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Classic Cassegrain Popularity?

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#201 John59

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Posted 04 August 2019 - 08:49 PM

Hummm..I would would have thought that both the primary and secondary are adjustable on any classical cass except the peculiar system used for the Tak CN-212 which has a movable mirror. 

 

Ed

Ed, My mistake they are there just not where I thought they would be.  They are actually on the grip ring where the the focuser attaches.   I hope I never have to adjust these. 

When I first received it I did a collimating with a Cheshire and got excellent rings.

However when I finally got a clear night the star collimation was off more that I would have thought it would be.

It took a bit of tweaking on the secondary to get it right.



#202 Ed Wiley

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Posted 04 August 2019 - 09:10 PM

This is what I used back in the day. I found collimation very tricky.

http://bobmay.astronomy.net/CassNotes/

 

Ed


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#203 555aaa

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Posted 05 August 2019 - 01:57 PM

Tanks for the link, Ed.



#204 danielguo

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Posted 05 August 2019 - 07:25 PM

FYI, this is how I collimate my CFF CC250.

  1. (Once after delivery) Measure the distance between primary and secondary to make sure the distance is still correct after international shipping. Mine is still perfect.
  2. (Optional) Put a laser in the focuser and adjust the focuser tilt to let the laser hit the center marker of the secondary.
  3. Put a Takahashi Collimating Telescope in the focuser and adjust the secondary to align the dot to the secondary center marker.
  4. Center on a relatively bright star and adjust primary tilt to remove coma.

It sounds like a lot of work, but the scope holds collimation pretty well. The primary adjustment knobs are also clearly marked making it easier. Last week I was fine tuning primary collimation in a star party and it took me only half an hour to get it essentially perfect.


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#205 Bomber Bob

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Posted 13 August 2020 - 07:06 PM

What a long strange trip it's been...

 

6 Years Ago, I got my one-of-a-kind Tinsley 6" F20 Cassegrain:

 

Saturn Restore 2020 S99 - Original Condition.jpg

 

Today, I finished all the external restore & upgrade work:

 

Saturn Restore 2020 S37 - Finders (Both Mounted RS).jpg Saturn Restore 2020 S38 - Finders (Both Mounted LS).jpg

 

Mirrors go back in this weekend, and she'll be ready to take on Mars / Jupiter / Saturn.


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#206 jgraham

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Posted 13 August 2020 - 08:32 PM

Wow, that's gorgeous! Please let us know how performs. I recently had a chance to refurb a 6" f/20 Cassegrain that I believe was originally assembled from Coulter mirrors and Novak components...

 

Novak 6in f_20 CC (5-2-2020)-3.jpg

 

Noval 6in f_20 CC (5-2-2020)-2.jpg

 

It has proven to be a solid performer once I got the mirror spacing and collimation under control.

 

 


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#207 Bomber Bob

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Posted 14 August 2020 - 07:11 PM

My 2nd (& Final) restore of my antique Tinsley 6" F20 Cassegrain OTA is done:

 

Saturn Restore 2020 S82 - Restore COMPLETE (Meade SF Full RS).jpg Saturn Restore 2020 S84 - Restore COMPLETE (Meade SF Full LS).jpg

 

It's riding on 1 of my 2 vintage 1980s Meade StarFinder EQ mounts -- the tall pedestal version.  No motor drives on the matching Tinsley EQ yet -- but it's on my Project List...


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#208 TG

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Posted 14 August 2020 - 08:32 PM

Absolutely stunning, Bob. Well done!
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#209 Bomber Bob

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Posted 14 August 2020 - 09:14 PM

Thanks!



#210 jgraham

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Posted 15 August 2020 - 03:41 AM

Wow, that's gorgeous! Congratulations on a fine restoration!
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#211 Starman27

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Posted 15 August 2020 - 11:33 AM

Beautiful restoration.



#212 Bill Barlow

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Posted 15 August 2020 - 03:09 PM

Hopefully the optics will perform as good as it looks.

 

Bill



#213 Bomber Bob

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Posted 15 August 2020 - 06:53 PM

The Views were good before I had Majestic re-coat the mirrors in 2016.  The Views were outstanding after that.  In fact, it was while testing the new coatings that I saw an albedo feature on Ganymede -- for the first time in almost 50 years of observing.

 

Here it is on the 200# Tinsley EQ:

 

Saturn Restore 2020 S90 - Restore COMPLETE (Tinsley EQ Full RS).jpg Saturn Restore 2020 S95 - Restore COMPLETE (Tinsley EQ Full LS).jpg

 

The OTA weighs 26# -- no trouble at all for the massive mount.  It's restore is next...


Edited by Bomber Bob, 15 August 2020 - 09:05 PM.

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#214 TG

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Posted 15 August 2020 - 10:12 PM

The Views were good before I had Majestic re-coat the mirrors in 2016. The Views were outstanding after that. In fact, it was while testing the new coatings that I saw an albedo feature on Ganymede -- for the first time in almost 50 years of observing.

Here it is on the 200# Tinsley EQ:

Saturn Restore 2020 S90 - Restore COMPLETE (Tinsley EQ Full RS).jpg Saturn Restore 2020 S95 - Restore COMPLETE (Tinsley EQ Full LS).jpg

The OTA weighs 26# -- no trouble at all for the massive mount. It's restore is next...


I thought the mount had been restored as well. We shall await its restoration with anticipation.

TG

#215 Bomber Bob

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Posted 16 August 2020 - 08:12 AM

I finished the functional restore months ago -- all the gearing is smooth as silk.

 

The cosmetic restore is all that's left.  The mount, counterweight, & feet will be satin black -- will have the mount head powder-coated.



#216 TG

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Posted 16 August 2020 - 05:00 PM

I finished the functional restore months ago -- all the gearing is smooth as silk.

The cosmetic restore is all that's left. The mount, counterweight, & feet will be satin black -- will have the mount head powder-coated.


We are shallow people, is all I can say. :lol:
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