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Newt Mirror Cell

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#1 zoddette

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Posted 06 December 2018 - 02:00 PM

Anyone know of reasonably priced mirror cells. This is for my 8' f3.5. I had saved budgeted to buy an Aurora Precision and filled out the order form but, I was informed by email today that they have a 42% price increase that's not reflected in the website or order forms. Puts that out of my budget.

L&Z



#2 drneilmb

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Posted 06 December 2018 - 02:02 PM

At that size, depending on the thickness of your mirror, it is entirely possible to construct a very good mirror cell. How thick is your mirror? What sort of tube or box does the cell need to attach to?

#3 Pinbout

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Posted 06 December 2018 - 02:26 PM

How thick

 

https://www.youtube....h?v=aFi7gxWSS_Q

 

oops

 

this one  grin.gif

https://www.youtube....h?v=1RZCgcWufww


Edited by Pinbout, 06 December 2018 - 02:29 PM.


#4 sg6

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Posted 06 December 2018 - 02:33 PM

Orion Optics UK make an 8" at £160, at I guess a 1.4 exchange rate that is $225 and then you have shipping and import to add in, likely little saving. I see the Aurora says $225 which I assume is before the 42% increase. The OOUK may be a little less at the end but not by much is at all.

 

Dobstuff may be worth a look: http://www.dobstuff.com/components.htm

Astrogoods: https://www.astrogoods.com/cells.shtml

 

Easy way to locate a few is enter "mirror cells" in to google and scroll down to the "Images of mirror cells" and open that up. Lots of mirror cells and who produces them.



#5 Starman47

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Posted 06 December 2018 - 02:40 PM

I am not sure what you need. But you may try Dobstuff mirror cells. http://www.dobstuff.com/components.htm

 

 

I have one of his mirror cells in my 12 inch telescope. It works just fine. Just be sure to use a double spring at each collimation bolt. Put one smaller spring inside the larger spring. When you install the cell into the telescope you should tighten the bolts as far as possible, and then collimate by loosening the bolts as needed. This creates a tighter fit, which means that collimation stays in place.



#6 Sam Danigelis

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Posted 06 December 2018 - 04:34 PM

I did this one and it was inexpensive, and easy to make. Works well...

http://garyseronik.c...your-reflector/
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#7 daviddecristoforo

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Posted 06 December 2018 - 04:59 PM

I have an 8” mirror cell from an Orion newt that you can have if you want it. Just cover the shipping. PM if interested...

 

 

Attached Thumbnails

  • 9225CF9E-4EAD-4FF2-9EB3-80DB0BE11C9A.jpeg

Edited by daviddecristoforo, 06 December 2018 - 04:59 PM.

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#8 Pinbout

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Posted 06 December 2018 - 08:02 PM

gallery_106859_3508_13403.jpg



#9 zoddette

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Posted 08 December 2018 - 01:35 AM

Thanks for all the ideas, lots of home grown wood and aluminum cells. I'm looking at the Orion UK or the TS optics now cells now, but as someone said, exchange rates and $50 to ship eats into cost savings. We have a lathe with DRO and lots of aluminum plate, maybe I'll look these designs over have hubby make one us one. Only drawback there is it will take him a month, this wasn't supposed to be a huge project.

 

zo



#10 zoddette

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Posted 08 December 2018 - 01:39 AM

David,, thanks for the offer but we have a 247 mm tube OD, some mounts just don't work for us. Our mirror is a true 203 mm f3.5.  Some cells won't fit a 203 mm. 

 

zo



#11 Lognic04

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Posted 08 December 2018 - 01:46 AM

My 10" cell took a day, it's really simple :)



#12 brebisson

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Posted 08 December 2018 - 02:48 AM

hello,

 

cells for a 200 are quite easy to do, so do not fret too much...

 

assuming a 25mm thickness and 63 mm secondary, plop gives a 3nm RMS deformation with a 3 point cell (this is a lambda /180 roughly)..

 

More interesting, in your case, it calculates the 3 points at 4cm from the mirror center. very close to the secondary. this means that you should be able to just silicone glue the mirror to the cell, making the cell even simpler!

 

Good luck.

 Cyrille



#13 Garyth64

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Posted 08 December 2018 - 08:50 AM

Here's a mirror cell made from ½" aluminum:

 

mirror.jpg

 

Made a pattern on paper, transferred it to the aluminum, and cut it out on a band saw.The two sections are basically the same.


Edited by Garyth64, 08 December 2018 - 08:52 AM.


#14 daviddecristoforo

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Posted 08 December 2018 - 02:47 PM

David,, thanks for the offer but we have a 247 mm tube OD, some mounts just don't work for us. Our mirror is a true 203 mm f3.5.  Some cells won't fit a 203 mm. 

 

zo

FWIW, I measured it and the mirror that came out of it is 203mm. The overall diameter of the cell is 220mm. Don't know the ID of your tube but this might fit...


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#15 pjmulka

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Posted 19 December 2018 - 12:33 AM

You don't need a Lathe. I made my mirror cell with a jig saw and a drill and it works great.
Check out Stellafane website if I can do it anyone can and it took me a couple of days.
Even better I think Danny has plans for his on sketch up.
Good luck,
Pete.

Edited by pjmulka, 19 December 2018 - 12:35 AM.


#16 Chucky

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Posted 19 December 2018 - 07:35 AM

<<  Made a pattern on paper, transferred it to the aluminum, and cut it out on a band saw.The two sections are basically the same  >>

 

Nice simple, clean looking cell Gary.  Also noticed plenty of space between the mirror and the tube walls.  Great job.


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#17 Pinbout

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Posted 19 December 2018 - 09:32 AM

 

We have a lathe with DRO and lots of aluminum plate, maybe I'll look these designs over have hubby make one us one.

use a jigsaw or bandsaw to cut alum plate. don't need a lathe.

 

10mm plate is fine.

 

I like a triangle for the mirror and circle for the thumbscrews.

 

 

again nothing wrong with Baltic birch plywood either, it keeps the weight down if the newt is suppose to be use on a gem.

 

wood expands and contracts more with humidity, alum expands and contracts with temperature.


Edited by Pinbout, 19 December 2018 - 03:28 PM.


#18 kb58

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Posted 19 December 2018 - 01:22 PM

FWIW, ordinary steel expands and contracts about 1/3 less than aluminum, and stainless is slightly more. If you seal the wood, that's your best bet for that size cell.


Edited by kb58, 19 December 2018 - 01:23 PM.


#19 stargazer193857

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Posted 19 December 2018 - 03:16 PM

You don't need a lathe unless you are going full circle, which is only needed if the tube has no ring. Even six scree hole points may bipass the need for a ring. A cell could be made simple. I would not buy one commercially unless you have lots of money.

#20 stargazer193857

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Posted 19 December 2018 - 03:18 PM

FWIW, ordinary steel expands and contracts about 1/3 less than aluminum, and stainless is slightly more. If you seal the wood, that's your best bet for that size cell.


Aluminum can be made lighter and stiffer. As for tube length changing, that is what the focuser is for.

#21 stargazer193857

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Posted 19 December 2018 - 03:25 PM

Use a compass to cut a circle out of plywood. Be accurate at 6 equally spaced points. Cut or better yet sand a bit inside the circle in between. Drill screw holes at the 6 points. Cut a central vent hole. That is your tube ring. Now mount your cell to that. Lots of ways depending on what you need.

#22 pierce

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Posted 19 December 2018 - 03:25 PM

I rather like the inexpensive cell I got from www.astrogoods.com and used for my 10" f/4.5 Coulter mirror.   it fits mirrors from 8 to 12 ro so and is fully adjustable for different size tubes.   Small mirrors like these do NOT need fancy wiffletree things unless they are ridiculously thin, a simple 3 point support using felt or rubber pads works just fine.

 

IMG_7699-X3.jpg



#23 stargazer193857

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Posted 19 December 2018 - 03:30 PM

Anyone know of reasonably priced mirror cells. This is for my 8' f3.5. I had saved budgeted to buy an Aurora Precision and filled out the order form but, I was informed by email today that they have a 42% price increase that's not reflected in the website or order forms. Puts that out of my budget.
L&Z


Agenaastro.com sells GSO mirror cells. Depends what style you want.

#24 Pinbout

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Posted 19 December 2018 - 03:34 PM

look at those commercial cells, they all block the middle where you want to blow a fan...

 

the donut then triangle keeps the center open for a fan to help cool a mirror.

 

 

https://www.youtube....fqQcW8rBwA&t=0s

 

then in a real life 6inf5

 

https://www.youtube....CtC5BfqQcW8rBwA



#25 pierce

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Posted 19 December 2018 - 04:51 PM

an 8" doesn't really need much of a fan, it doesn't have the same sort of thermal mass as a larger mirror.

 

i don't even turn the fan on my 20" that often, if I set it up around sunset, by the time its dark ~90 mins later, its thermally stable  enough unless there's an ongoing drastic temperature drop til much later.




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