PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Hi Kerry, The 3rd one is incase I have more problems with the carbon fiber upper ring. We can put the scope together and be testing it as I work out the problem.
Currently, I've been using glass over the 5 lb density Divynacel a blown PVC core material. That with the VARTM and a caul plate of 1/8" masonite that fit the OD and ID profile of the core material so that when everything was vacuumed down and the resin was introduced the edge of the glass would lay flat after curing.
I worked up this system, as without the caul plates...there would be a little kink or wrinkle at the 45 degree transition of the core to just glass edge. It works very well with 3-4 layers of 10 oz glass as the glass drapes very well.
However, when I luckly tested 2 layers of 5.6 oz graphite 12.5 x 12.5 strands per inch on each side...I ended up with and edge that was tapered outward and not flat.
I need the edge flat in order to be able to bond two of these pieces back to back.
Thus, to save time I had the 3rd ring cut.
Regards,
Preston
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A few I enjoy,
and a few more in the works ;<)
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Mike I. Jones
Pooh-Bah
Reged: 07/02/06
Posts: 1102
Loc: Fort Worth TX
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Jaw Welcome, Preston!
For anyone interested, here's a ray diagram showing how I finalize the Cass baffles in ZEMAX. I first use CassDesign to get an approximate optimized baffle layout that minimizes the central obstruction. I set up the baffles as dummy surfaces and check "Hide Rays" to the surfaces. Then I use the Multi-Configuration editor to generate 29 field angles from bottom to top of the field, and trace 10000 rays at each field in 3D Layout to approximate a solid volume of light. Then it's easy to see where light ain't goin', and put the baffles there.
Usually one iteration is required to converge the central obstruction position and diameter to the secondary baffle rear surface.
The secondary baffle is tapered smaller toward the sky to prevent graze-angle reflections from it to reach the primary.
The forward section of the primary baffle is tapered to follow the converging light from the primary surrounding the central obscuration rim to the secondary. The rear section of the baffle can be straight, as it is hidden in the shadow of the secondary baffle obstruction. That makes it easier to mount with a pair of equal diameter support rings.
The baffles in this process have zero thickness. When realistic wall thickness is added in using a follow-on CAD program, half the wall thickness is offset outboard of the baffle, and half is offset inboard. For these smaller telescopes, baffles don't have to be very thick; 24 gauge sheet aluminum (0.0201" thick) is probably enough. So, the wall thickness doesn't significantly affect image vignetting.
Mike
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56 mirrors, lenses, 16" f/6 Newt, 6" f/10 refractor, TOA-130S, Tinsley 5" f/15 Mak, 6" f/4 RFT, Coronado PST. Still to build: 24" f/10 Modified Dall-Kirkham, 10" f/26 Mak, 8" f/12 apo, spectrohelioscope, Herrig, Schupmann, and a new design you'll like.
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Ok Kerry aka "Sky CAptain" sent me these pictures of the back plate being machined.
Looks like they have just about all of the larger 1 inch diameter lightening holes just about done.
Next with be the 3/4" and 1/2" in the areas that look uneven around the outer edge and fan holes.
I heard from Grant at Specialty Sheetmetal, the folks doing the fine work in Kent, Washington and they recieved the tooling plate for the triangular collimation plate yesterday and will be starting on that next week...
Regards,
Preston
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A few I enjoy,
and a few more in the works ;<)
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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And a close up of machining the back plate.
You can see the nice rounded bottom of the lightening holes. They are using a ball end mill for the finishing pass.
They first milled the smaller holes to releave the internal stresses in the metal, and here are opening the holes up on the final pass.
Regards,
Preston
--------------------
A few I enjoy,
and a few more in the works ;<)
Edited by PrestonE (05/10/08 10:52 AM)
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Sky Captain
Scope Builder
Reged: 11/07/04
Posts: 5743
Loc: Seattle Washington
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Preston, what method of mounting your scope to the EQ head will you use? In mine I had a raised flat spot that was 4" wide to mount my dovetail too. Will yours use a bolt on devise to the edge of the rings? I was trying to figure it out when I was at the shop the other day.
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Equipment Overload!
Kerry.
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Kerry, That is one of the details that I'm working on currently.
Because the mounting plate will be aluminum and the tubes are CF if one were to solidly fix the mounting plate to the back and mid plates, there would be a large stress develope with temperature changes.
It's likely that we will machine a spot on the rear plate.
To this spot bolt the rear end of the mount.
At the mid rings, I'm thinking of bolting 2 cars from a pricision linear rail. Then mounting the short rail sections to the mounting plate.
That way, any thermal movement in the length of the mounting plate will not stress the CF tubes or structure in general.
Once I get the plates all here, and assembled with the capture blocks, tube ends and all...I can get a better fell for it...
I'll post the CAD drawings when done.
Regards,
Preston
--------------------
A few I enjoy,
and a few more in the works ;<)
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Michael Miles
professor emeritus
Reged: 02/11/05
Posts: 604
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Hi Preston:
Contrats on the new project. I'm watching with interest. I'm envious as I've had to shelve my project for a while as I gear up for a second career.
Have fun,
Michael
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LXD-75 w/
Stellarvue 102ED
Hardin 10" Newt
Antares 8" Newt
Meade AR-5
Meade N-6
Celestron 102mm refractor
Canon 300D, Meade DSI guiding
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Hi Michael, Thanks...it's been a long haul. Started I think almost 18 months ago with getting the group together to finance the project. I had the optic set, which I sold to the group with the promise to design and build the OTA...
Along the way many things have slowed things down, but seeing Kerry's build and his help in locating someone to to our large parts has us back on track I think...
Sorry to here about you project.
Best Regards,
Preston
ps...The machine work that Kerry helped arange is done and ready to ship, but we've been informed that the shop does not ship ;>(
We'll work something out I am sure.
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A few I enjoy,
and a few more in the works ;<)
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Sky Captain
Scope Builder
Reged: 11/07/04
Posts: 5743
Loc: Seattle Washington
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Quote:
ps...The machine work that Kerry helped arange is done and ready to ship, but we've been informed that the shop does not ship ;>(
We'll work something out I am sure.
No worries Preston, I'll take care of it. 
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Equipment Overload!
Kerry.
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Thanks Kerry, First you give me a shop to do the work,
And now you offer to act as their shipping department!!!
You deserve an award!!!!!!!!!
Perhaps 5 jumping smiley faces???
Well, I'm sure we can do better than that.
Thanks Again and Best Regards,
Preston
Quote:
Quote:
ps...The machine work that Kerry helped arange is done and ready to ship, but we've been informed that the shop does not ship ;>(
We'll work something out I am sure.
No worries Preston, I'll take care of it.
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A few I enjoy,
and a few more in the works ;<)
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The bear
professor emeritus
Reged: 02/11/08
Posts: 727
Loc: rushville, indiana
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i tell you the world of ATM is great isn't it i have had so much help here on this forum in getting the pieces (and i mean piece by piece) of materials and things needed for my telescope and accessory projects i am dumb founded by generosity of wisdom and the sharing of things between us i can only hope to match these acts as best i can.
doc
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Longitude -85.42786 Latitude 39.59153
when all else fails use duct tape "works for me"
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Hail Kerry!!!!!!
He has offered to pickup, crate, and ship our machined parts to me....
Of course, we will pay all cost...
And we are moving forward!!!!!!
Thank Again!!!!!!!!
If there is anything that I can do for you, just ask...
Very Best Regards,
Preston
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A few I enjoy,
and a few more in the works ;<)
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Sky Captain
Scope Builder
Reged: 11/07/04
Posts: 5743
Loc: Seattle Washington
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Quote:
Thanks Again!!!!!!!!
If there is anything that I can do for you, just ask...
Very Best Regards,
Preston
Not a problem Preston, glad to help.
(Got a 12" F4.5 mirror laying around) 
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Equipment Overload!
Kerry.
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Atm's are the best!!!!!!!!!
Best Regards,
Preston 
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A few I enjoy,
and a few more in the works ;<)
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Quote:
Quote:
Thanks Again!!!!!!!!
If there is anything that I can do for you, just ask...
Very Best Regards,
Preston
Not a problem Preston, glad to help.
(Got a 12" F4.5 mirror laying around)
12 inch f4.5.??
I'll have to look...
What final figure are you looking for....
spherical, parabola, or other...
There is a Lot of glass gathering dust around here...
Best Regards,
Preston
ps...how about a 24 inch by 1.060" thick quartz/fused silica blank??? 
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A few I enjoy,
and a few more in the works ;<)
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Sky Captain
Scope Builder
Reged: 11/07/04
Posts: 5743
Loc: Seattle Washington
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Quote:
ps...how about a 24 inch by 1.060" thick quartz/fused silica blank???
 OMG...I feel a folded newt. project taking shape in my busy little mind. 
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Equipment Overload!
Kerry.
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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We would need to start another thread for a folded refractor...
Sorry Kerry...
All, I'll be out of touch until Monday the 19th...
Donna and I will enjoy our 15th wedding anivercery tomorrow...
Best Regards to All
Preston
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A few I enjoy,
and a few more in the works ;<)
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The bear
professor emeritus
Reged: 02/11/08
Posts: 727
Loc: rushville, indiana
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congrads PrestonE have fun
doc
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Longitude -85.42786 Latitude 39.59153
when all else fails use duct tape "works for me"
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Thanks Doc,
When I get back, things will start to get busy.
Machined parts that Kerry is packaging and shipping to me will likely get here during the week of the 25th and I'm traveling the following week...so it will likely be the 2nd week of June before a lot more starts to happen.
Then we'll be cooking, I hope...
Best Regards,
Preston
--------------------
A few I enjoy,
and a few more in the works ;<)
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Hi Kerry, Any word on pickup yet???
As I wait with baited breath
Best Regards,
Preston
--------------------
A few I enjoy,
and a few more in the works ;<)
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