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Equipment Discussions >> Classic Telescopes

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terraclarke
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Reged: 05/29/12

Loc: Just South of the Mason-Dixon ...
Re: Elli Buk Cave 10" Cassegrain [Re: Escher]
      #5912804 - 06/10/13 11:00 AM

Gosh, that thing gets more beautiful all the time Tom. You are doing an amazing job.

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starman876
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Reged: 04/28/08

Loc: VA
Re: Elli Buk Cave 10" Cassegrain [Re: Escher]
      #5912830 - 06/10/13 11:20 AM

You would have been the man in the scout troop during pine box derby car racing making sure those axles were like glass .

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turk123
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Reged: 07/09/10

Loc: N.E. Ohio
Re: Elli Buk Cave 10" Cassegrain [Re: starman876]
      #5912931 - 06/10/13 12:12 PM

Quote:

You would have been the man in the scout troop during pine box derby car racing making sure those axles were like glass .



Troop 25 and I did get first place!


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starman876
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Reged: 04/28/08

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Re: Elli Buk Cave 10" Cassegrain [Re: turk123]
      #5912966 - 06/10/13 12:27 PM

welcome to the winners circle

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R Botero
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Reged: 01/02/09

Loc: Kent, England
Re: Elli Buk Cave 10" Cassegrain [Re: Escher]
      #5913130 - 06/10/13 01:44 PM

Work of art!

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terraclarke
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Re: Elli Buk Cave 10" Cassegrain [Re: turk123]
      #5913184 - 06/10/13 02:04 PM

Quote:

Quote:

You would have been the man in the scout troop during pine box derby car racing making sure those axles were like glass .



Troop 25 and I did get first place!




I was up in Akron during a weekend around 15 years ago and they were having the international soapbox derby there. Just stumbled on it by coincidence. It was pretty neat. It was also almost impossible to find a room there then. Wound up staying in those grain elevator/silos they converted into a hotel. Had a round room. That was pretty cool too.


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DAVIDG
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Reged: 12/02/04

Loc: Hockessin, De
Re: Elli Buk Cave 10" Cassegrain [Re: terraclarke]
      #5913190 - 06/10/13 02:06 PM

Did your secondary have any markings on the back to indicate a radius or spacing ?

- Dave


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turk123
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Reged: 07/09/10

Loc: N.E. Ohio
Re: Elli Buk Cave 10" Cassegrain [Re: DAVIDG]
      #5913560 - 06/10/13 04:47 PM

Quote:

Did your secondary have any markings on the back to indicate a radius or spacing ?

- Dave




It did have some marks but I will have to look again. It is also offset or not centered. I will check again when I get home from work. I have to go back through my pictures to see if I have the exact position of the secondary and spider to see how this offset was positioned. I should have been paying more attention to this when it came off. Maybe you know. What I mean is, the barrel probably was either closer to the eyepiece or further away from the eyepiece. I can't imagine the offset being sideways to the eyepiece.

I purposely did not take the secondary completely apart. I did not touch the adjustments on the mirror or barrel.


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turk123
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Reged: 07/09/10

Loc: N.E. Ohio
Re: Elli Buk Cave 10" Cassegrain [Re: terraclarke]
      #5913568 - 06/10/13 04:49 PM

Quote:



I was up in Akron during a weekend around 15 years ago and they were having the international soapbox derby there. Just stumbled on it by coincidence. It was pretty neat. It was also almost impossible to find a room there then. Wound up staying in those grain elevator/silos they converted into a hotel. Had a round room. That was pretty cool too.




The Quaker Square Inn made from the old quaker oats factory silos. Pretty neat place. Shopping mall also.


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turk123
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Reged: 07/09/10

Loc: N.E. Ohio
Re: Elli Buk Cave 10" Cassegrain [Re: DAVIDG]
      #5914089 - 06/10/13 09:29 PM Attachment (13 downloads)

Quote:

Did your secondary have any markings on the back to indicate a radius or spacing ?

- Dave




Here is the picture of the back of the secondary. The only markings I found were the two arrows marking that Hexhead screw. The other marks were mine.


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turk123
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Loc: N.E. Ohio
Re: Elli Buk Cave 10" Cassegrain [Re: turk123]
      #5914103 - 06/10/13 09:37 PM Attachment (14 downloads)

I took a look at my old paint sprayer from the seventies and said, "What am I doing with this?" I picked up this bad boy from Lowes. Gravity feed with two heads and pressure gauge. Uses forty pounds. My tank compressor is 10-12 gallon and will run this fine. I can't wait to get painting! Building my paint booth in the next few days.

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herrointment
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Reged: 03/12/11

Loc: North of Hwy. 64
Re: Elli Buk Cave 10" Cassegrain [Re: turk123]
      #5914140 - 06/10/13 09:56 PM

Have a photo of the mountain of soiled rags/paper towels?

Lots of work showing here. Very Nice!


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turk123
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Reged: 07/09/10

Loc: N.E. Ohio
Re: Elli Buk Cave 10" Cassegrain [Re: herrointment]
      #5914179 - 06/10/13 10:23 PM

Quote:

Have a photo of the mountain of soiled rags/paper towels?

Lots of work showing here. Very Nice!




I've gone through 3 rolls of paper towels. Best material to use for cleaning. Especially with all the nasty chemicals.

My fingers are turning yellow though and my dog has informed me she will no longer be going on walks but will be driving my pickup and tomorrow morning the little guys running around in my basement will be taking me to Alpha-centari for lunch. Pass the acetone and Hydrofluoric acid. Oh, and the gin.


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starman876
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Re: Elli Buk Cave 10" Cassegrain [Re: turk123]
      #5914313 - 06/10/13 11:39 PM

Look at my post that provides a link to a program that provides all the information you will need to set the spacing. at the top they provide a link to an Excell spread sheet that you will love to use.

http://www.oldham-optical.co.uk/Design.htm


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Datapanic
Carpal Tunnel
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Reged: 10/17/09

Loc: Tucson, Arizona
Re: Elli Buk Cave 10" Cassegrain [Re: starman876]
      #5914322 - 06/10/13 11:46 PM

Get some Chemical Grade gloves! Don't let that stuff get into your system. That Aircraft Remover stuff and other cleaners and solvents can really do some damage to your skin.

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turk123
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Reged: 07/09/10

Loc: N.E. Ohio
Re: Elli Buk Cave 10" Cassegrain [Re: starman876]
      #5914538 - 06/11/13 05:33 AM

Quote:

Look at my post that provides a link to a program that provides all the information you will need to set the spacing. at the top they provide a link to an Excell spread sheet that you will love to use.

http://www.oldham-optical.co.uk/Design.htm




Johann

That is a great program and a very useful website! It has giving me a bit more confidence in putting this thing back together. Thanks much.

Edited by turk123 (06/11/13 05:35 AM)


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DAVIDG
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Reged: 12/02/04

Loc: Hockessin, De
Re: Elli Buk Cave 10" Cassegrain [Re: starman876]
      #5914778 - 06/11/13 10:27 AM

Quote:

Look at my post that provides a link to a program that provides all the information you will need to set the spacing. at the top they provide a link to an Excell spread sheet that you will love to use.

http://www.oldham-optical.co.uk/Design.htm



To set the spacing between the primary and secondary you need to know the radius of curvature of both the primary and secondary. A small change in either one will make a large change in the back focal length and also the optical correction of the system. You can show this for yourself with the spread sheet by change the the focal ratio in the example of Classic Cass from 2.8 to 2.9 and the distance between the primary and secondary will change from 959mm to 984.4mm but at the same time to hold the back focal length constant, the spread sheet is also changing the radius on the secondary which isn't what happens when the optics are already made. There is only ONE spacing distance that results in the best correction for spherical aberration.
For someone who already has a set of optics this spread sheet can be misleading. To set the optics up correctly one needs to know the exact radius of the primary and also that of the secondary, then you can calculate the spacing.
If the spacing is wrong the telescope WILL focus and give an image and many people that are not trained in optical testing might state the image is pretty good but your not doing yourself any favors by not taking the time to understand how to setup the optics correctly to give the very best image and to be sure that optics do not have any problems.

- Dave


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Bob Myler
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Reged: 05/18/06

Loc: St Louis, MO
Re: Elli Buk Cave 10" Cassegrain [Re: DAVIDG]
      #5914946 - 06/11/13 12:09 PM

I really do enjoy this thread.

Earlier, there was mention of Aircraft remover from Autozone to remove unwanted paint. I'm looking to safely lift some black krinkle off of aluminum. Specifically the back cell and focuser plate of the 6" Fecker listed below.

Is 'Aircraft Remover' its exact name?


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rdandrea
Carpal Tunnel
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Reged: 06/13/10

Loc: Colorado, USA DM59ra
Re: Elli Buk Cave 10" Cassegrain [Re: Bob Myler]
      #5914983 - 06/11/13 12:31 PM

There's a picture of the can on page 4 of this thread.

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turk123
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Reged: 07/09/10

Loc: N.E. Ohio
Re: Elli Buk Cave 10" Cassegrain [Re: DAVIDG]
      #5915038 - 06/11/13 01:02 PM

Quote:


If the spacing is wrong the telescope WILL focus and give an image and many people that are not trained in optical testing might state the image is pretty good but your not doing yourself any favors by not taking the time to understand how to setup the optics correctly to give the very best image and to be sure that optics do not have any problems.

- Dave




Which begs to ask the obvious question, "How do you calculate the secondary radius?" The primary is 80 7/8" as it is written on the back. I did not see any marks on the secondary although I need to check one more time under good light. We know the scope is an f/16 from the catalog literature. I can also put it back together and measure as I have not changed the secondary and I measured the primary mirror position on the rear cell. Of course, none of the original setting may be correct. What would you suggest I do Dave?


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