D&G 5" f/20 - info wanted
Posted 27 July 2013 - 04:33 PM
5.375" clear aperture, approx. 117" long, so 5" f/20 is just a guess. Unknown history, unknown previous owner deceased. Written in lens cell is "Refigured D&G OBJ" and then some illegible words. I don't know if this is an original D&G or a refigured ATM lens. The cell and tube look just like my previous D&G.
The previous owner used Parallax rings with a strongly curved base, so I bought new rings to attach the 19" Losmandy dovetail.
I had the tube shortened and powdercoated by Binoscope Company. Looks brand new.
Just had first light (for me) last night, amazing optics. Sharp and color-free. I didn't have a lot of time so I just used the DM4 for testing.
If you know anything about this scope please share.
Posted 27 July 2013 - 04:51 PM
Posted 27 July 2013 - 06:36 PM
Posted 27 July 2013 - 06:39 PM
Posted 27 July 2013 - 09:37 PM
Posted 28 July 2013 - 03:59 PM
That is an amazing telescope! I'm green with envy. (No Freud jokes, please.)
Posted 28 July 2013 - 05:57 PM
Posted 28 July 2013 - 06:20 PM
Shopping list: Dewshield and longer saddle for the EQ mount.
I plan to have this scope set up for at least two public events at Crockett and Sky Meadows in the fall.
Posted 28 July 2013 - 06:46 PM
Posted 28 July 2013 - 08:12 PM
i have a couple myself.
Posted 28 July 2013 - 08:32 PM
What's the best way to measure focal length? Aim at the moon and use an index card to find the focus point? Or will a streetlight work as well?
Posted 28 July 2013 - 08:47 PM
Posted 28 July 2013 - 08:53 PM
The lens equation is 1/f = 1/(d image) + 1/(d object) were "d image" is the distance from the lens to were the image is formed, "d object" is the distance to object your looking at, and f is the focal length of the lens. When the object is at infinity "1/(d object)" goes to zero so 1/f = 1/(d image) so your measuring the focal length directly.
Posted 01 August 2013 - 06:29 PM
After a little searching and advice from some of you I found this:
They support telescopes! The shipping seems a little high, but I don't think they can make a living selling to hobbyists. If they're willing to help a non-commercial client I'll pay the fees. The rolling service looks interesting.
Posted 01 August 2013 - 07:56 PM
Posted 01 August 2013 - 09:02 PM
Posted 13 August 2013 - 04:47 PM
Posted 26 August 2013 - 10:36 AM
The scope rode well. Balance was easy to achieve and maintain.
We were able to view a number of doubles and DSO's: Nu Sco, Beta Sco, Izar, M8, M20, M22 and several others. Star images were sharp with no aberrations.
No finderscope. "Gunsighting" with a Brandon 48mm put most targets in the FOV right away.
Photo by Mr Catapoman.
Posted 26 August 2013 - 01:56 PM
Posted 26 August 2013 - 02:05 PM
Posted 26 August 2013 - 04:51 PM
I've recently made a 5" f15 with D & G lens. Still not had a lot of time to use it but it has certainly been fun so far. A lot easier to manage than my 6" f15, though that is fun too despite the size and weight.
Posted 26 August 2013 - 05:47 PM
Posted 16 December 2013 - 02:48 PM
I believe this scope was a guidescope for a much larger refractor, possible a similar setup to the one for sale
in California. Discussed here on CN post #5884694 and here
I have seen a few giant refractors with the really long guidescopes.
My scope came from a setup based on the north shore of Long Island. I'm still looking for the origin of the lens, and the unusual sapphire coating.
Posted 16 December 2013 - 02:57 PM
Ive had the scope out several times for public outreach, and the optics are excellent. No false color or distortions. Was able to binoview the moon last time out.