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Restoring my 8" f/6 Springfield

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#1 tim53

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Posted 04 February 2012 - 02:07 PM

I've decided to slowly start restoring my 8" f/6 Springfield (with Optical Craftsmen primary and cell). I won a merit award for the scope at the 1981 RTMC.

This scope was my main scope until the mid 90s, when I acquired or built a number of others, including some goto Tak mounts I bought several years ago. But there have been things I've needed to correct on the Springfield, and I'd like to put it back into use again. So, I started with getting the mirror recoated. Original coatings lasted 40 years!

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#2 tim53

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Posted 04 February 2012 - 02:08 PM

The original coating looks pretty good in the above pic. The mirror was still pretty clean, as I'd cleaned it within the last several months.

However, this is what it looked like backlit!

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#3 tim53

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Posted 04 February 2012 - 02:10 PM

It was translucent, and had a couple spots where the coatings had come off.

Here it is now. I just got this and two other 8" mirrors back from OWL yesterday:

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#4 tim53

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Posted 04 February 2012 - 02:12 PM

Here's an old pic of the scope, taken in the late 80's from our previous home in Whittier.

Posted Image

-Tim.

#5 tim53

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Posted 04 February 2012 - 02:14 PM

And here it is, taken a couple years ago, just after I bought another Springfield mount head (on table at right), that I'll probably remount my 12.5" Cassegrain on one of these days:

Posted Image

-Tim.

#6 tim53

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Posted 04 February 2012 - 02:17 PM

I'd taken the finders off the side of the saddle, and the 4" Meade spotting scope out of the counterweight arm (where I used to have a single right angle finder).

I've got optics from a big binocular microscope that I might use for finders, or maybe one of the many old binoculars I bought cheap at the swap meet could be sacrificed for finders. I still have the Meade 4" (mirror lens, NOT SCT), and could put it back, but it needs a lighter mount than what I had in there.

-Tim.

#7 tim53

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Posted 28 April 2012 - 12:45 PM

I haven't forgotten my old Springfield (or the larger mount I bought off ebay a couple years back).

For the finders, I'm leaning towards using optics and parts from binocular purchases that I have made where the binocular was incomplete or damaged in some way, but I hadn't paid so much for them that I couldn't sacrifice a cheap pair I'd picked up at the swap meets I go to.

Recently, I purchased an old Mechanics Illustrated article that I found on ebay. It's from 1957, from a column they ran in the magazine called "The Amateur Telescope Maker's Page", conducted by Robert Brightman (anybody know who he is/was?). I had no idea they had such a column! (well, I was only 4 years old at the time!). Anyway, the article is entitled "A Springfield Mounting", and while it describes a rather spartan-looking mount, it's got all the right ingredients for a first-rate telescope of the day, with a clock drive, setting circles, and slow motion controls. Even better, the article describes the workings and construction in detail, and the exploded diagrams an pictures are detailed and thoroughly labeled. There's even a detailed blueprint! (though it's reduced to fit the small page format). The seller nicely sealed and protected the article for shipping.

I plan to scan it into my computer so I can put the original away. I'll probably use it mostly to help improve some of the elements of the larger mount I bought off ebay, but I may incorporate some of the ideas into my 8" (on this thread) while undertaking the restoration of that instrument.

Mechanics Illustrated is still around, of course, so I probably can't post pictures from the article here. (mods, correct me if I'm wrong, because if there is a way to show some of it here, I wouldn't mind being able to do that).

-Tim.

#8 Lew Chilton

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Posted 29 April 2012 - 01:39 PM

Tim,

What do you know about F.M. Hicks and his connection to the Pasadena version of the Springfield mount? I recently came across some interesting bio. info. on him. I can't verify it yet, but I believe he was an early president of the L.A. Astronomical Society. (He definitely was a member and I have a picture of him in a group shot with Russell W. Porter taken around 1929.)

-Lew

#9 tim53

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Posted 29 April 2012 - 02:04 PM

Hi Lew!

Not much. I do have an original blueprint of the Pasadena mount though

Tim

#10 Lew Chilton

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Posted 30 April 2012 - 01:55 AM

Tim, check out this excerpt from Frank M. Hick's bio. He made his fortune as a railroad locomotive, passenger car and street car manufacturer in Chicago.

- Lew

FRANK M. HICKS, ASTRONOMIST OF CALIF., DIES HERE (1860-1930)
Frank M. Hicks, brother of A. M. Hicks of this city, passed away Sunday evening at St. Vincent hospital following a long illness. Mr. Hicks had lived in Pasadena, Cal., for the past 17 years, where he was well known both in social and philanthropic circles. For several years he was deeply interested in astronomy and was one of the leading amateur telescope builders of southern California. He worked out a design for a telescope mounting with a stationary eye piece which has come to be well known in amateur telecope circles throughout the United States.

#11 tim53

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Posted 30 April 2012 - 09:15 AM

Interesting! So, the Pasadena version of the Springfield mount must have come from the 20s, then? Russell Porter didn't write the 2nd major article about machining the Springfield mount until 1935.

I'll have to go find that blueprint to verify, but I believe it was signed by Hicks.

-Tim.

#12 tim53

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Posted 23 June 2012 - 11:06 AM

Hi Lew:

I was just looking over the blueprint for the Pasadena mount, to see if I could find a date. There doesn't seem to be one on the blueprint.

Here's the credits, though. If you're interested, I scanned the blueprint and assembled it in Canvas then saved it as a jpeg. It's still pretty big (about 8 megs), but if you're interested, I could email it to you as an attachment:

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#13 tim53

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Posted 23 June 2012 - 11:14 AM

Hicks' house is still there, and it's less than 5 miles from me.

-Tim

#14 amicus sidera

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Posted 24 June 2012 - 05:36 PM

The original coating looks pretty good in the above pic. The mirror was still pretty clean, as I'd cleaned it within the last several months.

However, this is what it looked like backlit!


Firstly, beautiful telescope, Tim! I can easily see why it won that award.

Regarding that mirror: I've seen new coatings that looked like that, with sufficient backlighting! The original aluminizing job must have been pretty good, indeed. The 30-year-plus coatings on my Edmund mirrors are still opaque, except for a few pinholes, so I don't plan on realuminizing any time soon.

One question: what are the three half-round areas on the refinished mirror - reflections, or unaluminized areas?

#15 tim53

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Posted 24 June 2012 - 06:09 PM

Those are clip shadows from when OWL recoated the mirror. I wasn't too worried about them, because my cell has clips that I'll just put in line with the shadows.

I had my 8" f/9 mirror coated at L&L, though, and it has no clip shadows. Cost about 3 or 4 times as much for that coating as OWL's current discount. I plan to make that a planet killer without clips over the face of the mirror.

-Tim.

#16 amicus sidera

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Posted 24 June 2012 - 06:22 PM

Thanks for that info, Tim; fwiw, out of all the mirrors that I've had coated, either for myself or other observers' mirrors that I handled for them, I never had one come back with unaluminized areas due to clips used during the process. Used primarily EVM out of Ithaca, some others. No slam on your newly-coated mirror, but it's hard to understand why a coater would do this, except to make life easier for themselves.

#17 Bill Griffith

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Posted 25 June 2012 - 01:41 AM

I certainly agree it makes life easier for a coating house and this is also in the best interest of the customer (my opinion). Gravity is not your friend in this instance.

Vacuum deposition take place with an emission source stationed below the parts being coated.
Depending on the size of the vacuum chamber several mirrors can be coated at the same time. A planetary system is often used. Each part rotates on axis while rotation on a central axis is conducted. To minimize shadowing of all these spinning parts clips are utilized.

This keeps the cost down to do one run and coat several.

If a customer has a requirement of a no non coated surface, certainly that can be provided.

The other benefit much like in a mirror cell is; this reduces stress by not clamping the part tightly on the sides or being placed in a housing.

Some application such as AR coatings(MgF2)takes place at pretty high chamber temps. you want to allow for CTE.

Or, we're just lazy! :grin:

I should mention that these statements are not implied as to why other coating houses use clips. I'm not employed at O.W.L..

Bill




#18 Jim Curry

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Posted 25 June 2012 - 07:26 AM

Tim:

The Pasadena (Springfield) mount has always intrigued me. Looking at your Whittier photo, what is that object bolted on the wood counterweight arm just "above" the handle? Also, in the restored photo I see what looks to be another set of focuser knobs above the focuser, what are they for?

THanks.,
Jim

#19 tim53

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Posted 25 June 2012 - 08:51 AM

Hi Jim:

The thing in the counterweight arm between the OTA and the "Armstrong slewing motor = handle" is a Meade 4" Mirror Lens spotting scope that I used a few times as a guide scope. When I first built the telescope, I had the finderscope there.
Posted Image.
But I didn't like using right angle finders in those days, so by the late 80's I'd switched to using two straight-through finders on either side of the tube.

There are a number of knobs in that picture. Some I made out of teak and threaded rod. These are used mostly in place of the small set screws in the focuser and for clamping the guidescope bracket's adjustments. The two aluminum knobs are on the tangent arm and are for manual slow motion.

The focuser has a funny history. We used it as a jig at Meade to drill the holes in tubes for placement of the 2" #680 focusers on the OTAs. The holes were rather chewed up from running a drill bit through them hundreds of times. I got it for nothing when we went to a better designed jig for that purpose. Since the Springfield has a flat base where the focuser lives, I had a friend with a lathe (I didn't have my own at the time) cut the base off the Meade focuser and machine a step that we pressed a new base on that insures that everything is concentric with the hollow dec axis. This is needed to maintain collimation, since the tube rotates around the dec axis but the focuser doesn't.
I kept losing that tiny set screw in the eyepiece hole, so I drilled the hole out and tapped it for 10-24 threads and put one of my teak knobs in there.
There's also a teak knob on the clamping screw for the Dec tangent arm.

-Tim.

#20 amicus sidera

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Posted 25 June 2012 - 03:27 PM

I certainly agree it makes life easier for a coating house and this is also in the best interest of the customer (my opinion). Gravity is not your friend in this instance.

Vacuum deposition take place with an emission source stationed below the parts being coated.
Depending on the size of the vacuum chamber several mirrors can be coated at the same time. A planetary system is often used. Each part rotates on axis while rotation on a central axis is conducted. To minimize shadowing of all these spinning parts clips are utilized.

This keeps the cost down to do one run and coat several.

If a customer has a requirement of a no non coated surface, certainly that can be provided.

The other benefit much like in a mirror cell is; this reduces stress by not clamping the part tightly on the sides or being placed in a housing.

Some application such as AR coatings(MgF2)takes place at pretty high chamber temps. you want to allow for CTE.

Or, we're just lazy! :grin:

I should mention that these statements are not implied as to why other coating houses use clips. I'm not employed at O.W.L..

Bill



Thanks much for that excellent explanation, Bill!

Until recently, I had never seen a mirror that had been aluminized while held by clips on its face. I'm sure that it's easier for the coater, and just as certain that today many folks wouldn't mind, as their mirror cell's clips would hide the bare areas.

Funny, though, that those firms that coated all those old Upco, Edmund, Cave, etc. mirrors, never used clips, at least to my knowledge. Write me off as an oldtimer, but I believe that back then using clips, and leaving areas unaluminized, would have been deemed unacceptable by the vast majority of amateurs... and still is, in some quarters (ahem). :grin:

#21 amicus sidera

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Posted 25 June 2012 - 03:30 PM

Tim wrote:

(snip)There are a number of knobs in that picture. Some I made out of teak and threaded rod.(snip)


Are the main tube and mount of that Springfield also made out of teak, Tim?

#22 tim53

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Posted 25 June 2012 - 03:36 PM

The tube is made out of Indian Rosewood plywood, which is basically a mahogany plywood with a 1/64" veneer of Rosewood on one side. I haven't seen this stuff available since I bout that sheet in about 1980. It's faded considerably, unfortunately.

The tripod is red oak, and the mount is aluminum 1/2" plate.

-Tim.

#23 tim53

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Posted 27 June 2012 - 12:49 AM

Okay, so a friend posted on facebook that the ISS was going overhead this evening, so my son and I went out and gandered it. Then I got inspired to get the Springfield out, collimate it, and see how it stacks up against the other two Optical Craftsmen mirrors I have.

2 nights ago, it was a shootout between the 8" Connoisseur and the 8" Discoverer OTA, so the seeing was similar for those two. Tonight, the seeing was a bit worse, a 3/10 instead of 4/10 for the other night. Still, I think the image is decent, if not as good as the view through the Connoisseur.

Connoisseur:
Posted Image

Discoverer:
Posted Image

Springfield (mirror from another Discoverer):

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#24 tim53

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Posted 27 June 2012 - 12:55 AM

So, I'm figuring 2 outa 3 ain't bad...

...well, actually 2 out of 3 are actually pretty good, with the Connoisseur being a tad better than the Springfield, even though the seeing was a factor tonight, I bet the two in a shootout would still wind up with the Connoisseur on top.

The other mirror is a 2rd. It's just that simple. I'm going to put that OTA in the back of my shop, and next time I get a chance to attend the Delmarva mirror class, I'm going to bring it along and give it a new figure!

-Tim.

#25 Fred Ley

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Posted 27 June 2012 - 05:03 AM

Hello Tim,

Here is an image of your telescope from the 1984 RTMC. Taken with Kodachrome 64 slide film.

Fred

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