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New APM 6“ f/6 SD Apo design> need your all input

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#51 Astrojensen

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Posted 04 July 2021 - 09:19 AM

 This would simply be an improved version of those that would give you better color correction and better ability to handle higher magnifications with more portability than the 6” ED and triplet APOs available. 

But the issue I'm trying to explain is that the spherochromatism in a 6" f/6 ED doublet could be severe enough that its ability to handle higher magnifications wouldn't be better than a 6" f/6 achromat! 

 

It's a complete mystery to me, why people don't understand that color correction in a lens is NOT the only serious aberration a designer has to deal with. And the more you push a design to its limits, the more ugly things pop out of the mud. 

 

I would very much like to see some design proposals from one of Markus' designers, so we can evaluate how viable the idea is in the first place. 

 

 

Clear skies!

Thomas, Denmark 


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#52 AstroPotamus

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Posted 04 July 2021 - 10:29 AM

Design is all about compromise (so is security!).  So until I hear more from Markus about pricing and target market, nothing else matters.



#53 russell23

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Posted 04 July 2021 - 12:31 PM

But the issue I'm trying to explain is that the spherochromatism in a 6" f/6 ED doublet could be severe enough that its ability to handle higher magnifications wouldn't be better than a 6" f/6 achromat! 

 

It's a complete mystery to me, why people don't understand that color correction in a lens is NOT the only serious aberration a designer has to deal with. And the more you push a design to its limits, the more ugly things pop out of the mud. 

 

I would very much like to see some design proposals from one of Markus' designers, so we can evaluate how viable the idea is in the first place. 

 

 

Clear skies!

Thomas, Denmark 

Of course CA is not the only serious aberration.  But people use their achromat’s at high magnification all the time despite the limitations.  

 

Part of this for me is seeing how significantly improved for higher magnification deep sky a large fast achromat can be with the use of a CA reducing filter such as the Baader 495 LP.  If you can significantly improve the scope with a filter then you can do it with the glass as well.   The blurring effect from CA in a large achromat is quite significant at higher magnifications.  When I’ve used a filter with such a scope the star images were significantly sharper at higher magnifications than without the filter. Adding an ED element should accomplish this as well.   

 

A Petzval design would be even better, but again now you are significantly increasing the cost. 

 

But like I said in my last post - a 6” f/6 ED doublet I would consider - but a 130mm f/9.2 doublet I would jump at as long as the weight was under ~9 kg.  Neither one exists right now so I’ll go for whichever first appears on the market.  I’m not interested in a triplet because I don’t want the added weight, cost, and cool down time.  Nor do I like the idea of the shifted weight balance point for the OTA. 

 

The odds are that what I want is not going to appear on the market.  But a 6” f/6 ED doublet is one of the scopes I would want - the other is a 130 f/9ish ED doublet. 



#54 ihf

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Posted 04 July 2021 - 12:38 PM

The question to would be if the focusser and optics can handle ES 30/82, ES12/17. That’s 75x?

#55 Astrojensen

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Posted 05 July 2021 - 12:56 AM

The question to would be if the focusser and optics can handle ES 30/82, ES12/17. That’s 75x?

The focusers APM are already using on their 140mm and 152mm ED doublets have no problems at all with heavy eyepieces. The 3.7" R&P in particular is a fantastic focuser. 

 

 

Clear skies!

Thomas, Denmark


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#56 stevew

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Posted 05 July 2021 - 02:05 AM

But the issue I'm trying to explain is that the spherochromatism in a 6" f/6 ED doublet could be severe enough that its ability to handle higher magnifications wouldn't be better than a 6" f/6 achromat! 

 

It's a complete mystery to me, why people don't understand that color correction in a lens is NOT the only serious aberration a designer has to deal with. And the more you push a design to its limits, the more ugly things pop out of the mud. 

 

I would very much like to see some design proposals from one of Markus' designers, so we can evaluate how viable the idea is in the first place. 

 

 

Clear skies!

Thomas, Denmark 

I can live with less than perfect color correction, but Thomas is correct, spherical aberration can soften the view dramatically.

I once had a 127mm ED that had enough S/A that my 101mm Televue showed more details on Jupiter than the 127mm.


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#57 Deadlake

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Posted 05 July 2021 - 02:56 AM

Interested to know what the plus/minuses for this scope would be compared to my LZOS 130/F6?

I can see extra aperture versus better correction of the triplet lense given the discussion above.

A fast APO makes a great wide field scope, not just limited to AP use, NV as well so I can see the market for this scope but more a question of compromises made.

#58 fate187

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Posted 06 July 2021 - 01:52 AM

Of course CA is not the only serious aberration.  But people use their achromat’s at high magnification all the time despite the limitations.  

 

Part of this for me is seeing how significantly improved for higher magnification deep sky a large fast achromat can be with the use of a CA reducing filter such as the Baader 495 LP.  If you can significantly improve the scope with a filter then you can do it with the glass as well.   The blurring effect from CA in a large achromat is quite significant at higher magnifications.  When I’ve used a filter with such a scope the star images were significantly sharper at higher magnifications than without the filter. Adding an ED element should accomplish this as well.   

 

A Petzval design would be even better, but again now you are significantly increasing the cost. 

 

But like I said in my last post - a 6” f/6 ED doublet I would consider - but a 130mm f/9.2 doublet I would jump at as long as the weight was under ~9 kg.  Neither one exists right now so I’ll go for whichever first appears on the market.  I’m not interested in a triplet because I don’t want the added weight, cost, and cool down time.  Nor do I like the idea of the shifted weight balance point for the OTA. 

 

The odds are that what I want is not going to appear on the market.  But a 6” f/6 ED doublet is one of the scopes I would want - the other is a 130 f/9ish ED doublet. 

an LZOS 130 F9 is ~10kg with rings, vixen bar and Kruppax tube. Including a Feathertouch 2.5" focuser. Of course its twice $3000, but the weight already there....



#59 russell23

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Posted 06 July 2021 - 04:38 AM

an LZOS 130 F9 is ~10kg with rings, vixen bar and Kruppax tube. Including a Feathertouch 2.5" focuser. Of course its twice $3000, but the weight already there....

And that is the problem with the triplet.  If that was a doublet the weight would be 9 kg or less and the cost would be a lot less - still probably more than $3000 though if a LZOS lens. 



#60 APM M.Ludes

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Posted 06 July 2021 - 07:53 AM

Gerd Düring, our designer for the APM 6" F/8 doublet  will do some design Ideas. He say with FCD 100 and LAF53 as matching glas, we should come out with the 6" F/6 similar or slightly better

 

soon I will show some design ideas


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#61 AstroPotamus

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Posted 06 July 2021 - 08:18 AM

Gerd Düring, our designer for the APM 6" F/8 doublet  will do some design Ideas. He say with FCD 100 and LAF53 as matching glas, we should come out with the 6" F/6 similar or slightly better

 

soon I will show some design ideas

Thanks for the update!  Can't wait to see where this goes!



#62 Ben the Ignorant

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Posted 08 July 2021 - 01:07 AM

I'd rather deal with the extra cost and weight of a triplet than with the spherochromatism in a 6-inch f/6 doublet. The 140mm f/7 is a only semi-apo with its FPL-53 glass so a 150mm f/6 doublet would only be an improved achromat.

 

Maybe using carbon fiber, magnesium or a special polymer could make the cell lighter, or a combination of polymer and metal, like in pistol frames, I'm not sure. Same for the focuser, could be a compound polymer/metal or carbon chassis would be rigid enough and save weight. A resin Krupax tube seems like a must, but resorting to a doublet brings too many challenges and too much compromise, a triplet would be more appealing to me if I was looking for a 150mm apo.



#63 jprideaux

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Posted 08 July 2021 - 07:33 AM

Basically the size would be the same as our APM 140 mm F/7 Apo , weight would be very similar, maybe 1 kg more

but a F/6 needs more then a 2.5" focuser

big back focus is no problem, we could use a extension between tube and focuser which can be removed for binoviewer use


This proposed scope would get attention from those that like binoviewers if a removable extension tube were part of the tube design.

I also like the idea of a matched corrector or filter set so buyers wouldn’t have to figure out the best options to buy.

#64 garret

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Posted 08 July 2021 - 11:07 AM

 

This proposed scope would get attention from those that like binoviewers if a removable extension tube were part of the tube design.

Or Binocular telescopes with EMS mirror system.


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#65 Astrogarage

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Posted 08 July 2021 - 11:15 AM

Back in the last century around late 90's, I recall Markus had setup a refractor with a fat and short tube, (6" f6 IIRC) fluorite scope at Riverside Telescope Makers Conference. I think it was an LZOS lens.

 

I looked though the scope and thought it was magnificent, very wide field and pinpoint stars. Although he said there were zones in the glass, and was not up to his standards.

 

I was ready to get out my credit card right then and there.

 

I asked the price and he mentioned a number that was well out of my range.

 

Very dejected I looked one more time and then ambled off.

 

To this day, I still think about that scope every now and then, and wonder if I should have sold a few AP refractors and got that scope. 

 

Maybe Markus remembers this scope and can comment on the performance.


Edited by Astrogarage, 08 July 2021 - 01:06 PM.

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#66 Moravianus

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Posted 08 July 2021 - 02:08 PM

Possibly Aries 6" f/6 fluorite APO. Not at the price level for the scope discussed here.



#67 APM M.Ludes

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Posted 09 July 2021 - 07:56 AM

te 6" F/6 was a earlier original LZOS designed triplet airspacest Fluorite Apo, optimized for best colorcorrection on axis and due that a bad field correction for imaging. I believe only 2 or 3 pc has been made



#68 Charon71

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Posted 10 July 2021 - 02:27 AM

te 6" F/6 was a earlier original LZOS designed triplet airspacest Fluorite Apo, optimized for best colorcorrection on axis and due that a bad field correction for imaging. I believe only 2 or 3 pc has been made

A new 150 f6 triplet optics from LZOS would be desirable.
I would buy one of these.

Sure, it's expensive, but it would be worth the money

Why is this optics not newly developed or produced again?

I don't find a doublet from China interesting



#69 Marcsabb

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Posted 11 July 2021 - 02:23 AM

I like the idea. May I suggest to keep the weight of the complete scope as low as possible? I would use the weight of the old Celestron/Skywatcher 150mm achro as upper limit. This way it can be mounted on a portable mount for a powerful grab and go setup.



#70 hama-san

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Posted 11 July 2021 - 07:19 PM

In developing 150SD BINO, Markus mentioned to the sight of the 350x by HR2.4mm eyepiece, "even at that 350 power there is no CA visible".

Does it means you've already gotten the basic idea of the optics design? or without the prism, the difficulty is fairly different?

 

I'm wondering if I have to change the plan to get 140SD... (More budget should be needed of course bawling.gif )



#71 APM M.Ludes

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Posted 14 July 2021 - 09:45 AM

the 6"F/6 in Astrorefractor design will have a similar correction as our 152 F/8 ED, better is almost imossible. it is designed for universal use, not with prism in the optical path


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#72 Phillip Creed

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Posted 14 July 2021 - 10:25 AM

the 6"F/6 in Astrorefractor design will have a similar correction as our 152 F/8 ED, better is almost imossible. it is designed for universal use, not with prism in the optical path

Markus,

I wouldn't worry about trying to make it better than the 152mm f/8.  If it's merely close to matching its correction, you'll have a real winner on your hands with the 6" f/6 ED doublet.

Clear Skies,

Phil


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#73 Sarkikos

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Posted 14 July 2021 - 01:27 PM

the 6"F/6 in Astrorefractor design will have a similar correction as our 152 F/8 ED, better is almost imossible. it is designed for universal use, not with prism in the optical path

Agreed.  I don't think a refractor should be designed to work optimally with any specific diagonal.  The refractor should work optimally on its own, straight-through, no diagonal.  It's up to the observer to match the diagonal - or the eyepiece or any other accessory - with the refractor.

 

Just my penny.gif penny.gif

 

Mike



#74 ihf

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Posted 15 July 2021 - 06:53 AM

That sounds good enough! Now if it could be constructed for easy transport and lightweight/carbon for mounting?

#75 Jon_Doh

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Posted 15 July 2021 - 09:45 AM

Markus, the specs you mentioned are fine.  I hope you can manufacture it and offer it at a competitive price point. Good luck to you and the team.




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