Wes James
Post Laureate
Reged: 04/12/06
Posts: 3460
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After seeing Dick Parker's double pass autocollimator test bench in use, and understand the testing method- if I were looking for a premium mirror, one of the questions I would ask is "How was it tested?" Autocollimation tells you in one glance what it takes many calculations in zonal testing- each reading subject to interpretation- to do. Ross null testing also tells you in one glance what you need to know.
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Wes
Atlantic Beach, FL
Some bino’s from Miyauchi 5x32 Binon's up through Garrett 20x110 Signature's,
Some telescopes from a Stellarvue 80mm NHNG up through a couple of 8” reflectors…
And a wonderful 4.25" Delmarva Shiefspiegler!
Some good friends, made here on C/N.
Oh- several cats and a wonderful wife!
Anyone want a cat???? :-O
"When your work speaks for itself- Don't Interrupt" -Gamble Rogers
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mark cowan
Vendor (Obsidian Optics)
Reged: 06/03/05
Posts: 2159
Loc: salem, OR
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Quote:
Hi Mark - is that mirror for sale?
One day I might want it.
I have yet to fully test my telescope as it wasn't fully aligned before.
Never. 
And I only go down to 10" (well, ok, 9.8") now.
Best,
Mark
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alpal
sage
Reged: 06/15/09
Posts: 204
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Quote:
Normand Fullum has been mentioned a few times in the thread already, but I will put his name forward again. I have 2 of his mirrors, and have looked through a number of others. All have been incredible, and all people I have talked with that have them are incredibly pleased.
Thanks Gord,
I just went to his website & it's interesting.
Check out the "sandwich" mirrors at the bottom of the photo.
See this link for his mirror prices:
http://www.normandfullumtelescope.com/mirror_en.html
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Location: Melbourne Australia.
8" f6 custom built Newtonian with
EQ6 Pro mount.
Takahashi LE 5mm eyepiece & 2 x Tak. Barlow.
Williams Optics Eyepieces - 2" 40mm & 25mm, 1.25" 15mm & 9mm.
Saxon 11 x 70 binos.
Set of 11 Hirsh Optics 1.25" filters.
Set of 4 Orion 2" filters.
Antares 1.25" ALP filter.
+ One cheap 4.5" Newt. complete with eyepieces.
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Jim Romanski
scholastic sledgehammer
Reged: 01/02/05
Posts: 844
Loc: Guilford, Connecticut
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Quote:
don't believe any so-called experts.
the coulters were indeed made of Pyrex.
they just had horrible figures.
I wouldn't state this as an absolute. There are good ones out there. I have two coulter mirrors that I never had tested but give very nice images. I'm sure they could be improved upon but they are good enough in my opinion that I don't plan to re-figure them for quite a while.
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Jim
17.5" Dob "Project"
13.1" Coulter
8” Cave
NP 101 on a CG-5
25x100 binos
Naglers, Ethos, etc.
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dave b
Post Laureate
Reged: 05/10/05
Posts: 3548
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some of the thicker blank, longer focal length mirrors i have seen tested at 1/4 wave, but ive never seen a good coulter 17" ever (unless it had been refigured)
i really want to see one of the coulter 29" mirrors on the bench....
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dave bonandrini
30" f/5.2 Dobsonian
President of GCAC
Astromart Moderator
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Jim Romanski
scholastic sledgehammer
Reged: 01/02/05
Posts: 844
Loc: Guilford, Connecticut
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Well, for what it's worth, last weekend I observed next to a friend with a 16" Lightbridge and I'd say that my 17.5" was at least as good.
One of my best views of Jupiter was with the 17.5" (while the NP101 looked on).
That said, I've seen some real stinkers too.
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Jim
17.5" Dob "Project"
13.1" Coulter
8” Cave
NP 101 on a CG-5
25x100 binos
Naglers, Ethos, etc.
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Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1166
Loc: Gateshead.NSW Nth Coast,Austra...
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Quote:
here is a 36" sandwich mirror:
http://www.normandfullumtelescope.com/Gallery/displayimage.php?pid=3&fullsize=1
That thing weights 376 pounds .... he's a strong lad or a brave one to be lifting it like that.
I bet he put it back on the bench quick smart after the picture was taken.
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Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1166
Loc: Gateshead.NSW Nth Coast,Austra...
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Quote:
That 16" f/4 mirror has been in the works since January... it took a *long time* for Newport to cast it and get it to me, I received the blank in mid August.
The delivery date for the finished mirror is not yet known, maybe in the next month or so with any luck... as soon as I know how it performs I'll post more info.
The mirror is designed for fast cooling, not only the radial fins and open design but also the array of holes in the back surface where I can blow air in between the front and back.
cheers, Bird
If you don't mind telling us , or PMing the answer , how much did the sandwich 16" FS blank cost you and how much will it cost to have it figured and polished ?
Do you apply the same flotation as a solid mirror to these ?
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llanitedave
Humble Megalomaniac
Reged: 09/26/05
Posts: 12945
Loc: Amargosa Valley, NV, USA
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Quote:
Quote:
don't believe any so-called experts.
the coulters were indeed made of Pyrex.
they just had horrible figures.
I wouldn't state this as an absolute. There are good ones out there. I have two coulter mirrors that I never had tested but give very nice images. I'm sure they could be improved upon but they are good enough in my opinion that I don't plan to re-figure them for quite a while.
I had a 10" full thickness Coulter that I bought in 1977 that was an excellent performer. It gave essentially perfect images in focus, although at the time I didn't know enough about star testing to give it the in and out of focus tests.
Unfortunately, I stupidly scratched it up when I was trying to remove the old coating myself, and replaced it in the 1990's with one of their thinner mirrors. It's figure was fair at best, and the roughness was visible in good seeing.
My plan is to send the newer one out to have it refigured (in a year or two), and keep the original as an experimental blank, so that someday I can say I actually did produce my own mirror.
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"Since the process of science generates more mysteries than it solves, I predict that we'll never learn everything: and we'll continue to generate new ignorance at the speed of knowledge."
"S.O.E." (Sauron's Other Eye), with 16" Royce conical mirror: A permanent work in progress.
10" Homebuilt dob, old Coulter mirror
Under Construction: The "Eye of Sauron" Observatory!
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pstarr
Pooh-Bah
Reged: 09/17/04
Posts: 1280
Loc: NE Ohio
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I had one of the early Coulter f-5.6 10" mirrors I bought new. Before I finished the scope, I took it to a local ATM who made mirrors to have it tested. He didn't do any zonal measurements but said it was very smooth and free from any zones, with a good edge. The mirror was an excellent performer.
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Paul
10" Home built F-6 Eq Newt. w/Zambuto mirror, built for lunar and planetary viewing.
12'x12' roll-off roof observatory
6" Home built f-6 Newt. w/Dick Wessling mirror on CG-5 Eq. mount, built for high resolution work.
4.5" Orion Starblast on Eq. mount
TV Radians 4,5,6,8,10,12,
Pentax XL 10.5mm
Pentax XW 14mm
Baader Hyperion 17mm
4&5mm UO Abbe Orthos.
3.2mm TMB planetary
TV 2.5x barlow, TV 1.8x barlow
My equipment philosophy... If it ain't broke, fix it anyway.
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auriga
scholastic sledgehammer
Reged: 03/02/06
Posts: 795
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Quote:
I think Dick Wessling deserves a mention here. He is right up there with those who were mentioned so far. Dick's web site.
I agree with this. I own 3 Wessling mirrors and all three are superb.
Bill Meyers
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alpal
sage
Reged: 06/15/09
Posts: 204
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Pity Dick Wessling doesn't give the pricing of his mirrors & the
optical specifications on the website.
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Location: Melbourne Australia.
8" f6 custom built Newtonian with
EQ6 Pro mount.
Takahashi LE 5mm eyepiece & 2 x Tak. Barlow.
Williams Optics Eyepieces - 2" 40mm & 25mm, 1.25" 15mm & 9mm.
Saxon 11 x 70 binos.
Set of 11 Hirsh Optics 1.25" filters.
Set of 4 Orion 2" filters.
Antares 1.25" ALP filter.
+ One cheap 4.5" Newt. complete with eyepieces.
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pstarr
Pooh-Bah
Reged: 09/17/04
Posts: 1280
Loc: NE Ohio
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Quote:
Pity Dick Wessling doesn't give the pricing of his mirrors & the
optical specifications on the website.
He may not give the info on the web site but if you contact him, you will find a very nice and helpful person. His target accuracy is 1/40th wave and his prices are reasonable IMO. He will answer any email inquiries you may have. Here is the final results on a 6" he figured for me.
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Paul
10" Home built F-6 Eq Newt. w/Zambuto mirror, built for lunar and planetary viewing.
12'x12' roll-off roof observatory
6" Home built f-6 Newt. w/Dick Wessling mirror on CG-5 Eq. mount, built for high resolution work.
4.5" Orion Starblast on Eq. mount
TV Radians 4,5,6,8,10,12,
Pentax XL 10.5mm
Pentax XW 14mm
Baader Hyperion 17mm
4&5mm UO Abbe Orthos.
3.2mm TMB planetary
TV 2.5x barlow, TV 1.8x barlow
My equipment philosophy... If it ain't broke, fix it anyway.
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PrestonE
Pooh-Bah
Reged: 04/29/05
Posts: 1171
Loc: Houston,Texas
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Hi Ian, try closer to 100 pounds...look at the front and back plates...calculate their weight and that is most of the weight...
The bars that space the plates likely do not weigh 10 pounds total...
JMHO 
Best Regards,
Preston
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A few I enjoy,
and a few more in the works ;<)
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alpal
sage
Reged: 06/15/09
Posts: 204
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Quote:
He may not give the info on the web site but if you contact him, you will find a very nice and helpful person. His target accuracy is 1/40th wave and his prices are reasonable IMO. He will answer any email inquiries you may have. Here is the final results on a 6" he figured for me.
Those results on the graph are so good that they seem
almost impossible. It's much better than 1/100th wave PV!
Who did the graph?
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Location: Melbourne Australia.
8" f6 custom built Newtonian with
EQ6 Pro mount.
Takahashi LE 5mm eyepiece & 2 x Tak. Barlow.
Williams Optics Eyepieces - 2" 40mm & 25mm, 1.25" 15mm & 9mm.
Saxon 11 x 70 binos.
Set of 11 Hirsh Optics 1.25" filters.
Set of 4 Orion 2" filters.
Antares 1.25" ALP filter.
+ One cheap 4.5" Newt. complete with eyepieces.
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pstarr
Pooh-Bah
Reged: 09/17/04
Posts: 1280
Loc: NE Ohio
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The graph is the test results from Dick Wessling. Numbers are just that. I don't put a whole lot of faith in them. What I can say for sure is that the mirror star tests and performs very similar to the 10" Zambuto mirror I have. To my eye, they both have almost text book diffraction patterns. It is really not surprising that a high degree of accuracy could be reached on a small mirror like a 6", especially by someone highly skilled who wants to spend the time on it. Dick had just completed a 16" f-4 before doing my 6". He commented on how easy the 6" was to figure by comparison. It gives excellent planetary, lunar and double star images. I'm very happy with it.
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Paul
10" Home built F-6 Eq Newt. w/Zambuto mirror, built for lunar and planetary viewing.
12'x12' roll-off roof observatory
6" Home built f-6 Newt. w/Dick Wessling mirror on CG-5 Eq. mount, built for high resolution work.
4.5" Orion Starblast on Eq. mount
TV Radians 4,5,6,8,10,12,
Pentax XL 10.5mm
Pentax XW 14mm
Baader Hyperion 17mm
4&5mm UO Abbe Orthos.
3.2mm TMB planetary
TV 2.5x barlow, TV 1.8x barlow
My equipment philosophy... If it ain't broke, fix it anyway.
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alpal
sage
Reged: 06/15/09
Posts: 204
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Quote:
It gives excellent planetary, lunar and double star images. I'm very happy with it.
That's the most important thing.
I am just waiting on good weather to test my Newtonian
after it has been aligned & I've made new tube rings for it.
I am supposed to have a top grade mirror so it will be interesting.
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Location: Melbourne Australia.
8" f6 custom built Newtonian with
EQ6 Pro mount.
Takahashi LE 5mm eyepiece & 2 x Tak. Barlow.
Williams Optics Eyepieces - 2" 40mm & 25mm, 1.25" 15mm & 9mm.
Saxon 11 x 70 binos.
Set of 11 Hirsh Optics 1.25" filters.
Set of 4 Orion 2" filters.
Antares 1.25" ALP filter.
+ One cheap 4.5" Newt. complete with eyepieces.
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