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Thread: Diy 12" sct

  1. #21
    DrLeoB's Avatar
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    Default Scope is working well....



    Spent the weekend finishing the CG5 mount tweaks ... found that the clutches needed to be evened out with a clean bastard file and also found that using a rubber compression washer from my plumbing spares provided just the right grab for the tensioner know to get the mount tracking properly.

    Addressed the issue of "mirror flop" by using Teflon faucet gland packing thinned to the right thinness to fit into the gap in the baffle tube. Works like a champ and is really smooth now. Collimation is easier now that I have my variation of the knobs on the screws. Storm window latches, nice little nylon levers which exactly fit the screws.

    I actually spent the evening doing some observing!!!
    C8, CPC8 w/Fastar, 2xQ3.5, 2xLX200 classics, one with 12" Homebrew hardware, Nexstar 4si,6" homebrew/ground Newt, Meade SN10 and a BUNCH of project OTA's.

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  3. #22
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    Default Fruits of My Labor - The Moon Tonight

    Mount tracking, scope collimated, zero image shift focuser mounted on 6.3 focal reducer with Meade Flip Mirror box and Microsoft LifeCam in focus....
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    C8, CPC8 w/Fastar, 2xQ3.5, 2xLX200 classics, one with 12" Homebrew hardware, Nexstar 4si,6" homebrew/ground Newt, Meade SN10 and a BUNCH of project OTA's.

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  5. #23
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    Default

    Great and inspirational project DrLeoB, thanks for sharing! (You should let the SCT guru Uncle Rod know about this unique SCT, I'm sure he'll include it in his new book. )

    Best,

    Hernando

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  7. #24
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    Default Wow! That is one heavy telescope

    Quote Originally Posted by DrLeoB View Post
    The weight of the OTA is pretty much a wash vs. the Al tube from Meade at about 35-37 lbs.
    Wow! It sure doesn't look to be that heavy from the earlier photos. It does answer why all those nice chrome plated balance weights on the CG-5.

    Not being at all familiar with these scopes, it's hard to determine how much weight might be saved using engineered composites. Apparently not much.

    Looks like a fun project. Thanks for sharing it.


  8. #25
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    Default

    Yep, almost 2/3 of the weight is in the frame and mounting attachment. For the next iteration, I am considering using some kind of closed cell material for the endplates to get rid of the plywood. The wood is quite heavy, but has worked out well for this proto version. The initial design for the focuser, using galvanized rod has been replaced with stainless steel threaded rod and brass furniture threaded inserts for the bearings. I also have added a 3 point mirror lock to eliminate the "Flop" effect when moving the scope around. Have had to mothball the whole rig until the rains slow down here, tho. We've had 4+ inches since Christmas!! Sunny California????

    Thanks for the continued interest.
    C8, CPC8 w/Fastar, 2xQ3.5, 2xLX200 classics, one with 12" Homebrew hardware, Nexstar 4si,6" homebrew/ground Newt, Meade SN10 and a BUNCH of project OTA's.

  9. #26
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    Default Weather finally gave us some nice days and I am back at it.,..

    This winter has been a total rain-out and couldn't even work on the big stuff, but now we have some nice days for awhile and I'm back at the big SCT. Looking at ways to drop some weight by simplifying the mount. Have added a push-pull system to align the central tube which carries the main mirror and have spring loaded a number of the screw sets in the base plate. I am also looking at making an hexagonal expanded web to support the corrector plate to drop the weight at the top of the tube. Thanks to everyone who offered comments, I'm very heartened that some of you out there might try something similar. Also, I'll post some more detailed pictures of the individual solutions I've come up with.

    Regards All.
    C8, CPC8 w/Fastar, 2xQ3.5, 2xLX200 classics, one with 12" Homebrew hardware, Nexstar 4si,6" homebrew/ground Newt, Meade SN10 and a BUNCH of project OTA's.

  10. #27
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    Default

    Leo, I would be interested in some detailed pics of the focusing mechanism, the better to gain insight into the practise of focusing by moving the main mirror, which, I understand, is how SCTs work, and seems counter-intuitive to me.
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    Default

    Pierre,

    Here is a link of a CT scan of a SCT that shows the focus mechanism fairly well: http://www.cloudynights.com/documents/ctscan.pdf

    Joe
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    The CT scan is kind of cool. Can see what the inards of my scope may look like. Thanks for sharing the link.

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    WWP - I'll be taking the focuser out to make the final bearing cutouts so I'll be glad to take a set of detailed shots for you. The final version of the focuser uses a brass furniture Nut clamped between two PVC fittings and setu up to rotate ina pair of flat thrust roller bearings. Pic's to follow.

    That CT scan is "Way Kooollll ..." thanks for posting it.

    I have everything back together and spent the day today moving the OTA onto a new (to me) CG5 mount. The old one had a lot of service on it before I got it and the weight was enough to strip out the Dec. gear teeth. Have to pay more attention to balancing the scope when it is this large. Anyway, the new mount handles the weight very well and the scope not moves and tracks very smoothly. Now if we can just get some clear, dry nights. Patience.... Patience....
    C8, CPC8 w/Fastar, 2xQ3.5, 2xLX200 classics, one with 12" Homebrew hardware, Nexstar 4si,6" homebrew/ground Newt, Meade SN10 and a BUNCH of project OTA's.

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