22 replies to this topic

[Tom Duncan]

Picked this up recently off CL, what looks to be a 4" Jaegers achromat with a cute little Jaegers 50mm guide/finderscope on what looks to be a 1" shaft Optical Craftsman EQ mount with working AC drive on top of what looks to be a hand made aluminum hub and wood legs. 

 

Questions I have:

 

Is this indeed a Jaegers? I have one old Jaegers catalog but it doesn't show anything like this. The focuser and one photo of an apparently identical scope found with an internet search are the only evidence I have. The focal length is about 36" (rough measure from the center of the cell to the center of an EP) so this is likely an f9 or so.

 

The finderscope is straight through and has what looks to be the original 1.25" Jaegers eyepiece, no crosshairs, unmarked as to maker or specs of course but it looks all the world like a Jaegers. The focuser has just enough in-travel to let the image come to focus with this EP so a diagonal cannot be used. 

 

Are the blue/green colors of the OTA and finderscope typical of Jaegers? The paint in both cases appears to be original but note they are slightly different. 

 

Both objectives have severe discoloration (but no apparent separation) of the cementing between the two elements. I initially thought about re-cementing them but last night I used the scope on a star test, M13 and the Moon and the viewed images were incredibly sharp (with a 24mm Panoptic and a 10mm Pentax XW so they  helped). I'm concerned about being able to get the same results after doing so. The Moon had quite an amber look to it. 

 

The mount looks very much like an Optical Craftsman but can anyone confirm that? 

 

The hub and legs look like they could be home-made...any comments? 

 

Thanks

 

Tom Duncan 

 

 

Attached Thumbnails

• 
• 
• 

[tim53]

That's definitely the Optical Craftsmen version of the Pacific Instruments 1" shaft mount.  I still have the one that came with my 8" Discoverer in 1972, though it's currently holding my 4" f/15 goto with the rude and crude homemade OTA:

 

 

The Dec slow motion gismo was something I made in the late 70s to guide manually while shooting film through a 4.25" f//5 Newtonian I had mounted on it back then.  It hit the clock cover when used with a refractor (such that the guiding knobs were on the south side with me sitting on a beach chair to guide through a 2.4" refractor mounted on the Newt). I still have the cover, but am not using it with this scope.  

 

The tube rings on your scope are interesting.  They look like Optical Craftsmen rings, but I don't think they made them smaller than for a 6" Newtonian.  I'll check the catalogs and make sure.  It also isn't impossible that OC sold a refractor on that mount at one time or another.  If they did, they would have likely used someone else's lenses, like Jaegers (Unless, and this is highly unlikely, Dick Brandt made a few refractors while working at OC).

 

Neat scope, and I bet it'll be fun to use!

 

-Tim.

[tim53]

Ah, go here https://wiki.telesco...964_Catalog.pdf and scroll down to the 4.25" Altair.  It shows this mount with rings for a 4.25" Newt, which might suggest that the rings are factory as well as the mount.  

[Tom Duncan]

I was wondering about the rings as well. They fit the OTA perfectly and the felt pads are in great shape. The base of the rings fits the top of the platform perfectly, but the bolts on one end are captive due to the DEC slow motion assembly (which is called something but I can't remember). The paint is also very similar. 

 

Hmm, so this scope might be an Optical Craftsman assembly? I wasn't aware they ever made any scopes besides reflectors. 

 

Tom 

[Bill Jensen]

Tom, my first scope 50+ years ago was a Jaegers 5 inch f/5 and its color as I recall was green, similar  what you have. It was light green, but not turquoise . that said, the tube could have been sourced by someone else, and they just put the lens cell on it. Mine was on a woefully inadequate EQ mount, and it had a sliding focus, nothing as nice as the scope you have pictured. 

[Tom Duncan]

Funny you'd suggest that catalog, I just found mine (a downloaded copy), the same exact one and I found the Altair page, agreed, looks at least very similar. Upon closer examination I think the felt that's in my rings has been added later as it's very thick and in too good of condition. See the attached photo. 

 

However the ID of the rings without the felt is just 5"...enough to accommodate the tube of a 4.5" reflector? 

 

Tom 

Attached Thumbnails

• 

[Kasmos]

I saw the FB ad and wondered about it's size since it looked like a 4".

I don't think Jaegers offered a air spaced 4" shorter than the f/15. I'll check my catalog.

The cell on my 4" is completely different but maybe they changed based on year.

 

I could be mistaken, but I believe Jaegers really only sold components and their kits were really just a pack of components that you assembled.

Therefore, I don't think any of their tubes came painted.

 

The focuser with red knobs match mine, but I don't have a photo on the computer I'm on.

Edited by Kasmos, 02 July 2020 - 06:17 PM.

[Terra Nova]

The focuser with red knobs match mine, but I don't have a photo on the computer I'm on.

The focuser is definitely Jaegers. They’re just like the ones on my Jaegers focuser on the 6” Newt I built in 1967. Same as on my Jaegers 1” shaft GEM too. Red knobs = Jaegers, black knobs = Edmund.

 

Very cool old refractor btw! It’s profile reminds me of the 4” ATM refractor JW (Bomber Bob) has. I think he said his objective is B&L.

[Tom Duncan]

I saw the FB ad and wondered about it's size since it looked like a 4".

I don't think Jaegers offered a air spaced 4" shorter than the f/15. I'll check my catalog.

The cell on my 4" is completely different but maybe they changed based on year.

Jaegers-Lynbrook.jpg

 

I could be mistaken, but I believe Jaegers really only sold components and their kits were really just a pack of components that you assembled.

Therefore, I don't think any of their tubes came painted.

 

The focuser with red knobs match mine, but I don't have a photo on the computer I'm on.

The objective is cemented, not air spaced. As an aside,  has anyone tried separating a cemented doublet and then air spacing it? Subject for another posting I think. 

 

The one Jaegers catalog I have (AO69, but no date) shows only components so you might be right about that point. 

 

The diameter of the objective is a bit larger than the 4-1/8" I measure at the cell. Looking on page 41 of the catalog I see under "Big Lenses, Achromatic Objectives" a listing for a 4-1/4" 36"/914mm FL cemented doublet so mine is probably that. Item number 1460, coated (as is mine), $60 in the mid 60s is about $500 today! However the description at the top of the page says they are cemented achromats but under the listing it says they are air spaced. That's helpful...

 

Tom

 

Tom 

Edited by Tom Duncan, 02 July 2020 - 07:01 PM.

[RichA]

Time to dissolve the Canada Balsam (likely) holding the lenses together, using acetone.  Then you could try them air-spaced to see if that works.  Be sure to make pencil (not pen or magic marker) marks on the sides to indicate orientation of the lenses.

Edited by RichA, 02 July 2020 - 07:26 PM.

[DAVIDG]

 You don't want to air space a lens that was designed to be cemented  or cement or oil a lens that was designed to be air spaced. The air space is a  refractive element just like the glass. You have light going from  a high refractive index material to lower one if it is air spaced and then back to a higher refractive material. Snells Law shows what happens when the light enter and exits materials of different refractive index. So the design uses the air space or lack of it,  so if you change it, the correction will change.

   The yellow color looks like the cement is causing it. I would place the lens in pot of water and slowly heat it so  cement soften and then you can separate the elements . Then I would use Norland UV activated cement to recement the elements back together. Here is a link to my thread that shows how it done, it is easy. 

https://www.cloudyni...ecement-a-lens/

 

                  - Dave 

Edited by DAVIDG, 03 July 2020 - 10:11 AM.

[Mikefp]

Hi Tom,

I have an 4" f/15 Air spaced Jaegers with the same Pacific Instruments 1" shaft mount.  Pictures below.  My lens cell looks different and is flush with the tube.  Attached is a Jaegers 80mm finder scope.   The 80mm scope also has an air spaced objective.   Obviously Jaegers made different versions of their objective lenses and cells.   You should not try to change the spacing design as mentioned by Dave.  

 

 

 

I just notice the need to change my signature status!

Edited by Mikefp, 02 July 2020 - 09:09 PM.

[Tom Duncan]

When I can get the time I'm going to try the recementing, in addition to Daves's there's a lot of info on the process online. 

 

I'll report back once I get it done. 

 

Tom

[davidmcgo]

If re cementing is too scary you could oil it with a drop or two of mineral oil and wrap the edge with kapton tape if the cell has room.

 

Dave

Edited by davidmcgo, 04 July 2020 - 08:55 AM.

[Tom Duncan]

I've been reading about the oil solution, will look further into that option. 

 

Tnx

 

Tom

[Terra Nova]

The refractive index of canada balsam which is what it was probably cemented with varies from n 20/D 1.522 to n 20/D 1.542.

 

The refractive index of mineral oil is n 20/D 1.420.

[DAVIDG]

 A lens that is designed to be cement usually has the two inner radii that are the same. This makes the  thickness of the cement  layer to be very thin. The result is that the  refractive index of the cement  which is not that different then either the crown or the flint does not effect the correction.  Astrophysics I believe used mineral oil with their oiled  lenses.  

    With an air spaced design the refractive index of air is 1.00  and the air space usually goes from 0.003 to 0.25" depending on  the design.  In an air spaced design the two inner radii are different so the thickness of the air space varies. Crown glass has a refractive index or around 1.52 and flint around  1.65 so there is good bit of difference between the glasses and the air and with the air spacing being a measurable thickness, the result is that the air space is a refractive element. 

 

           - Dave 

[clamchip]

I've never seen cement decay to yellow like that.

The yellow tint can be your friend filtering out the unwanted purple.

This might be why you are finding the performance very high.

It maybe some kind of synthetic cement, I know these were available

during the moonwatch years cementing the big 5 inch objectives.

It takes much more effort to undo the synthetic cements, usually

more heat.

I would clean the lens and see if it comes out clean but yellow.

I personally would not like a heavy yellow tint on the moon or

planets or anywhere for that matter.

I'm not a big fan of purple fringe ether though.

 

Robert

[DAVIDG]

It is very common for Canada Balsam to turn yellow as it ages .   It also become hazy. See my thread about using Norland cement since it has pictures of lenses that have yellowed  You can also see that when I heated the lens in the toaster oven the cement left on the elements when separated is very yellow. So my guess is that the lens was exposed to heat.  Maybe the scope was stored in a hot attic. 

    If the lens was clear it most likely transmitting well over 90% of the visible wavelengths. The yellowing has most likely  reduced  this by a fair amount across these  wavelengths both from the yellowing and the haziness. 

 

https://www.cloudyni...ecement-a-lens/

 

 

                - Dave 

Edited by DAVIDG, 04 July 2020 - 10:09 PM.

[Terra Nova]

It is very common for Canada Balsam to turn yellow as it ages .   It also become hazy. See my thread about using Norland cement since it has pictures of lenses that have yellowed  You can also see that when I heated the lens in the toaster oven the cement left on the elements when separated is very yellow. So my guess is that the lens was exposed to heat.  Maybe the scope was stored in a hot attic. 

    If the lens was clear it most likely transmitting well over 90% of the visible wavelengths. The yellowing has most likely  reduced  this by a fair amount across these  wavelengths both from the yellowing and the haziness. 

 

https://www.cloudyni...ecement-a-lens/

 

 

                - Dave 

Here's a small vial of Canada Balsam that I've had for over fifty years. It definitely has a yellow cast!

Attached Thumbnails

• 

[Tom Duncan]

So I used the Edmund #61 UV cement and re-cemented both the finderscope and main scope objectives, with mostly success.

 

I soaked the objectives in acetone for about a week, watching the Newton rings slowly march towards the center until the two elements finally came apart.

 

Got a pair of cast iron V-blocks from Ebay and set up a working tray, photo of the setup attached. Of course I noted the factory alignment marks of both objectives. 

 

Unfortunately one element of both doublets had what I would describe as a stained surface on the side that faced the other element. Probably a bad run of coatings or some such. Bad day at the factory for coatings and cementing! So while I did get rid of the deep amber tone to the glass (see the initial post and compare with the setup photo) there is still a residual staining that can be seen in the right light and angle with the naked eye. It has no effect on the viewed image, and certainly nothing like the previous amber it had before but nonetheless not a perfect fix. I tried every solvent/cleaner I was willing to breath but none had any effect. 

 

The other less than perfect outcome was I didn't put quite enough drops of cement on the main objective so I had to slide the elements apart a bit to add another drop and in doing so introduced a small bubble, about 2mm, fortunately very near the edge. And of course I didn't see it until the job was done. 

 

I used a reptile UV lamp for curing as it has a very high UV output and creates little in the way of heat, you can see the setup in the photograph with the lamp upside down so you can see the bulb. I use that same lamp to remove the amber tone to post WWII fast photographic lens glass like the M42 Pentax 50mm f1.4's. I layed the lamp over the two Meade counterweights so it was about 2" above the glass and left the light on for a few hours.  

 

As to the amount of cement to use, I used two drops on the 50mm finderscope set which was just barely enough. It took some pushing and shoving to get the cement all the way out to the edge but eventually did so and required no edge clean up. I then figured out what the area of the two objectives was and calculated about 8 drops would just barely work for the main objective and added one more. Not enough, should have done 10, hence the aforementioned bubble.

 

I can say getting the amount of cement correct is a good idea, problems with too little noted above, too much and it spills out the sides, gets all over including onto the air sides of the elements and is sticky and gooey, quite the mess. Acetone is a good cleanup solvent but it was still a mess and it can remove pencil or pen alignment marks. Someone should work out a chart for the proper number of drops by objective diameter/area.  

 

I tried the scope last night on the Moon, Jupiter and Saturn with a variety of eyepieces and the scope continues to impress regarding sharpness. With a 24mm Panoptic (granted, a great EP and likely to do well) the image was tack sharp all the way to the field stop as well as with other EPs. I couldn't judge color fringing as there was none to be seen, most likely because of the amber skies I have currently with all the California fires effectively blocking it. I'll try to find a bright star through the smoke tonight to do a star test and once the smoke clears I'll check for CA. 

 

Tom

Attached Thumbnails

• 

Edited by Tom Duncan, 28 August 2020 - 10:18 AM.

[Tom Duncan]

Had some significant clearing of the fire smoke last night and used Vega as a target for a star test as it was directly overhead and the results were excellent. Excellent fine rings well distributed on one side, a bit fuzzier on the other but well within what I have experienced with other good achromats. The one aberration I can't account for was the outer rings being slightly flattened along about 30 degrees on one side of focus. I loosened the three cell retaining bolts but that had no effect but if I was to keep this scope I'd look into them further. Very little CA but I was using a Takahashi prism diagonal which tends to suppress it in achromats. On the other hand this is an f8.5 so some CA suppression is expected. 

 

I also looked at the Moon specifically for CA and there was just a very slight amount but there was more smoke effect as it was lower in the sky.

 

Bottom line is the views are very good, I'm pleased...nice scope! With further refurbishment (paint the tube and tighten up the focuser mainly, perhaps fit a dew shield) this is going to be an even nicer scope for someone. 

 

Tom

[Bomber Bob]

The focuser is definitely Jaegers. They’re just like the ones on my Jaegers focuser on the 6” Newt I built in 1967. Same as on my Jaegers 1” shaft GEM too. Red knobs = Jaegers, black knobs = Edmund.

 

Very cool old refractor btw! It’s profile reminds me of the 4” ATM refractor JW (Bomber Bob) has. I think he said his objective is B&L.

Pretty sure my Dakin 4's cell is a custom machining job:

 

 

A heavy machined aluminum cap threads in after the retainer.  Pretty good evidence that the lens is a B&L discard, but no smoking gun -- no markings.  It is a Baker, with a 7mm steel ring to hold the Gap!

 

Here are the lens specs:

 

CA = 104mm (4.1")
FL = 1052mm (41.4")
F-Ratio = 10.1

Crown = 110x13
Flint = 110x17
Spacer = 110x7

Edited by Bomber Bob, 28 August 2020 - 10:51 AM.