Image of the day

From the
ATWB Customer Gallery

IC 5070 + NGC 7000

My Account

New to Astromart?

Register an account...


2020 President - NO COMMENTS (take to Politics Forum)

Previous Polls

Need Help?

Classical cassegrain matching mirrors unknown maker mid 1980s

Auction No.:
Current Bid:
High Bidder:
Bid History:
23 Bids [View History]
Spokane Vly, WA - United States
09/25/2020 09:21AM
10/05/2020 09:21AM
Buyer pays shipping
PayPal, Personal or Cashier's Check, Money Orders
This is an interesting auction to come across...

These are a matching mirrors set for a classical cassegrain. Here's what we do know..

Primary Mirror

Aperture:  6.0-inches
Design:  parabolic pyrex
Thickness:  0.95-inches
Center hole diameter:  1.75-inches
Weight:  1 pound 14 ounces

Secondary Mirror

Aperture:  2.34-inches
Design:  hyperbolic pyrex
Thickness:  0.57-inches
Weight:  3.4 ounces

These mirrors were originally housed in a lovely homemade "Celestron orange" iron and cork tube. ALL of the components; the 4-vane spider assembly, primary cell, cassegrain backplate, even the focuser; ALL came from Kenneth Novak & Co circa 1985. There are no dates on these mirrors, but we could assume pretty safely they are from near those dates.

Interesting is that both mirrors are inscribed on their sides "C6-3". The hyperbolic secondary, in addition, has inscribed "15.9" SEP."

In all the years I've owned this scope before I decided to part it out, I never could convince myself that it was a Tinsley mirror set only because I have almost always found their tubes to be longer. Cave made cassegrain mirrors, but I didn't think they went down to a 6-inch size. And I don't believe A. Jaegers manufactured cassegrain mirrors.

The tube that these mirrors originally housed in (and before you get too many ideas, this was DEFINITELY a homemade optical tube) was 24.15-inches L x 6.95-inches W. The placement distance the secondary sat from the primary was right at 15.8-15.9 inches; and so I feel this is the reasoning behind the further inscriptions on the secondary mirror. But I cannot be absolutely certain because I am well versed in refractors and standard reflectors; not with cassegrains. And because of such, this is also why I have not stated the focal length or ratio. Though, if I were to make a very close GUESS, it would be in the f/12-f/13 range as when I was using it years ago alongside my ETX-125 with the same eyepieces, I found the views to literally match in magnification size.

When this was in a functional cassegrain optical tube I was mainly doing planetary and lunar observation work and the images given were equal to that of a well-made Super C8. They do not perform at maksutov/slow refractor levels of resolution, but at the same time, much sharper than what I get in the older Celestron C6 reflectors or Comet Catchers.

The primary mirror has a chip near the donut hole. It came to me this way and was almost not evident to see when looking down the tube. It wasn't until I removed the Novak Cassegrain Baffle assembly that I realized one of the screws holding the cast aluminum baffle base had come into contact with the primary; causing a small stress chip. 
This isn't a huge defect because nearly all of it will be hidden anyway once a baffle tube is mounted with this mirror. But it is there and it is evident in the photos. It is a clean chip and is no clamshelling or cracking near it. The rest of the mirror is fully intact without additional chips, scratches, ect.
The optical coating on the primary is definitely great for its age and nearly no light passes through other than where the chip is. So the coating is in VERY good shape, a new coating not needed anytime soon.

The secondary mirror is in perfect form, free of any chips, clamshells or cracks. Its optical coating is equal to that of the primary. No scratches to the figure and no major pitting signs...And really I don't see it needing a recoat for quite some time still.

And hey, before I sign-off this description chat, if you do happen to know who made this mirror set, do let me know. I love to learn all that I can from the experienced. 

All nations welcome to bid!
Time Placed User Bid Amount
10/01/2020 02:05PM JOHN NORMAN III $68.03 [ Auto Bid]
10/01/2020 02:05PM mikhail malei $67.03
09/30/2020 01:00PM JOHN NORMAN III $66.03 [ Auto Bid]
09/30/2020 01:00PM Steve McDaniel $65.03
09/30/2020 01:00PM JOHN NORMAN III $60.03 [ Auto Bid]
09/30/2020 01:00PM Steve McDaniel $59.03
09/30/2020 10:16AM JOHN NORMAN III $52.03 [ Auto Bid]
09/30/2020 10:16AM David Richards $51.03
09/30/2020 10:14AM JOHN NORMAN III $50.00 [ Auto Bid]
09/30/2020 10:14AM David Richards $49.00
09/30/2020 10:13AM JOHN NORMAN III $41.00 [ Auto Bid]
09/30/2020 10:13AM David Richards $40.00
09/30/2020 10:12AM JOHN NORMAN III $26.00 [ Auto Bid]
09/30/2020 10:12AM David Richards $25.00
09/30/2020 10:12AM JOHN NORMAN III $22.72 [ Auto Bid]
09/30/2020 10:12AM David Richards $22.22
09/30/2020 10:11AM JOHN NORMAN III $16.19 [ Auto Bid]
09/30/2020 10:11AM David Richards $15.69
09/28/2020 09:14PM JOHN NORMAN III $10.50 [ Auto Bid]
09/28/2020 09:14PM Gary Fick $10.00
09/27/2020 08:50PM JOHN NORMAN III $0.15
09/25/2020 05:24PM Gary Fick $0.10
09/25/2020 01:09PM Louis Fico $0.05