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Equipment Discussions >> ATM, Optics and DIY Forum

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Mike I. Jones
Post Laureate
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Reged: 07/02/06

Loc: Fort Worth TX
Re: 10" f/3.5 Astrograph with Rosin focal reducer new [Re: MKV]
      #5549065 - 12/01/12 04:32 PM

Visually, yes, the system focal ratio does not affect limiting magnitude. The retina is a non-integrating detector, so staring continuously at an object does not make it appear brighter, unless you happen to still be dark adapting at the time.

At lower powers and large eyepiece exit pupils, though, high-brightness light pollution increases the background brightness, and can also interfere with dark adaptation, both of which affect limiting magnitude.

Photographically, the f-number and T-number directly impact photographic exposure times, as cameras are integrating detectors.

Mike


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Ed Jones
Carpal Tunnel
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Reged: 04/06/04

Loc: Sin-sin-atti
Re: 10" f/3.5 Astrograph with Rosin focal reducer new [Re: Mike I. Jones]
      #5553474 - 12/04/12 07:37 AM Attachment (39 downloads)

I deleted my previous post, Zemax found a better design. This is a telecompressor/coma corrector for a F/5 Newt primary. It makes it an f/2.8.

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kfrederick
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Reged: 02/01/08

Re: 10" f/3.5 Astrograph with Rosin focal reducer new [Re: Ed Jones]
      #5553485 - 12/04/12 07:45 AM

Great work .Will it work for all size telescope?

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Mark Harry
Vendor
*****

Reged: 09/05/05

Loc: Northeast USA
Re: 10" f/3.5 Astrograph with Rosin focal reducer new [Re: kfrederick]
      #5553549 - 12/04/12 08:40 AM

Duel of the Joneseys! I'm eatin' popcorn.....
M.


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MKV
Carpal Tunnel
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Reged: 01/20/11

Re: 10" f/3.5 Astrograph with Rosin focal reducer *DELETED* new [Re: Ed Jones]
      #5553868 - 12/04/12 12:18 PM

Post deleted by MKV

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MKV
Carpal Tunnel
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Reged: 01/20/11

Re: 10" f/3.5 Astrograph with Rosin focal reducer *DELETED* new [Re: MKV]
      #5553964 - 12/04/12 01:14 PM

Ed, could you show the spots?

Mladen

Edited by MKV (12/05/12 04:33 AM)


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Ed Jones
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Reged: 04/06/04

Loc: Sin-sin-atti
Re: 10" f/3.5 Astrograph with Rosin focal reducer new [Re: MKV]
      #5554430 - 12/04/12 06:43 PM Attachment (36 downloads)

Mladen,
Here is the spot diagrams. I optimized it for C,F and D so the deep blue 405 isn't so good but it could be optimized for other ranges. With 5 lenses it there won't be too many ATMs that can do this but it shows what's possible. It works with most focal length mirrors that can have enough BFL space.


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MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 10" f/3.5 Astrograph with Rosin focal reducer new [Re: Ed Jones]
      #5554551 - 12/04/12 08:02 PM

Quote:

Mladen,
Here is the spot diagrams. I optimized it for C,F and D so the deep blue 405 isn't so good but it could be optimized for other ranges. With 5 lenses it there won't be too many ATMs that can do this but it shows what's possible. It works with most focal length mirrors that can have enough BFL space.



Thanks Ed. Looks really nice. Obviously this type of corrector is the way to go with bigger mirrors.

For some reason OSLO didn't get the same results with your original configuration. I believe it's the limitation of OSLO.EDU to 10 surfaces, so in order to include the airgap between the two N-PSK57 lenses you'd need 11 surfaces in OSLO.

Also, I don't see why a five-lens corrector would be impossible for an amateur and a four or a three element wouldn't. It wouldn't be cheap, but results are great, and the shapes are not exotic.

Mladen

Edited by MKV (12/05/12 04:35 AM)


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Ed Jones
Carpal Tunnel
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Reged: 04/06/04

Loc: Sin-sin-atti
Re: 10" f/3.5 Astrograph with Rosin focal reducer new [Re: MKV]
      #5554599 - 12/04/12 08:31 PM

Mladen,
I only have 10 surfaces, seems like it should work. I've played around with this design and it can be pushed even better including 405nm.


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MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 10" f/3.5 Astrograph with Rosin focal reducer new [Re: Ed Jones]
      #5554779 - 12/04/12 10:33 PM

Quote:

Mladen,
I only have 10 surfaces, seems like it should work. I've played around with this design and it can be pushed even better including 405nm.



I just noticed that I was using a wrong glass for the third lens, so disregard any previous attachments.

No doubt the performance can be pushed even better, but what's really attractive and practical about this configuration is that the primary mirror is a relatively slow paraboloid (f/5) and therefore relatively easy to figure to high precision, yet the system operates at f/2.8.

Mladen


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ismail
journeyman


Reged: 10/22/10

Re: 10" f/3.5 Astrograph with Rosin focal reducer new [Re: kfrederick]
      #5979155 - 07/19/13 04:37 AM

Dear Dr.Mike and Ed ALL Friends here,
I have removed the MEADE 12 inch LX200 Telescope optics.
Primary mirror is 310 mm diameter and Radius of curvature is -1200mm, Sec mirror is 75 mm Diameter and Radius of curvature is 364 mm. Distance between primary and sec is 470 mm. Any option to convert to a cass telescope of this optical Mirrors with 1 deg field or less.


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Mike I. Jones
Post Laureate
*****

Reged: 07/02/06

Loc: Fort Worth TX
Re: 10" f/3.5 Astrograph with Rosin focal reducer new [Re: ismail]
      #5979526 - 07/19/13 10:17 AM

Kind of confused here, ismail. You took the mirrors out of a Meade 12 inch LX200 Cassegrain, measured them, and want to make a Cassegrain out of them, which is what they already were, in?
Mike


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hellojabil
journeyman


Reged: 05/28/13

Re: 10" f/3.5 Astrograph with Rosin focal reducer new [Re: Mike I. Jones]
      #5979645 - 07/19/13 11:25 AM

Thanks Mike. Yes I know it is cass telescope but I would like to know the quality of the image it will have without corrector plate?

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Mike I. Jones
Post Laureate
*****

Reged: 07/02/06

Loc: Fort Worth TX
Re: 10" f/3.5 Astrograph with Rosin focal reducer new [Re: hellojabil]
      #5979698 - 07/19/13 11:50 AM

Experience is the best teacher in this forum. Set them up and try it for yourself, answer your own question, then let everyone here know what you found out.
Mike


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hellojabil
journeyman


Reged: 05/28/13

Re: 10" f/3.5 Astrograph with Rosin focal reducer new [Re: Mike I. Jones]
      #5980895 - 07/20/13 04:54 AM

Thanks Yes I am doing that. I have done the primary mirror with ronchi setup it is good sphere. I have tested the sec mirror with ZYGO Interferometer and found one fringe circular. planing for Hindle test for secondary and autocollimation test soon with combination of both mirrors. And planing to enter the values in ZEMAX. hope you can suggest any other things which i can plan for it.

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