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Astro-Tech 102ED vs 102EDL

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#51 daquad

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Posted 05 April 2021 - 10:54 AM

I believe the EDL is supposed to meet a minimum strehl specification, and its less expensive cousin doesn’t have to clear that hurdle. 
 

“AT102EDL doublet refractor optics: 102mm (4”) ... with a .95 strehl ratio minimum guarantee.”

 

So, if the claim is factual, I assume it doesn’t have better figure because it costs more, it costs more because it has better figure. 

It costs more because of the items I mentioned --  glass/mechanics.  The higher strehl, (if in fact it is), is due to the glass, not necessarily a better figure.  The ED could have just as good a figure, but with the higher dispersion glass has lower strehl.

 

Dom Q.


Edited by daquad, 05 April 2021 - 10:56 AM.


#52 Joe1950

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Posted 05 April 2021 - 11:01 AM

I think it’s obvious when you read through all the different scope reviews for a long time now, that although  it’s not 100% true, it’s 95% true that opticians have a higher standard figuring expensive glass over normal.... it’s the one thing you can count on to increase your chances of getting a great scope.... it’s definitely true that you can get a great scope with regular ED, just believe your odds increase, the factory has a box for venders to check, for a price they will ensure the extra attention. Mike decided to check that box on the edl and has stated he unchecked the box for a case to keep the price down.... so that’s my rationale for believing the edl will most likely have a better figure..... if this same ota shows up without the strehl claim then I would bet they are the rejects.... does not mean they are bad scopes, just means the vender didn’t check the box

 

You have to factor in the fact that the lenses from the ED version and the EDL are not the same, thus not part of the same manufacturing batch. It isn’t a situation where the manufacturer is making 1000 objective lenses, testing them and assigning the ones over 0.95 Strehl to the EDL scopes and the rest to the ED scopes. They are entirely different lenses with different glass elements.

 

Logically, aside from the difference in the glass, the ED lenses aren’t tested for Strehl at all. That would lend itself to being a factor in lower cost. We who have the ED scope don’t know where they fall regarding Strehl and likely the manufacturer doesn’t know either.

 

That doesn’t automatically make them a lesser quality. If the lenses are polished to a null in one of several simpler optical tests, they may, in fact, be 0.95 Strehl.

 

Going by the many comments by owners that the optical quality seen at the eyepiece is excellent, the obvious consistency of these positive opinions and the statement when these scopes first came on the market that they would be optically superior to the original $900 version, I’ve no doubt it is a high quality objective with a very good polish and figure.


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#53 GSBass

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Posted 05 April 2021 - 11:14 AM

I have to assume QA does randomly test their ED scopes, I don’t know what their internal numbers they use are but it’s likely pretty high considering how happy our community has been with them, As far as edl, I am unsure whether they are making this set for several venders, if they are and all vendors have asked for the .95 guarantee then they are probably testing all of them, if only astrotech choose to pay for the guarantee then probably only our scopes are being tested, the ones that don’t pass will go into the pile for those other vendors

You have to factor in the fact that the lenses from the ED version and the EDL are not the same, thus not part of the same manufacturing batch. It isn’t a situation where the manufacturer is making 1000 objective lenses, testing them and assigning the ones over 0.95 Strehl to the EDL scopes and the rest to the ED scopes. They are entirely different lenses with different glass elements.

 

Logically, aside from the difference in the glass, the ED lenses aren’t tested for Strehl at all. That would lend itself to being a factor in lower cost. We who have the ED scope don’t know where they fall regarding Strehl and likely the manufacturer doesn’t know either.

 

That doesn’t automatically make them a lesser quality. If the lenses are polished to a null in one of several simpler optical tests, they may, in fact, be 0.95 Strehl.

 

Going by the many comments by owners that the optical quality seen at the eyepiece is excellent, the obvious consistency of these positive opinions and the statement when these scopes first came on the market that they would be optically superior to the original $900 version, I’ve no doubt it is a high quality objective with a very good polish and figure.


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#54 Joe1950

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Posted 05 April 2021 - 11:40 AM

Very possible. I have read instances where that kind of sorting is done, based on quality. All or most of the manufactured pieces are sold to someone.

 

Very good GS.


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#55 GSBass

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Posted 05 April 2021 - 11:52 AM

Yes, I think it highly likely that the optics that don’t pass will end up in some scope, maybe a local for the China market if it’s small numbers, my guess is what they don’t do is attempt to re polish .... it’s all speculation on my part but I suspect if they offered the spec to vendors then they probably have very few they have to toss, the vender is mainly paying for the extra QA only

Very possible. I have read instances where that kind of sorting is done, based on quality. All or most of the manufactured pieces are sold to someone.

 

Very good GS.


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#56 SeattleScott

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Posted 05 April 2021 - 12:57 PM

It costs more because of the items I mentioned -- glass/mechanics. The higher strehl, (if in fact it is), is due to the glass, not necessarily a better figure. The ED could have just as good a figure, but with the higher dispersion glass has lower strehl.

Dom Q.

That would be the case for polychromatic Strehl, which factors in CA correction. Typically CA correction is not part of “regular” Strehl.

Scott

#57 SeattleScott

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Posted 05 April 2021 - 01:11 PM

You have to factor in the fact that the lenses from the ED version and the EDL are not the same, thus not part of the same manufacturing batch. It isn’t a situation where the manufacturer is making 1000 objective lenses, testing them and assigning the ones over 0.95 Strehl to the EDL scopes and the rest to the ED scopes. They are entirely different lenses with different glass elements.

Logically, aside from the difference in the glass, the ED lenses aren’t tested for Strehl at all. That would lend itself to being a factor in lower cost. We who have the ED scope don’t know where they fall regarding Strehl and likely the manufacturer doesn’t know either.

That doesn’t automatically make them a lesser quality. If the lenses are polished to a null in one of several simpler optical tests, they may, in fact, be 0.95 Strehl.

Going by the many comments by owners that the optical quality seen at the eyepiece is excellent, the obvious consistency of these positive opinions and the statement when these scopes first came on the market that they would be optically superior to the original $900 version, I’ve no doubt it is a high quality objective with a very good polish and figure.

Original $900 version? The 102 Access was normally about $1100, so about the same as the AT102EDL. Sometimes it went on sale for $1,000. If someone bought one for $900 brand new, they got quite a deal. The fact that the price is essentially the same makes me wonder if these really are any better than the Access scopes, which were fine scopes by all accounts but not generally regarded as premium. Maybe some had premium optics but this did not seem to be consistently the case. Like most Chinese Apos, people who didn’t already have a premium Apo tended to be quite happy with them. But usually they fell a little short compared to premium brands, as expected for the price point.

As for Jon’s point about Norman being lower cost than Sacramento, well that’s obviously true, and maybe a factor if AT can really deliver on premium optical figure for budget price. But of course these scopes are imported from China so I’m not sure how much cost of living in the US matters, other than SV possibly feeling like they need a higher profit margin.

Early reviews would certainly be a good indicator. It is a pretty new product and I get the impression most people are still waiting for theirs, so not sure how much quality feedback is out there. But maybe there is some good information already available, which would be helpful. Of course it is really best if the feedback compares the EDL to other known quantities, as opposed to I just got this EDL, it is my first Apo and I love it, but have no real basis for comparison. Which represented a lot of the Access reviews. So comparisons between the EDL and either recognized premium brands, or established budget models (ES 102 triplet, SW 100ED, etc.) would certainly be insightful.

Scott
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#58 GSBass

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Posted 05 April 2021 - 02:25 PM

Unfortunately when my edl arrives I won’t be able to report anything other than my impressions, I know a lot about things to look for but I certainly won’t be able to compare to other scopes of same size and f stop..... the reviews I have read though seemed to think the access did fall in to the premium doublet scope category, I guess it is human nature to start splitting hairs though when your comparing a 1k scope to one you dropped 3 or 4 grand on.... ie indistinguishable  at 100x but at 500x my tak was the clear winner lol

Original $900 version? The 102 Access was normally about $1100, so about the same as the AT102EDL. Sometimes it went on sale for $1,000. If someone bought one for $900 brand new, they got quite a deal. The fact that the price is essentially the same makes me wonder if these really are any better than the Access scopes, which were fine scopes by all accounts but not generally regarded as premium. Maybe some had premium optics but this did not seem to be consistently the case. Like most Chinese Apos, people who didn’t already have a premium Apo tended to be quite happy with them. But usually they fell a little short compared to premium brands, as expected for the price point.

As for Jon’s point about Norman being lower cost than Sacramento, well that’s obviously true, and maybe a factor if AT can really deliver on premium optical figure for budget price. But of course these scopes are imported from China so I’m not sure how much cost of living in the US matters, other than SV possibly feeling like they need a higher profit margin.

Early reviews would certainly be a good indicator. It is a pretty new product and I get the impression most people are still waiting for theirs, so not sure how much quality feedback is out there. But maybe there is some good information already available, which would be helpful. Of course it is really best if the feedback compares the EDL to other known quantities, as opposed to I just got this EDL, it is my first Apo and I love it, but have no real basis for comparison. Which represented a lot of the Access reviews. So comparisons between the EDL and either recognized premium brands, or established budget models (ES 102 triplet, SW 100ED, etc.) would certainly be insightful.

Scott


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#59 Joe1950

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Posted 05 April 2021 - 02:36 PM

I was referring to the AT-102ED that came out about 10 years ago. I guessed at the price. It was around $1k. Jon had one. Actually he had the first one made.

 

The promotion, if I recall correctly, said the new version of the 102ED would cost $499 on sale and then go to $599 as a regular price. And that the objective lens is an improvement over the original. Jon has observed through both, I believe, so he could probably offer a good comparison.

 

I bought my scope used, but in excellent condition. It is #2 of the first run. I also have an excellent C-80 ED.Here is a green DPAC test of that scope with a 150 lpi grating...

 

29CEE987-5F33-480D-8AFE-34A770F2E4CD.jpeg

Celestron C-80ED.

 

Good scope. Not a premium brand name, but it has a very good polish and figure. And no visible CA, in focus or inside/outside focus.

 

Using the AT102ED, even though it is not 100% apochromatic with the FK-61 element, I truly feel the image it presents is very good. And from observing the in-focus Airy disc and diffraction pattern, as Roland does, not that I can ever come close to his skills and talents, it appears to have a very good distribution of light, most (80% ideal) in the disk and the rest in the rings. Of course what you see is affected by seeing. And, from my point of view, the contrast of the images is very, very good.

 

I’m in no way saying the EDL in not a better overall scope than the ED. It has a better build factor and the optics are guaranteed to be better than 0.95 Strehl. Fine. If one can comfortably afford the price, get it, by all means.

 

Or if one can afford a TV, AP, TEC, TAK, etc., and one feels they are optically and mechanically better than the EDL, again, great.

 

I’ve never observed with any of those scopes, save one look at the moon through a 200mm AP. Years ago at a star party. It was a memorable look.

 

I just do not agree that because a scope costs less than another, the optical performance is automatically less, or just average, or poor. And this bias always comes up in these comparison, this vs. that topics. Not that honest comparisons are not good for someone buying a scope. But comparisons based on assumptions, cost, name brand do a dis-service to those reading the topic and those who own the lesser product.

 

Same thing happens with eyepieces as you well know, Scott.

 

I can’t personally afford to try different scopes and assess them. I’ve looked through telescopes for over 50 years and I do like what I see in the AT-102ED. I’ll leave it at that and retire from this particular topic, wishing the OP gook luck, in choosing a scope.


Edited by Joe1950, 05 April 2021 - 02:42 PM.

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#60 SeattleScott

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Posted 05 April 2021 - 03:31 PM

I have heard some of those Celestron 80 EDs were fantastic. True premium performance at a bargain price. I’m not sure how consistent that is, but certainly a number of them have been reported to be outstanding.

Scott
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#61 Joe1950

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Posted 05 April 2021 - 05:21 PM

It’s the same objective lens used on the Orion ED-80, which is still sold. The tube and focuser are different but the objective is the same. Very good consistency from what I’ve heard. I bought it used as well a few years back.


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#62 daquad

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Posted 05 April 2021 - 06:22 PM

That would be the case for polychromatic Strehl, which factors in CA correction. Typically CA correction is not part of “regular” Strehl.

Scott

Agreed, Scott.  I was trying to make the point that the higher price does not necessarily mean better figure.

 

Dom Q.


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#63 gwlee

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Posted 06 April 2021 - 01:07 PM

Strehl numbers can vary considerably depending on the equipment used (Zygo interferometer?) and the individual doing the test.

 

That’s true for any procedure, protocol, or technique ever used to measuring anything, including simply looking through the eyepiece with our own eyes to evaluate the images produced by a telescope. We all have our favorite techniques, which we can use alone or in combination with several others to reach a conclusion in which we have confidence. 

 

I believe the importer is making a claim that the EDL is figured to a higher standard than his less expensive imported products, and justifying the higher price based, in part, on a higher figure. If in fact the EDL is figured to a higher standard, I think it’s reasonable to expect it to cost the manufacturer more, so I would expect to pay more to obtain it.

 

As evidence of higher figure, I believe the importer is relying on his own considerable experience as well citing the results of formal test protocols, none of which can be perfect, but each can be useful. Whether the incremental improvement is worth the incremental cost is a question the buyer must decide for himself.


Edited by gwlee, 06 April 2021 - 02:08 PM.


#64 SeattleScott

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Posted 06 April 2021 - 01:31 PM

The concern with the advertised Strehl figure is two fold. For one, as mentioned, it can be gamed depending on how you do the test. Like testing in Red to boost the Strehl score. The other issue is the manufacturer could basically be building to a Strehl number. Which is not a universal indicator of good figure. It is possible to have a mediocre lens with a high Strehl number. So the manufacturer might figure to a Strehl number at the expense of other factors that impact performance. Buying strictly based on Strehl is like buying a vehicle to haul a boat strictly based on horsepower. A Corvette has the horsepower but I wouldn’t use it to haul a boat.

That being said it seems like AT has a good reputation for providing good value. I would expect the AT102EDL to be a very good scope. I don’t know if it will keep pace with a Tak100 at 300x. If it does, that’s gravy. If you expect a high quality Chinese scope that approaches the performance of premium brands, you probably will be happy. And maybe you will get lucky and it will perform basically just as well as premium brands. I would not expect that given the price point. But you never know. If you expect it to perform like a $1000 Apo you should be happy. If you expect it to perform just as well as a $2500 Apo based on some vague Strehl guarantee, you might be disappointed.

Scott
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#65 dhferguson

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Posted 06 April 2021 - 01:42 PM

Cheers,

 

The AT102EDL and the now closed-out SV102A ("Access") are/were both manufactured by KUO and indeed are very similar. Both use FCD100 or FPL-53 combined with a lanthanum glass element.  Another option still offered for sale is the similar telescope from TS. Incidentally, the purportedly excellent APM 152mm scopes, I think now also being closed out by Markus Ludes, are also manufactured by KUO.

 

Both AT and SV promise(d) "0.95 Strehl" or better. As many have noted, being monochromatic and for other reasons, Strehl ratio is an imperfect metric of optical quality.

 

That said, after being stunned in a good way (> 0.98 in the green!) by the star test from my SV125A, purchased during the summer 2019 closeout sale BTW, I had a discussion with Alan of SV. He noted they rejected HALF the KUO telescopes due to not meeting spec'd optical criteria. One might suspect Astronomics has had similar experience? Stellarvue had also taken lots of heat because they'd been measuring Strehl only out to 95% of the radius of the entire aperture. They explained this was due to reflections from the lens cell, which makes sense. I wonder how many others' interferometric tests were performed similarly? Anyway, Stellarvue dropped the Access line to concentrate on premium refractors, which by all accounts are optically superb but out of the OP's price range.

 

Regarding AP, I've been using an unmodded DSLR with both an SV125A and SV80A (the latter a fine telescope but not fantastic), both with FCD100/La glass doublets. I can't see any difference in star size with or without an Astronomik L-3 UV/IR blocking filter with either scope. I suspect the AT102EDL would give the same wonderful result. However, the wavelength range for a sensor with no blocking filter--like for all dedicated astro-cams--is broader on both ends, so perhaps such a filter might then be needed, I don't know. 

 

In summary, the AT102ED should be fine visually, with a bit of contrast to be gained with the AT102EDL. For AP, the AT102EDL might yield sharper star images.

 

Happy observing always,

 

Don


Edited by dhferguson, 06 April 2021 - 01:48 PM.

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#66 Joe1950

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Posted 06 April 2021 - 02:55 PM

That’s true for any procedure, protocol, or technique ever used to measuring anything. 

I don’t think everyone considers the possible variability in testing when they are told or promised a certain level of quality. If someone buys a scope and it comes with a printout of an interferometer test saying it is an optic with a Strehl of 0.98 most people will consider it accurate. Maybe it is, maybe it isn’t.

 

In the case of the AstroTech AT-102EDL claiming a Strehl better than 0.95, I certainly do believe it to be accurate. Why? Because the integrity and reputation of Astronomics is second to none! If it were a document given with a scope sold on eBay I would have less confidence.

 

My main statement to consider is this...

 

If the ED and EDL objectives were exactly the same, made with the same glass elements, made from the same batch etc. and so on, one may conclude that the lenses that exhibit a Strehl of 0.95 or greater were used in the EDL scopes, and the remainder, likely less than 0.95 Strehl, went to the ED scopes.

 

But, the lenses are NOT the same and had to be made independent of each other. They have different types of ED glass. So the conclusion would have to be that the lenses in the less expensive ED version are of a quality only known by the manufacturer. Perhaps they are spot checked as someone suggested. But due to the lesser cost, they are not guaranteed to have a specific level of quality.

 

One cannot assume, or should not assume that the objectives used in the AT-102ED are automatically noticeably inferior, regarding figure, to the AT-102EDL, simply based on the cost difference. The EDL uses FPL-53 glass. It has a better lens cell. It has a better focuser - I’ve read these things and have no reason to dispute them. So right there along with the guarantee of 0.95 Strehl are reasons for a price difference.

 

Okay? The EDL version is a better scope than the ED version. No argument. It’s worth the extra money. Would I have spent the extra money for the EDL? Yes, if I had the extra money to spend. But I didn’t. If I had unlimited funds for this hobby, I might have purchased a Takahashi or TeleVue or TEC or a used AstroPhysics in the 100mm class. But it’s a moot point.

 

All I’m saying, as a result of my experience with observing with telescopes since the 1960s, and as a result of the observations of others who have the ED scope, is that the objective lens is one of quality, giving very good views with a low level of visual chromatic aberration, giving very good views at higher magnifications and giving very good views with a noticeably high level of contrast. That’s all I really care about. For my cost, and I bought the AT-102ED used, I feel I have a really good scope, not lacking in optical performance.

 

Is it optically as good as an AT-102EDL or  like size TeleVue, Tak, Tec, AP scope? I don’t know and I don’t/can’t care. It’s what I can afford and it’s good enough for me.

 

Furthermore, if I set it up next to another brand 102 size scope and I felt the optical performance in my scope was obviously better than the other scope, I would not say so to the owner or say so in a post. Someone spent their hard earned money on the scope and they don’t want to hear it isn’t as good. It’s just the way I approach things. If they are happy with it and use it with enjoyment I think that’s great!

 

But here on CN, a wonderful site for astronomy and telescopes, many seem to constantly compare this vs that. “My _______ scope beat up the _________ scope and left it in the dust!” Often if think this site should have been named CN, for Comparisons ad Nauseam. wink.gif

 

So that’s my story, gwlee. If you want to comb through all this nonsense, pick out a sentence, quote it and dispute it, that’s fine. I was often told to avoid this vs. that topics especially in the refractor and eyepiece forums. I’m going to try and follow that advice and leave the daunting task of assessing relative quality to others. waytogo.gif

 

Ciao.


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#67 GSBass

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Posted 06 April 2021 - 03:31 PM

To expand on that, even if the edl are figured the exact same way as the ED then that would make me quite happy given how good the ED scopes are, obviously the better glass will do better color correction but nothing wrong with the ED, and as mentioned before numerous times, the glass is not the only upgrade

I don’t think everyone considers the possible variability in testing when they are told or promised a certain level of quality. If someone buys a scope and it comes with a printout of an interferometer test saying it is an optic with a Strehl of 0.98 most people will consider it accurate. Maybe it is, maybe it isn’t.

 

In the case of the AstroTech AT-102EDL claiming a Strehl better than 0.95, I certainly do believe it to be accurate. Why? Because the integrity and reputation of Astronomics is second to none! If it were a document given with a scope sold on eBay I would have less confidence.

 

My main statement to consider is this...

 

If the ED and EDL objectives were exactly the same, made with the same glass elements, made from the same batch etc. and so on, one may conclude that the lenses that exhibit a Strehl of 0.95 or greater were used in the EDL scopes, and the remainder, likely less than 0.95 Strehl, went to the ED scopes.

 

But, the lenses are NOT the same and had to be made independent of each other. They have different types of ED glass. So the conclusion would have to be that the lenses in the less expensive ED version are of a quality only known by the manufacturer. Perhaps they are spot checked as someone suggested. But due to the lesser cost, they are not guaranteed to have a specific level of quality.

 

One cannot assume, or should not assume that the objectives used in the AT-102ED are automatically noticeably inferior, regarding figure, to the AT-102EDL, simply based on the cost difference. The EDL uses FPL-53 glass. It has a better lens cell. It has a better focuser - I’ve read these things and have no reason to dispute them. So right there along with the guarantee of 0.95 Strehl are reasons for a price difference.

 

Okay? The EDL version is a better scope than the ED version. No argument. It’s worth the extra money. Would I have spent the extra money for the EDL? Yes, if I had the extra money to spend. But I didn’t. If I had unlimited funds for this hobby, I might have purchased a Takahashi or TeleVue or TEC or a used AstroPhysics in the 100mm class. But it’s a moot point.

 

All I’m saying, as a result of my experience with observing with telescopes since the 1960s, and as a result of the observations of others who have the ED scope, is that the objective lens is one of quality, giving very good views with a low level of visual chromatic aberration, giving very good views at higher magnifications and giving very good views with a noticeably high level of contrast. That’s all I really care about. For my cost, and I bought the AT-102ED used, I feel I have a really good scope, not lacking in optical performance.

 

Is it optically as good as an AT-102EDL or  like size TeleVue, Tak, Tec, AP scope? I don’t know and I don’t/can’t care. It’s what I can afford and it’s good enough for me.

 

Furthermore, if I set it up next to another brand 102 size scope and I felt the optical performance in my scope was obviously better than the other scope, I would not say so to the owner or say so in a post. Someone spent their hard earned money on the scope and they don’t want to hear it isn’t as good. It’s just the way I approach things. If they are happy with it and use it with enjoyment I think that’s great!

 

But here on CN, a wonderful site for astronomy and telescopes, many seem to constantly compare this vs that. “My _______ scope beat up the _________ scope and left it in the dust!” Often if think this site should have been named CN, for Comparisons ad Nauseam. wink.gif

 

So that’s my story, gwlee. If you want to comb through all this nonsense, pick out a sentence, quote it and dispute it, that’s fine. I was often told to avoid this vs. that topics especially in the refractor and eyepiece forums. I’m going to try and follow that advice and leave the daunting task of assessing relative quality to others. waytogo.gif

 

Ciao.


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#68 GSBass

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Posted 06 April 2021 - 03:37 PM

One more thing, your right that people can be quite nasty here... but thinking maybe some people just don’t age well haha , I just try to ignore them but you have some just chomping at the bit to run down your equipment and photos, not sure what it is about getting older and meaner but it’s seems to be a real thing

To expand on that, even if the edl are figured the exact same way as the ED then that would make me quite happy given how good the ED scopes are, obviously the better glass will do better color correction but nothing wrong with the ED, and as mentioned before numerous times, the glass is not the only upgrade


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#69 Joe1950

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Posted 06 April 2021 - 03:42 PM

I know what you mean GS. It seems that way at times. Or as I get older my thick skin is wearing down lol.gif .

Thanks bud.


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#70 gwlee

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Posted 06 April 2021 - 04:50 PM

I don’t think everyone considers the possible variability in testing when they are told or promised a certain level of quality. If someone buys a scope and it comes with a printout of an interferometer test saying it is an optic with a Strehl of 0.98 most people will consider it accurate. Maybe it is, maybe it isn’t.

 

In the case of the AstroTech AT-102EDL claiming a Strehl better than 0.95, I certainly do believe it to be accurate. Why? Because the integrity and reputation of Astronomics is second to none! If it were a document given with a scope sold on eBay I would have less confidence.

 

My main statement to consider is this...

 

If the ED and EDL objectives were exactly the same, made with the same glass elements, made from the same batch etc. and so on, one may conclude that the lenses that exhibit a Strehl of 0.95 or greater were used in the EDL scopes, and the remainder, likely less than 0.95 Strehl, went to the ED scopes.

 

But, the lenses are NOT the same and had to be made independent of each other. They have different types of ED glass. So the conclusion would have to be that the lenses in the less expensive ED version are of a quality only known by the manufacturer. Perhaps they are spot checked as someone suggested. But due to the lesser cost, they are not guaranteed to have a specific level of quality.

 

One cannot assume, or should not assume that the objectives used in the AT-102ED are automatically noticeably inferior, regarding figure, to the AT-102EDL, simply based on the cost difference. The EDL uses FPL-53 glass. It has a better lens cell. It has a better focuser - I’ve read these things and have no reason to dispute them. So right there along with the guarantee of 0.95 Strehl are reasons for a price difference.

 

Okay? The EDL version is a better scope than the ED version. No argument. It’s worth the extra money. Would I have spent the extra money for the EDL? Yes, if I had the extra money to spend. But I didn’t. If I had unlimited funds for this hobby, I might have purchased a Takahashi or TeleVue or TEC or a used AstroPhysics in the 100mm class. But it’s a moot point.

 

All I’m saying, as a result of my experience with observing with telescopes since the 1960s, and as a result of the observations of others who have the ED scope, is that the objective lens is one of quality, giving very good views with a low level of visual chromatic aberration, giving very good views at higher magnifications and giving very good views with a noticeably high level of contrast. That’s all I really care about. For my cost, and I bought the AT-102ED used, I feel I have a really good scope, not lacking in optical performance.

 

Is it optically as good as an AT-102EDL or  like size TeleVue, Tak, Tec, AP scope? I don’t know and I don’t/can’t care. It’s what I can afford and it’s good enough for me.

 

Furthermore, if I set it up next to another brand 102 size scope and I felt the optical performance in my scope was obviously better than the other scope, I would not say so to the owner or say so in a post. Someone spent their hard earned money on the scope and they don’t want to hear it isn’t as good. It’s just the way I approach things. If they are happy with it and use it with enjoyment I think that’s great!

 

But here on CN, a wonderful site for astronomy and telescopes, many seem to constantly compare this vs that. “My _______ scope beat up the _________ scope and left it in the dust!” Often if think this site should have been named CN, for Comparisons ad Nauseam. wink.gif

 

So that’s my story, gwlee. If you want to comb through all this nonsense, pick out a sentence, quote it and dispute it, that’s fine. I was often told to avoid this vs. that topics especially in the refractor and eyepiece forums. I’m going to try and follow that advice and leave the daunting task of assessing relative quality to others. waytogo.gif

 

Ciao.

I don’t own either 100mm scope being discussed here, so can’t offer an informed opinion about which is better, whether the EDL meets the claims made for it. Like you, I am very satisfied by the inexpensive, good quality refractors I have bought from the same importer, my AT72EDII for example. 
 

For a buyer who wants a better than average scope, who is willing to pay what it costs to get one, and who intends to expend the effort required to confirm that it’s better than average, I think it makes sense to start looking at scopes that are claimed to be better than average no matter the basis of the claim. 

 

For that buyer, a Strehl number claim is certainly no less useful than a “diffraction limited” claim and potentially more useful. Both can be gamed, and both should be thoughtfully evaluated before purchase and eventually confirmed using whatever protocols the buyer deems best, and any scope that doesn’t meet the claims made for it should be returned. 


Edited by gwlee, 06 April 2021 - 04:51 PM.

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#71 Mitrovarr

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Posted 06 April 2021 - 05:02 PM

The average buyer has basically no way to confirm a Strehl claim, though.
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#72 Joe1950

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Posted 06 April 2021 - 05:22 PM

I don’t own either 100mm scope being discussed here, so can’t offer an informed opinion about which is better, whether the EDL meets the claims made for it. Like you, I am very satisfied by the inexpensive, good quality refractors I have bought from the same importer, my AT72EDII for example. 
 

For a buyer who wants a better than average scope, who is willing to pay what it costs to get one, and who intends to expend the effort required to confirm that it’s better than average, I think it makes sense to start looking at scopes that are claimed to be better than average no matter the basis of the claim. 

 

For that buyer, a Strehl number claim is certainly no less useful than a “diffraction limited” claim and potentially more useful. Both can be gamed, and both should be thoughtfully evaluated before purchase and eventually confirmed using whatever protocols the buyer deems best, and any scope that doesn’t meet the claims made for it should be returned. 

 

You know GW, you made me chuckle when you mentioned ‘diffraction limited.’ I don’t know how far back you go with the hobby, but as I mentioned, I started in the 1960s. Newtonians were the primary scopes along with some refractors. No DOBs and no SCTs until about 1970 with the C8.

 

Anyway, the standard back then was 1/4 wavelength mirror or optics. And I guess most manufacturers were believed. Then the competition started to ramp up and 1/8 wave became the gold standard. And, you guessed it, the claims started to reach the stratosphere! 1/10 wave, 1/12 wave, 1/15 wave, 1/20 wave. It kinda’ got out of hand. This was in the 70s and into the 80s and was later known as the time of the ‘Wave Wars.’ lol.gif 

 

To say some of the claims were inflated, would be an understatement.

 

Well, eventually, someone decided enough was enough and marketed their optics as ‘Diffraction Limited.’ The meaning was that, without quoting an actual surface error, the optics were at a level where they were only limited by the diffraction of light for a given aperture, as required by the laws of physics.

 

Who could argue with that? The ‘diffraction limited’ standard stuck and soon everyone was using it.  You still see it today at times, but sometimes the translation comes out as ‘limited diffraction!’ grin.gif

 

Amazing how the more things change, the more they stay the same. Had to share that from the memory banks!


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#73 Mitrovarr

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Posted 06 April 2021 - 05:37 PM

The wave wars must have gone further than the 80s, because I remember it. 90s for sure and maybe early 200ps.
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#74 Joe1950

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Posted 06 April 2021 - 05:38 PM

Very possible. My recollection Is foggy.



#75 SeattleScott

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Posted 06 April 2021 - 06:45 PM

One more thing, your right that people can be quite nasty here... but thinking maybe some people just don’t age well haha , I just try to ignore them but you have some just chomping at the bit to run down your equipment and photos, not sure what it is about getting older and meaner but it’s seems to be a real thing


It’s nothing to do with being nasty. People get into the hobby, usually with modest equipment like myself. Then the government gives them a bunch of free money and they decide to upgrade some things. They can’t go to star parties to see how much better this scope or that eyepiece might be compared to what they currently have. They see a $600 4” Apo and a $2500 one, or a $35 eyepiece and a $500 one, and they want to legitimately know what the difference is. So people who have experience with expensive scopes and eyepieces share their experience about why one costs more and what you get for the price difference, so people can gauge how far up the ladder of diminishing marginal returns they want to go. And it seems like often some longer tenured users of modest equipment get offended by that. Ultimately if the $600 telescope was just as good as the $2500 one there wouldn’t be a $2500 one. People want to understand what the difference is so they can decide how much of an upgrade they want to commit to. We are just helping them understand so they can make an informed decision. Nobody is saying your $600 Apo is a bad scope or insulting you because you can’t afford anything better. We are just addressing the question posed by the OP. If you don’t want to hear about why a $2500 Apo is better than your $600 one, don’t read the thread.

People ask about this versus that comparisons all the time, especially in the eyepiece forum! We aren’t being rude or judgmental. We are using our experience to answer legitimate queries.

Scott


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