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ED vs SD - Worth It?

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#1 Keith-in-Texas

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Posted 16 October 2019 - 12:38 PM

Hi All,

 

It seems we now have at least three levels of binocular telescopes from which to choose, Semi-APO, ED and SD.

 

I understand the Semi-APO vs ED glass differences, however, I am less clear on the primary advantages one would actually realize with the move to SD glass for the application where these devices are typically used.

 

Please help me to understand the advantages of the SD glass at the 82mm and 100mm size instrument.

 

I'm trying to decide if the move to the SD level is worth the added expense.

 

Keith



#2 Richard O'Neill

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Posted 16 October 2019 - 01:19 PM

https://www.cloudyni...apm-100-ed-apo/



#3 Jawaid I. Abbasi

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Posted 16 October 2019 - 02:31 PM

If you are in telephotography or daytime viewing or trying to get detail in planets and moon or the close doubles (masking to see doubles nicely) then both kind ED and apo will really facilitate to see more clearer picture. For DSOs ; Non ED or Non apo will work well.

Just my personal experience.


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#4 Beg

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Posted 16 October 2019 - 02:58 PM

Figure at $2,500 I have spent enough already in the 100mm size brackett.


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#5 Mr. Bill

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Posted 16 October 2019 - 05:24 PM

IMO, ED best "bang for the buck"; I don't push my 100 APOs past 61x (9mm Morphs)....more mag + small exit pupil (dimmer image)

 

Want more power, SCT + Denk BVs.

 

As always, YMMV.


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#6 Jon Isaacs

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Posted 17 October 2019 - 09:25 AM

Marcus may have specific types in mind for SD and ED glass but in general I don't think there is a distinction.  ED glasses include glasses similar to FPL-51 and glasses similar the FPL-53.

 

Jon



#7 ArsMachina

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Posted 17 October 2019 - 11:50 AM

What you get is what you pay for ...

 

Jochen



#8 csrlice12

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Posted 17 October 2019 - 12:49 PM

Basically ED = SD, they're marketing terms, not glass terms.



#9 GamesForOne

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Posted 17 October 2019 - 01:19 PM

There is a difference between FK61/FPL-51 (ED) and FPL-53 (SD). At the same focal ratio, FPL-53 is superior.

 

For more detail see: http://www.ianmoriso...jective-lenses/

 

Whether that is observable to the average user is another question.

 

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Edited by GamesForOne, 17 October 2019 - 02:20 PM.


#10 hallelujah

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Posted 17 October 2019 - 02:36 PM

There is a difference between FK61/FPL-51 (ED) and FPL-53 (SD). At the same focal ratio, FPL-53 is superior.

 

For more detail see: http://www.ianmoriso...jective-lenses/

 

Whether that is observable to the average user is another question.

 

Michael Mc

If it's not observable sct.png  to the user it would serve no real purpose. graduate.sml.gif



#11 GamesForOne

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Posted 17 October 2019 - 02:51 PM

If it's not observable sct.png  to the user it would serve no real purpose. graduate.sml.gif

From reports of experienced users in this group, it is observable to the trained eye.

 

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#12 Alan French

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Posted 17 October 2019 - 03:04 PM

Lots of marketing games with nomenclature. Fluorite and fluorcrown glasses like FPL55, 53, and their cousins offered by Hoya (FCD100) and others are all Extra-low Dispersion (ED) materials. SD (Special Dispersion?) and HD (Swarovski, High-Definition) are just different ways to market the same stuff. The marketing folks love anything that will set them apart in some way from the competition - even when everyone is using essentially the same materials. 

 

Clear skies, Alan


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#13 Jon Isaacs

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Posted 17 October 2019 - 03:33 PM

There is a difference between FK61/FPL-51 (ED) and FPL-53 (SD). At the same focal ratio, FPL-53 is superior.

 

 

FPL-51 and FPL-53 are both ED glasses. As Alan said, HD, SD, ED are just terms that venders use to try the differentiate their scopes.

 

SD has been used by William Optics the signify scopes with FK61 based objectives. 

 

In my experience, there's a definite different in the color correction of similar focal ratio/aperature doublets based on ED glasses with Abbe indexes of ~82 (FPL-51) and those with indexes around 95 (FPL-53). At lower powers the difference is small.. at high mags.. it matters.

 

Jon


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#14 hallelujah

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Posted 17 October 2019 - 03:59 PM

https://www.birdforu...ad.php?t=207723


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#15 junomike

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Posted 17 October 2019 - 04:17 PM

I'm quite content with my APM 100 Semi's.  I don't use them for Planets or Lunar and there's only a few DSO's bright enough to show any CA.

Much like Mr.Bill, I find small aperture burns out fast, thus my Newts take over  for fainter DSO's.


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#16 KennyJ

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Posted 17 October 2019 - 04:33 PM

In many areas and aspects of wordly goods, it has long been the case that relatively highly increased premiums are paid for relatively minor "improvements".

 

Often, around 50% of the "top offering" price can buy around 90% the quality of a similar product.

 

Whether or not that extra 10% of product quality is worth that extra 50%  price will always be open to debate, but generally speaking, "the best" more often than not is, by definition, "the best" money can buy, and some people who can more comfortably afford "the best", choose to do so.

 

Kenny



#17 Rich V.

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Posted 17 October 2019 - 04:39 PM

To the point of this thread, the topic is noting that APM is now making available three levels of correction in their BT's optics; semi-apo, "ED" which uses FK61, and now "SD" which uses FCD100.  These are the ED glasses being used in these BTs. Users of the new SD models claim a noticeable improvement in color correction over the ED version under demanding conditions.  It may be an improvement for some who demand it.

 

In the 100mm sized APM BTs, the ED models are currently on sale for $2000, $400. off, so anyone who is on the fence about which glass to get, here's an incentive if they want to save some money.

 

Rich


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#18 GamesForOne

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Posted 17 October 2019 - 05:20 PM

...

 

In the 100mm sized APM BTs, the ED models are currently on sale for $2000, $400. off, so anyone who is on the fence about which glass to get, here's an incentive if they want to save some money.

 

Rich

Yep, and that discount is a killer for selling used at the moment.  frown.gif

 

The FCD100 glass models (thanks for the clarification) are presently requiring a $700+ USD adder which is a considerable percentage of $2000 for the FK61 models on clearance.

 

Buyer's market today for the older model.

 

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Michael Mc



#19 range88

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Posted 18 October 2019 - 08:44 AM

As far as United Optics produced binos(apm,etc) are concerned, SD is optically better than ED. For example, 100sd is much better than 100ed IMO. I don't think it needs a trained eye to discern the differences. They are just of 2 different levels. I will never go back to ed after I saw the sd version.



#20 j.gardavsky

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Posted 18 October 2019 - 11:23 AM

Hello all,

 

here are some similar discussions for reference by the birders,

https://www.birdforu...ad.php?t=207723

https://www.birdforu...ead.php?t=40468

 

There is not only the ED/SD glass you can buy in Far East, but the mating flints to make a well corrected objective.

And some optics companies are still cooking the glass sorts they don't find on the web.

 

The pic shows in large color discs which glass materials have been designed and manufactured by Leica to get a match with SHOTT and others in objectives, EPs, etc

 

Continent+of+Optical+Glasses.jpg

 

Best,
JG

 



#21 garret

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Posted 18 October 2019 - 02:27 PM

As far as United Optics produced binos(apm,etc) are concerned, SD is optically better than ED. For example, 100sd is much better than 100ed IMO. I don't think it needs a trained eye to discern the differences. They are just of 2 different levels. I will never go back to ed after I saw the sd version.

I rather have a ED with 1/6 wave then a SD with 1/3 wave optics.


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#22 Rich V.

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Posted 18 October 2019 - 03:12 PM

"I rather have a ED with 1/6 wave then a SD with 1/3 wave optics."

 

Who wouldn't?  Clearly, the quality of the optical figure matters a lot.  I doubt a maker would opt to upgrade and use the most expensive glass but then decide to cut costs by figuring it poorly, though.    wink.gif

 

Optical figure being equal, if you're going to push the magnification to extreme levels or frequently view high contrast targets at night or in the daytime with fast f5.5 focal ratios like these BTs, the SD glass design will likely be helpful.  I doubt the SD design used at 60x or less for astronomy would benefit much over the ED design, though, so it may not be the best choice.  IMO, choose the degree of color correction you need by considering the intended use.

 

It doesn't hurt to have options; how and what you view will determine what works best for you.

 

Rich


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#23 Jon Isaacs

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Posted 18 October 2019 - 10:57 PM

"I rather have a ED with 1/6 wave then a SD with 1/3 wave optics."

 

Who wouldn't?  Clearly, the quality of the optical figure matters a lot.  I doubt a maker would opt to upgrade and use the most expensive glass but then decide to cut costs by figuring it poorly, though.    wink.gif

 

Optical figure being equal, if you're going to push the magnification to extreme levels or frequently view high contrast targets at night or in the daytime with fast f5.5 focal ratios like these BTs, the SD glass design will likely be helpful.  I doubt the SD design used at 60x or less for astronomy would benefit much over the ED design, though, so it may not be the best choice.  IMO, choose the degree of color correction you need by considering the intended use.

 

It doesn't hurt to have options; how and what you view will determine what works best for you.

 

Rich

 

I am very uncomfortable using Markus's definitions for SD and ED glass. As far as I know they only refer to APM binos and as such, should only be used in that exact context.

 

FPL-53 is ED glass, FPL-51 is ED glass. What SD is a vague term and I do not believe Ohara uses the term in their literature.  In my mind, discussions should be specific.. Abbe indexes around 83 can be discussed as FPL-51 class glasses, indexes around 95 can be discussed as FPL-53 class glasses..

 

Jon


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#24 Allan Wade

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Posted 18 October 2019 - 11:25 PM

Buying an APM binoscope with FPL-53 glass is a bit like buying an insurance policy. That's the way I approached it. Even though I don't think they are especially suited to high power planetary observing, I still opted to buy the 'SD' versions knowing I would have the best colour correction no matter what targets I observe with them. The lunar and planetary observing I do with them is still very pleasing, and I wouldn't hesitate to buy the 'SD' versions again.


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#25 Rich V.

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Posted 19 October 2019 - 02:18 AM

I am very uncomfortable using Markus's definitions for SD and ED glass. As far as I know they only refer to APM binos and as such, should only be used in that exact context.

Since Keith, the OP, seems to be referring to APM's 82mm and 100mm BT offerings, ED and SD are the marketing terms they use in their website descriptions to differentiate the two levels of ED glass used. "ED" being FK61  and "SD" being either FPL53 or FCD100  depending on the model. For APM's purposes, "ED" means Abbe Vd ~81.5 and "SD" means Vd ~95.

 

So when you're reading Markus' APM site, the above terms apply.  I have no desire to see confusing marketing terms like SD/HD or whatever becoming any kind of standard one way or another. By now, most CN members interested in this stuff know there are the two tiers of ED glass.  Call them by their company designation and that works fine for me; why make it more confusing?  wink.gif

 

Rich


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