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Reflector Telescope

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#1 Antony.Smith

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Posted 30 October 2017 - 04:54 AM

Hello I have had this Reflector Telescope in my possession for many Years. I have finally decided or have the time to do something with it. It was bought by my father and I believe it was part of he blue streak Missile/Rocket project, we had the multi rotational mount but this was disposed of. Can any one give me information as to its magnification suitability and the best way to adapt it for Astronomy. 

 

Thanks Anthony

 

RFz-6.jpg



#2 luxo II

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Posted 30 October 2017 - 05:59 AM

For a start it's a lens, not a telescope. Probably had a photographic plate at the back for wide-field B&W photos to determine the trajectory of something.

 

To help identify what it is, it would be a big help if you turned it round and took another photo so we can see what the rest of the lettering says around the front.

 

It also appears to have a yellow filter (not uncommon for B&W plate cameras) screwed on the front, if that's the case please unscrew that and let's see what the lettering says under that.

 

If it's what I suspect it is, it's not much good for astronomy compared to current technology - sensors have shrunk and so have modern lenses.


Edited by luxo II, 30 October 2017 - 06:05 AM.

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#3 aneeg

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Posted 30 October 2017 - 06:12 AM

It is a Carl Zeiss Jena aerial camera lens from former East Germany, probably used for cartography. Quality should be very good. 

 

Arne


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#4 Ulmer Spatz

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Posted 30 October 2017 - 06:34 AM

Possibly the objective lens of a missile tracking scope/camera used at the Australian Woomera Range Complex during the 1960s BlueStreak test flights. The best view of the scope/camera comes at 12:50 into the video. I don't have the knowledge to comment on the usefulness of the lens, so I'm posting my guess here just as a footnote.

 

http://www.nationala...page_rocket.htm


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#5 aeajr

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Posted 30 October 2017 - 07:37 AM

My first impression was also that it was a lens, not a telescope, but I don't know much about such things.

 

For what it is worth, if that were a telescope it would be a refractor, not a reflector, as there is no mirror that I can see.

 

Telescope Terms Dictionary
http://www.hioptic.c...copes/index.htm


Telescope Basics - Eye on the Sky video series
http://www.eyesonthe...copeBasics.aspx

 

 

If you are interested in getting into astronomy, we can help. 


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#6 Jon_Doh

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Posted 30 October 2017 - 07:56 AM

It looks like a camera lens, definitely not a reflector.  Zeiss makes some very fine camera lenses.


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#7 Antony.Smith

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Posted 30 October 2017 - 09:07 AM

Thanks for your help, I have posted some more pictures, the lens does not have any other writing around the lens front element but has a military designation 22.

Thanks and I would like to start exploring astronomy as a interest..

Anthony

 

 

Rfz-21.jpg Rfz-31.jpg



#8 Antony.Smith

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Posted 30 October 2017 - 09:08 AM

Rfz-4.jpg More Jpegs



#9 Antony.Smith

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Posted 30 October 2017 - 09:10 AM

Rfz-3.jpg



#10 Antony.Smith

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Posted 30 October 2017 - 09:10 AM

Rfz-7.jpg



#11 aeajr

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Posted 30 October 2017 - 09:17 AM

Thanks for your help, I have posted some more pictures, the lens does not have any other writing around the lens front element but has a military designation 22.

Thanks and I would like to start exploring astronomy as a interest..
Anthony


Welcome to the universe Anthony. I will let others discuss that lens as I know nothing about it. 

 

You will be pleased to know that the quality of amateur astronomy equipment is pretty good and the costs have come down a lot over the years, or so the old timers tell me. I am only in this for 2.5 years.  And, if you want it, there are computerized mounts that will help you find almost anything you want to see.

 

Budget drives the discussion so consider how much you are willing to invest to get started.

 

If you have binoculars, 7X35 or larger you already have your first optics and can get going with those.  I started my journey in astronomy with 10X50 binoculars that cost $25.   Inexpensive and easy to use.   It is amazing how much more you can see with cheap binoculars.    And, even though I have 3 telescopes, I use the binoculars often though I have upgraded a bit since that first set.

 

 

 

Introduction to Binoculars for Star Gazing 

( use this one all the time to show the value of starting with binoculars)
Seeing targets in Taurus -  Now is a great time to explore Taurus.
https://www.youtube....h?v=6fHKG9tkPQU

 

 

 

Here are some general introductory resources.

 

Turn Left at Orion - probably the best first book for someone getting involved.   It will help you understand the terms and the types.  The
biggest benefit is that it is NOT full of pretty color photos that don't look anything like what you will see in the eyepiece.  It  has realistic
sketches that show you what you will see.
http://www.amazon.co...n left at orion

 

 

Choosing your first telescope – Orion
Ignore that this is an Orion Video, the other MFG have similar offerings but I feel they do a good job of overviewing the types and benefits of each telescope.
https://www.youtube....h?v=ZFJP1RguLXI

 

 

What's Out Tonight
http://whatsouttonight.com/

 

 

Orion Constellation - Orion is rising in my eastern sky around 11:30 pm and will rise earlier and earlier as the season goes forward.   
https://www.youtube....h?v=UkYkSqGQCZ4


Edited by aeajr, 30 October 2017 - 10:29 AM.


#12 Eikonal

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Posted 30 October 2017 - 11:16 AM

Hello Anthony,

 

it would help a great deal to have a view of the full text on that front ring.

Does the front ring with the Zeiss/Jena serial number really attach to the thing or was it just lying on top of the instrument.

Judging from the spring-loaded bearing elements for the entrance element, I wager that the engraved ring comes from another instrument rather than from this one.

The number on the side is clearly not German (the typeface is nothing which would have been used by any German company), and Zeiss would not have used unpainted screw-heads anywhere in (or near) the instrument.

Even the small brass screws would have been chemically blackened and painted.

 

From what I am seeing here, my best guess at the moment would be that this is a catadioptric photographic system.

The mounting brackets are a strong point in favour of an aerial reconnaisance/geodesic lens. Anything that points downward through the bottom of a plane with a camera of some description mounted on top of it. There even sems to be one of the original bushings in one of the mounting holes.

 

Please look through the aperture at the back: Does that black three-vaned spider assembly contain a secondary mirror?

 

(If this is the case, and there is a secondary mirror in there, you can try out whether you can produce an image with the thing:

Best place the system horizontally onto a table looking out some window, and, unsing a piece of white cardboard as a screen, you can try finding the image plane of the system. This is where the film holder of the camera would have sat.)

 

In any case, please post two more images: one looking straight into the system from the front; the other looking straight at it from the back.

 

 

All the best,

Kai.



#13 Antony.Smith

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Posted 30 October 2017 - 02:03 PM

Thanks Kai I will wait until its light tomorrow and try with a piece of card and also post the pictures as requested.

 

Regards Anthony



#14 luxo II

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Posted 30 October 2017 - 07:54 PM

Interesting. Looks like a very fast cassegrain with a corrector at the front, approx 160mm clear aperture.:

 

a) there's clearly a secondary inside supported on 3 vanes,

b) small hole at the rear suggests cassegrain, not a refractor,

c) in the image with the tape measure across the front the reflection of the tape appears curved suggesting its a meniscus (ie maksutov) not a schmidt corrector.

 

If it's a cassegrain the stubby tube suggests its well under f/10, possibly f/7.

 

OP your next problem is to point this at a distant bright target (streetlight or tall building) and find out where the focal plane is (hold a business card up). If the focal plane is well out of the rear it should be possible to rig up an adapter to put an eyepiece behind it.

 

if the focal plane is close to the back or somewhere inside it will require relay lenses to transfer the image to where its accessible. This will be hard to do and achieve good image quality.


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#15 Antony.Smith

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Posted 31 October 2017 - 09:18 AM

Kai and Vostok Here are some more Pictures through the Len's. I have had a attempt at focusing an image but with only a little success. I am going to try again this evening in the dark, what success I had rendered an image well behind the lens back Plate.

 

Thanks Anthony.

 

 

Lrt-1.jpg

 

Lrt-2.jpg

 

Lrt-4.jpg

 



#16 Antony.Smith

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Posted 31 October 2017 - 10:06 AM

Here are the pictures of the filter as requested and a plate which was attached to the dolly mount that the lens was originally in.

 

Thanks 

 

 

Legt-1.jpg

Legt-2.jpg



#17 aneeg

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Posted 31 October 2017 - 11:26 AM

The yellow filter was typical an anti-haze/fog device during the analog film era and a standard filter for aerial use. So probably this lens was mounted in front of a 4" X 5" plate camera.

Try to test it in the dark with a hand-held low power EP.

 

Arne



#18 Eikonal

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Posted 31 October 2017 - 12:21 PM

Ah. That clears a lot:

 

The ring is that of a green photographic filter, made of green or yellow glass by Schott (GG3 = "Grünglas3" or "Gelbglas3"). All of these filter glasses are long passes, meaning they block short wavelengths.

 

As for the serial number with that Zeiss logo:

This can have come from anywhere. But it looks quite old. This type of label was in use up to the 1950s at most. And you can be quite certain that no US military installation would have been able to buy anything from Zeiss/Jena after 1948.

Unfortunately, knowing the serial number by itself is not very useful: Zeiss always had some hundred specialist departments making anything from spectacles to whole observatories, and every single department had their own system of serial numbers. There are, for any given serial number literally dozens of parts bearing that same number.

(As a small historical side-note: The main problem, however, for pre-war and WWII documents by Zeiss is the treaty of Yalta:

Eisenhower and Patton retreated some hundred kilometers in April 1945 to allow the Soviets to enter Berlin and to occupy eastern Germany. This meant that Jena was first occupied by the Americans, then, after only a few weeks they left again and the Soviets captured the city. Before leaving, the Americans took with them whatever documents they could grab, and also some specialists from the Zeiss works. This means that the documents of the period are very much in disarray.)

 

But now for the important bit: this really is a catadioptric objective, no matter where it came from.

Now, you can play around with it: try finding the focus plane, first.

 

To start with the basics:

1) you cannot find an image through this with a camera when you have an objective lens attached: You would be looking through two camera objectives set behind each other.

 

2) We do assume at this point that the objective lens is complete, viz. there are no missing parts which would contribute to image formation in any crucial way. This may be incorrect, but it's the only thing we can do at this point.

 

-> Just start out like this: build a small translucent screen: Make a small frame of cardboard strips, say 3/4 inches wide strips and connect them to form a square with an internal size of about 3" x 3". Onto this frame you glue some tracing paper (or sandwich paper).

-> Place the objective lens on a table, so that it faces a bright scene like a street or a garden in day time. Most elements of this scene should best be at least some 30 ft away.

-> Now, move the screen backward and forward behind the objective untill you find an image of any kind.

-> Then measure the distance between the screen and the back of the lens.

-> Build a rig which will hold your camera at this distance from the lens.

To this day, camera housings have a mark to indicate where the sensor is in the housing: a circle with a long line bisecting it. This mark has to sit at the same distance from the back of the system you tested as your screen did. Then the chip will be in the vicinity of the focus.

However, as this will be a very fast objective, be prepared for the focus to be a very narrow region along the optical axis.

 

3) The easiest way to measure the focal length is to take an object that has about half a degree of angular size and measure how big its image is. The focal length would then be 109 times that value.

For example, the moon or the sun have this angular size. Say, the image of the full moon, as produced by your optics is 20 mm in diameter. Then the focal length of the instrument producing this image would be 109 x 20 mm = 2180 mm.

This will give you both an idea of how large the field is and of the scale of the images.

 

Good luck!

Kai.


Edited by Eikonal, 31 October 2017 - 12:49 PM.


#19 Antony.Smith

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Posted 31 October 2017 - 01:40 PM

The plaque with the Zeiss logo came off the swivel dolly that the lens was in, the equipment was bought at a UK military services surplus sale in the mid to late 70's by my father, the dolly was scrapped as it was too big and acted only as a way of manipulating the lens into different positions, Unfortunately he was only into optics hence his disinterest in the dolly. But like you say that's not relevant getting the lens functioning is, as i want to be able to use it to explore the sky.

 

However Earlier this evening I tried the lens with a X15 Microscope Objective and an imagine was produced at 5 inches approximately from the back of the lens. Like wise I used a piece of card and obtained the same result. I was aiming in the direction of a building some 1/3 rd of a mile away 5 stories High( a hospital well lit) it produced an image the size of which it was not possible yet to judge, due to the somewhat heath robinson attempt but that is something I can refine.

 

Thanks Again Anthony


Edited by Antony.Smith, 31 October 2017 - 01:56 PM.


#20 luxo II

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Posted 31 October 2017 - 04:39 PM

Ok 5”!should be enough to accommodate a star diagonal and eyepiece behind it, maybe an SCT Crayford focusser.
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#21 Antony.Smith

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Posted 31 October 2017 - 05:33 PM

O k which would you advise ? I will have to make some sort of adapter.

 

Thanks Anthony

 

Focusser.png

 

os-cfsct-2inch-sct-focuser-crayford-dual-speed-1_1024x1024.jpg

 

 



#22 mark cowan

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Posted 31 October 2017 - 11:26 PM

Better to verify this thing actually does what you hope it does. If strictly photographic and for a 4x5 plate size the resolution for visual use may not be all that much.  :shrug:  Plus there's that large central obstruction - not a problem for film but not good for eyeballs.

Try to figure out the illumination circle - you can do this easily with a piece of wax paper or ground glass held up to the exit aperture while having the scope pointing at the landscape.  This can also tell you the effective FL, which you don't know yet, if you can measure the size of an object in the focal field that you can also measure the angular size of in the landscape.


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#23 luxo II

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Posted 01 November 2017 - 01:12 AM

Pretty sure it was originally a Zeiss aerial camera possibly RB75, hence the complete assembly being on a dolly to wheel around.

As above I’d set it up carefully to check out the image first to see if it’s much good visually (distant buildings or lights would do).

There is however a firm clue, already - the size of the secondary obstruction is roughly 40-50% of the aperture, and the vanes supporting the secondary are grossly thick. The size of the secondary and vanes do not bode well for visual use and suggest it really was intended for photographic use with the emulsions of that era - about 50 lines per mm. That’s fairly coarse, and nowhere near diffraction limited.

First question is image quality - primarily sharpness across the useful field of view. You may need someone experienced to confirm visually from the image quality whether it’s worth taking it further, or not.

Next question is the state of the mirror coatings, and the corrector at the front. From your photos they look startlingly good for it’s age. Mirror coatings that have deteriorated look a bit “grey” implying there’s a fair bit of light lost or scattered. If you can figure out out how to dismantle it, it is possible to have mirrors re-coated with modern materials and the cost isn’t prohibitive.

The corrector likewise probably isn’t coated (can’t tell from your pics) and if so the light transmission may be down to 85 or even 80% as a result. Add in the losses from the mirrors and the result is probably quite poor transmission. Likewise you could get it multicoated and the cost is not prohibitive.

Then there’s the challenge of mounting this beastie.

All up though, assuming the optics are sharp, I’d guess you’re looking at at least $1k to refurbish this and possibly double if you need a mount - in order to make this a useable telescope. Whether you want to do that vs just buying a modern 7” mak for less is up to you.


Edited by luxo II, 01 November 2017 - 04:16 AM.

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#24 caveman_astronomer

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Posted 01 November 2017 - 07:52 AM

Now the next question to answer, before going further or spending any money, is:

 

What does this optic weigh?



#25 Antony.Smith

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Posted 01 November 2017 - 10:16 AM

The Optic weighs just under 3kg which for me is quite manageable, the length is 23.4 cm and the back plate barrel diameter is 16.5 cm. As for quality of a image, it is very good but not easy to manage with a hand held eyepiece due to the small width of focus. The secondary mirror is not visible, when viewing with the eyepiece, both the primary and secondary mirrors silvering is excellent as far as I can see, but it will need a clean as it is dusty. As for a mount I should be able to machine something in the workshop but I will have to have a think as to how I am going to do it. I have an Orion mount which initially I can make an adapter for and I have ordered a 2x Achromatic Barlow Lens 1.25” (Cheap), so I will have a experiment with these when I get the parts organized.

 

AnthonyOrion-1.jpg


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