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Posts Made By: David Simons

August 20, 2005 03:02 AM Forum: Telescope Making

Testing optical flats redux

Posted By David Simons

Hi Tim,

I have been told that to test a mirrored flat, it is usually tested in reflection against a known good sphere. I suppose if the the Ronchi pattern of the mirror does not change, then the flat is good. Not sure if this will get you quantitative numbers though.

Vladimir Sacek should have some info on this subject I would think ?

August 28, 2005 10:05 PM Forum: Deep Sky Observing

Sugraloaf State Park, 8-9, 8-10

Posted By David Simons

... There is an observatory housing a 40 inch scope, a 12 inch, and an 8 inch. ...

Hi Zack,

It sounds like you had some great observing up there. Although I've seen lots of deer, never heard a mountain lion before !

I just finished the Docent training at RFO. I agree, it is a very special place. They used to have a 40" that sort of self destructed (mirror too thin) and they have a 24" on loan for now while their 2nd 40" is in polishing stages wink They have an unusual 8" triplet refractor, and a very nice C14 CCD setup on a Paramount mount.

At only 15 minutes away from me, it's been a weekend favorite. Lot's of great folks there ! Hope to see you up there again with your Dob !

September 5, 2005 09:37 PM Forum: Equipment Talk

Cleaning of water deposits from mirrors

Posted By David Simons

HI Floyd,

Great post !

I have a military surplus off axis sector mirror that was left outside for a while, and has lots of hard deposits. I was about to send it out for a re-coat, but will try your technique first, as not much harm can be done at this point.

September 6, 2005 12:06 AM Forum: Refractors

Magic Glass (8inch F/7 Simi-Apo)

Posted By David Simons

Keith Lawson said:

This is for the lens designers out there. Just something to play with. The design uses all common glasses except for one. Can anyone tell me if the "magic glass" can be made? If not, why? Just trying to learn something so please don't flame me 8) BTW, the design at F/9 is an APO. If anyone is interested I will post the data.

Hi Keith,

Can you show the layout, and the off axis plots ?


September 7, 2005 06:10 PM Forum: Equipment Talk

Achromatic refractors

Posted By David Simons

Freddy WILLEMS said:

I do not know where to begin..
I have a Meade 14" LX 200 UHTC GPS telescope which is quite heavy to move around.. It now sits on a permanent pier on my roof and it's a great scope.
I just want to go to star parties and cannot take that 14" with me so ...Freddy

Hi Freddy,

If you can figure out a way to get your 14" off the forks, I have had some success building an alt-az mount for my old C14. It collapses down easily, and the OTA goes in the front seat. Setup time around 15 minutes. This scope has made it to several starparties, and the comfort level is quite good.

As for refractors, you could get an Orion ST120 and mount it on top of the Meade 14", that would be a nice setup !

December 7, 2005 07:00 PM Forum: Equipment Talk

Orion Astroview 120ST

Posted By David Simons

bill wolford said:

Does anyone have any comments, pro or con on the Orion Astoview 120ST refractor? I'm thinking about trying one.

Hi Bill,

I like mine a lot.

Quality does vary, and if you get it from Orion, you can easily send it back.

I now have a ST150, and the ST120 does not get as much use.

January 8, 2006 03:47 PM Forum: Telescope Making

large binos

Posted By David Simons

Gary Klein said:

Neil Barnett suggested that I describe my bino project to this group.

I had arranged to purchase 4) 30 inch x 1.5 inch pyrex mirrors from Vaughn Parsons a year and a half ago. I had asked for two of these to be F4.5 and two to be f6.

He completed one of the 30 inch f4.5 mirrors and I have it. Unfortunately for me, he has a consulting job in Hawaii and his shop in Salt Lake City is shut down. He also used the remaining 3) 30 inch blanks for other projects.

I would like to make a 30 inch binocular in f4.5 and a 30 inch binocular in f6. I think these will be a reasonable size to construct and transport in an air ride truck trailer. I think the scope can roll out the back of the trailer on a ramp with a winch or can extend on a pair of beams like a drawer slide.

I guess currently I am one tree shy of a hammock.

Thank you,

Gary Klein

Hi Gary,

I have one of the other 30" mirrors from Vaughn. They sure are impressive. Mine is still in it's box though. However, I definately plan to get my dob done this summer. Right now I am building a truss dob structure for a 16" Meade optic I have, and hopefully will learn enough to scale up for the 30". Since I have not done any ATM projects of this scale before, I thought it would be good to learn incrementally.

Have you done any smaller bino projects before? From what I have read, they have a lot of alignment issues. Please post pictures of anything you have !

Also please post any pictures of those monster 50" blanks !!


January 8, 2006 04:06 PM Forum: Telescope Making

image quality of optical fiber for astro use?

Posted By David Simons

jess tauber said:

... I've wondered whether one could use light fiber (such as is utilized in endoscopes in medicine) to carry stellar images between the primary and other lens elements. Obviously micro applications already exist- but are these materials good enough quality for astro viewing?...

Jess Tauber

Hi Jess,

I like your out of the box thinking. Don't worry about getting shot down all the time (as I'm about to do wink ) just keep brainstorming as some of the best new ideas usually come from way outside the conventional wisdom ie. John Dobson etc.

I usually go to one of the big optics shows in the either San Jose or San Francisco every year, and there are a fair number of these high resolution fiber optic imaging systems available to play with. The big issue I see, is they seem have to have a lot of losses, either in getting the light into the fiber, or transmitting it. (other optimized Telecom fiber optic systems have very high transmission though) As light throughput is King in a telescope, these devices would have to very specially made to compete with the standard designs. I suppose if these were heavily optimized, they could work, but I would imagine with a very high cost, then they would likely be only as good as the existing solutions. I know these have been used as faceplates in image intesifiers, but this was after the bright phospher screen.

Keep on brainstorming, and don't forget to build some stuff every now and then, then post pictures and tell us all how it worked grin


January 28, 2006 10:58 PM Forum: Equipment Talk

Apodizing Screen Revisited

Posted By David Simons

Judson Mitchell said:
Herb Highstone requested that I post this item in the equipment forum and suggested that I am in line for some criticism (oh well, here goes).

Tonight (Jan 26)I had my best view of Saturn yet. ....


Hi Judson,

Sorry I can't offer any vigorous criticism, but I did make a short trip to the exhibits at the San Jose Photonics West show this week, and saw a vendor of metallic coatings offering "apodizing filters". So these types of things are commercially available for some applications, although these folks were not using wire screens, it was a metal film on glass. I didn't get a chance to find out the application, but in this case, it did not look like they were for astronomy. Maybe there is a more standard use for these ?

Keep us updated !

January 30, 2006 10:32 PM Forum: Refractors

FS-128...... value

Posted By David Simons

Rich McNutt said:
Please forgive me in advance, I dont know if this is the appropriate forum for this question. I have an TAK FS-128 for sale and I have no idea how much to ask for it.
Lafayette, CO

Hi Rich,

Very sorry to hear about your eye problems.

I did a quick search on astromart going back to 2000:

and prices vary quite a bit. Although I think the standard used price is around 70% of new.