54 replies to this topic

[asaint]

D&G 6" f/12 Refractor

[edwincjones]

Thank you for the report. I have not heard much of D&G for a while, their web site is old, so I have been wondering if they are still around. I would like to get the 5 or 6" scope, and you article convinced me I should get one, and the photo convenced me that the 6" is way too big and I need to consider the 5"

edj

[Scott Beith]

I want an 8" f/15, but I would need a SERIOUS mount for it.
Thanks for the excellent article - I enjoyed it quite a bit.

[Mr. Bill]

VERY sweet! How well does the G11 mount handle the moment arm in a breeze?

[thomas wade]

Under normal conditions the G11 mount does an excellant job . However on one occasion I was using it at a public star party on a very breezy night and the images were not steady. The wind was blowing between 15 and20 miles per hour. normally I wouldnt have bothered setting up on this kind of night but I was doing this for the parks department and this was a heavily adveritied event for them. the planets were shakey but everyone seemed to enjoy the view. tom

[CharlesStG]

Absolutely the best review I've ever read! Loved it!

[Sky Captain]

Thanks Tom for the wonderful review, and welcome to CN.
It put a smile on my face in the midst of all this rain in the NW.

Oh yeah, it reaffirmed my wanting one of those fine refractors!

[miniventures]

Tom, Great review...about a year ago I researched these fine refractors and wanted one, then (yes, Scott, a REFRACTOR). After reading your review, my interest has been reignited. Thanks!

[CharlesStG]

Ah, the high virtues of a simple (not simple to make!) D&G doublet!

Because those with large $$ "normally" go for big APOs these days, it doesn't mean everyone does - or even wants to. Small APOs, sure - big APOs, not so sure..........

On an absolute basis, the very, very finest APOs can "potentially" give the very finest visual images in the best of conditions (no temp drift), with the most light focused in the airy disc.

That said, D&G doublets are still preferred by some, price no object. Why? Well, as a highly regarded former director of ALPO once told me: "A D&G doublet is worth the wait no matter how long - - one from anyone else is likely not worth the wait no matter how short". (a couple of other quality american makers have joined the scene since that comment was made to me 12 years ago).

Here's what keeps 'em coming back:

When it comes to practical observing with LARGE refractors, an air-spaced doublet has distinct advantages over an oil-spaced triplet, perhaps less so over an air spaced triplet. When you go out to view, if you live in an area like me (Kansas) where temps drop and keep dropping 'till dawn, an air-spaced Achro like the D&G equalises very quickly and the design is optimized to make temp changes less noticeable at the eyepiece than triplet designs. This means that while the APO-man is often waiting for the slight softness in the image to "go away", the achro-man is getting maximum performance from his lens.

And with maximum performance in a long focal length doublet, carefully optimized for most color-free possible with spherical correction to 1/10 wavefront (not just surface ptv) or better, what you have is a perfectly corrected lens which has the capability to perform, big time!

A 5" doublet of this quality will often have planetary images preferred by most over the highest quality 7" Maks, for instance (and that's assuming the Mak has temp stabilized). Contrast does not always beat greater aperture for what you want to see, but it does do so often enough on planets, the moon, doubles and open clusters.

With only two elements up front and as few as three in the eyepiece, you have the potential of superb contrast which more glass or reflections can hardly match and blackest contrast is what some of us CRAVE.

Another virtue of this design is the very long focal length which makes for a scope that an owner takes such pride in as it "looks" like a real scope. I don't think too many of us realize the pride of showing off one of these long boys -- a point "visitors" certainly DO appreciate - it creates a sense of anticipation in them that makes their (often long awaited) time at the eyepiece doubly rewarding.

Long focal length, as we all know, but most of us seem to forget, allows higher powers without normally using barlows. This scope type simply puts the least amount of glass between you and the universe - think about it.

Great designs for relatively inexpensive roll-roof observatories have never been better or cheaper to build.

Put one of these in your backyard with a scope like a D&G in it and many could call that good enough - for life.

Want a little better even - get a chromacor corrector instead of that next Nagler or two and you will reduce what tiny chromatic aberration is remaining by as much as 60%.

Everything is a compromise of performance objectives when it comes to scopes. I don't think you'll find many who would trade a large, perfectly figured doublet scope for anything else.

It performs when sometimes the great names are "too hot" to handle and most of us don't have time to wait. Do you?

Wishing all the best of scopes under perfect skies!

p.s. I hear the nay-sayers - the ones who need to justify buying that huge APO instead of putting their kids through college saying things like - :"well, put that scope on Venus or Sirius and..." - Hey, get Serious! Fact is, a touch of color "may" be seen by some, but not by all. And if your idea of astronomy is looking at Sirius all night -- I'm sure we'd find it "interesting" to read an article about your observations.

[sectorzed]

Thanks for the report Tom and welcome to Cloudy Nights!

I have to admit that I've been curious about D&G refractors for some time now, especially in the larger apertures...

Now please, somebody lash me to the mast!!!

-Gary:refractor:
hearing the siren's call..

[Dr. Dave]

I have a 5" f/10 D&G that I dearly love and don't get to use nearly enough. I also lust in my heart for a 8" f/12!

Someday!

[Gaz O'C]

Thanks for a very enjoyable report Tom. I loved the picture, I've got/had quite a few different types of scopes, but theres no denying theres something special about a big, long refractor.

[Daniel Mounsey]

Tom,
I have not been on cloudynights lately, however after reading your review I was compelled to say it's one of the nicest I've read. I love when people just simply speak from the heart and say it like it is. I am working on two 6" F-15 D&G's at the moment which unfortionatly will be a little longer than yours is. Pons is helping with the designing of the tubes. One tube is being made of wood while the other will be metal. I will just be getting the lenses in their cells and doing the rest.

A long time ago I built a Zeiss replica case for a Telementor. About 3 years later the customer called me back and said he'd give me a completed D&G lens in the cell, an AP focuser and a Zeiss 50mm F-11 doublet lens for the finder in exchange for a wooden tube for his 6" F-15. I agreed and I'm working on them now since the lenses are still being made. I plan to use and ATLAS mount with custom wood legs, so we'll see how it goes.

I should also mention that at these focal lengths with good glass, the color correction is great on the D&G's and another thing many color correction fanatics forget is how sharp these long scopes are. They are really tack sharp! with gorgous black backgrounds. Good job!

[billyo]

Thanks for the report. I have the same telescope & agree with everything you said.I have one question. Did you put a knob in the center of the lens cap? I added one to mine.Thanks.

[CharlesStG]

My two D&Gs lens caps both came with the knob, standard and it really looks great. That's another thing I like about D&G - the attention to important details. The lens caps fit perfectly, look great. The lens cells aren't just a one piece unit like most others' cells, but are a two-piece unit for precision collimation using the three spring-loaded adjusters and three locking screws - NICE! Honestly, I don't know how they make any money on these lenses - I think maybe they use amateur work as a time filler for gov't and commercial work which must be more profitable. I'd say the amateur work is a labor of love - it takes a long time on delivery, but his love-labor is well appreciated by most of those fortunate enough to have a Barry Greiner lens to look through.

[Nebhunter]

Thank you very much for the wonderful review. I enjoyed every word of it. I would only as you for one more thing. Another review, once you have had more time with it on doubles and other objects. Meat and potatoe reviews - love them.

[Nebhunter]

Well thought out, and well said.

[Nebhunter]

Daniel, please let us know how the Atlas handles those scopes. It would be very meaningful to many just to know how capable that mount is with the F15. I'm assuming you will probably be doing some mod's to it as far as the saddle plate goes, etc.???

It would be great to read a comparison on the D&G F12 vrs F15 visually, and if the extra length really makes that much difference, with considerations to the mount.

[Daniel Mounsey]

Yea, that's right, we will be making some mods to the Atlas and I'll surely give mention to its performance once it's completed.

[Peter Argenziano]

Tom,

Thanks for the review. For me it is quite timely as I am considering acquiring one of these refractors.

To be honest, my current 'scope quest' has been going on for about a year. I do most of my observing with my 18 Obsession, and I expect that will continue even after the next scope arrives. But, I have been longing for something nice to use for lunar and planetary studies... OK, open clusters and doubles too.

I had a very nice Intes MK-66 6" Mak-Cass (that I wish I still had) that served me quite well. I especially liked its performance with Denk II binoviewers on the Moon.

Questions I have are:

Any current D&G owners using a binoviewer?

What about mount requirements?

I am thinking of getting an Orion Atlas with the pier extension. Will this work out with a 6" f/12 model? I am undecided as to whether I'll get a 5" or 6", but it will be f/12. To me this is more appealing than the last scopes being considered, all 4" apos.

All comments appreciated.

Peter

[spaceydee]

I'm not a D&G owner but I believe that there are mount suggestions on D&G's website.

[Peter Argenziano]

Thanks Dee. I've read their recommendations and was curious as to what folks were using. I think the Atlas will work well with the 5", just not sure with a 6.

Peter

[Peter Argenziano]

In communications with Barry Greiner today, he confirmed that the 5" f/10 scopes are all gone and he doesn't have another run planned. The f/12s are in production with a 4 to 6 month lead time.

Peter

[Scott Beith]

I keep coming back to this article. That is one beautiful scope!