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What did you work on today?

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#26 Steve OK

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Posted 24 February 2015 - 06:00 PM

Well, I didn't really do this all today, but it all came together.  The UTA for my 10" Dob rebuild, going from Sonotube to truss.  The carriage bolts through the vertical tubes are just in temporary service, to be replaced with proper length hex bolts.  There will be a Formica "shell" in the rings.

 

UTA-1-800-CN.jpg

 

 

Steve


Edited by Steve OK, 24 February 2015 - 06:01 PM.

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#27 Sean Cunneen

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Posted 24 February 2015 - 08:37 PM

Looks good Steve!  I dig the spider hub...



#28 Pinbout

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Posted 24 February 2015 - 08:53 PM

I sewed my shroud, still need to trim it down and then hem it.

 

shroud 2..jpg


Edited by Pinbout, 24 February 2015 - 09:41 PM.

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#29 cpr1

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Posted 24 February 2015 - 09:08 PM

Nice scope Danny.



#30 Pinbout

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Posted 25 February 2015 - 12:36 AM

also today I put together this prototype cell for my $#!* HO mirror.

 

18pts

20150225_003034.jpg

 

rockers on the wiffle tree edge support

 

20150225_002952.jpg


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#31 Eden Orion

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Posted 25 February 2015 - 09:12 AM

New Alt-Az Mount for a 12" scope.

The old mount was a very nice Horseshoe Mount that could track the stars but did not come easy into the car...

It was built originally by Yossi Huri.

This mount is made so I can take this wonderful scope to the desert.

 

11016822_10153584536163912_4718692502181


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#32 Stephen Kennedy

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Posted 25 February 2015 - 06:44 PM

About a year ago, for some reason, there was a huge ant infestation for the hand controller of my Pentax MS-5 GEM.  I took the cover off the back of the hand controller and sprayed the circuit board with insecticide leaving a layer of dead ants.  I wiped them off as best I could but in the process dislodged a wire from its connection that I think was crucial to slewing the mount.  I taped it back on with scotch tape and screwed the back cover on the controller.  Also the red lamp on the hand controller no longer worked.

 

Today, I could no longer stand the thought that a premium mount was only working because of piece of ant covered scotch tape.  I unscrewed the back cover of the hand controller, removed the piece of scotch tape that was just barely holding the wire to the connection and soldered the wire to its proper connection.  I then used an eyepiece to carefully examine the wiring to the non-functioning red lamp on the front of the hand controller and noticed that a very fine wire had been dislodged from it connection point.  I also soldered this as well.  I then screwed the back cover on the hand set, plugged it into the mount and put the MS-5 through its paces.  Every thing worked flawlessly, including the red lamp, it was as good as the day it left the Pentax factory.

 

Now I realize, compared to what other people on this thread have done, unscrewing a few screws, soldering two wires and screwing the cover back on the hand controller does not seem very impressive.  However, to me it was quite an accomplishment.  All my life I have been the butt of jokes about my complete lack of handiness and inability to fix anything around the house.  Several years ago I suffered a near fatal stroke which made the situation one hundred times worse.  Therefore, the success of this minor repair has really made my day.   


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#33 abberation

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Posted 25 February 2015 - 08:28 PM

More research.

 

I found a PDF discussing the stiffness and resonant frequencies of various telescope mounts.  Split ring compares well because the ring and yoke make essentially a large and lightly loaded tapered bearing.  Very stiff and not terribly heavy.  It is still bulky so I was investigating ways to reduce the size of the ring.  I was thinking offset the declination axis up and away from the center of the split ring and add a counterweight to the bottom to keep it balanced on the ascension axis.  I really need to figure out the CG location of my scope to figure out if that would be needed.  When I got tired of that, I thought about how to make a light and stiff split ring that stays round despite the split (plus temperature fluxuation and wear).  I think a foam core fiberglass ring with the circumference ground after curing and a laminated Invar strip "tire" should do it with plenty of strength, minimum weight, good accuracy, weather resistant and a bit more durable than wood.

 

Flat grinding begins Friday


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#34 Sean Cunneen

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Posted 25 February 2015 - 09:41 PM

I contemplated a split ring myself. I thought maybe aluminum bicycle rims to form the arcs. I even bought a set of 4, but it turns out that how I would call the size of a rim is quite different than hoe the cycling industry, so I would need about  36" tire. As far as I know, no Penny farthing bikes around here!



#35 mattyfatz

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Posted 26 February 2015 - 01:24 PM

Trying to figure out correct element separation for a 40in f8 Telestigmat.

 

You'll see another thread asking for Help!

 

-Dave G. (noob)

That's awesome!



#36 Sean Cunneen

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Posted 26 February 2015 - 04:31 PM

Today I picked up a counterweight from my machinist. I asked him to press a 3# synta iron weight into a brass donut I had laying around. I got it home and stuck it in my drill press and used a file to grind off all the tarnish. I then did the same with a regular brass donut I had picked up some time ago...  Looks good to me!

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#37 abberation

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Posted 26 February 2015 - 11:37 PM

I bought a box to carry my 14 3/4" quartz mirror blank.

 

It's surprisingly hard to find something appropriate.


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#38 Jon Isaacs

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Posted 27 February 2015 - 12:13 AM

On Tuesday, I did a fair amount of stuff.  First I cut the focuser hole in a 5x5 x 1 inch piece of Birch and mounted an Astromart Feathertouch focuer to the board and made the bracket to mount it to the upper ring of my 16 inch Strut scope. Then I loaded up some tools, drove up to our place in the high desert.. 

 

When I got there, I made a cover for the mirror box for my 12.5 inch.  I had a piece of quite nice 0.325" plywood that had showed up with something I had bought..  I cut it with the Saber Saw and glued it it all fit fine and dandy.  It was a nice replacement for the cover I had been using for the past 8 years, a piece a foam sleeping bag pad.. doubled.  

 

Then I went about mounting the focuser board to the upper ring. I took awhile.  I set position by clamping the board to upper ring and focusing on the moon until I had enough outward travel with the 41mm Panopic and no Paracorr.   That night I worked quite nicely, a nice upgrade from the GSO focuser that was on the scope.  But I realized that the larger bore of the Feathertouch was allowing some light in and I was having problems with ghosting from the moon. I wasted some time working on that when I should have been observing.  

 

The next morning I was pondering the problem, it really called for a larger baffle which I did not have.  The GSO Focuser with it's 2 inch straight bore and longer drawtube did not have this problem.. I decided to unbolt the Feathertouch and see what it looked like with the GSO.  I needed to lower the GSO about 1/4-3/8" and was looking around for a shim and realized that the 0.325" plywood was perfect.

 

Then I had a brainstorm and realized that I could use one of the leftover pieces from the mirror box cover project to stiffen the upper ring where the focuser mounts, I had enough to span the distance from one strut to the next.  The next few hours were spent cutting the contour with scroll saw, sanding it and mounting it.  It's screwed in place and also held by the focuser board bolts.   The original 0.70" upper ring hadn't been stiff enough and for about 7 years I had used an upper ring made from laminate pine but it broke so I had been using the thinner upper ring.  

 

It all worked out very nicely.  The workmanship is crude but effective, the focuser board and upper ring are much stiffer, since most such bending stiffnesses are 3rd power of the thickness, going from 0.70" to 1.02", it should be about 3x stiffer.  

 

Wednesday night, it was again clear. The ghosting problems were gone, the focuser board was noticeably stiffer and the scope, it seems like after more than 8 years, it's still getting better. The next step.. switching back to the Feathertouch.. 

 

In the photo, the reinforcing plywood can be seen and also on the strut on the right is a 1 lbs sliding counterweight. It's just a piece of heavy wall tube painted and drilled for a nylon locking screw.  It works very nicely to balance the scope.. 

 

The long term plans, take a wood working class.... 

 

Jon

 

 

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#39 Pinbout

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Posted 27 February 2015 - 07:56 AM

 

The long term plans, take a wood working class....

 

Jon

 

you could go get a new body by sending a dwg file to the cnc... :grin:

 

don't need a woodworking class for that...unless they have a cnc.

 

there has to be a lot of small shops out in San Diego.


Edited by Pinbout, 27 February 2015 - 07:58 AM.


#40 Jon Isaacs

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Posted 27 February 2015 - 08:30 AM

 

 

The long term plans, take a wood working class....

 

Jon

 

you could go get a new body by sending a dwg file to the cnc... :grin:

 

don't need a woodworking class for that...unless they have a cnc.

 

there has to be a lot of small shops out in San Diego.

 

 

I have no problem getting other people to make parts for me, as an engineer that's what I know how to do and I have those resources.   But I would like to be able to make the parts myself.. I would like to get that nice clean edge that was cut to size..  I see some of the neat scopes people here make, Ross's for example. I have no such expectations but I would like to be able to have an idea, come up with a design and built it myself, crude as it might be.  

 

Jon


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#41 Pinbout

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Posted 27 February 2015 - 01:45 PM

not make the parts, just cut them...the big parts.

 

get a bandsaw, drill press and chop saw for all the small stuff, even a small table saw to mod parts.


Edited by Pinbout, 27 February 2015 - 02:22 PM.


#42 abberation

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Posted 27 February 2015 - 02:06 PM

I'm getting ready to start grinding tonight.

 

I am going to start by grinding optical flats for folding mirrors.

 

I will be using the ABC method copied from here:

 

http://www.jeffbaldwin.org/flats.htm

 

It's a good idea, you use three pieces so that as you rotate through all three and test them to each other you can approach very high degrees of flatness.  Since you grind three flats at a time you get one flat to make a mirror diagonal, one spare and one to leave as an uncoated optical flat for testing.  I will be doing ABCD because I'm thinking about making three prototype scopes before I begin my full size 14 3/4" scope.  One will be for my niece, one will be for me and one will be a bribe to a friend who I want to talk in to letting me pour a small concrete slab on his property which has fairly unobstructed views and dark skies.  I want to have that uncoated test flat so I wind up at 4 flats to grind.

 

Per the instructions, I need three pitch laps and I intend to make them with the same glass blanks.

 

After talking to the mirror grinders at Chabot, the flatness of my mirror grinding board needs to be good so I want to use another glass blank under the blank I'm grinding to distribute the stress in to a 3/16" sponge rubber pad.  I think that should give me a good flat grinding platform.

 

That makes a total of 8 blanks.  It's a good thing I bought a box full of 5" Schott glass blanks (about 1/4" thick).

 

I think my first step is to polish the back sides of my blanks so that they become see-through for fringe testing.  That should be a good introduction, then the serious work begins.



#43 Cary

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Posted 28 February 2015 - 01:08 AM

I finished hooking up my Keaser regenerating desiccant air dryer for the shop air!

 

1559614_10153257164229050_4984903290780335984_n.jpg


Edited by Cary, 28 February 2015 - 01:09 AM.

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#44 Jon Isaacs

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Posted 28 February 2015 - 01:49 AM

not make the parts, just cut them...the big parts.

 

get a bandsaw, drill press and chop saw for all the small stuff, even a small table saw to mod 

 

I want to have the skills to start with a sheet of plywood and make the parts by myself...

 

Jon



#45 Pinbout

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Posted 28 February 2015 - 12:55 PM

 

not make the parts, just cut them...the big parts.

 

get a bandsaw, drill press and chop saw for all the small stuff, even a small table saw to mod 

 

I want to have the skills to start with a sheet of plywood and make the parts by myself...

 

Jon

 

 

Yeah, that's what I did for my 12.5 traditional dob.

 

I still laid out the parts on a sheet to make sure the grain was in the correct direction

then rough cut any round parts while cutting all square stuff true.

 

it took about 3 hours to cut all the parts.

med_gallery_106859_3508_80248.jpg

 

12dob cut up.jpg

 

med_gallery_106859_3508_106100.jpg


Edited by Pinbout, 28 February 2015 - 12:56 PM.

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#46 Brett Carlson

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Posted 28 February 2015 - 01:43 PM

I did a couple test Carbon fiber layups using two 19.7 oz carbon sheets with a 4mm Coremat core.   This is a layup to test the strength so I can continue rebuilding my 16" Starfinder into a Truss tube dob. 

 

Having fun!



#47 jtsenghas

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Posted 28 February 2015 - 04:28 PM

I've spent a fair amount of time this weekend working out the dimensions and cut sequences for the sectors on my equatorial platform.  The controls are all done.  It will have a hand-held speed control box for fine-tuning the speed that should have just enough range of speed to fine-tune either the sidereal or lunar rates.  The hand-held unit also has a button for toggling between the high speed rewind direction and the tracking speed forward direction.  Magnetic switches will also be used on warning and end limits of travel.

 

How does this look for a hand-held unit on a strict budget?  It needed four low current wires on a flexible cord,   so......

 

handcontroller.jpg

 

(J.T....phone....home....)


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#48 Pinbout

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Posted 28 February 2015 - 04:42 PM

I know strict  budget but Edmund scientific sells a board that lets you make play-doh as buttons

 

http://media.scienti...d.1000x1000.jpg

 

http://www.scientifi...uct/makey-makey

 

 

anyway I just came in from shooting some vid of the sun. the wife took the camera out of my hands and said," oh that's where my camera is..."

 

so I didn't get to download anything.


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#49 abberation

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Posted 28 February 2015 - 04:54 PM

I made a version 1.0 mirror holding board and a pitch lap last night and used them to 1/2 way polish the back side of one folding flat.

 

Hopefully my progress will get faster as I learn.

 

I'm going to work on version 2.0 of my mirror holder because my glass blanks are very thin, when I'm going for flat, I need to hold them flat and a little more height over the board would be nice too.  That means I need a plastic base that won't swell with water like plywood can.  To provide the flattest base possible I'm going to use some thin sponge rubber under a spare glass blank with the blank I'm grinding on top.

 

I got a lot of help from the people at Chabot, I have to thank them.

 

For woodworking and circles in particular, a plunge router is a great tool.  There are bushings and guide bearings for following templates, circle jigs are easy to make for accurate circles and a router table can be made which will make it even more versatile.

 

A jigsaw would be good for a hobbyist.  For most jobs I prefer a band saw but they are pretty large.

 

A table saw is the next step.  It can do almost everything a chop saw can and a whole lot more but they are bulky.

 

Some people might include sanders on their list but if you have the tools to cut wood accurately you won't have to use sanding to remove material, only to smooth edges and surfaces so sanding blocks and a jitterbug can be more useful than a belt or disk sander on many jobs.

 

Oscillating saws are pretty cool, I use them for some tricky freehand cuts but they aren't particularly fast, they can be helpful but are not a real replacement for more traditional tools.



#50 mattyfatz

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Posted 28 February 2015 - 08:55 PM

I stared at wood that will one day be an altitude bearing... But I only stared  :hmm:


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