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More Edmund Scientific!

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#301 highfnum

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Posted 20 March 2017 - 05:44 PM

I got an edmund 50mm f25 lens 

that I made into telescope and use for solar like a madman lunt 50



#302 Bomber Bob

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Posted 27 March 2017 - 03:59 PM

Edmund / 3B 4" F15 Cassegrain

 

Edmund DK4 S11 (First Optics Test).jpg

 

I'm very happy to report that the Little Cassy passed its first test today.  Between clouds I got a very sharp solar disk, and even the clouds crossing the sun were impressive.

 

Edmund DK4 S12 (First Optics Test).jpg

 

No baffles yet, and the secondary holder was made from a vintage 1.25" eyepiece case (a Meade I think), but when I checked out the budding oaks, I saw well resolved leaves and true greens.  With mirrors spaced at 12" the back focus is 8" -- longer than expected.  I'm fine with that if it doesn't hurt the image quality, as I planned on using one of the vintage 60mm Royal focusers with the long manual draw tube + rack & pinion.  (Yes, I tripled checked the mirror separation.  I'm well aware that I'm a Humanities Major.)

 

Anywho, now I know this old mirror set works, even after decades in storage.  Before the next test, I'll add baffles and a focuser.


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#303 Bomber Bob

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Posted 25 May 2017 - 10:12 AM

Edmund DK4 Complete

 

Edmund DK4 S71 (V1 Complete).jpg  Edmund DK4 S72 (V1 Complete).jpg

 

I re-tooled the stalk, and got it collimated this morning.  Then I added a quick-release finder bracket to the back hinged ring.  She's all ready for sky testing tonight.  The air should be clear & dry, but turbulent.  I'm okay with double stars and bright DSOs in a moonless sky.

 

Daylight testing:  Once again, she passed my cellphone tower "Airy Disk" test.  With the spectros eyepieces, the field is flat edge-to-edge.  Very good resolution.  The views are brighter than expected from a small F15 system -- reminds me of the Questar as a long-range microscope -- could see the veins in tree leaves on the north side of the back yard.  And of course, no false color, and no fringing.

 

While pointed toward the Sun, I noticed several small spots on the primary -- less than dime-size -- where the coatings are thinner.  Maybe it rubbed against that brown padding over the years?  Doesn't affect daytime views, but star-gazing...  Hopefully I'll find out tonight.

 

The complete scope + finder is heavier than it looks.  No plastic here!   Takes both c/w's on the Polaris to balance it.  Another Keeper?  Mercy!!  I'm trying to downsize some...  [I said trying.]


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#304 TOM KIEHL

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Posted 25 May 2017 - 03:27 PM

" I'm trying to downsize some...  [I said trying.] "

 

Downsize ? scratchhead2.gif .... What is this word you speak of rofl2.gif


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#305 terraclarke

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Posted 25 May 2017 - 06:42 PM



Edmund DK4 Complete

 

attachicon.gifEdmund DK4 S71 (V1 Complete).jpg attachicon.gifEdmund DK4 S72 (V1 Complete).jpg

 

I re-tooled the stalk, and got it collimated this morning.  Then I added a quick-release finder bracket to the back hinged ring.  She's all ready for sky testing tonight.  The air should be clear & dry, but turbulent.  I'm okay with double stars and bright DSOs in a moonless sky.

 

The complete scope + finder is heavier than it looks.  No plastic here!   Takes both c/w's on the Polaris to balance it.  Another Keeper?  Mercy!!  I'm trying to downsize some...  [I said trying.]

What makes it so heavy? It's not a Mak. I wouldn't think it would weigh more than the donar 4.5" F8 Newonian? The new focuser is heavier, but you have cut the steel tube in half. What is accounting for the difference?



#306 Bomber Bob

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Posted 25 May 2017 - 07:07 PM

It's at least twice as heavy as the PS114 OTA, which had a plastic focuser, and almost weightless diagonal holder.  The helical is all machined aluminum & brass, and the new secondary cell & baffle is thick wall brass & stainless steel.  Add the GSO 8x50 RA finder & bracket...  And, most of the weight is on the tail end -- a smaller version of the Tinsley.



#307 mattyfatz

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Posted 26 May 2017 - 10:48 AM

Did you machine that focuser yourself, or is it salvaged from something else? 



#308 Bomber Bob

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Posted 26 May 2017 - 11:53 AM

I bought the focuser from a fellow CNer.  It looks like well-done ATM -- sure haven't seen another one like it.  It is HEAVY.  The work reminds me of my Mystery Mak 6 -- there are calibration marks for machining on both.


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#309 Bomber Bob

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Posted 10 June 2017 - 10:20 AM

1974 Edmund (3B) 4" F15 Cassegrain - Version 1 COMPLETE

 

Edmund DK4 S304 - OTA Complete (Mounted).jpg

 

Rather than scatter posts around the Forum, I'll post updates to the scope here, as Version 1 is just the test rig.  Have y'all seen Tom Kiehl's fantabulous Edmund 6" Cass restoration?  Here's my end goal --> https://www.cloudyni...-5#entry6079305

 

I think the Edmund 1" shaft mount is overkill for my Junior Cass, but long term I can see it on one of the 1970s white mounts with motor drive.  For now, it does well on a Vixen Polaris.

 

Linking here to Dave's comments on Coulter, Mars, & 3B --> https://www.cloudyni...-3#entry5465674   I vaguely recall seeing 3B ads in S&T.

 

Mirror Spacing

 

My 4" F15 set was supposed to be 11.88 inches.  Mine would not reach focus at that distance.  Re-measured it yesterday, and got 12.22" for objects at infinity.  The tolerance either side is very close.  My cell lets the secondary move forward 6mm & back 10mm -- that's overkill, and way tighter than my Tinsley mirror set.  A + 3mm change throws the focal plane past the max length of the focuser; and, a - 3mm change puts the focus about .75" inside the focuser housing.

 

How many 3B kits did Edmund sell?

 

Took me almost 40 years, but I finally built a Cass as I planned in 1979.  But, back then, I wanted a 6" model.  Seems Edmund sold more in that size than the 4" versions.  Besides Dave and Tom, do others own kit Casses?


Edited by Bomber Bob, 10 June 2017 - 03:39 PM.

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#310 terraclarke

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Posted 09 January 2018 - 10:45 AM

I just ran across this. I thought folks might enjoy it. :)

 

https://www.vintagep...ector-plans.pdf


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#311 Joe1950

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Posted 15 January 2018 - 07:06 AM

I don't recall that particular publication, Terra, but my first 6" f/8 was built with a finished mirror, the aluminum cell, which I still have, and the $4 cardboard tube (thicker than today's sonotubes and black on the inside and outside).

 

Then I bought the heavy mount/clock drive and a pedestal. 

 

Very enjoyable scope to use. Thanks.

 

Added: First two eyepieces were a 1/2" and a 1/4" (yes, not mm back then) Ramsdens, fully uncoated. Later I got some Orthos that were an outrageous $15 each!


Edited by Joe1950, 15 January 2018 - 07:28 AM.

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#312 ScottAstroNut

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Posted 15 January 2018 - 11:00 AM

Very nice article, Terra.  Brought back lots of memories, dreaming as a teenager of building a six-inch Newtonian as an upgrade to my much loved and used Edmund 4.25" f/10.  Spent hundreds of hours pouring over books and magazines, especially Sam Brown's "All About Telescopes."    I didn't get the "upgrade" until much later as an adult, but certainly had a blast dreaming about it.  I've since built a number of six-inch reflectors over the years, and all have met or exceeded expectations.  Great fun.


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#313 Bomber Bob

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Posted 15 January 2018 - 01:43 PM

"THE 6-inch f/8 Newtonian reflecting telescope is probably the most popular star gazing instrument in use by amateur astronomers."

 

Later I got some Orthos that were an outrageous $15 each!

 

Wow?!  Have times changed, or what??

 

The 2 APOs have hogged enough time, so tonight I'll take out my 2 old Edmund 4s -- both F15 -- but very different scopes!  The Cass is a pretty decent double-star splitter, but I think Edna can hold her own.


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#314 Joe1950

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Posted 15 January 2018 - 02:24 PM

Bob, I’d buy the entire set and then some at those prices!  I still have 3 Orthos, 7mm, 9mm and 12.5mm. Hard to beat for sharpness.


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#315 actionhac

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Posted 13 February 2018 - 11:06 AM

I found a interesting Edmund Scientific variation.

Someday these variations may help date Edmund telescopes.

The single stalk black finder was the first of the Edmund finders, from the early 50's to the end of the 1950's.  

The 1960's brought a twin mounting ring white finder, which remained unchanged until the red tubes in the

late 70's when it received a coat of red paint. 

This interesting variation to the single stalk is a port hole so you can align the adjustment screws with the

adjustment screw groove cut in the tube. I have noted the port with a red arrow.

I must admit, it's a fiddley job finding that groove without the port, so I'm going to SWAG the port came later.

Or, the port may have been eliminated as a cost-saving step, deemed non-essential.  

Robert

 

IMG_8362.jpg

IMG_8363.jpg


Edited by actionhac, 13 February 2018 - 11:44 AM.

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#316 highfnum

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Posted 13 February 2018 - 10:56 PM

my 3 inch edmund
ed3inch.jpg
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#317 terraclarke

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Posted 14 February 2018 - 12:31 PM

That 3” Edmund is a beauty! A good 3” refractor can do a lot! Back in the day, it was the commonly recommended amateur instrument along with a 6” F8 Newt.


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#318 grif 678

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Posted 14 February 2018 - 05:51 PM

That 3” Edmund is a beauty! A good 3” refractor can do a lot! Back in the day, it was the commonly recommended amateur instrument along with a 6” F8 Newt.

Yes. back in the day, the 6 inch reflector and the 3 inch refractor were always mentioned in the same sentence. In the old Sky Observers Guide, one page has an illustration with a  man standing with both as the most popular scopes of that era.


Edited by grif 678, 14 February 2018 - 05:53 PM.

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#319 highfnum

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Posted 15 February 2018 - 03:25 AM

Cool 

I'll do. Pic of edmund 3 plis my rv6


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