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modification to CGE PRO / CGEM DX tripod

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Posted 13 February 2012 - 10:52 AM

Hi all,

I recently received a CGE PRO which clouds have largely prevented me from using so far. Perhaps the lack of activity has made me look for other things to do while waiting for clear skies. Overall I really like the CGE PRO mount, but there are two things I would have done differently had I been the designer: make the tripod a bit lower and the base of the legs a bit wider. The reason I'm interested in this modification is to make observing a bit more convenient and, more importantly, make the mount a bit more tip resistant. While set up on a very firm surface (like cement) the mount is completely stable, but I have noticed that while setup up on mushy grass or mud (yes, the weather has been that bad) that tipping might be an issue if you weren't paying attention to what you were doing.

My impression is that I may well be able to make both of these improvements by simply modifying the bottom spreader on the tripod and I was wondering if anyone had tried this before.

The bottom spreader has three metal rods connecting the legs to a central attachment point. It looks as if these can come off without too much work and could be replaced by somewhat longer bars which would spread the tripod wider and make the mount overall lower. The accessory tray would then slide up slightly for the second brace with no modification necessary.

Thoughts?

#2 DaveJ

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Posted 13 February 2012 - 11:24 AM

The bottom spreader has three metal rods connecting the legs to a central attachment point. It looks as if these can come off without too much work and could be replaced by somewhat longer bars which would spread the tripod wider and make the mount overall lower. The accessory tray would then slide up slightly for the second brace with no modification necessary.


I've had exactly this same mod in mind for a while - actually, ever since getting the same tripod with my CGEM DX. Perhaps replacing the bars with threaded rod so fine adjustments could be made? You're correct that this can't be that difficult to do.

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Posted 13 February 2012 - 11:41 AM

Out of curiosity, are you interested in the modification more to lower the height of the mount or more to increase stability?

#4 DaveJ

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Posted 13 February 2012 - 12:08 PM

Out of curiosity, are you interested in the modification more to lower the height of the mount or more to increase stability?


To increase stability. I actually raise the mount by extending the bottom legs about 10" or so. I use mine primarily with refractors, hence the preference for the additional height.

#5 Jim Romanski

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Posted 13 February 2012 - 12:24 PM

I have a CGEM DX mount with the same tripod. I bought the DX rather than the CGEM in order to get the better tripod.

I'm using it for refractors and will try some astro photography as well. But I also wanted to use the tripod with my 8" Cave Newtonian.

When I got the tripod I realized that it's very tall and too tall for the newtonian in order to have a convenient eyepiece height.

I wanted to see if the tripod would work with the legs spread out farther so I disconnected the bottom spreader. It's easy to do as you only have to remove a single allen head bolt from each of the three legs. The legs will spread out as far as needed and I can get the height down by about a foot without spreading them out too far. I might cut and drill some aluminum bars to make a new spreader for use when I have the Newtonian mounted or just use wire and run it trough the bolt holes so the legs don't splay out.

As for stability, Mine is quite stable without spreading the legs. But the first thing I did with mine is to rotate the mount so as to move the counterweight over a leg instead of between two of them. Celestron sets up their mounts by default with the counterweight between two legs. This is less stable but necessary for someone at a lower latitude since the counterweight would interfere with the mounts movements when the mount isn't tipped back as much. I live at latitude 41 degrees so this is never a problem. I had to unscrew the azimuth stop piece and move it to the other side of the tripod over the top of one of the legs. Now my mount doesn't want to tip even without the scope mounted on it.

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Posted 13 February 2012 - 12:32 PM

Very interesting Jim, thank you for your input. When you removed the bottom spreader, what keeps the tripod from just collapsing? I would think you'd need something to hold the legs from completely splaying out. Or are you saying you just removed the spreader to test the idea and haven't actually used the scope in that configuration? Either way, it sounds like this will be a very viable solution for me and others.

#7 DaveJ

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Posted 13 February 2012 - 12:37 PM

But the first thing I did with mine is to rotate the mount so as to move the counterweight over a leg instead of between two of them. Celestron sets up their mounts by default with the counterweight between two legs. This is less stable but necessary for someone at a lower latitude since the counterweight would interfere with the mounts movements when the mount isn't tipped back as much. I live at latitude 41 degrees so this is never a problem. I had to unscrew the azimuth stop piece and move it to the other side of the tripod over the top of one of the legs. Now my mount doesn't want to tip even without the scope mounted on it.


Hi Jim,

I did exactly the same thing when I first assembled my CGEM DX last May. I wouldn't put a GEM in the default setup position for love nor money. That 22lb counterweight out there on the CW-bar between the legs of the tripod would make me mighty nervous. It amazes me that it comes that way as the default position.

#8 Jim Romanski

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Posted 13 February 2012 - 01:02 PM

Very interesting Jim, thank you for your input. When you removed the bottom spreader, what keeps the tripod from just collapsing? I would think you'd need something to hold the legs from completely splaying out. Or are you saying you just removed the spreader to test the idea and haven't actually used the scope in that configuration? Either way, it sounds like this will be a very viable solution for me and others.


So far I only took off the spreader to see how much lower the mount would go. I did not put the scope or the mount on the tripod though I think I could have.

There's a bit of resistance at one point in the legs as you move them out wider but one of mine moved past that easily. I think on grass I could have used the mount without it splaying out but it's not worth the risk. If you simply want to try it out this way or aren't sure what the widest is you want to use it use wire or rope. You can thread wire or thick cord through the holes where the allen bolts come out of run it around all three holes and tie it off. Not elegant but it will keep the mount from splaying out. If you want to save money you can just use the wire/rope or make your own longer bars when you figure out just how long you want them to be.

#9 MRNUTTY

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Posted 13 February 2012 - 05:47 PM

I tried to move the spreader up the legs a bit to lower the height, but the mount wont close afterward, and it broke some material off the spreader hub when the hub went lower than normal. So, don't do that :-)

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Posted 18 February 2012 - 11:51 PM

I've mostly completed the tripod modification. It wasn't too hard and didn't cost much either. The spreader on the bottom is easily disassembled. The three black bars that set the spread width of the legs are made from aluminum and I was able to buy a 1"x.25"x6' aluminum bar for $15 and cut three 18" pieces from it. After drilling holes and filing the parts to fit this was finished.

Posted Image

This picture shows the tripod portion before (left) and after (right) the modification. With 18" spreader bars I lost about 3" of height and gained about 9" of distance between feet. I could have lost more height / gained more spread, but going further was going to make moving it through the back door difficult.

You may note that with the wider version the central rod is poking up and would impale the electronics pier if it were placed on top. In order to fix this I could cut it down to size pretty easily, but I wanted to make this project completely reversible so instead I purchased a new threaded rod (which hasn't yet arrived) that I will cut to size. If you are interested, the central rod is metric M12-1.75mm threaded. This is unfortunate because it made buying a replacement much more expensive than if it had just been standard english 1/2 inch thread.

At some point I might make an additional set of spreaders that make the tripod even wider, but for now I think this is a substantial improvement.

#11 DaveJ

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Posted 19 February 2012 - 02:40 PM

This picture shows the tripod portion before (left) and after (right) the modification. With 18" spreader bars I lost about 3" of height and gained about 9" of distance between feet.


Beautiful job! You've inspired me to make the same modification. Nicely done. :bow:

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Posted 19 February 2012 - 03:37 PM

Beautiful job! You've inspired me to make the same modification. Nicely done. :bow:


Thanks. If you don't have an issue with going in and out a door, or if you have a larger width door, you should consider making your spreaders a bit longer than the 18" I chose, though 20" is probably about as large as I'd recommend.

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Posted 23 February 2012 - 08:40 AM

I finished the tripod modification project. The last step was cutting a M12 threaded rod to the right size to replace the original central rod. While I haven't had an opportunity to view with it yet (*%$&! clouds!), I'm happy with the way it looks and the improved resistance to tipping. Honestly, when I look at the original configuration of the tripod it is hard to understand why they chose such a high/narrow disposition.

Posted Image
CGE PRO carrying EdgeHD 11 using modified (wider) tripod.

#14 DaveJ

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Posted 23 February 2012 - 10:00 AM

I finished the tripod modification project. The last step was cutting a M12 threaded rod to the right size to replace the original central rod. While I haven't had an opportunity to view with it yet (*%$&! clouds!), I'm happy with the way it looks and the improved resistance to tipping. Honestly, when I look at the original configuration of the tripod it is hard to understand why they chose such a high/narrow disposition.


You are absolutely right...it looks much more stable and, well, just better with your mods. :waytogo: :ubetcha: Don't you wish we had access to the designers?

#15 Jim Romanski

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Posted 23 February 2012 - 10:22 AM

That looks great!

Don't forget to make the other mod that some of us mentioned above:

But the first thing I did with mine is to rotate the mount so as to move the counterweight over a leg instead of between two of them. Celestron sets up their mounts by default with the counterweight between two legs. This is less stable but necessary for someone at a lower latitude since the counterweight would interfere with the mounts movements when the mount isn't tipped back as much. I live at latitude 41 degrees so this is never a problem. I had to unscrew the azimuth stop piece and move it to the other side of the tripod over the top of one of the legs. Now my mount doesn't want to tip even without the scope mounted on it.



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Posted 23 February 2012 - 10:46 AM

Can that adjustment (moving the counter weight over a leg) be done on a CGE PRO? It has a completely different azimuth adjustment system. I didn't look closely, but it didn't appear obvious that this could be done.

#17 Jim Romanski

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Posted 23 February 2012 - 11:50 AM

I have a CGEM DX so I'm not sure about the CGE PRO. On my mount there's a metal stop called an "alignment peg" that sticks up where the azimuth adjustment screws push off of to adjust in azimuth. On mine this metal stop is screwed into the top piece of the tripod. There's also another threaded hole 180 decrees away. I took a wrench and unscred it from one hole and screwed it into the other hole then put the mount head back on top of the tripod but oriented 180 degrees from where it was.

My old CG5 worked the same way so I was assuming that Celestron made this for all their mounts.

On the CGEM DX there's an adapter piece that goes on top of the tripod which allows the CGEM tripod head to be mounted to it. The "alignment peg" is on that piece.

I just downloaded the CGE PRO manual from the support tab at:
http://www.celestron...-pro-mount.html

On page 7 they show how to assemble the mount and in the picture they show the mount with the counterweight over the north leg. In fact the description says - "Rotate the equatorial mount on the electronics pier
until the holes in the mount line up with those in the
pier and the DEC opening (where the counterweight shaft will go) is positioned directly over the north tripod leg."

Here are the figures from the manuals (they don't appear to be copyrighted) with the CGEM DX on the left and the CGE PRO on the right.

Attached Files



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Posted 24 February 2012 - 10:35 AM

Thanks for the information. I took a closer look at the orientation of the tripod with respect to the GEM head and indeed it can be oriented that way. In fact it is quite a bit easier than it is on a CG-5. I don't know why I didn't see this the first time I assembled it. Anyway, that's the way I have it setup now - counter weights over the North leg.

#19 Dave Yates

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Posted 31 July 2012 - 01:01 PM

I actually make a spreader that will also do this same widening of the tripod! See TPIASTRO.com
Also have Leveling mounts that make the stance even wider.
Cheers
Dave

#20 shark-bait

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Posted 31 July 2012 - 05:58 PM

Great idea. I am going to give this a go. How much did you have to shorten the M12 threaded rod?

#21 mclewis1

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Posted 31 July 2012 - 07:56 PM

My old CG5 worked the same way so I was assuming that Celestron made this for all their mounts.

Jim,

Nope, the higher end CGE and CGEPro mounts don't have that azimuth alignment peg. The CGE has an eccentric cam structure to move the plate the mount rests on in azimuth. The Pro has something similar to the CG-5/CGEM concept, using two bolts in a push me/push me arrangement but there's no removable post. In either case the electronics pier is solidly attached to the tripod head and there's no central bolt/threaded rod holding it together (there is however a rod going down to the spreader bar). You can easily re orient the CGE and CGEPro by rotating the electronics pier to one of the 3 mounting points 120° apart.

If you want to see how an azimuth adjustment should have been done by Celestron have a look at the product that Dave Yates created for the CGE (on his website TPIastro.com as the Fine Azimuth Adjuster link ).

#22 gnowellsct

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Posted 31 July 2012 - 09:32 PM

Overall I really like the CGE PRO mount, but there are two things I would have done differently had I been the designer: make the tripod a bit lower and the base of the legs a bit wider. The reason I'm interested in this modification is to make observing a bit more convenient and, more importantly, make the mount a bit more tip resistant.


Amen. I have no idea why they put that thing so high. And tip resistance is non trivial with for example a 14 Edge HD. The truth is I don't understand the design principle that makes this a good set up so I'll have to let it go at that. If I were using a CGE Pro I'd probably be looking to put it on a different tripod.

However, we get very few posts from people that are doing the port of the GEM head to a different tripod. So either they're happy or they don't know what they're missing or both. I don't recall any reports of a CGE Pro tipping over which come to think of it is surprising given how paranoid I am about that extra height. But I think it would be a difficult tripod to work with.

my 2c. GN






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