498 replies to this topic

[Terra Nova]

In the world of long achromats, it’s all relative!

 

The Yerkes refractor is 40” @ F19, (A. Clark and Sons); R = N/D = 0.475

 

The Lick refractor is 36” @ F19, (A.Clark and Sons); R = N/D = 0.528

 

The Lowell (Mars Hill) refractor is 24” @ F16 (A. Clark and Sons); R = N/D = 0.667

 

Jaegers 6” @ F15; R = N/D = 2.5

 

Generic 4” @ F15; R = N/D = 3.75

 

Generic 3” @ F15; R = N/D = 5.00

 

Generic 2.4” @ F15; R = N/D = 6.25

 

Generic 2” @ 15; R = N/D = 7.50

 

Where N is the F-ratio, D is the aperture diameter in inches, and R ~ 1/ chromatic aberation

[Alan French]

At f/15 a 6" will still have damaging CA on bright objects, so the main advantage of a refractor is lost at the outset. Now a Baader semi-APO filter will knock out most of the color, to be sure. You need to be at f/20 to be essentially colorless.

 

-drl

How perceptions have changed. Back in the 1960s many of us would have loved owning a 6-inch achromat, in spite of the secondary color. Yes, in a 6-inch f/15 it will be obvious, but it's still an unobstructed aperture, and I think you protest too much.

 

Today we have better options, with the superior color correction and shorter focal lengths of modern apochromat. 

 

Clear skies, Alan

[Terra Nova]

How perceptions have changed. Back in the 1960s many of us would have loved owning a 6-inch achromat, in spite of the secondary color. Yes, in a 6-inch f/15 it will be obvious, but it's still an unobstructed aperture, and I think you protest too much.

 

Today we have better options, with the superior color correction and shorter focal lengths of modern apochromat. 

 

Clear skies, Alan

So true! As the simple table I constructed in post #26 above illustrates! Consider two lines of folks want to look at Jupiter. Which line will be longer? The line to look at Jupiter through the 40” Great Refractor at Yerkes Observatory, of the line to look through the guys Unitron model 128 (2.4” F15) out in the Yerkes parking lot. Even tho the the little Unitron shows a far more apochromatic view, I guarantee you, I (and probably a whole lot more folks) are gonna wanna look thru the 40”!

[bobhen]

Lets see, typical C8 sells for about $450-$650. Trading one for Jaegers 6" then comparing that with a AP 152? Remember we are talking classics here.

That’s why I said “unless” it was “dirt-cheap” or a “project scope.”

 

The AP 152 F9 is a classic scope.

 

To be honest “for me” there are just too many downsides to a 6” F15 achromat like: size, mount needed and the cost of said mount, poor for deep sky imaging, chromatic aberration, images produced compared to today’s ED refractors, etc. that no matter how cheap I would never consider one. For others, have fun. 

 

Bob

[apfever]

In the world of long achromats, it’s all relative!

 

The Yerkes refractor is 40” @ F19, (A. Clark and Sons); R = N/D = 0.475

 

The Lick refractor is 36” @ F19, (A.Clark and Sons); R = N/D = 0.528

 

The Lowell (Mars Hill) refractor is 24” @ F16 (A. Clark and Sons); R = N/D = 0.667

 

Jaegers 6” @ F15; R = N/D = 2.5

 

Generic 4” @ F15; R = N/D = 3.75

 

Generic 3” @ F15; R = N/D = 5.00

 

Generic 2.4” @ F15; R = N/D = 6.25

 

Generic 2” @ 15; R = N/D = 7.50

 

Where N is the F-ratio, D is the aperture diameter in inches, and R ~ 1/ chromatic aberation

Oh creek, you stopped just short of our 20" F17 Alvin Clark lens at Chamberlin Observatory in Denver. 

R=0.85,  we beat the big guys. 

[Mikefp]

I love using my 6" f15 Jaegers to help with the crowds at Mount Wilson Observatory lectures and dome events.  Very nice visual images of the planets.  Pictures show the Jaeger scope outside the historic 100" Dome.  Not to compare but Hubble used the 100" scope inside the dome to help define the size of the universe.

 

[Mikefp]

One more picture of the yard canon.   You should enjoy if you can handle onto a adequate mount. 

 

[clamchip]

I would love to own a 6 inch f/15, one of these days I will.

I'm close, I have everything but the objective lens. I even have the

tube which is the hardest part.

Robert

 

Edited by clamchip, 22 December 2021 - 05:08 PM.

[Terra Nova]

If I was younger and had the strength to handle one, and the room to store one, I would have a 6” F18 achromat, or better yet, I’d have one in a domed backyard observatory. However neither is going to happen and so I’m happy with my Vixen 120S Petzval. I do still occasionally entertain the thought of another 4” F15; that would be a fork-mounted Unitron 150 if the right deal ever came along. 

[Kasmos]

I still have lingering hopes of building a 6"Jaegers f/15. A departed friend gave me a old Edmund Extra Heavy GEM with the pier and feet, so I have something to put it on. I think they were made from a Neutron Star. That thing is so heavy that even in pieces lifting each component threatens a hernia. 

 

It would have to be a roll out scope or under a roll off roof.

Edited by Kasmos, 22 December 2021 - 06:40 PM.

[CHASLX200]

I can live with the color at F/15 on the planets with a 6". But no way at F/8.  Just too big to deal with at my house unless the mount could stay outside. My 5" F/12 D&G was fine also.

[jragsdale]

Sorry for the delay guys, been super busy all day, but the scope has been acquired! More photos to follow.

 

Here is everything loaded up; scope, pier, mount, finderscope.

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[jragsdale]

Here is the OTA, 7" OD x 8 foot long from the end of the dew shield to the focal point at the focuser.

 

Finderscope looks to also be a Jaegers, a 76mm x 1200mm. Aluminum tube, Jaegers focuser with red bakelite knobs that have been painted white.

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[jragsdale]

Here is the mount included, needs a LOT of work. Appears to have Hurst stepper motors on both axis but all the wires have been cut, no connectors on controllers on anything. Mount head weighs 88lbs with the counterweight included. Gears all look ok, it should be salvageable, but I don't even know WHAT it is yet, so a long way to go.

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[jragsdale]

Lens cell removed from the scope. Upon closer inspection, the foil spacers are gone, but the adhesive remains, as you can see right through where they are. The lens elements aren't touching, but I assume I'll need to add some spacers. Side of lenses had index marks, matching serials and a date of 12/2/69.

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Edited by jragsdale, 22 December 2021 - 08:36 PM.

[jragsdale]

Focuser is a 2.7" version with a 2.7 to 1.25" adapter with drawtube extension.

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[jragsdale]

Pier is 77" tall, 5.75" ID, 6.25" OD and 45lbs and the "pier adapter" is just a chunk of wood that had tape used as a spacer to hold it in tight.

 

The height of the pier and mount together will make this scope rather unwieldly to roll around as I have a regular 7' high garage door. I'm thinking of building a handcart into the pier so I can lean it over and roll the whole thing out at an angle.

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[ccwemyss]

The Hurst motors are synchronous. You just feed them 60Hz AC and they turn at a set rate. No magic controller is needed, unless you want a variable frequency supply for guiding. 

 

Chip W. 

[Kasmos]

Dude, you scored!   and a 3"Jaegers to boot.

 

I wasn't completely sure you'd be getting the mount. Interesting palcement of the motors.

 

Love it but why would someone paint over everything in white? Personally I'd restore it too it's old fashion glory!

 

It would be nice to track down it's history and also see if it was really was once at Lick. 

[jragsdale]

Love it but why would someone paint over everything in white? Personally I'd restore it too it's old fashion glory!

 

It would be nice to track down it's history and also see if it was really was once at Lick. 

Yeah, that's my goal, definitely going for a full restore and invest in it to restore to fully functionality. Powder coating, full mount tear down, optical testing to get correct spacer thickness, new baffles.

[AstroKerr]

Rags,

 

Look thru it, first. If it passes - meaning stars and planets or even far away tree branches or plastic flowers look good to you - 

 

Do the trade

 

Everything else can be fixed and fiddled later. You can DPAC in 32 colours, send it off for eval at a lab, blahblahblah AFTER you latch on to it.

 

That Scope, your eyes, your skies - All Other Priorities Rescinded.

 

Best of Luck!

 

edit: well, bit late, wasn't I? Good Job, Rags! 

Edited by AstroKerr, 22 December 2021 - 09:12 PM.

[apfever]

This is a pure Mr. Bean episode, you can probably search it.

Just imagine it.

 

Mr. Bean wanted to paint a room white. He taped off everything then put a gallon of paint in the middle of the room with a stick of dynamite in it. And did it. 

I have to give credit to the stage craft crew. The final picture was extremely well done. It looked like this scope.

[telesonic]

Nice score J!

 

One of my friends down here has a Jaegers 6" (F/15 also I think) that I've seen several times, but never had a chance to look through yet. I don't recall what his was / is mounted on, other than he hauls it *and his dob* around in an old Hearse / ghostbusters style ambulance.... probably not the same dude you bought this from, however. If it was though, I'd be mighty surprised.

 

It's been awhile since I chatted with him, so over the holidays I'll stop by there, and let him know about this thread. Perhaps he might log back in and share some tips, as he used to be an active member on here also. He did mention something to me about the objective spacers.... but I don't remember if it was in regards to the Jaegers cell, or one of the other refractors in his scope aresenal.

 

Cheers man, and happy upcoming holidays!

Temp

[Linn]

This is a pure Mr. Bean episode, you can probably search it.

Just imagine it.

 

Mr. Bean wanted to paint a room white. He taped off everything then put a gallon of paint in the middle of the room with a stick of dynamite in it. And did it. 

I have to give credit to the stage craft crew. The final picture was extremely well done. It looked like this scope.

Mythbusters did a similar thing.

[deepwoods1]

Can’t wait to follow the restoration thread! Very happy for you!