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8" f/15 refractor project

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#51 rwiederrich

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Posted 12 January 2011 - 06:04 PM

My 5 baffle ring/stringer was 13ft long and slit nicely into the tube of my 12" OTA. It doesn't need to be secured because it rests up against the back plate...and since it is firmly placed and the scope aims high...it isn't going anywhere. However...I cn easily grab it and slide it out if need be..after I remove the cell adapter from the tube.

Rob

#52 Sean Cunneen

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Posted 12 January 2011 - 07:14 PM

Stringers are the way. You can't see them from the tube and you have precise control making them square. Baffles that you press fit or screw in to attach can look slightly off unless your lucky...


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#53 Jeff B

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Posted 13 January 2011 - 08:20 AM

With a larger instrument, tube currents are an issue. The warm air can pile up and spill over the baffle and into the light path. so I've adopted a best practice of "ventilating" my baffles. This is basically leaving a small gap between the tube and baffle OD, which allows the warmer air to cling to the tube wall and not pond or pool behind the baffles. There are many ways to do this. One of the simplest with the stinger arrangeement is to simply allow the stinger to stick out from the baffle OD a bit, thus creating the desired gap between the tube ID and baffle OD. Also, this makes assembly into the tube very easy as the baffles tend to self-center and you're only sliding them in along stingers instead of the baffle ODs. With a long & large baffle array, sliding them in on the baffle ODs can be a challenge as each baffle adds its own friction against the tube wall. This couple with the fact that the tube will not be perfectly round at some points along its length can make baffle installation with that design a very fustrating and tense experience.

And don't forget the PICTURES (!!)

Jeff

#54 GShaffer

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Posted 13 January 2011 - 09:03 AM

Thanks guys.....I had considered using wood but want the scope to remain as light as possible....the carbon graphite shafts and thin aluminum sheet for the baffles seemed the best solution.....

Jeff B....I had not considered this regarding the tube currents so I will put some thought into that....thanks!

#55 Mirzam

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Posted 13 January 2011 - 10:19 AM

I think you would want a pretty close fit of the baffle rings to the tube, but not so tight as to make it difficult to insert the baffle assembly. The reason for this is to avoid leakage of low angle reflected light around the outer edges of the baffles. If you build an assembly that is too loose you will see what I mean (been there already).

JimC

#56 Darkenergy426

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Posted 13 January 2011 - 01:02 PM

The optic world lost out, but I'll bet that the lawyers didn't.

#57 rwiederrich

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Posted 13 January 2011 - 01:19 PM

And as one can recall..that is the very design I utalized for my 12" tube. It is(IMV) a must to allow heat access..and as you accurately described, it permits 3 points of contact instead of the entire OD of the individual rings.

It worked for me that's for sure. :grin:

Rob

#58 rwiederrich

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Posted 13 January 2011 - 01:22 PM

Visit my yahoo site..*Homemade refrator telescopes* and check out the images of what I did for my 10"f/15.
Jeff B has some images there as well of what he did.

Rob

#59 Jeff B

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Posted 13 January 2011 - 02:01 PM

Thanks Rob!

And even more helpful hints:

I usually use a fully illuminated field spot at focus of ~35-40MM and I don't recommend using the IDs of the focuser drawtube or the diagonal nose to set the spot size. Those restrictions can create a bit of scatter as they typically are not "knife edge" and they are behind the baffling, who's mission is to absorb stray light.

Rather, I use one of the stops about 30-50% back from the lens to set the spot and , even though the other stop ID's have been calculated for a certain axial position, I actually position them a couple of inches behind where they should be. But why he asks? Well even knife edge baffles have scatter and if you position them exactly where the calculations say they should go, that means their IDs are touching the light cone and the small scatter from their IDs can intrude. Backing them up a couple of inches from their "ideal' location removes them and their scatter from the light path.

TAH DAH.

Jeff

#60 rwiederrich

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Posted 13 January 2011 - 03:50 PM

Thanks Rob!

And even more helpful hints:

I usually use a fully illuminated field spot at focus of ~35-40MM and I don't recommend using the IDs of the focuser drawtube or the diagonal nose to set the spot size. Those restrictions can create a bit of scatter as they typically are not "knife edge" and they are behind the baffling, who's mission is to absorb stray light.

Rather, I use one of the stops about 30-50% back from the lens to set the spot and , even though the other stop ID's have been calculated for a certain axial position, I actually position them a couple of inches behind where they should be. But why he asks? Well even knife edge baffles have scatter and if you position them exactly where the calculations say they should go, that means their IDs are touching the light cone and the small scatter from their IDs can intrude. Backing them up a couple of inches from their "ideal' location removes them and their scatter from the light path.

TAH DAH.

Jeff


You're so smart. :grin:

Rob(Did I teach you that?) :lol: :roflmao:

#61 GShaffer

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Posted 14 January 2011 - 08:18 AM

Very nice to have the input of those who came before me :) Thanks guys!!

#62 Robert Bupp

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Posted 12 April 2011 - 07:46 AM

Mike,
I can continue the Muffoletto Optical Company story a bit. Your description so far is quite accurate, and leaves the lingering question about what happened to its people and equipment. Subsequent to the falling apart as you described, a group of (N)ine (U)nemployed (Tek)nicians regrouped formally as Nu-Tek Precision Optical Corporation, first in a basement, then in a warehouse facility, and finally in a manufacturing facility in Aberdeen MD where it (we) have been operating since 1998. Nu-Tek was born in a hostile environment, with a daunting (baseless, and ultimately dismissed) lawsuit hanging over it in its early years. There was no cooperation with at all with equipment, so the opticians were starting from scratch, with only their abilities. Not exactly a seamless transition.

The group of nine worked for several years as Nu-Tek, and over half are still working here now. With about 16 employees in manufacturing, the talent, techniques, and experiences are being passed down already through two generations from the original group.

As for the equipment, we understand that it was unceremoniously set out in the parking lot in the end, and the Nu-Tek group had no knowledge and no opportunity to purchase or acquire any of it.

We regularly work with university and government labs, as our emphasis continues to be very high quality, prototyping and low rates on optical components and subassemblies, including diamond turning and massive (up to Ø1.5m) optics.

If someone is looking to connect with one of the old Muffoletto guys that they used to know, there is enough information above to find Nu-Tek on the web, and somebody here would be happy to fill in what we know.
Kind Regards,
Robert Bupp

#63 Mirzam

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Posted 12 April 2011 - 08:31 AM

Hello Robert,

Welcome to Cloudy Nights!

I was wondering if your company does small diamond generation projects, such a generating a rough curve on 16" pyrex mirror blank? (Which I happen to have sitting in my basement not too far away from Aberdeen).

JimC

#64 Jim Curry

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Posted 13 April 2011 - 07:01 AM

So Herb, where's the pics? :poke: :4

Jim

#65 mikey cee

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Posted 13 April 2011 - 09:28 AM

Come to think of it I haven't seen any pics yet either!! :shocked:

#66 GShaffer

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Posted 13 April 2011 - 09:30 AM

Sadly due to some health issues the project has been on hold for a while now. Things are getting better though and I am back to about 90%.....Will likely start back to work on it in a month or two....

So Herb, where's the pics? :poke: :4

Jim



#67 Jim Curry

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Posted 13 April 2011 - 01:59 PM

I'm sorry to have harassed you.
Get well soon!!

Regards,
Jim

#68 JohnBuilt

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Posted 10 January 2013 - 11:02 AM

I too wonder about the old Muffoletto Optical shop. I worked there from 1978 - about 1982 I believe, on Everall Ave. There were a great group of guys, lets see if I can recall ~ Big Mike & Little Mike, Chuck the engineer, Bob, Frank the crazy grinder operator, Bill the mad machinist, Pat, Emil, John, Pete, Ron Athey, And the Coating Room Guy. I personally trained in grinding and polishing, and was working with Verne, and Chuck, training in the coating operation. I was sent to Denton for a class, after that it seemed a bit strained between Carl Jr = Vern's son, and myself, I think he wanted the coating room position, but never pursued it until I got involved. So I moved on. But yes, a tremendous group of talent, concentrated in such a small area.






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