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#726 Bomber Bob

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Posted 26 November 2019 - 06:02 PM

Another Edmund blast from the past.  30mm multipurpose telescope.

 

I think that's what this finder is from the Edmund red scope days:

 

Edmund DK4 S601 (ESC Red Finder & Diagonal).jpg


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#727 sdedalus83

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Posted 26 November 2019 - 06:15 PM

Much shorter focal length, though.



#728 Bomber Bob

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Posted 26 November 2019 - 06:29 PM

Yeah, the objective is about halfway down the tube -- an F5 / F4 I guestimate.



#729 sdedalus83

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Posted 26 November 2019 - 06:56 PM

Mine is stuck there, for use with the erecting prism. Set up for straight-through viewing it would be pretty close to the front of the tube.  I get the feeling Edmund was cranking these out with whatever they had,  not actually following the published specs. They're supposed to be user-configurable by sliding the lens cell fore or aft, but mine appears  to be welded into the aft position. 



#730 clamchip

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Posted 26 November 2019 - 09:00 PM

The lens cell in these finders is very hard to push around.

You guy's are correct in that if its a 90 deg finder with star prism the lens cell is

about half way down the tube.

The straight through version the lens cell is very near the front of the finder.

I think if I remember correctly I made a push stick from wood to move the cell

around. To clean the lens I think your better off doing it in place with the kitchen

faucet flooding the tube.

 

Robert


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#731 DAVIDG

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Posted 29 November 2019 - 11:11 AM

 Thanksgiving was wonderful. Before dinner the skies cleared and I was able to spot the Crescent Moon, Venus and Jupiter with the Sun still a few degrees above the horizon. I pulled out my homemade 6" f/4 that I built to use especially with 28mm  Pretoria eyepiece. The Pretoria was designed to correct coma for 6" f/4 and the focal length gives 7mm exit pupil and a magnification of 22x. The combination results in an excellent Richfield scope in terms of well corrected field of view and magnification.

   After dinner and before the full effects of the Turkey would kick in  and I won't be able to be extracted from my chair in front of the fireplace  I went back out and enjoyed the view. You can just make out Venus straight below the Moon and just above the clouds in the cellphone shot. I also took a cellphone picture through the eyepiece. with Venus at the very edge of the field. The camera picked up the shadow of the secondary which you didn't see visually..

 

                 Happy Holidays !!!

                   - Dave 

 

6f4newtonian.jpg

venusmoonthanksgiving2019.jpg

venusmoon28mmpretoria.jpg

 


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#732 DAVIDG

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Posted 01 December 2019 - 12:33 PM

 I've been off for the last week for Thanksgiving and getting a ton of projects done around the house, both the stuff that needs to get done and also some hobby projects. With the cold weather, evenings are a good time for me to work on optics. I have  an old Edmund Palomar Jr ( 4.25 f/10)  that I have enjoyed using for many years. Actually I think it was assembled from part vs a true Palomar Jr since  I bought  it from  a club member maybe 30 years ago. Years ago I replaced the diagonal which was nowhere near optically flat. That made a huge difference in the image quality. The primary  mirror was professional made and  if it was from Edmund it should be a clean sphere. If  it was a  clean sphere it would be close to true 1/8 wave system. When I tested it and had good size ring zone. It been on my list of projects to fix the mirror for many years. It finally made to thetop of the list  so over the last few evenings I have been refiguring it to parabola. 

    The first task was to strip the old aluminium coating. I took a paper towel, placed it on  the front surface of the mirror and added about teaspoon of Ferric Chloride solution. The solution soaks the paper towel and then I wrap the mirror and towel up in clear food wrap. Wait about an hour and the coating is gone.

   Next is to make a pitch lap. I use a soup can about 1/2 filled with optical pitch and melt it on my gas grill. I  used another 4.25" mirror blank as the base for the pitch lap, wrapped some tape around the edge and poured the pitch. I awaited for about 15 minutes for the pitch  too cool enough so it was still soft put won't run and pulled the tape off the rim.  With the mirror coated with cerium oxide polish so the pitch wouldn't stick to the glass I pressed the mirror into the pitch so it  molded to the curve of the mirror. Then ran it under cold water to full harden the pitch. Next I used a razor blade to cut a square pattern of channel in the lap. This allows the pitch to conform to the mirror as it chances shape  from polishing and also allow polish to be evenly distributed.

   It only took about 15 minutes of polishing to remove the ring zone and I was at a nice sphere. I could have stopped there but I wanted to parabolize the mirror for the very best image. A parabola for a 4.25 f/10 mirror is very shallow so one can easily over correct it ( make it too deep) and the shadows you see in Foucault test are very weak. The mirror almost looks like it is still a sphere. 

So the next step was to parabolize the mirror. I polished for only 5 minutes and when I tested it , I went too far. The correction was almost 2x larger then what it should be. So the next evening I slowly worked the figure back to where it should be. It only took a total of about 15 minutes of polish to bring it back but it took almost an hour of polishing for only a few minutes then going down to the basement to test, then back up to the kitchen for a few minutes more of polishing.  The result is now a velvet smooth parabola that tests dead on the money. The image is a standard Ronchi test not double pass and while the  cellphone image is not very good, visual you can just see a slight bowing of  the Ronchi band from the shallow parabola.  

  I know the image in this scope will now be as good as it gets. It will be great  outreach scope, and good for viewing  the planets and especially splitting doubles star. since being  an all reflective system, it will have no false color and it will show me the true colors.

 

                         Happy Holidays !

                            - Dave 

4f10stripping.jpg

4f10pitchlap.jpg

4f10.jpg

4f10ronchitest.jpg

 


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#733 Terra Nova

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Posted 12 December 2019 - 10:18 AM

I ran across this article that I thought some here might find both useful and interesting, (I did):

 

http://www.ianmoriso...jective-lenses/

 

(If it’s been posted previously, please forgive me for overlooking it.)


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#734 Terra Nova

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Posted 18 December 2019 - 10:43 AM

Here you’ll find some fun reading on Mars, from a 1950s historical perspective.

 

http://www.cufos.org...II 1955-56R.pdf

 

And remember, “Watch the skies, everywhere, keep looking! Keep watching the skies!”


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#735 rcwolpert

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Posted 18 December 2019 - 11:37 AM

Here you’ll find some fun reading on Mars, from a 1950s historical perspective.

 

http://www.cufos.org...II 1955-56R.pdf

 

And remember, “Watch the skies, everywhere, keep looking! Keep watching the skies!”

That was fun to read.


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#736 DAVIDG

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Posted 20 December 2019 - 06:16 PM

 So I have been on vacation for  a week now and trying  to catch up on a couple of projects. One has been to make a Blue Tooth interface for a DS2000 Meade mount I have. While the mount and the Autostar 497 aren't a classic just yet I plan to mount a 3" refractor I'm building around Brandon vintage lens from the 50's which is. 

   I have been a fan of Push To and Go To technology for many years. I made my first Push To DSC system using a Commodore C-64 back in the 80's 

   Things have got a lot easier with inexpensive and  great Apps like Sky Safari. It does all the work and best of all of you can see what is in the sky that you might want to observe in real time vs looking at a Star Chart or pushing buttons on a hand controller.

  So this afternoon I dug through my collection of parts and dug up  a HC06 bluetooth interface and a  MAX3232 RS232 to TTL converter along with some other parts. A total of maybe $10 in parts.  I soldered everything to together and fired it up. Sky Safari found the interface and soon I was slewing  the mount around by just tapping on the screen of my tablet. 

   Next step is to build the OTA for the vintage 3" lens and start enjoying all the objects I can view by just tapping on the screen. Looking forward to making  a double star list in Sky Safari and using the classic objective to view their wonderful colors. 

 

                        Happy Holidays !

                            - Dave 

    BTTOAUTOSTARINTERFACE.jpg                     


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#737 jcruse64

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Posted 21 December 2019 - 07:39 AM

That's cool!!



#738 Bomber Bob

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Posted 05 February 2020 - 05:50 PM

Debra & I had our eye exams earlier today -- my vision is still a bit blurry from the drops!   My left is 20/10, my right is 20/15, and my color vision is well above the curve for an old guy.  And all of that means... Nothing, in our Seattle South cloudy / rainy weather.  But, IF we had our clear winter skies, and IF I could sketch worth a hoot, the wonders I could share...


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#739 clamchip

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Posted 05 February 2020 - 07:00 PM

I  can't believe they kick us out the door after those drops!

I can hardly see my nose and I'm supposed to drive a automobile!

 

Robert


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#740 Bomber Bob

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Posted 05 February 2020 - 08:19 PM

I reported my test results because:  We post DPAC, star test, planetary test, etc. results for optics, yet don't for that final optical system -- makes no sense to me.  When Ol' BB says he saw canals on Mars, he saw canals on Mars -- just kidding!  Y'all lighten up.  Seriously, knowing that I have very good visual acuity means I see what I report & report what I see.  And, though I thought my color vision was slipping, it's better than average.  HOWEVER, their tests aren't the same as what we see at the eyepiece, with all the chaotic factors of object, seeing, optical train, etc.  But it's better than no measurement.


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#741 Chuck Hards

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Posted 05 February 2020 - 08:30 PM

These are some hardwood cones I've made to assist with taking dents out of dewcaps and other tubes.   You can see that each takes up about where the last one left off. 

 

Cones 01.jpg

 

Cones 02.jpg

 

 

 

 


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#742 Ben H

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Posted 06 February 2020 - 01:18 AM

I have seen the hardwood cones recommended in the Tinsley restoration thread as well. What method is used to draw the cone through the tube? Is the tube simply pushed onto it? 



#743 Chuck Hards

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Posted 06 February 2020 - 08:37 AM

I don't draw the cone through the tube, these are more for rounding-out ends and dents very close to the end of the tube.  For interior dents, I use steel shafting slid into the tube as an anvil.

 

For the cones, you place the dewcap on a hard flat surface, then stick the appropriate-sized cone into the out-of-round end (facing up), and pound it down carefully with a dead-blow mallet.  Then repeated tapping around the edge with a small machinist's hammer, as needed.  A few minutes work will restore just about any dewcap to circularity.


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#744 Senex Bibax

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Posted 06 February 2020 - 09:06 AM

Is that after cataract surgery? Something I'll probably have to deal with in the future, but not yet.

 

Too bad they can't implant a zoom lens!

 

Debra & I had our eye exams earlier today -- my vision is still a bit blurry from the drops!   My left is 20/10, my right is 20/15, and my color vision is well above the curve for an old guy.  And all of that means... Nothing, in our Seattle South cloudy / rainy weather.  But, IF we had our clear winter skies, and IF I could sketch worth a hoot, the wonders I could share...



#745 RalphMeisterTigerMan

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Posted 06 February 2020 - 12:21 PM

A Funny Thing Happenend To Me On The Way To The Forum....

 

While clicking onto thie Miscel. thread, a swirling multi-coloured noisy vortex appeared right in front of my...next thing I knew I found myself being pulled into dark tunnel where I was able to see snipets of the 1900's being displayed before me. Pictures of telescopes from the past that I recognized from the pages of Sky and Telescope and documentaries that I had watched in my early teens.

 

Waves of dellusional multicoloured dreamlike anesthesial HD videos filled my mind. I saw pictures of telescopes that I had fallen in love with as a kid. The Celestron C5 filled my hopes and dreams and seemed so real! I saw so many beatiful pictures of telescopes from my past and I was overcome with a compulsion to press something that said "I like this" over and over. Each time that hit that button I was overwhelmed with feelings of joy and happiness! Time seemed to pass without me being able to feel the passage of time! I was so strange and yet so beautiful and the feelings of wonder and joy become increasingly more and more intense...

 

...and then I found myself back sitting on the couch in the living typing on the keyboard of my laptop. Before I knew it, I had signed it and hit "Post". 

 

What-ever I had typed, I hope all who read it enjoyed it!

 

RalphMeisterTigerMan


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#746 Terra Nova

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Posted 07 February 2020 - 03:34 PM

I reported my test results because:  We post DPAC, star test, planetary test, etc. results for optics, yet don't for that final optical system -- makes no sense to me.  When Ol' BB says he saw canals on Mars, he saw canals on Mars -- just kidding!  Y'all lighten up.  Seriously, knowing that I have very good visual acuity means I see what I report & report what I see.  And, though I thought my color vision was slipping, it's better than average.  HOWEVER, their tests aren't the same as what we see at the eyepiece, with all the chaotic factors of object, seeing, optical train, etc.  But it's better than no measurement.

I had my cataracts removed in both eyes and the lenses replaced with the new toric lenses. Now I have no more astigmatism in either eye, each eye is 20/20 distance vision and they’re apochromatic. Best money I ever spent! It was soooo worth it. I never realized it would make such a difference. Beware tho, you will be doing some serious culling of your achromats and some of your cheaper eyepieces too! You will be much more aware of the color purple, and views that you thought were sharp in some scopes you may find to be sharper and others to be not as sharp. 


Edited by Terra Nova, 07 February 2020 - 07:47 PM.

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#747 DAVIDG

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Posted 10 February 2020 - 12:08 PM

  Surplus Shed has some 1/20 wave optical windows for $10. If you use the code 30PERCENT you can get 30% off as of today. These would be great to test the flatness of diagonals and other surfaces that are suppose to be flat. You need a monochrome or semi-monochrome light source but a common CFL bulb will work. I haven't purchased one myself since I have tons of flats so I'm just passing along the information. https://www.surpluss...tem/L14855.html

   It amazes me how many diagonals I have tested that are far from flat and having a known good one to use as a reference allows one to determine the quality of others. A bad flat  causes astigmatism in the image and other problems. The University of Delaware gave my club  a very nice 10" reflector OTA made from a  Parks fiberglass tube and high end parts The story goes that it had been stored in the closet of the Physic building for many years. I tested the primary which is most likely a Coulter and it tested very well. Then I tested the secondary,  it was WAVES from flat, just junk ! The flat was killing the image quality and most likely why the OTA was living in a closet. One of the club members,  under my direction is  polishing the diagonal to a true flat surface. He is pretty close and when done, I know the scope will now give an excellent image.  So my advice continues to be test all your optics to be sure they are the quality that you believe 

 

             - Dave 


Edited by DAVIDG, 11 February 2020 - 09:39 AM.

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#748 steve t

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Posted 10 February 2020 - 04:24 PM

  Surplus Shed has some 1/20 wave optical windows for $10. If you use the code 30PERCENT you can get 30% off as of today. These would be great to test the flatness of diagonals and other surfaces that are suppose to be flat. You need a monochrome or semi-monochrome light source but a common CFL bulb will work. I haven't purchased one myself since I have tons of flats so I'm just passing along the information. https://www.surpluss...tem/L14855.html

   It amazes me how many diagonals I have tested that are far from flat and having a known good one to use as reference allows one to determine the quality of others. A bad flat  causes astigmatism in the image and other problems. The University of Delaware gave my club  a very nice 10" reflector OTA made from a  Parks fiberglass tube and high end parts The story goes that it had been storied in the closet of the Physic building for many years. I tested the primary which is most likely a Coulter and it tested very well. Then I tested the secondary it was WAVES from flat, just junk ! The flat was killing the image quality and most likely why the OTA was living in a closet. One of the club members,  under my direction is  polishing the diagonal to a true flat surface. He is pretty close and when done, I know the scope will now give an excellent image.  So my advice continues to be test all your optics to be sure they are the quality that you believe 

 

             - Dave 

Dave,

Thanks for the heads up, got mine on order. After reading posts on CN, I've become a believer in testing optics. 

 

I'm currently building a 4" F/10 Newtonian around a NOS mirror. A great CNer (thanks Dale) came to the rescue and kindly offer to test/sort through five mirrors, that I've had laying around for years, on a Bath interferometer (sp).

 

The test results ranged from a Strehl of .8 to .987 (provided the outer 1mm is masked).

 

The last thing in the system to be tested, in the system, is the 1.0" diagonal, so this flat should help give me an idea on it's quality.

 

Thanks

 

Steve T


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#749 Terra Nova

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Posted 11 February 2020 - 07:34 PM

I found this history of PZO (Poland) and their products quite interesting.

 

https://www.lenstip.....__part_II.html

 

In the past we’ve discussed their tiny 70mm Mak here in this forum. Several of our members own one. In the article you can read about the full range of optics they produced after WWII.


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#750 steve t

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Posted 11 February 2020 - 09:10 PM

I found this history of PZO (Poland) and their products quite interesting.

 

https://www.lenstip.....__part_II.html

 

In the past we’ve discussed their tiny 70mm Mak here in this forum. Several of our members own one. In the article you can read about the full range of optics they produced after WWII.

Terra,

Thanks for the link. It was a very interesting read.

Steve T


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