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Equipment Discussions >> ATM, Optics and DIY Forum

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starman345
Wait, I'm Thinking
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Reged: 07/06/10

Loc: New Brunswick, Canada
Re: 14" Hubble Optics Project new [Re: starman345]
      #5545601 - 11/29/12 02:02 PM Attachment (46 downloads)

Then all inside surfaces were painted flat black and outside surfaces were given several coats of polyurethane.

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starman345
Wait, I'm Thinking
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Reged: 07/06/10

Loc: New Brunswick, Canada
Re: 14" Hubble Optics Project new [Re: starman345]
      #5545609 - 11/29/12 02:06 PM Attachment (33 downloads)

Then the glue up. I had to really move along to get glue on all the surfaces needing it and get things assembled and squared before the glue dried. Worked out nicely, but I think I would have used slower setting glue had I realized how much time it would take.
Mirror box glued up...no screws, nails or other hardware, just glue and tongue and dado joints


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starman345
Wait, I'm Thinking
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Reged: 07/06/10

Loc: New Brunswick, Canada
Re: 14" Hubble Optics Project new [Re: starman345]
      #5545617 - 11/29/12 02:12 PM Attachment (40 downloads)

Cell finally gets a fit in the mirror box. This was where I had to do a lot of head scratching. I spent quite a while getting the mirror/cell centered in the mirror box, finally I used string lines corner to corner to locate the mirror donut while in the cell and mounted in the mirror box. This allowed me to secure the cell to the mirror box in the right position. After I figured that out things went a little quicker.

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starman345
Wait, I'm Thinking
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Reged: 07/06/10

Loc: New Brunswick, Canada
Re: 14" Hubble Optics Project new [Re: starman345]
      #5545625 - 11/29/12 02:17 PM Attachment (37 downloads)

Today I put the mirror in the cell, I was a bit concerned there wouldn't be room for my fingers when lowering the mirror into the cell but there was lots. I adjusted the collimation bolts to get smooth action before putting the mirror in the cell but now with the weight of the mirror the action is not so smooth. It definately needs improvement. The bolts will turn but it takes some effort.

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starman345
Wait, I'm Thinking
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Reged: 07/06/10

Loc: New Brunswick, Canada
Re: 14" Hubble Optics Project new [Re: starman345]
      #5545629 - 11/29/12 02:20 PM Attachment (36 downloads)

Now I need to make a mirror box cover and make something to anchor the secondary cage and mirror box so I can take it outside and see where my eyepieces focus.

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careysub
Carpal Tunnel
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Reged: 02/18/11

Loc: Rancho Cucamonga, CA
Re: 14" Hubble Optics Project new [Re: starman345]
      #5545763 - 11/29/12 03:58 PM

Did you post a picture of your cell with side-supports? I looked through most of the links but didn't see one.

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starman345
Wait, I'm Thinking
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Reged: 07/06/10

Loc: New Brunswick, Canada
Re: 14" Hubble Optics Project new [Re: careysub]
      #5545825 - 11/29/12 04:44 PM Attachment (40 downloads)

I probably didn't. There are no side supports, only the supports at 45 degrees and one other at the top of the cell to keep the mirror from tipping forward. This is the cell when I had fashioned wooden dowels as contact points....

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starman345
Wait, I'm Thinking
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Reged: 07/06/10

Loc: New Brunswick, Canada
Re: 14" Hubble Optics Project new [Re: starman345]
      #5545828 - 11/29/12 04:45 PM Attachment (39 downloads)

Since then I have changed out the wooden dowel for PVC..

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frito
Pooh-Bah


Reged: 10/05/12

Loc: Fremont, CA
Re: 14" Hubble Optics Project new [Re: starman345]
      #5546321 - 11/29/12 09:50 PM

that hubble optics mirror is interesting. definitely soda lime clear glass looks like two pcs of 1/2" or 5/8" (12mm or 15mm) clear glass glued together with UV glue and some sort of spacer piers.

neat concept, should cool rapidly for a mirror that thick.

btw i work in the architectural flat glass industry.


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frito
Pooh-Bah


Reged: 10/05/12

Loc: Fremont, CA
Re: 14" Hubble Optics Project new [Re: starman345]
      #5546322 - 11/29/12 09:50 PM

double post :S

Edited by frito (11/29/12 09:51 PM)


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sopticals
professor emeritus


Reged: 03/28/10

Loc: New Zealand
Re: 14" Hubble Optics Project new [Re: frito]
      #5546358 - 11/29/12 10:14 PM

Its all coming together really nicely Brian. All the best with the remainder of the construction. Im sure you will be pleased with the HO primary.

Best regards,
Stephen.(44deg.S.)


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careysub
Carpal Tunnel
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Reged: 02/18/11

Loc: Rancho Cucamonga, CA
Re: 14" Hubble Optics Project new [Re: frito]
      #5546460 - 11/29/12 11:40 PM

Quote:

that hubble optics mirror is interesting. definitely soda lime clear glass looks like two pcs of 1/2" or 5/8" (12mm or 15mm) clear glass glued together with UV glue and some sort of spacer piers.




The piers are soda-lime glass also (naturally) and I had supposed they were fused in a furnace. But you could glue glass as easily than anything else.

Quote:


neat concept, should cool rapidly for a mirror that thick.

btw i work in the architectural flat glass industry.




One comment I have about HO's execution of this concept is that the pier cluster is pretty thick, and they seem to be randomly (if densely) scattered about.

Granting that this is no doubt perfectly adequate for the engineering requirement, I am surprised that they don't use a uniform grid - an optimized grid has got to give a better weight savings and a more uniform product, and placing the glass cylinders into a spacing template seems like it might even save effort overall.

I have corresponded with someone with an HO mirror who was having it refigured and the (highly regarded) optician was having trouble with its surface due to some sort of non-uniformity in this surface properties. My suspicion would lie in the lack of positioning control of the support piers.


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frito
Pooh-Bah


Reged: 10/05/12

Loc: Fremont, CA
Re: 14" Hubble Optics Project new [Re: careysub]
      #5546480 - 11/30/12 12:00 AM

or improperly annealed glass perhaps.

the company i work for buys plently of glass from overseas. one the the biggest problems with many of the Chinese flat glass manufactures tends to be poor annealing of their heavier glass thicknesses. i have no doubt looking at photo's of the HO mirrors that they are using mass produced soda lime float glass on those mirrors. the 3 un-figured surfaces would not be clear enough to see the support piers clearly if it was not float glass because in a telescope mirror there is no reason to do any surface polishing or smoothing yet those other 3 surfaces appear to be very smooth to me. HO does say the glass is fused together and that would make sense i suppose looking at the photo's of the mirror the rear surface esp. shows a dull but smooth surface indicating that the glass was put into a kiln and heated at some point. the surface reflections i can see on the inner 2 surfaces appears much smoother and more like float glass. plus there is the whole the only reason soda lime glass is significantly cheaper than borosilicate glass types (pyrex) is because its mass produced in a much greater number and there's no reason not to use it


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starman345
Wait, I'm Thinking
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Reged: 07/06/10

Loc: New Brunswick, Canada
Re: 14" Hubble Optics Project new [Re: careysub]
      #5548679 - 12/01/12 12:10 PM Attachment (33 downloads)




Quote:

I am surprised that they don't use a uniform grid - an optimized grid has got to give a better weight savings and a more uniform product, and placing the glass cylinders into a spacing template seems like it might even save effort overall.





Mine seems to have a uniform grid. Maybe I'm missing what you are saying here? BTW I measured the pier in the center and it is dead on in the center from my measurements to the mirror edge in several places. I'm curious, does your 18" look similar?


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frito
Pooh-Bah


Reged: 10/05/12

Loc: Fremont, CA
Re: 14" Hubble Optics Project new [Re: starman345]
      #5548990 - 12/01/12 03:38 PM

looks pretty uniform to me, if you look at it the wrong way though i could see how one might think its not

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starman345
Wait, I'm Thinking
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Reged: 07/06/10

Loc: New Brunswick, Canada
Re: 14" Hubble Optics Project new [Re: frito]
      #5559607 - 12/07/12 04:59 PM Attachment (36 downloads)

I built a gizmo to hold the mirror box and secondary cage in rough alignment and took it outside to see where my eyepieces came to focus. I was astounded when putting in the 21mm stars appeared!
I had calculated where the optics should be placed but I didn't expect things to go that well. All three, 21mm, 13mm and 6.7mm came to focus at the same distance. I am going to take it out again just to make sure, I ran out of time last night and I want to try things with my camera in the focuser to see if I have enough travel.
Dont' laugh at the picture, I know its not a thing of beauty.


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Pinbout
Postmaster
*****

Reged: 02/22/10

Loc: nj
Re: 14" Hubble Optics Project new [Re: starman345]
      #5559803 - 12/07/12 06:49 PM

Quote:

I built a gizmo to hold the mirror box and secondary cage in rough alignment




your thingy is very cool.

Quote:

All three, 21mm, 13mm and 6.7mm came to focus at the same distance.




most of my eyepieces focus around the same, except my tv 40mm plossl, that eyepiece uses almost all of my racked out focuser travel.


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starman345
Wait, I'm Thinking
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Reged: 07/06/10

Loc: New Brunswick, Canada
Re: 14" Hubble Optics Project new [Re: Pinbout]
      #5575742 - 12/17/12 01:40 PM Attachment (25 downloads)

I built some lower truss connectors out of several layers of glued up 12mm ply. Drilling the angled holes for the truss poles was a challenge. My drill press table required several adjustments on sacrificial trial blocks before I finally got the required 9 degrees. Besides the truss angles, because the secondary truss connectors were an inch or so wider than the lower connectors I also had to adjust for a small amount of tilt. Sort of like doing a compound miter, only on a drill press. I installed the T-nut on the back, then cut out the chock. A picture of the glued and clamped connector..

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starman345
Wait, I'm Thinking
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Reged: 07/06/10

Loc: New Brunswick, Canada
Re: 14" Hubble Optics Project new [Re: starman345]
      #5575744 - 12/17/12 01:42 PM Attachment (20 downloads)

And with the clamps removed

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starman345
Wait, I'm Thinking
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Reged: 07/06/10

Loc: New Brunswick, Canada
Re: 14" Hubble Optics Project new [Re: starman345]
      #5575750 - 12/17/12 01:46 PM Attachment (22 downloads)

With the chock installed and a view of the T-nut on the back of the connector

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