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My 16" f7.2 Newt project code named "Grace"

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#101 Sean Cunneen

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Posted 22 September 2013 - 08:25 PM

I added mounting tabs to the bottom of the UTA. I wanted to make sure that the trusses were angled in one axis only. I got pretty close!

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#102 Sean Cunneen

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Posted 22 September 2013 - 08:34 PM

The secondary holder was constructed from parts I had laying around. One part was pretty crazy, I had a magnesium base from a Monfrotto tripod head that was reversible for 3/8" or 1/4-20. That became the top mounting disk. 4 8/32 threaded rods, some thumbwheels and some springs from every click-pen we had in the house. The mirror holder is cut from a piece of PVC tubing on my chopsaw. All in all, everything made for a nice secondary holder! I don't know that I could make another like it in my lifetime though!

#103 Sean Cunneen

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Posted 22 September 2013 - 08:49 PM

Last for this weekend is the construction of a three curbed-vane spider. I wasn't going to do a curved vane spider originally, but I was going through my scrap shelf and found a 2" thick section of 7" diameter tube from my refractor build. The thing i hate most about curved vane spiders is forming the curve and for a span as long as 17", any excess curvature beyond the main curve will affect the final image. My last curved vane spider had one vane torqued a bit which caused a flare in dark skies.

I figured if I could cut the section into two 1" rings and cut each ring in half, I could have three vanes with curves that I know maintain their parallelism with each other.

My favorite way to cut tubing is using a hacksaw, using hoseclamp as guide. I get perfectly square cuts. Then each ring is cut in half...

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#104 Sean Cunneen

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Posted 22 September 2013 - 08:53 PM

For the hub I had a 1" dia 1/8" wall aluminum tube that was originally a roller for some piece of manufacturing equipment. I had a couple of aluminum washers that I press-fit into each end(again, pure luck that they fit!) and I drilled the center to fit a 3/8" shaft. I marked the 120deg sections and started drilling and tapping...

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#105 Sean Cunneen

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Posted 22 September 2013 - 08:55 PM

Another view...


It turned out well. Stiff enough (you can see the secondary holder in the background). If it doesn't work, I might end up buying a 4 vaned straight spider and commercial secondary holder.

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#106 Jeff Morgan

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Posted 22 September 2013 - 10:59 PM

My deadline for first-light is the Illinois Dark Sky Star Party Oct 6th-ish. Hopefully a deadline will help! I have been working on all the little parts. What you gain in portability with truss construction, you pay for in complexity.


October 6th is coming up pretty fast ...

Good luck on the truss connectors. After my third failure at making my own, I vowed to buy that part commercial in all future scopes. I burned up a lot of days in the shop trying to get a functional and attractive solution - to no avail. I hope your experience is better.

#107 Sean Cunneen

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Posted 24 September 2013 - 07:29 AM

I was up pretty late last night(or early this morning) trying to mock up the OTA. My truss connectors aren't going to do the trick, at least not how I had intended. There is too much force for the clamping action to handle and the tubes slide and twist too easily. Fixing that is going to require pinning each tube into either bracket end :( Not the end of the world, but not the super cool adjustability I was shooting for. Oh well, I make the mistakes so you don't have to!

#108 Jeff Morgan

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Posted 24 September 2013 - 10:54 AM

Don't feel too bad. I recall Dave Kriege at AstroFest 20 years ago saying that it took him three prototypes on the Obsession design.

#109 Sean Cunneen

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Posted 24 September 2013 - 12:15 PM

The fix isn't too bad. I was thinking almost solely in terms of compression and standing straight up the assembly was a piece of cake and the OTA looked great! As I moved it to horizontal so I could find the balance point, everything turned into limp spaghetti and I had tubes coming apart all over. All I could hear was the Benny Hill theme as I tried to wrangle 3 poles with two hands!

#110 Sean Cunneen

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Posted 11 October 2013 - 10:36 PM

Okay, I admit it, this post jumps the gun a bit, but at least you see it is a scope!

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#111 Sean Cunneen

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Posted 11 October 2013 - 10:36 PM

Doesn't look quite so huge in this pic...

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#112 magic612

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Posted 11 October 2013 - 10:42 PM

Sean. like I said on Facebook: Ladder.

Or should I say: TALL LADDER!!

#113 Jeff Morgan

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Posted 11 October 2013 - 10:55 PM

Sean. like I said on Facebook: Ladder.

Or should I say: TALL LADDER!!


:lol:

Congrats Sean!

Here is a ladder worthy of such a scope. The tape measure I am holding is set to 110", the original planned eyepiece height of my 16" f/7 scope Stripe.

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#114 Sean Cunneen

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Posted 11 October 2013 - 11:29 PM

I tried grabbing one of those Home Depot stocking ladders but the guards caught me before I could get it in the car.

#115 Mirzam

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Posted 12 October 2013 - 07:35 AM

Holy elevator shoes Batman!

JimC

#116 Pinbout

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Posted 12 October 2013 - 08:14 AM

Sean. like I said on Facebook: Ladder.

Or should I say: TALL LADDER!!


facebook is for oldtimers

kids say hashtag #tall ladders.

#117 Darren Drake

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Posted 12 October 2013 - 10:38 AM

Looking forward to looking through it very soon!

#118 azure1961p

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Posted 12 October 2013 - 09:24 PM

These 16" f/7s are my dream scopes - it was the largest I thought Id go if I were to go in that direction. As it is Ive been too busy and honestly, happy with the 8" F/9 bit I do envy you guys with those awesome systems. Great work on both 16s.

Pete

#119 Jeff Morgan

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Posted 12 October 2013 - 10:59 PM

These 16" f/7s are my dream scopes - it was the largest I thought Id go if I were to go in that direction. As it is Ive been too busy and honestly, happy with the 8" F/9 bit I do envy you guys with those awesome systems. Great work on both 16s.

Pete


Thats so funny ... we have a sloped property, and the limited flat spots are just too small for Stripe (and the accompanying ladder). So Stripe is strictly a remote session telescope.

But I often wake up in the early morning and need a scope for quick yard sessions. I have been sketching out a solution to this problem over the past couple of weeks. No ladder is one requirement, the other is fast and easy set -up. The solution I am closing in on is a 8" f/9 scope!

At some point, I will become too old and frail to use my 16" f/7, at which point it will come up for sale. But since Clyde Tombaugh used his long focus 16" well into his 80's .... don't hold your breath. :grin:

#120 Sean Cunneen

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Posted 28 January 2014 - 12:11 PM

I have spent a good month working on this project however I had a catastrophic Update with my computer which deleted all pictures of the finishing steps :foreheadslap: :bawling: :bawling: :bawling: Here is a photo of the UTA and LTA together...

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#121 Sean Cunneen

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Posted 28 January 2014 - 12:16 PM

The OTA is finished in red-oak stain and the oak base is finished in Ebony. My atrocious basement lighting doesn't do the contrast justice, but until our "Polar Vortex" calms down, my basement lighting is all you get! This is by far the largest and most complex wood project I have ever undertaken. I thought painting would take a couple of days, but it took many days over a month to sand and paint everything to a proper amateur standard (thank goodness for soft-focus!)

Some features like the Azimuth-brake and lazy-susan bearing have been removed in favor of a Berry&Kriege-like ball-bearing assembly. I'll revisit that concept in an inevitable re-fitting prior to the Equatorial table-build. For now movements are smooth enough in AZ and fantastic in altitude!

I'll take some photos of the completed interior tonight and post them soon.

#122 Jeff Morgan

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Posted 28 January 2014 - 10:43 PM

The OTA is finished in red-oak stain and the oak base is finished in Ebony. My atrocious basement lighting doesn't do the contrast justice, but until our "Polar Vortex" calms down, my basement lighting is all you get!


It already looks great even under that light!

Any sightings of glaciers crossing the Wisconsin border yet?






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