as with dob I can seat for all altitudes
3. setting up and breaking up takes more time with GEM
4. some tube rotation method is reguired
5. not clear if overload may cause system failure in future

So in the end I just went back to dob and so far not looking back. One day I may build tracking platform.

Alex


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Skylook123
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Reged: 04/30/05

Loc: Tucson, AZ
Re: Can you attach a dobsonian newt ota to a gem? new [Re: avarakin]
      #4483634 - 03/30/11 01:14 AM

You could deal with the eyepiece rotation cheaply with Wilcox rings, but the balance in DEC will be a real stresser on larger newts. The balance point is back near the mirror, so that eyepiece end will be way out there, as mentioned already.

The biggest mass produced item I can recall seeing was the 16" Meade Starfinder Equatorial, but the mount was made to set lower than you can get with a CGEM or EQ6 tripod; there are reasons that these setups with newtonians are so rare, and SCTs fill the bill. Chasing the ol' eyepiece is an acquired taste.

Easier to mount the dob on an equatorial platform.


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eric_zeiner
Phoenix's Dad
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Reged: 12/09/06

Loc: Georgia USA 34 31'57.18N 83 53...
Re: Can you attach a dobsonian newt ota to a gem? new [Re: Skylook123]
      #4483719 - 03/30/11 03:10 AM

If you have not experienced an under mounted scope, it is not pretty and can be rather frustrating. It will even get to the point where the mount/scope combo will set up its own harmonics and never stop shaking. Even though there are some mass produced 10"rs that are on a CG5 type mount, it has got to be a hot mess.

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idealistic
scholastic sledgehammer
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Reged: 12/31/10

Loc: massachusetts
Re: Can you attach a dobsonian newt ota to a gem? new [Re: eric_zeiner]
      #4484373 - 03/30/11 11:39 AM

I use an 8 inch newt on a GEM, the trick is balance.
Spend the time to get everything balanced, and mark the ideal spot on the dovetail, and the ideal orientation of the OTA in the rings and youll be fine. When mine is perfectly balanced the eyepiece is almost straight up in the air in the "home" position, but when do you observe in that orientation anyway? Certain situations require you to rotate the tube in the rings, but not as often as you might think.

My only issue is rarely being able to sit down, which may be a problem for some.


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user8881
member


Reged: 06/27/07

Re: Can you attach a dobsonian newt ota to a gem? new [Re: idealistic]
      #4484792 - 03/30/11 02:55 PM

Thanks for all the info, I guess I'll abandon my dream of having a big newt on a gem. I remember a while ago companies like Meade offered big newts on gems, up to 16" iirc. Now I see why they are no longer made. I'll probably look into an Orion xx14g when I'm ready for a bigger scope since it has a tracking mount. I don't care about goto or AP, but I love my high power views of planetary nebulas, globulars etc making tracking desireable.

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Cotts
Just Wondering
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Reged: 10/10/05

Loc: Toronto, Ontario
Re: Can you attach a dobsonian newt ota to a gem? new [Re: user8881]
      #4485867 - 03/31/11 12:17 AM


I had a 10" Lightbridge + Parallax rings on an EQ6 and, later, a G11 with no problems. Careful balance is vital, though.

The cell on the Lightbridge is ideal for this because it supports the mirror all around the circumference. Any dob with a sling won't work at all, as was said upthread...

Dave


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Asimov
Post Laureate
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Reged: 05/11/10

Re: Can you attach a dobsonian newt ota to a gem? new [Re: Cotts]
      #4488354 - 04/01/11 01:01 AM Attachment (39 downloads)

I think it depends on the circumstances. About a month ago I purchased the SW collapsible 14" with Synscan GOTO. The OTA weighs in at exactly 25KG.

I bought this in the hope that the tracking was good enough for planet imaging, but it's not. My next recourse was to try mounting the standard SW OTA on my EQ6. I didn't even bother trying that scenerio seeing the EQ6 is rated at between 20-25KG.

Anyway the end result was to see me making a light weight OTA for the 14" optics to mount on the EQ6. Total weight of the OTA is just over 14KG & the EQ6 holds it easily & tracks nicely. As for lever arm action due to OTA length: Not a concern for me as it'll be going in an observatory.

Since taking this photo a couple of weeks ago, I have taken out 8 or so inches off the height of that portable pier.


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SPACEMAN
sage


Reged: 01/30/05

Loc: grömme,Belgium
Re: Can you attach a dobsonian newt ota to a gem? new [Re: Asimov]
      #4488486 - 04/01/11 03:36 AM

Indeed if you place the telescope on a EQ6 mount, normally it will hold. a EQ6 can be very strong. But LX75 no.....

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hottr6
Carpal Tunnel
*****

Reged: 06/28/09

Loc: 7,500', Magdalena Mtns, NM
Re: Can you attach a dobsonian newt ota to a gem? new [Re: SPACEMAN]
      #4490032 - 04/01/11 06:51 PM Attachment (33 downloads)

I started with a used Byers 812 GEM, picked up an el-cheapo Meade Starfinder OTA and with some Parallax Rings, I was up and running. The Byers is definitely underwhelmed by this OTA.

"Chasing the eyepiece" is problematic. I did rig up some "rotating rings" that still require me to unlatch the Parallax' to rotate the OTA. No biggy; it's habit now.

I'm contemplating purchasing some 16-18" optics and building my own OTA for the Byers. That is a big step and may overwhelm my highly modified ScopeBuggy, in which case a more permananent solution would be required. Mo' $$$$.

Nevertheless, it is a great feeling to walk away from an object and return many minutes later to find the object still perfectly centered in the FOV.


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Asimov
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Reged: 05/11/10

Re: Can you attach a dobsonian newt ota to a gem? new [Re: hottr6]
      #4490544 - 04/02/11 12:23 AM

Nice work there. Yes the Byers could stand a way bigger OTA than that.

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