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John Jarosz
Astro Gearhead


Reged: 04/25/04
Posts: 3026
Loc: Chicago area, IL
First Light - 8" Dall Relay Scope
      #1385712 - 01/26/07 09:35 PM Attachment (131 downloads)

Well after two years of research, design, construction, and collimation I finally got this project to a point where the views are pretty good and I can start to put some finishing touches on the whole thing without worrying if I have to keep working on the quality of the image,
The inspiration for this scope is originally from a photo in the earlier editions of ATM 1,2,3 of Horace dall looking thru a 3" version of this scope in 1933 or so. There's a picture of Robert Cox looking thru his version of this design on page 409 of the Willman=Bell reprint of Terexeau's "How to Make a Telescope".
My version is an 8" F11 optically designed by Ed Jones (Thanks, Ed ). It uses commercially available lenses for the relay section. The mirrors were done by Mark Harry (Thanks, Mark ). Everything else was made on a lathe and tablesaw plus an assortment of hand tools. The design is intended to disassemble into 4 parts that fit into a pelican case. For travel, I'll use this on a large Bogen photo tripod. The relay lenses eliminate the need for a solid tube, so that aspect of the scope makes it suitable for travel.
It's mounted on a fork mount from an old Criterion 8000 scope ($37 ). The old synchrous drive tracks pretty well - this is just for visual use. Homemade wedge and tripod completes it.

Attachment

--------------------
6" F4.6(w/Paracorr) Reflector , 8" F11 Dall Relay Scope ,
6" F5 RFT Refractor w/Istar Obj , G11 Mount Gemini1 Level 4


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Tony B



Reged: 07/11/06
Posts: 979
Loc: Minnesota
Re: First Light - 8" Dall Relay Scope new [Re: John Jarosz]
      #1385722 - 01/26/07 09:40 PM

that thing looks sweet!, how do you keep the objective from getting dirty?

--------------------
*-Tony Bombardo-*
4.5" Orion SpaceProbe f/8 reflector
Meade 70AZ-ADR 70MM f/10 refractor
ATM 6" f/4 reflector
Bausch & Lomb 8001 8" Cass
Celestron StarHopper 6" Dob
*-all this light pollution is making me cough-*


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John Jarosz
Astro Gearhead


Reged: 04/25/04
Posts: 3026
Loc: Chicago area, IL
Re: First Light - 8" Dall Relay Scope new [Re: John Jarosz]
      #1385723 - 01/26/07 09:40 PM Attachment (65 downloads)

The "Y" shaped part at the rear hold the primary collimation screws, 3 little fans, the pinch clamp for the secondary support,the diagonal, the primary cell support and the focuser. The mirror is held in place by 3 spotys of the plastic industrial hook & loop (velcro type) material.

Attachment

--------------------
6" F4.6(w/Paracorr) Reflector , 8" F11 Dall Relay Scope ,
6" F5 RFT Refractor w/Istar Obj , G11 Mount Gemini1 Level 4


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John Jarosz
Astro Gearhead


Reged: 04/25/04
Posts: 3026
Loc: Chicago area, IL
Re: First Light - 8" Dall Relay Scope new [Re: John Jarosz]
      #1385728 - 01/26/07 09:47 PM Attachment (66 downloads)

Collimation is the toughest part of this scope. I can get it close with a chesire eyepiece, but the final collimation must be done via star test. The Primary is F3. When collimation changes it's really noticeable. There is a plastic cover for the primary when it's in the case. It really doesn't get that dirty.
You can see modifications made to be able to position the relay elements correctly. It's hard to describe the sensitivity of the positioning of the relay and secondary, but you have to get it right. Apparently the tolerances of the lenses cause the final positioniong to vary from the design numbers. Now I have to go back & finalize the relay tube and connection to the structure. Sometime in the future I want to anodize everything.

Attachment

--------------------
6" F4.6(w/Paracorr) Reflector , 8" F11 Dall Relay Scope ,
6" F5 RFT Refractor w/Istar Obj , G11 Mount Gemini1 Level 4


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philipdo
sage


Reged: 12/06/06
Posts: 248
Loc: Flanders, Belgium, Europe
Re: First Light - 8" Dall Relay Scope new [Re: John Jarosz]
      #1386199 - 01/27/07 07:14 AM

neat looking scope John.
How does it perform on the moon and planets? If collimation is that critical, maybe a closed tube with an optical window could provide more rigidity. Is this optical design similar to the Dillworth relay telescope, with all spherical optics? Maybe Ed can shed more light on this. Love the inventivity of the construction!

--------------------
-philip doutreligne

-ETX 90
-Orion Atlas mount
-Kutter Schiefspiegler 200/4000
-70/1000 Cardoen-Lichtenknecker coronagraph



http://users.telenet.be/philipdo


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Mark Harry
Vendor


Reged: 09/05/05
Posts: 5450
Loc: Northeast USA
Re: First Light - 8" Dall Relay Scope new [Re: philipdo]
      #1386211 - 01/27/07 07:38 AM

I like the construction, and design of the finished scope! I never imagined it'd look so good. The view of the back is fascinating. Congrats! That's a carbon fiber secondary rod, I take it?
Mark

--------------------
Vendor- accurate small to medium telescope optics


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daev
Technically Enlightened


Reged: 03/10/04
Posts: 6587
Loc: On the edge of the desert
Re: First Light - 8" Dall Relay Scope new [Re: Mark Harry]
      #1386215 - 01/27/07 07:45 AM

Unusual design, very nice!

dave

--------------------
"Yes, I know it's flat here. When the seeing is good you can stand on a beer can and see Toronto...."



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Chriske
Kijkerbouw Urania


Reged: 08/15/04
Posts: 2317
Loc: Boechout, Belgium
Re: First Light - 8" Dall Relay Scope new [Re: daev]
      #1386234 - 01/27/07 08:20 AM



--------------------
Chris



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Darenwh
Carpal Tunnel


Reged: 05/11/06
Posts: 2783
Loc: Covington, GA
Re: First Light - 8" Dall Relay Scope new [Re: Chriske]
      #1386251 - 01/27/07 08:36 AM

Very nice looking scope. The workmanship I see on this site is usually exceptional and quite often amazing... This scope falls in the later.

--------------------
Daren
Covington, GA


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NHRob
Post Laureate


Reged: 08/27/04
Posts: 4111
Loc: New Hampshire
Re: First Light - 8" Dall Relay Scope new [Re: Darenwh]
      #1386266 - 01/27/07 08:49 AM

Sweet scope! I can see Mark Harry's logo on the back of the mirror, through one of the holes in the rear plate.
Very nice. I'm working on a 6" f/6 newt right now with a Mark Harry mirror. I'm hoping to craft the scope into a planet-buster !!

Rob

--------------------
Rob ... my avatar pic is me ... on a good day!
**********************
Canon 12x36 IS binos
Spooner 6.5" f/8.6 dob w/Dobstuff mount
Past Scopes:
Starstructure 14.5", Starmaster 14.5", 10" f/6 Zambuto homemade dob
AP130EDSF, AP130EDT, Traveller, AP152 f/9, 6" AP Christen triplet,FS-102(x2),FC-100,FS-152,TOA-130,TEC-140(x2),TV-101, TV-102,TV-76,TV-85, WO Z80FD, SV105/LZOS, WOLZOS100/800, TEC-6,TEC200/15,MN56,APM130/1200/LZOS,Mewlon180, Jaegers 6" f/15 achro, Palermiti 6" f/15 achro



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John Jarosz
Astro Gearhead


Reged: 04/25/04
Posts: 3026
Loc: Chicago area, IL
Re: First Light - 8" Dall Relay Scope new [Re: Darenwh]
      #1386267 - 01/27/07 08:51 AM

Thanks, guys.
Philip: It is not a rigidity issue. Once the scope is collimated it holds it quite well. The problem was the initial collimation (and axial positioning) of the primary. As the angle of the primary is adjusted, focus and aiming change. Then you must change the position of the secondary and relays. Now that it's done, the design allows the connecting parts to register with one another and permanently fix the relationship.

A Dilworth is made from 100% spherical elements. On this scope the primary is ellipsoidal. If you want to read Horace dall's accounts of his designs they can be found in Scientific American of Dec. 1947; and in Sky & Telescope of Jan. 1962 and March 1968. There is a small webpage describing dall and some of these scopes. Horace dall pocket telescopes

John

--------------------
6" F4.6(w/Paracorr) Reflector , 8" F11 Dall Relay Scope ,
6" F5 RFT Refractor w/Istar Obj , G11 Mount Gemini1 Level 4


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philipdo
sage


Reged: 12/06/06
Posts: 248
Loc: Flanders, Belgium, Europe
Re: First Light - 8" Dall Relay Scope new [Re: John Jarosz]
      #1386285 - 01/27/07 09:07 AM

thanks for the info, John.
I did not know that in the relay design the primary mirror was elliptical as in the dall-Kirkham. How is stray light with this open construction? can the scope be used for daytime viewing?

--------------------
-philip doutreligne

-ETX 90
-Orion Atlas mount
-Kutter Schiefspiegler 200/4000
-70/1000 Cardoen-Lichtenknecker coronagraph



http://users.telenet.be/philipdo


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Bruce MacDonald
Pooh-Bah


Reged: 01/12/06
Posts: 1126
Loc: Devizes, Wiltshire, UK
Re: First Light - 8" Dall Relay Scope new [Re: philipdo]
      #1386303 - 01/27/07 09:23 AM

Beautiful scope.



I really must get around to finishing my 6" mirror....

--------------------
Bruce MacDonald
Devizes, Wiltshire, UK
Per Mare Per Terras
Schneider (dkl) 10x80 Flakfernrohr, Canon 10x30 IS binoculars, Synta 80mm f/5 refractor, Televue 24mm Panoptic


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John Jarosz
Astro Gearhead


Reged: 04/25/04
Posts: 3026
Loc: Chicago area, IL
Re: First Light - 8" Dall Relay Scope new [Re: philipdo]
      #1386313 - 01/27/07 09:29 AM

Yes, that was the intent. The relay lens arrangement incoporates a field stop that limits the view of the relay lenses to trhat of the secondary. All other light is blocked. That's why a big tube is un-necessary. On my design the diagonal in the rear can be unscrewed and removed. The focuser can then be screwed into that location giving an in-line path. In this configuration the view is erect and correct R to L. As for stray light, my neighbors have two porch lights constantly burning 15 meters away. Those lights never affect the scope when I'm using it at night.

The moon and planet views are quite nice. I think this scope design is more appropriate to the past when premium performing eyepieces were not available. The design gives one a long FL in a small package so you can use long FL eyepieces to get a good view. These days one can simply put a $$ short FL long eye relief eyepiece in a standard objective and get high magnifications.

In a nutshell this scope is my way of having the performance of the scope in my avatar - the 7" Questar. There's no way I could justify the $$ for that scope, although if you added up my labor hours @ $10/hour maybe the total cost would approach the Q.

John

--------------------
6" F4.6(w/Paracorr) Reflector , 8" F11 Dall Relay Scope ,
6" F5 RFT Refractor w/Istar Obj , G11 Mount Gemini1 Level 4


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MMICKELS
Aluminum Knight


Reged: 01/20/04
Posts: 36050
Loc: Land of Shake and Bake
Re: First Light - 8" Dall Relay Scope new [Re: John Jarosz]
      #1386323 - 01/27/07 09:40 AM

Wow!

--------------------
Mark


I'm going outside to stand, so if anyone asks I am outstanding.






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Brian Reed



Reged: 10/29/04
Posts: 471
Loc: North East Illinois
Re: First Light - 8" Dall Relay Scope new [Re: MMICKELS]
      #1386334 - 01/27/07 09:48 AM

Cool scope !!!

--------------------
Brian
10-F5 Videocam Scope
8-F7 Cave Optics Planet Killer
RV-4 Vintage Criterion Newt
Round Table Platform
Member of Northwest Suburban Astronomers



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Ed Jones
Carpal Tunnel


Reged: 04/06/04
Posts: 2232
Loc: Sin-sin-atti
Re: First Light - 8" Dall Relay Scope new [Re: John Jarosz]
      #1386475 - 01/27/07 11:25 AM Attachment (48 downloads)

Congratulations John on a well executed, unique scope! You'll not see another scope like this one. For those interested here is the optical layout.

Attachment

--------------------
Ed Jones




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philipdo
sage


Reged: 12/06/06
Posts: 248
Loc: Flanders, Belgium, Europe
Re: First Light - 8" Dall Relay Scope new [Re: John Jarosz]
      #1386488 - 01/27/07 11:33 AM

John,

how do you focus? I don't see any focussing knobs or is it a helical focusser?

--------------------
-philip doutreligne

-ETX 90
-Orion Atlas mount
-Kutter Schiefspiegler 200/4000
-70/1000 Cardoen-Lichtenknecker coronagraph



http://users.telenet.be/philipdo


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philipdo
sage


Reged: 12/06/06
Posts: 248
Loc: Flanders, Belgium, Europe
Re: First Light - 8" Dall Relay Scope new [Re: Ed Jones]
      #1386503 - 01/27/07 11:40 AM

Ed,

is there any particular reason why the second relay lens has to be appr. twice the diameter of the first lens? From the raytracing it seems that the larger lens is not used over its full diameter.

--------------------
-philip doutreligne

-ETX 90
-Orion Atlas mount
-Kutter Schiefspiegler 200/4000
-70/1000 Cardoen-Lichtenknecker coronagraph



http://users.telenet.be/philipdo


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NHRob
Post Laureate


Reged: 08/27/04
Posts: 4111
Loc: New Hampshire
Re: First Light - 8" Dall Relay Scope new [Re: philipdo]
      #1386517 - 01/27/07 11:49 AM

John,
Very nice. Dose this design have any advantages over a classic dall-Kirkham?

Rob

--------------------
Rob ... my avatar pic is me ... on a good day!
**********************
Canon 12x36 IS binos
Spooner 6.5" f/8.6 dob w/Dobstuff mount
Past Scopes:
Starstructure 14.5", Starmaster 14.5", 10" f/6 Zambuto homemade dob
AP130EDSF, AP130EDT, Traveller, AP152 f/9, 6" AP Christen triplet,FS-102(x2),FC-100,FS-152,TOA-130,TEC-140(x2),TV-101, TV-102,TV-76,TV-85, WO Z80FD, SV105/LZOS, WOLZOS100/800, TEC-6,TEC200/15,MN56,APM130/1200/LZOS,Mewlon180, Jaegers 6" f/15 achro, Palermiti 6" f/15 achro



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