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Equipment Discussions >> ATM, Optics and DIY Forum

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kfrederick
Carpal Tunnel


Reged: 02/01/08

Re: 17 inch spotplots new [Re: kfrederick]
      #4986541 - 12/27/11 07:46 AM

Ed Jones is who helped build and design my 20 f8 and where I got the offaxisitis .Mike changed everything/ the conic on the primary the secondary having power The lens have curves an the both sides .and diferent glass and all the decenters .Having this in OSLO is great .Great we can get designs like this .[THANKS]The spec for flex is no more than a cassagrain . Lens spec no more than a refractor .The only differents is it is not centered and tilted .At least no can say it canot work better then a newtonian the spot plots for this 17inch is half that of a 8inch newt. I think . kevin

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kfrederick
Carpal Tunnel


Reged: 02/01/08

Re: 17 inch spotplots new [Re: kfrederick]
      #4987009 - 12/27/11 01:47 PM

The first guy to work on this was FREDERICK William Herschel So it looks like a "Frederick" worked this before the "Jones"

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MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17 inch spotplots new [Re: kfrederick]
      #4987042 - 12/27/11 02:12 PM

After reading all this, I honestly wonder why there are no commercially available "chiefs".

Mladen


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kfrederick
Carpal Tunnel


Reged: 02/01/08

Re: 17 inch spotplots new [Re: MKV]
      #4988006 - 12/28/11 06:34 AM

Miaden Why aint NASA calling?

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Mike I. Jones
Post Laureate
*****

Reged: 07/02/06

Loc: Fort Worth TX
Re: 17 inch spotplots new [Re: kfrederick]
      #4988210 - 12/28/11 10:20 AM

My guess is that they just take more time and money to make properly than you could ever turn a profit from. A scope like Kevin is building could easily cost $20K or more each to produce commercially. Some designs are probably just best left to advanced amateurs with the skills and tools to build them. These are the kind of scopes that make going to telescope meets and star parties so worth it!
Mike


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MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17 inch spotplots new [Re: Mike I. Jones]
      #4988627 - 12/28/11 02:57 PM

Quote:

My guess is that they just take more time and money to make properly than you could ever turn a profit from. A scope like Kevin is building could easily cost $20K or more each to produce commercially. Some designs are probably just best left to advanced amateurs with the skills and tools to build them. These are the kind of scopes that make going to telescope meets and star parties so worth it!
Mike



What about smaller ones, say 8 - 12-inch scopes? They would certainly fall in the "affordable" range, wouldn't they? And never having looked through a "chief", I am still curious about the specifics as regards their reputed superiority.

As I said earlier, I can definitely see the advantage of "chiefs" having a somewhat more compact tube configuration and a more accessible eyepiece. But other reasons mentioned are a bit confusing. Someone mentioned the fact that they are f/8 (?). Others pointed out that this particular design has a one inch FOV. Well so does an f/8 CDK in a much more compact package without decenter or tilting. The only downside to an f/8 CDK is a 40% linear CO.

But for planetary views slower focal ratios are desirable, say f/18-f/20 for Cassegrains, with CO's of less than 20% of linear aperture, which is doable. Owners of such scopes (Mewlons or Classical Cassegrains, for example) say they are unbeatable.

Then there is a whole different issue with large telescopes, beginning at about 18 inches and becoming progressively worse with large apertures and it has to do with speckling, regardless of the design or central obstruction, so I am not exactly sure where or why 20-inch f/8 "chiefs" would surpass 20-inch f/15 Cassegrains or f/5 Newtonians.

Thanks.

Mladen


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kfrederick
Carpal Tunnel


Reged: 02/01/08

Re: 17 inch spotplots new [Re: MKV]
      #4988712 - 12/28/11 04:05 PM

Miaden Can you show anything[on paper]17inches that will give better visual image? I say congrads to Mike for this GREAT design .and posting the numbers in OSLO for anyone to check out and make .

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wh48gs
Carpal Tunnel
*****

Reged: 03/02/07

Re: 17 inch spotplots new [Re: Mike I. Jones]
      #4988926 - 12/28/11 06:16 PM Attachment (56 downloads)

Quote:

If you don't have the glasses used in this scope, you need to upload the latest version 6.5.4 of OSLO-EDU




I have both, EDU (which does have the Ohara glasses) and Light. For some reason, it is the latter, apparently older, that opens external OSLO files. The good thing about it is that it made me try different glasses. I played a bit more with your design, and found that the corrector can be made of BK7/BASF12 (about 2.5 times the price of BK7) combination, with the radii on the two lenses identical (attached). That makes the fabrication cheaper and easier. The system is not fully optimized, but I'd say is real close.

Vla


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MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17 inch spotplots new [Re: kfrederick]
      #4989598 - 12/29/11 06:40 AM

Quote:

Miaden Can you show anything[on paper]17inches that will give better visual image? I say congrads to Mike for this GREAT design .and posting the numbers in OSLO for anyone to check out and make .



Mike's and Ed's designs are superb. My questions were not meant to offend anyone or to critiques their design. Far from that! My questions were about the reasons for the (non)availability of "chiefs" on the market, and also about specific issues mentioned. In other words - why make a "chief"?

As for anything "better" on paper, that depends on what you think is "better". To me "better" is what's more practical. If it's compactness, I'd say field-corrected Cassegrains; if it's ease of production, alignment, etc., then field-corrected Newtonians, keeping central obstruction for both at 19% or less, which is hardly noticible over unobstructed. Besides, it's a moot point because at larger apertures the image will hardly ever be a sharply defined Airy disc.

Mladen


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kfrederick
Carpal Tunnel


Reged: 02/01/08

Re: 17 inch spotplots new [Re: wh48gs]
      #4989653 - 12/29/11 07:57 AM

Via That is good to know. The glass cost on this is not too bad having a matching surfaces is good also . Nice to have in Oslo so more can see .This is not much harder than making a newt just two small lens and mounting them .

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mark cowan
Vendor (Veritas Optics)
*****

Reged: 06/03/05

Loc: salem, OR
Re: 17 inch spotplots new [Re: MKV]
      #4990258 - 12/29/11 02:19 PM

Quote:

Mike's and Ed's designs are superb. My questions were not meant to offend anyone or to critiques their design. Far from that! My questions were about the reasons for the (non)availability of "chiefs" on the market, and also about specific issues mentioned. In other words - why make a "chief"?




Well, that's easy. Two parts - too new, and an "unknown" market appeal.

The apparent difficulty of physical alignment is a bugaboo, but the work that Kevin's doing with CNC punched alignment boxes should go a long ways. Still, there's not a lot of incentive to bring these to large production unless people want to buy them and can handle them consistently in the field.

For myself, I just want to build one to have, use, and show off. I don't want to build them to sell, ship, and support. From a mirror perspective the primary in any version is extremely simple, hence not much profit there - but the purchased (or custom made) bits are still relatively expensive.

I suspect the people who are interested in something like this are already capable of rolling their own.

Best,
Mark


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Mike I. Jones
Post Laureate
*****

Reged: 07/02/06

Loc: Fort Worth TX
Re: 17 inch spotplots new [Re: mark cowan]
      #4990558 - 12/29/11 04:46 PM

Agree Mark. I have lost count of the number of awesome one-of-a-kind telescopes Jerry Logan has brought up to Riverside over the decades. You will never, ever see any of those scopes made commercially. Yet, the optics are always simply first-prizeworthy spectacular, due to Jerry's extraordinary skills in working optical parts.

That's the most fun of telescope meets to me, to see and view through beautiful, unique scopes that will never get a part number or a price tag, and are as well made optically and mechanically as any commercial products. Kevin's 17" "apo" is going to get long lines at star parties for sure!

Mike


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Ed Jones
Carpal Tunnel
*****

Reged: 04/06/04

Loc: Sin-sin-atti
Re: 17 inch spotplots new [Re: Mike I. Jones]
      #4990905 - 12/29/11 07:49 PM Attachment (32 downloads)

Mike,
I think I would prefer this design to build. By making it a bit slower (f/9.5) you can get more of a fold and a lower eyepiece; about 4 feet from the primary to the focus. This is an analog to the RC and uses an aspheric secondary and hyperbolic primary. The secondary conic is nearly -800 but because it is very flat the aspheric deviation is only about .36 microns; not much figuring needed. It has zero field tilt and no coma. Other glass types can give only a minor improvement over the BK7 used here.


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Mike I. Jones
Post Laureate
*****

Reged: 07/02/06

Loc: Fort Worth TX
Re: 17 inch spotplots new [Re: Ed Jones]
      #4990921 - 12/29/11 07:59 PM Attachment (55 downloads)

Sweet! Put up prescrip? Here's the one I did for Kevin, in ZEMAX format. If Carl Zambuto wasn't already so far along with Kevin's mirror I'd say give he ought to give it a whirl.

I'm trying to talk Kevin into making two identical copies of his SuperChiefs and make Chiefoculars! Imagine the view through 17" aperture apo binoculars! Drool slobber...
Mike


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kfrederick
Carpal Tunnel


Reged: 02/01/08

Re: 17 inch spotplots new [Re: Mike I. Jones]
      #4991026 - 12/29/11 09:14 PM

I have a 17 f9.4 my 20 f8 chief mirror .What if you used a 17inch circle on the one side of the mirror that[ the corrector is on] off apture/ ofaxis could be very short.Or if you moved the secondary in the inconing light path .just a little .Not much more than a edge clip.Just ideas maybe not good ones .

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kfrederick
Carpal Tunnel


Reged: 02/01/08

Re: 17 inch spotplots new [Re: kfrederick]
      #4991037 - 12/29/11 09:24 PM

Or use a 17 inch circle on the side of my 24 f8.6 .might be very short.Looks like you are calling it a Super Chief .

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Dave O
sage
*****

Reged: 12/21/11

Loc: Sri Lanka
Re: 17 inch spotplots new [Re: kfrederick]
      #4991371 - 12/30/11 01:47 AM

Wow -- just gets better all the time. Nice tweak you made there Ed.

I too, think that a ~4' separation between the primary and the focal plain is "just about right" for comfortable viewing. BK7 lenses is a plus as well -- that glass is very stable and easily procured. Are they off-the shelf? If custom, could you get matching radii?

Very nice improvement on an already superb design. Dave O


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kfrederick
Carpal Tunnel


Reged: 02/01/08

Re: 17 inch spotplots new [Re: Dave O]
      #4991524 - 12/30/11 06:15 AM

HOW could you make a -800 convex conic secondary the edge is turned up 800x over a spherical .Having all spherical secondary optics is great .Any good lens maker can do them .

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Ed Jones
Carpal Tunnel
*****

Reged: 04/06/04

Loc: Sin-sin-atti
Re: 17 inch spotplots new [Re: kfrederick]
      #4991567 - 12/30/11 07:43 AM

This secondary is no different than making a Cass secondary, those who have made a Cass would have no trouble. But this may not be everyone; if anyone is really interested PM me and I can send a prescription.

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kfrederick
Carpal Tunnel


Reged: 02/01/08

Re: 17 inch spotplots [Re: Ed Jones]
      #4993536 - 12/31/11 08:43 AM

Ed will yours work with a f8 -1.4 conic primary ?What was the RC on your secondary? I went with f8 to keep it shorter.The good glass only costs less than a eyepiece more. On Mikes Design it helps a good bit.The thing I like on yours is the lower eyepiece and the field tilt .AtF 9.5 It is harder to get low power with avaible eyepieces.95% of the time It will be used for deep sky at 100x The 20f8 chief rocks deepsky.

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