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new 40" dob

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#1 Diabolo

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Posted 30 June 2011 - 08:00 AM

Hello, this is my first post on cloudynight,
I’m a ATM living south of France, on the limestone plateau of Larzac and I make dobs since 1993. A 16” was the first one, a 22” follow and later a 32”. All are visible on
http://www.astrosurf.com/altaz and some got an article in English at :
http://astrosurf.com/altaz/index_e.htm

Few years ago was the start of the last project, a pair of 40” instrument. The goal was to make to identical dob structure, one for the optician and one for me. So I made two structure. Basically, the 40” use most of the technique used to make the 32”. Plywood over Styrofoam, astatic cell and carbon truss. On the 40”, the cage is full carbon, including the spider (it’s a one part piece). The scope is around 280 kgs. They could have been made lighter but it was not the goal. The goal was to be able to use the FD3 primary at is maximum potential, so, the stiffness of the structure was more important than save few pounds. All alu part are anodized
It’s all home made, except the clement focuser and the motorisation from Siderealtech.
The motorisation is the last part of the job, got to set it up to see if everything is alright. I haven’t run it yet.

It takes me about 2000 hours for the structure, on 3 years. Not include a couple of year to design it. The scope is setup in about 30 minutes bye one person.

The jump from the 32” is obvious at the eyepiece. My 40” saw its first light last Saturday with some friends, Philippe Tosi, a French ATM was specially enthusiast as we can see on some pics !

I have never seen Saturn Nebula orange on all its edge or so warm color on some of the M27 parts. The Veil is so complex that it’s beyond description…

You can see some pics at :

http://astrosurf.com/altaz/T1000.html

http://www.stellarza...ons stellarzac/

http://www.stellarzac.com/T1000/

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#2 davidpitre

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Posted 30 June 2011 - 08:11 AM

Welcome to Cloudy Nights.
Those are amazing telescopes. You should be proud.
I'd like to pin a medal on you for the best first post .

#3 radicell2

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Posted 30 June 2011 - 08:38 AM

Few years ago was the start of the last project, a pair of 40” instrument. The goal was to make to identical dob structure, one for the optician and one for me. So I made two structure.


On the 40 incher,where did you get the slumped pyrex glass from?Can you give some details on how this mirror was tested and figured?

Quite the project.

Ric

#4 gatorengineer

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Posted 30 June 2011 - 08:41 AM

Wow Beautiful.....

Mirror support looks interesting, is there more information?

#5 Diabolo

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Posted 30 June 2011 - 09:00 AM

Thanks for your kind words !

The mirror cell is an astatic, their is an article about that : http://astrosurf.com/altaz/astatic.htm

I wrote it some years ago, might have change my mind on some points since but most is still good.

About the glass, I don't have much element about it because I work on the structures and let the optician work on the optic. If I'm right, the glass is slumped in a mold bye a friend of him who work on glass. The mold got the good shape of have the meniscus. The operation take time and the glass back is of course quite rough when the operation is finished. Sorry not to have much more info !

#6 BluewaterObserva

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Posted 30 June 2011 - 11:03 AM

I changed a full floating alt/azi cell to an astatic GEM cell for my .8 meter. Interesting project....

Used Styrofoam as well in the change.

#7 gatorengineer

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Posted 30 June 2011 - 12:15 PM

From your 32 to the 40 you changed back to a traditional truss structure. Was there any paricular reason for this? I was contemplating the inverted structure for a 24"

Mark

#8 Achernar

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Posted 30 June 2011 - 12:52 PM

You've really created a masterpiece, the craftsmanship is first rate. I'm sure the views through it are first rate as well. Thanks for sharing with us. :bow:

Taras

#9 Diabolo

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Posted 30 June 2011 - 01:32 PM

Thanks ! Yes, the views are really great. I will observe tonight, begin to be a drug !

The switch back from a square cage come from a fact, I made two, and as for all this kind of things, we have to agree on the design and the optician don't like square cage. Personnaly I love square cage but I'm quite happy with the final look of the octogone cage.

Plywood on styrofoam is a great solution to save weight. Steven Overolt found a great solution for scope makers !

#10 idealistic

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Posted 30 June 2011 - 04:11 PM

That 40" is incredible. Jealousy is not something that I feel often, but 40" in a carbon fiber structure... arrgh. Ill probably never own a scope like that, but I take pleasure in knowing that they exist.

#11 Brian Reed

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Posted 30 June 2011 - 05:31 PM

That is amazing!!!! :applause: :applause: :applause: :applause: :applause:

#12 herrointment

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Posted 30 June 2011 - 06:04 PM

Good Gravy,Gertrude!

#13 john nichol

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Posted 01 July 2011 - 04:11 AM

Amazing, can you give us more information about the optics please?

John

#14 John Carruthers

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Posted 01 July 2011 - 05:05 AM

:bow:
absolument superbe

#15 Diabolo

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Posted 01 July 2011 - 06:32 AM

Thanks for your comments !

John, Unfortunately I don't have much more detail about the primary, is about 53 mm thick and made of pyrex, diameter of 1006 mm if I'm right.

The highlight of the last night was ABELL 2151, a wonderfull view, full of galaxies with distinct shape and position. Also, M27 with a Denk and a pair of panoptic was photographic like... Never saw M51 that huge and full of details with an ethos 10 mm at 345x. One of the first time the galaxy seems to take a third dimension, like a "thickness".

#16 scopemankit

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Posted 01 July 2011 - 08:28 AM

What a superb instrument! I'm sure you will have hours of great viewing with it!

#17 Nop

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Posted 01 July 2011 - 03:47 PM

c' est formidable!
The Hammer. Will you build a holiday cottage to with those telescopes for rent? That would be the ultimate dream holiday.

#18 Diabolo

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Posted 02 July 2011 - 01:15 AM

Thanks for all those comments !

Scopemankit : oh yes ! Tonight was again a great moment. I'm still glued on classical objetc, M51 even if its not the best time of the year. With an ethos 10 an 8, I have tried adverted vision and waouuu !! The arms seems to float on a dark cloud, first time I see the galaxy "fill" with this "grey cloud". The arms are full of details with star like compact HII zone.


Nop : I don't want to be out of the rules of cloudynight, I'm still a TM in my hart(I have started 18 years ago) ! That was not the goal when I started to draw but now it is. The project take about 5 years from first ideas to first light. Life has changed and I now live in a good dark rural place at 2100 ft. Not that high but a good place to live. First people will arrived this afternoon, that's why I have spend as much time as possible at the eyepiece, as it will be more difficult later.

The scope is roll out a shelter and setup in about 6 to 8 minutes, that's why I jumpe on every available night even if, like currently, they are short.

#19 nytecam

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Posted 02 July 2011 - 02:02 AM

Greetings from London ;) Monster scopes - great projects :bow:

#20 Diabolo

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Posted 02 July 2011 - 03:34 AM

Some pics !

A 40" next to a 24 I made years ago. The 24" is also plywood on foam. I must thanks Steven Overholt for this idea and John Lightholder who send me Steven's booklet after he made a 22" based on this technics

Posted Image


Posted Image

Other pics are visible at :

http://www.stellarzac.com/T1000/

#21 ZielkeNightsky

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Posted 02 July 2011 - 06:53 AM

Wow what a great scope. Congrats and thanks for sharing with us.

Amazing....

#22 JKoelman

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Posted 02 July 2011 - 09:39 AM

Un seau de lumiere magnifique! Congratulations!

A 40" next to a 24 I made years ago.


So, you've made a 16", a 24", a 32", and now a 40". I look forward to your report here on your next creature, the amazing 48"... :shocked:

#23 Mike I. Jones

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Posted 02 July 2011 - 09:44 AM

Naah, he needs to get hooked up with those guys in Oklahoma with a 61" mirror and telescope project!

#24 reiner

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Posted 02 July 2011 - 09:59 AM

Hi Frederic,

wonderful telescopes, I have admired them for some time already at your web pages. They come extremely handy for a 40"!

I would also be very interested on the process of the mirror blank preparation (slumping) and the support of the blank during grinding and polishing. Is there any way to contact the optician ? If you don't want to discuss this publicly, you can also email me via my address below.

#25 Diabolo

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Posted 02 July 2011 - 12:28 PM

Again, thanks for all your comments !

Not sure I will make a bigger one, first the mirror specs change dramaticaly to jump to a 48" and all the structure got to follow... I know that like many, I got the "this this the last one" syndroma that leade you to a bigger one one day but... this time...

Reinter, the optician don't speak english at all, it will be hard to communicate with him. He is on french forum only. Sorry ! We spoke about english list and forum but he don't want give a try.






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