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Equipment Discussions >> Classic Telescopes

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The Ardent
Pooh-Bah
*****

Reged: 10/24/08

Loc: Virginia
D&G 5" f/20 - info wanted
      #5993347 - 07/27/13 05:33 PM

This is the D&G I bought from Camera Concepts at NEAF 2013.
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.

Thanks!!



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terraclarke
Post Laureate
*****

Reged: 05/29/12

Loc: Just South of the Mason-Dixon ...
Re: D&G 5" f/20 - info wanted new [Re: The Ardent]
      #5993361 - 07/27/13 05:51 PM

Interesting telescope. Looks like you either need a taller tripod or a shorter chair.

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Awesomelenny
Post Laureate
*****

Reged: 05/02/04

Loc: Long: 81.42 W Lat: 41.21 N
Re: D&G 5" f/20 - info wanted new [Re: terraclarke]
      #5993504 - 07/27/13 07:36 PM

I remember seeing this loooonng scope at NEAF! Wow! Should be virtually free of chromatic abberation with this long f/ratio. It's going to have to be some real planet killer! You will definitely want to make sure you collate this carefully in the beginning before you do anything. Use a 3rd magnitude star for that and you should get a really nice airey disk. Then enjoy this beauty. Wow I want to hear reports of performance!

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Awesomelenny
Post Laureate
*****

Reged: 05/02/04

Loc: Long: 81.42 W Lat: 41.21 N
Re: D&G 5" f/20 - info wanted new [Re: Awesomelenny]
      #5993507 - 07/27/13 07:39 PM

Oh by the way did you have a dew shield with it? If not, get a short 12 to 14 inch piece of aluminum tubing from a local company or Hastings Irrigation.

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bremms
Carpal Tunnel
*****

Reged: 08/31/12

Loc: SC
Re: D&G 5" f/20 - info wanted new [Re: Awesomelenny]
      #5993790 - 07/27/13 10:37 PM

That is Looooonnnggg. Very cool.. careful the moment arm of such beast will damage a mount.

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Chuck Hards
Post Laureate
*****

Reged: 05/03/10

Loc: The Great Basin
Re: D&G 5" f/20 - info wanted new [Re: bremms]
      #5995134 - 07/28/13 04:59 PM

I tried to commission a 5" f/20 doublet a couple of years ago, but the fabricator had to bow-out due to health issues. I have a 2" f/20 home-made refractor (unknown objective provenance) and have to agree, there just isn't a color issue at f/20.

That is an amazing telescope! I'm green with envy. (No Freud jokes, please.)


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starman876
Postmaster
*****

Reged: 04/28/08

Loc: VA
Re: D&G 5" f/20 - info wanted new [Re: Chuck Hards]
      #5995310 - 07/28/13 06:57 PM

what kind of finder are you planning to use. I am sure it also needs to be a long focal length?

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The Ardent
Pooh-Bah
*****

Reged: 10/24/08

Loc: Virginia
Re: D&G 5" f/20 - info wanted new [Re: starman876]
      #5995349 - 07/28/13 07:20 PM

All I need is a Telrad. With a 35 Ultima 7 Sgr and the M8 are framed in the FOV, that about 36', close to the same size as the central Telrad ring.
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.


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bremms
Carpal Tunnel
*****

Reged: 08/31/12

Loc: SC
Re: D&G 5" f/20 - info wanted new [Re: The Ardent]
      #5995380 - 07/28/13 07:46 PM

That baby needs a 55mm Plossl. Still a 2.75mm exit pupil!

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mustgobigger
Postmaster
*****

Reged: 06/12/07

Loc: Michigan
Re: D&G 5" f/20 - info wanted new [Re: bremms]
      #5995491 - 07/28/13 09:12 PM

love those long FL refractors....your going to love it.
i have a couple myself.


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The Ardent
Pooh-Bah
*****

Reged: 10/24/08

Loc: Virginia
Re: D&G 5" f/20 - info wanted new [Re: mustgobigger]
      #5995539 - 07/28/13 09:32 PM

I meant to ask this earlier:
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?
Thanks!


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Mirzam
Post Laureate
*****

Reged: 04/01/08

Loc: Lovettsville, VA
Re: D&G 5" f/20 - info wanted new [Re: The Ardent]
      #5995573 - 07/28/13 09:47 PM

You can use a streetlight or telephone pole but it needs to be far away--like about 500 yards at least. If you use an object that is too close the focal point will be shifted considerably.

JimC


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DAVIDG
Post Laureate
*****

Reged: 12/02/04

Loc: Hockessin, De
Re: D&G 5" f/20 - info wanted new [Re: The Ardent]
      #5995578 - 07/28/13 09:53 PM

It depends how accurate you want the know the focal length. The Moon will give it to you directly. If you use a streetlight it needs to be a couple of miles away or you need to know the distance if it is close.
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.

- Dave


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The Ardent
Pooh-Bah
*****

Reged: 10/24/08

Loc: Virginia
Re: D&G 5" f/20 - info wanted new [Re: DAVIDG]
      #6001971 - 08/01/13 07:29 PM

In my quest for a dew cap I called Astrozap since Ive used a couple of their nice flexible dew shields. No metal ones in my size. D&G did not return phone calls or emails. I thought AP might have some extra dew shields lying around, but again nothing in the right size. I wanted something finished, powdercoated, and meant for a refractor.

After a little searching and advice from some of you I found this:

http://hastingsirrigation.com/node/19

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.


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mikey cee
Postmaster
*****

Reged: 01/18/07

Loc: bellevue ne.
Re: D&G 5" f/20 - info wanted new [Re: The Ardent]
      #6002113 - 08/01/13 08:56 PM

Andy Beirow has always been helpful when I've called. Mike

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BigC
Carpal Tunnel
*****

Reged: 09/29/10

Loc: SE Indiana
Re: D&G 5" f/20 - info wanted new [Re: terraclarke]
      #6002213 - 08/01/13 10:02 PM

It occurs to me that a really big brother version of the crank-up camera tripod might be good.Leave the mast low for low angle,and crank it up for the zenith!Might need the viewing chair on rollers as the geometry changes.

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The Ardent
Pooh-Bah
*****

Reged: 10/24/08

Loc: Virginia
Re: D&G 5" f/20 - info wanted new [Re: BigC]
      #6023590 - 08/13/13 05:47 PM Attachment (19 downloads)

The Hastings pipe arrived today. Subtract the time for mailing my order and shipping the package UPS, was a two-day turnaround. Arrived in good shape. The rolled end looks and feels great. No burrs or sharp edges on the cut end. Only complaint, there is some machine oil inside the tube. I have a machinist friend who can help with fitting to the lens cell. Then some primer and paint, or powdercoat.

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The Ardent
Pooh-Bah
*****

Reged: 10/24/08

Loc: Virginia
Re: D&G 5" f/20 - info wanted new [Re: The Ardent]
      #6046828 - 08/26/13 11:36 AM Attachment (23 downloads)

Friday was the first decent night in two months. Set up the scope to test balance. Forgot the pier extension so tripod was only 50" high.
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.


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Mirzam
Post Laureate
*****

Reged: 04/01/08

Loc: Lovettsville, VA
Re: D&G 5" f/20 - info wanted new [Re: The Ardent]
      #6047160 - 08/26/13 02:56 PM

I know that this is sacrilage, but I would seriously think about folding the lightpath in half (at least).

JimC


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Dr Morbius
Post Laureate
*****

Reged: 02/06/07

Loc: ManorvilleNY-but not for long
Re: D&G 5" f/20 - info wanted new [Re: Mirzam]
      #6047171 - 08/26/13 03:05 PM

60 power with a 48mm Brandon......Heaven!!!! ..........and yes, folding the lightpath is sacrilagious, impious, and sinful. Please don't do it.

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