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Old 09-11-2018, 12:08 AM
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mental4astro (Alexander)
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CPC 1100 mount single arm mod

Hi all,

Thought I'd share my own CPC 1100 mount single arm mod after being so suitably inspired by Tony's (casstony) work! Thanks mate

The arm that is removed from the mount contains no motors, but it does hold the GPS antenna. If you want to keep the GPS capability of the mount, of course you need to keep the receiver. Where my mod differs from Tony's is the case I made to house the receiver is made out of 15mm marine grade ply and shaped to simulate the profile of the arm's coupling face. I also made the plywood box so massive/stout/strong in order for it to act as a "handle", or a point on which I can hold the mount, and because the mount weighs close to 20kg, this box needs to be sturdy in order to deal with the load. When carrying the mount, this "stump" is really practical!

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The clamp is a dual Losmandy/Vixen clamp that comes from Astroshop in Queensland. Another difference between my mod and Tony's is I only used two M6 bolts on the outer edge of the clamp, and did not use the M5 threads that are machined into the crappy aluminium casting that is the coupling surface of the mount - cast aluminium is brittle so careful consideration of its mechanical properties need to be considered. These M5 threads provide nothing structural to the mount, and the threads cut into this cast aluminium is not strong enough to be loaded & trusted with an expensive scope. These M5 bolts if used exclusively, would also flex when loaded with a hefty scope - not good for mount accuracy or scope over time! If you do contemplate a similar mod, YOU NEED TO ALSO USE THESE M6 BOLTS! Do not only use the M5 holes! The M6 stainless steel bolts held by nuts provide all the structural capacity needed. This anodized clamp also doesn't bind with the dovetail plate, which makes shifting the scope so much easier when doing small position adjustments when balancing the scope in the clamp. Painted/powder coated clamps and dovetails are a real pain in the neck!

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The main reason why I got this CPC 1100 fork mount was to carry my Intes 715 Deluxe Mak. The forks of the 8" and 9.25 SCT's do not provide the necessary clearance with a balanced scope using either a 1.25" diagonal or 2" diagonal. Also, this Maksutov is a heavy bugger, 9kg, and that's without finder, diagonal or EP, so it also needs a suitably strong mount. I certainly have the necessary clearance & muscle now!

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I'm very happy with the result. The mount works really well and I have a very easy mount to set up and use, especially for my lunar and planetary sketching - the NEQ6 mount I have is not the nicest thing to use with sketching.

Thanks again Tony for your inspirational work.

Cheers,

Alex.

Last edited by mental4astro; 09-11-2018 at 06:17 AM.
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  #2  
Old 09-11-2018, 09:05 AM
casstony
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Neat job Alex - nice to see more owners enjoying the mod idea. I keep expecting to see Celestron release a heavier duty Evolution.

Just a minor correction: the 9.25 fork arms are also suitable for the mod.
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Old 09-11-2018, 09:56 AM
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mental4astro (Alexander)
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Thanks Tony

Yes, the 9.25 is also good for such a mod. What I meant to say was the standard 8 & 9.25 forks are not suitable for a larger Mak like the Skywatcher 180 or my 7" Intes. These scopes need a longer spacing between the base of the mount and the pivot point of the clamp. I see now I could have been a bit clearer on that point! Thanks Tony

Now, the CPC 925 mount and that of the CPC 1100 are actually identical. Only difference between the two mounts is the 925 has a pair of spacers to compensate for the smaller diameter of the 9.25 OTA. Tony just pointed this out to me. So if you have or get your hands on a CPC 925, you can do the exact same single arm mod and end up with the same hefty mount as that of a modified CPC 1100!

Alex.

Last edited by mental4astro; 09-11-2018 at 10:42 AM. Reason: Additional info, thanks to Tony! :)
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Old 09-11-2018, 11:51 AM
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netwolf
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Hey Alex wow that has turned out great and love the 7” Mak.
I like you have gone through the SE Evolution and now finally the CPC (from Tony, needs a plaque first one ) for the same reason the previous two were just two short for the larger cats especially the 7” Mak. Can’t wait to get my Skywatcher on this. And Alex remember we are doing this for the rain our farmers need so please everyone go any buy Astro gear we need more rain. Just not this weekend ....
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Old 11-11-2018, 10:41 PM
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mental4astro (Alexander)
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I had first light with this modified mount. Works very well, and will suit my needs very well

Alex.
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Old 12-11-2018, 09:36 AM
casstony
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Quote:
Originally Posted by mental4astro View Post
I had first light with this modified mount. Works very well, and will suit my needs very well

Alex.


Even with a C11 the single arm is stable in calm conditions. Your Mak is a comfortable weight for the mount to handle.

In windy conditions the C11 with dew shield sways a bit.
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Old 14-12-2018, 08:45 AM
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mental4astro (Alexander)
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I've used this rig several times now. Under calm conditions and very windy ones.

Under calm, well there's nothing to say other than it works. My home sits beside a concrete road that has been hacked by the local council and the patch-up job they did has resulted in nasty vibrations being created by the thunk-thunk of car and truck wheels going over a very dense WWII road to a less dense and less reinforced "Australian Standard" slab. This rig though is a beauty here! It is so rigid and solid that these vibrations are bearly noticeable now and are killed very quickly. REALLY good when using 400X !!

Last week I took this rig to Pirrima Park in Pyrmont close to the Star Casino to do some sidewalk astronomy with the conjunction of Mars & Neptune. Where we set up we were somewhat protected from the very strong wind that was blowing that night. What can I say, wind is wind, and when it's blowing at over 50km/hr no one would usually have a scope set up, and for good reason. Of course the scope shook when gusts caught it, but again this shake was dampened very quickly. I was surprised at how well this rig stood up the poor conditions. Not very likely I will be doing this same windy stunt again any time soon, though a good experience all the same.

Tony, awesome re-purposing idea mate! Thanx! An Evolution mount would not be able to do this for me. Don't forget that it has been engineered to take a big C11, so the fork is much more solid as is the tripod, and greater clearance between base and the pivot point of the alt bearing. The Evolution mount looks like such a dinky little thing now...

Alex.
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Old 30-01-2019, 11:27 AM
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mental4astro (Alexander)
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I've been talking with a fellow IIS'er about doing this CPC single arm conversion, and it's made me reflect on a couple of aspects that need to be carefully considered and care taken.

The first is care needs to be taken when drilling into the mount's coupling plate to not let the shavings get into the bearing. One way to reduce this happening is to orientate the mounting plate down below the bearing so the filings don't fall onto the bearing. Another thing to do is put some paper/tissue behind the plate and around the bearing. Once the holes have been drilled, take care when removing this paper/tissue so you don't shake the shavings onto the bearing. The bearing is greasy, so if you drop shavings, they will stick and can mess things up too. Once you've done the holes CAREFULLY clean away any shaving before removing the paper and after removing the paper. DON'T use compressed air!!!!

One thing I REALLY LIKE about the dovetail clamp I used is the slots that it comes with align really well with where the holes need to be drilled. This means that only one pair of holes needs to be drilled, those into the mounting plate. To try to drill holes also into a dovetail plate and expect two sets of holes to line up cleanly really is just about impossible, and it will be necessary to stuff around filing one hole or two holes larger in order to allow the bolts to pass through. Unless you are getting a plate from Losmandy themselves that has these purpose made holes already put into the dovetail clamp, you will be creating a world of pain for yourself if you drill the two sets of holes into the clamp yourself. The tolerances are very small, and as the space to work is very tight, this world of pain will be torture. If you think measuring and drilling out recessed holes is a walk in the park and that everything will line up perfectly, then you either have the necessary machining skills and tools, or you have no blooming idea what you are getting yourself into.

You might not like the look of this red clamp, it may not carry the brand label you want, but the thing works a treat and its design will save you from so much anguish.
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Last edited by mental4astro; 30-01-2019 at 09:04 PM. Reason: typo
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Old 30-01-2019, 04:31 PM
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Camelopardalis (Dunk)
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Red looks good on black, Alex, not sure about the gold bits though
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Old 25-02-2019, 10:08 AM
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mental4astro (Alexander)
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A little update.

I can make the stump to replace the removed arm for folks who would like to undertake this CPC single arm conversion. I've changed the design from my first one just a little following my experience in using my first iteration of the stump. I've just made one for Dunk

I make these stumps out of 15mm marine ply, machined to fit the shape of the hollow, and comes with a shelf to fit the GPS receiver and hold the antenna cord. The underside of the front panel has a gap that acts as a grip to fit your fingers when you lift the mount. I can varnish the stump, or leave it for you to decorate it as you like - Dunk will be putting his own unique touch to his

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If you are interested in one, just drop me a PM,

Alex.
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