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frodriguez
sage


Reged: 12/03/06
Posts: 455
Loc: Honduras
FPL-51, 52, 53 glass
      #1289930 - 12/07/06 12:30 PM

Will an optic design (say, triplet) with FPL51 have the same color correction than an optic of same configuration with FPL 52 or 53?

--------------------
Francisco

TMB 100mm f/8 triplet apo
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LittleDob
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Reged: 12/10/04
Posts: 1444
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Re: FPL-51, 52, 53 glass new [Re: frodriguez]
      #1290004 - 12/07/06 12:59 PM

FPL-53 will provide better colour correction - provided every other factor is absolutely identical. Ahh, the rub. Not everything is equal and FPL-51 lenses can provide excellent colour correction.

Jason

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Jason

"Civilization exists by geological consent, subject to change without notice." Will Durant

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Kal
sage


Reged: 07/31/06
Posts: 217
Loc: Sydney, Australia
Re: FPL-51, 52, 53 glass new [Re: LittleDob]
      #1290673 - 12/07/06 06:29 PM

The difference between FPL-53 and FPL-51 is about 20% (abbe index of 95 compared to 81). Therefore a F5 fpl-53 doublet would have the same color correction of a F6 fpl-51 doublet, since increasing focal length by 20% provides 20% more color correction which counters the loss of correction through glass selection.

--------------------
CG-11 130mm f6.3 StarFire EDF Gran Turismo SV90TBV ETX90EC 25x100 BINOCULARS DBK21 Canon 1000D


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dominico4
professor emeritus


Reged: 10/06/05
Posts: 677
Loc: Winston Salem Area, NC
Re: FPL-51, 52, 53 glass new [Re: Kal]
      #1291056 - 12/07/06 10:13 PM

Here's a question to go with that. The AT80ED sold by AstroTech uses FPL-51 I think and the Orion 80ED uses FPL-53. They are both doublet designs and the Orion has a focal length of f/7.5 while the AT80ED has a focal length of f/6.8.

According to these, which would I be better off getting for the best color correction considering they're both near in price and mechanics...?

--------------------
Josh
Vixen ED80Sf w/ Vixen Portamount
Meade 12" Lightbride Deluxe
My Clear Sky Clock = Winston Salem Area, NC

The current estimate for the number of stars in our galaxy is 100 billion, while the U.S. National Debt is 8 trillion dollars. They used to be called astronomical numbers, but now they should be called economical numbers!


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frodriguez
sage


Reged: 12/03/06
Posts: 455
Loc: Honduras
Re: FPL-51, 52, 53 glass new [Re: dominico4]
      #1291066 - 12/07/06 10:17 PM

Going by what Kal explained, you're better off with the Orion 80 ED. f7.5 & FPL-53 > f6.8 & FPL-51.

--------------------
Francisco

TMB 100mm f/8 triplet apo
Universal Astronomics UniStar Deluxe w/ 7" saddle
Sokkia green heavy wood tripod
Televue 7mm Nagler T6
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Tom TrusockAdministrator



Reged: 02/26/02
Posts: 33846
Re: FPL-51, 52, 53 glass new [Re: frodriguez]
      #1291089 - 12/07/06 10:24 PM

There will be better color correction on the ED80, but the mechanics and fit and finish are MUCH better on the AT80 or WO EDII.

T

--------------------
You do not need a parachute to skydive, you only need a parachute to skydive twice...


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dominico4
professor emeritus


Reged: 10/06/05
Posts: 677
Loc: Winston Salem Area, NC
Re: FPL-51, 52, 53 glass new [Re: Tom Trusock]
      #1291137 - 12/07/06 10:47 PM

Tom, seeing as you've had experience with them apparently, where do the mechanics on the AT80 excel over the ED80? Obviously the color correction would be better, but is it too minor to be worried about on the AT80? I want reflector-like views, but if the moon is a little warm-hued, I can deal. What I DONT want would be any fringing or obvious discoloration inside the object that distracts the eye.

--------------------
Josh
Vixen ED80Sf w/ Vixen Portamount
Meade 12" Lightbride Deluxe
My Clear Sky Clock = Winston Salem Area, NC

The current estimate for the number of stars in our galaxy is 100 billion, while the U.S. National Debt is 8 trillion dollars. They used to be called astronomical numbers, but now they should be called economical numbers!


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Bill McHale
professor emeritus


Reged: 11/07/04
Posts: 582
Re: FPL-51, 52, 53 glass new [Re: dominico4]
      #1291198 - 12/07/06 11:23 PM

One thing we need to keep in mind is that no single glass, by itself ensures great color correction. FPL-53 has the potential for better color correction than FPL-51 but a well designed lens featuring FPL-51 will outperform a poorly designed FPL-53 lens.

--------------------
Bill
186,000 MPS, its not just a good idea, its the law.


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Kal
sage


Reged: 07/31/06
Posts: 217
Loc: Sydney, Australia
Re: FPL-51, 52, 53 glass new [Re: Bill McHale]
      #1291249 - 12/07/06 11:52 PM

Anyone can design a doublet. I've seen the average astronomer (ie. NOT someone who makes scopes) come up with a design in downloadable sofware. Designing a refractor is not a difficult or challenging process that needs 'experts' to do.

--------------------
CG-11 130mm f6.3 StarFire EDF Gran Turismo SV90TBV ETX90EC 25x100 BINOCULARS DBK21 Canon 1000D


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Kal
sage


Reged: 07/31/06
Posts: 217
Loc: Sydney, Australia
Re: FPL-51, 52, 53 glass new [Re: dominico4]
      #1291256 - 12/07/06 11:59 PM

Quote:

Here's a question to go with that. The AT80ED sold by AstroTech uses FPL-51 I think and the Orion 80ED uses FPL-53. They are both doublet designs and the Orion has a focal length of f/7.5 while the AT80ED has a focal length of f/6.8.

According to these, which would I be better off getting for the best color correction considering they're both near in price and mechanics...?




For a FPL-51 doublet to have the same color correction as a FPL-53 doublet it will have to have a FL 20% longer, so a focal ratio of F9. Therefore the orion 80ED will have approxiamtely 30% better color correction than the AT80ED if they use the glasses you mentioned.

--------------------
CG-11 130mm f6.3 StarFire EDF Gran Turismo SV90TBV ETX90EC 25x100 BINOCULARS DBK21 Canon 1000D

Edited by Kal (12/08/06 12:00 AM)


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NorthCoast
Carpal Tunnel


Reged: 12/05/04
Posts: 2308
Loc: Westerville, Ohio, U.S.A.
Re: FPL-51, 52, 53 glass new [Re: Kal]
      #1291280 - 12/08/06 12:17 AM

Quote:

Anyone can design a doublet. I've seen the average astronomer (ie. NOT someone who makes scopes) come up with a design in downloadable sofware. Designing a refractor is not a difficult or challenging process that needs 'experts' to do.




Quote:

For a FPL-51 doublet to have the same color correction as a FPL-53 doublet it will have to have a FL 20% longer, so a focal ratio of F9. Therefore the orion 80ED will have approxiamtely 30% better color correction than the AT80ED if they use the glasses you mentioned.




Given these two statements then wouldn't that be "may potentially have approximately 30% better color correction?"

Just wanted to be sure I am following this correctly.

--------------------
Mark



Hold the "Alt Key" and type 248 on the number pad for


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NorthCoast
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Reged: 12/05/04
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Re: FPL-51, 52, 53 glass new [Re: NorthCoast]
      #1291284 - 12/08/06 12:21 AM

This would assume both designs are optimal and manufacturing is executed without any compromises. Yes?

--------------------
Mark



Hold the "Alt Key" and type 248 on the number pad for


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Kal
sage


Reged: 07/31/06
Posts: 217
Loc: Sydney, Australia
Re: FPL-51, 52, 53 glass new [Re: NorthCoast]
      #1291341 - 12/08/06 01:29 AM

I would say that the execution of manufacturing would play a big part in the quality of the final product. Designing a lens and selecting glass is easy with the right software. Putting the processes in place to produce a consistant final product is the challenge In the end both the Orion 80ED and the AT80ED will both more than likely have happy customers. They are both affordable, one has slightly better optics, the other has a better package around the optics, such as a nice focuser.

--------------------
CG-11 130mm f6.3 StarFire EDF Gran Turismo SV90TBV ETX90EC 25x100 BINOCULARS DBK21 Canon 1000D


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dominico4
professor emeritus


Reged: 10/06/05
Posts: 677
Loc: Winston Salem Area, NC
Re: FPL-51, 52, 53 glass new [Re: Kal]
      #1291623 - 12/08/06 08:05 AM

Now I just need to decide between the AT80 and the 80ED... AND I still need a mount and diagonal to go with it...

This is going to be pricy.

--------------------
Josh
Vixen ED80Sf w/ Vixen Portamount
Meade 12" Lightbride Deluxe
My Clear Sky Clock = Winston Salem Area, NC

The current estimate for the number of stars in our galaxy is 100 billion, while the U.S. National Debt is 8 trillion dollars. They used to be called astronomical numbers, but now they should be called economical numbers!


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Bill McHale
professor emeritus


Reged: 11/07/04
Posts: 582
Re: FPL-51, 52, 53 glass new [Re: Kal]
      #1291700 - 12/08/06 09:34 AM

Quote:

Anyone can design a doublet. I've seen the average astronomer (ie. NOT someone who makes scopes) come up with a design in downloadable sofware. Designing a refractor is not a difficult or challenging process that needs 'experts' to do.




Coming up with a design is one thing, coming up with a good design is another. Not only does a good design need to control abberations as much as possible (And this gets harder with faster designs) but the design must also be one that is practical to manufacture. There are some designs out there that give great results but have a number of problems associated with them. There is a reason that Thomas Back is able to sell scopes with his name on them; not every design that corrects for Chromatic is going to produce a great telescope.

Mind you, some of the best names in Refractor Design today started as Amateurs. Both Roland Christen and Thomas Back got their starts as Amateurs (if I remember correctly) but they made their names through good designs that maximized the potential of the glasses they were using.

--------------------
Bill
186,000 MPS, its not just a good idea, its the law.


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Alan French
Night Owl


Reged: 01/28/05
Posts: 4009
Loc: Upstate NY
Re: FPL-51, 52, 53 glass new [Re: Bill McHale]
      #1291828 - 12/08/06 10:51 AM

Quote:

Quote:

Anyone can design a doublet. I've seen the average astronomer (ie. NOT someone who makes scopes) come up with a design in downloadable sofware. Designing a refractor is not a difficult or challenging process that needs 'experts' to do.




Coming up with a design is one thing, coming up with a good design is another. Not only does a good design need to control abberations as much as possible (And this gets harder with faster designs) but the design must also be one that is practical to manufacture. There are some designs out there that give great results but have a number of problems associated with them. There is a reason that Thomas Back is able to sell scopes with his name on them; not every design that corrects for Chromatic is going to produce a great telescope.

Mind you, some of the best names in Refractor Design today started as Amateurs. Both Roland Christen and Thomas Back got their starts as Amateurs (if I remember correctly) but they made their names through good designs that maximized the potential of the glasses they were using.




Actually, coming up with a good design is not all that difficult with software like ATMOS, and most folks could do it with a little work. The big issue, as you say, is creating a design that is suitable for production. The main problem seems to be the availability, quality, and cost of glass. Ohara FPL53 and BSM81 produce an absolutely superb doublet, but both glasses are expensive. I know FPL53 is readily available in high quality. I don't know about BSM81.

Clear skies, Alan

Edited by Alan French (12/08/06 10:59 AM)


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LivingNDixie
TSP Chowhound


Reged: 04/23/03
Posts: 17757
Loc: Trussville, AL
Re: FPL-51, 52, 53 glass new [Re: dominico4]
      #1291849 - 12/08/06 11:08 AM

Quote:

Now I just need to decide between the AT80 and the 80ED... AND I still need a mount and diagonal to go with it...

This is going to be pricy.




Check out astromart.com, I have seen several ED80 Orions show up on there with upgraded focusers. I would think then you would have the best optics and a better focuser.

--------------------
Preston
Meade 10in LX200R GPS UHTC
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Bill McHale
professor emeritus


Reged: 11/07/04
Posts: 582
Re: FPL-51, 52, 53 glass new [Re: Alan French]
      #1291853 - 12/08/06 11:09 AM

Cool, thanks Alan. Of course what I would like is a really good Doublet at like f/12, which should be easier. I would think that even FPL-51 could probably produce a good 4 or 5" f/12. I wonder what would be a good matching glass for FPL-51?

--------------------
Bill
186,000 MPS, its not just a good idea, its the law.


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lawrie
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Reged: 01/31/06
Posts: 2083
Loc: Okanagan Valley
Re: FPL-51, 52, 53 glass new [Re: Bill McHale]
      #1291864 - 12/08/06 11:18 AM

I am also thinking of getting a 80mm refactor, after reading these posts, I understand that design and production are as, if not more, important than the glass used. Where the problem comes up for myself and others, that live in areas where there isn't enough population to support an astro store, is we only have Internet pictures and manufactures descriptions to go by. I suspect the whole delima of choosing the right tube for yourself would be much easier if you where hands on.

As I understand;
Astro-Tech ED80 ( FPL-51)F/6.8 is a new manufacturer and is trying to make a name for itself. The tube is well put together, a little less, optically than others but they have added more goodies to their package, ie; duel speed focuser, case

Orion ED80(FLP-53) F/7.5 has better optics but the tube is somewhat less dazzling and everything else you would need is extra. ie case.

WO Zen-star ED80 (FLP-51)F/6.8 has great fit and finish on the tube and includes a two speed focuser and case. I have not heard any comments on how the optics compare.

Celestron Onyx 80EDF (FLP-53) F/6.25 finish looks good but haven't heard much about this scope. case included

Meade 5000 series 80 triplet looks nice if you like a white scope waiting to hear how it performs.


It would be great to hear from someone that has seen these tubes all together and hear their comments

--------------------
Clear Skies
Lawrie

9.25 Edge/Hyperstar
NP 101is
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spaceydee
Postmaster


Reged: 04/16/04
Posts: 17311
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Re: FPL-51, 52, 53 glass new [Re: lawrie]
      #1291908 - 12/08/06 11:39 AM

I'd like to know from someone who has actually looked through each scope before definitively saying which has a better optic.

--------------------
Dee
space-scientist
student violinist
Nexstar8i,SV80S,80/9D,FC100,94 Brandon,TMB92SS,GM8
8" f/7 Discovery,12.5" Portaball, PST



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