DeLite 1st Light Review

[ausastronomer (John Bambury)]

Originally Posted by Profiler

Thanks Don

With the benefit of a wife who speaks French the reviews are very interesting.

Let me throw a cat amongst the pigeons and make that magazine review worthless

Here is an extract from a post I made on Cloudy Nights regarding that very same review a couple of months ago.

The laboratory tests were conducted by a French Astronomy magazine with whom Televue is one of their major advertising contributors. Pentax on the other hand does not advertise its astronomy products outside Japan.

I have seen countless product reviews conducted by astronomy magazines over the past 40 years and very few of them have portrayed their major advertisers products as inferior to non advertisers products. That's just business. There are some exceptions to this and there has been a previous exception in this magazine. Would the publisher let Televue run second twice in an eyepiece review? Food for thought.

When I read that the overall scores from those tests were that the 10mm DELOS scored 16/20; and 10mm PENTAX XW scored 12/20; I though hmmmm !!! that's pretty amazing, the 10mm DELOS is a 33% better eyepiece than the 10mm PENTAX XW. That wasn't consistent with my experience based on extensive use of both eyepieces and with my extensive use of the 6mm DELOS and 7mm PENTAX XW.

I decided I needed to delve a bit deeper into the accuracy and basis of those laboratory tests.

Here are some very pertinent facts in regard to those laboratory tests.

1) The tests were conducted at F3.5 and at F7. Coma correction was not used in determining the results at F3.5. In the tests at F3.5 the 10mm TV DELOS outpointed the 10mm PENTAX XW, by quite a margin. Only problem here is I don't know anyone who uses a telescope faster than F4 that it is not a large aperture Newtonian and all of the large aperture Newtonian users that I know always use a paracorr at anything faster than F4; 95% of them use a paracorr in any Newtonian faster than F5. So I rate the testing at F3.5 without a paracorr absolutely pointless. Testing at F7 and maybe F4.5 would have been much more realistic and meaningful. If we remove the test results at F3.5 the overall result of the tests are much different.

2) Lets look at some of the specific optical tests

The one which tests optical quality on axis at F7 in red light is interesting. In this test the 10MM DELOS tested at lambda/109 and rated 5/6; whereas the lowly 10mm PENTAX XW only tested at lambda/53 (what a lemon). The same on axis test in green light showed the 10mm DELOS at lambda/133 with a 6/6 rating and the lowly 10MM PENTAX XW rated 4/6 at lambda/86 (what a lemon). Lambda / 53 was the worst on axis optical performance of the 10MM Pentax XW. Dayyam dud eyepiece !!

Now this poses an interesting situation.

Is there anyone out there who can detect the difference in optical performance between either of these eyepieces, in red light and green light?
Is there anyone out there who owns a refractor with a combined optical quality of objective and diagonal in excess of lambda/53?
Is there anyone out there with a Newtonian whose combined optical quality of primary and secondary mirror is in excess of lambda/53?
Is there anyone out there with a Catadioptic Telescope whose combined optical quality of primary, secondary, corrector plate and star diagonal is in excess of lambda/53?

Most importantly is there anyone out there with an eyeball that is close to lambda/53 and also with the ability to detect optical errors at lambda/53?

Truth is unless you satisfy both the telescope criteria and the eyeball criteria you won't see a difference. I know some very skilled observers with some very high end equipment and I don't know anyone who can satisfy both criteria. Consequently, I rate that review as being worth what it cost me to read it, "ZERO". I let my own eyes and telescopes do the analysis for me.

Cheers,
John B

[WilliamPaolini]

John,

Excellent points. I would only modify your contention and not that all magazine reviews are bad, but more than one should never take an assertion, or study or review, at face value of the conclusions. To get to the truth of the matter, as you showed, is to dive deep and assess the raw data like you did. Certainly interesting that any component that tests as lambda/53 would get anything other that a perfect rating. I would say that anything over lambda/30 would get a perfect rating. Better than that is in a does not matter category IMO.

[N1 (Mirko)]

Originally Posted by ausastronomer

I let my own eyes and telescopes do the analysis for me.

Best approach IMHO. Although I do wonder whether an otherwise negligible error may become relevant in a situation where several errors of the system compound. Or would that be more like a weakest-link scenario where the worst part determines overall performance?

In any case, this is why I like refractors:

Originally Posted by ausastronomer

Is there anyone out there who owns a refractor with a combined optical quality of objective and diagonal in excess of lambda/53?

Unlike with the other systems, you can throw away that mirror and overall performance improves.

[PlanetMan]

Originally Posted by ausastronomer

Let me throw a cat amongst the pigeons and make that magazine review worthless

Here is an extract from a post I made on Cloudy Nights regarding that very same review a couple of months ago.

The laboratory tests were conducted by a French Astronomy magazine with whom Televue is one of their major advertising contributors. Pentax on the other hand does not advertise its astronomy products outside Japan.

I have seen countless product reviews conducted by astronomy magazines over the past 40 years and very few of them have portrayed their major advertisers products as inferior to non advertisers products. That's just business. There are some exceptions to this and there has been a previous exception in this magazine. Would the publisher let Televue run second twice in an eyepiece review? Food for thought.

When I read that the overall scores from those tests were that the 10mm DELOS scored 16/20; and 10mm PENTAX XW scored 12/20; I though hmmmm !!! that's pretty amazing, the 10mm DELOS is a 33% better eyepiece than the 10mm PENTAX XW. That wasn't consistent with my experience based on extensive use of both eyepieces and with my extensive use of the 6mm DELOS and 7mm PENTAX XW.

I decided I needed to delve a bit deeper into the accuracy and basis of those laboratory tests.

Here are some very pertinent facts in regard to those laboratory tests.

1) The tests were conducted at F3.5 and at F7. Coma correction was not used in determining the results at F3.5. In the tests at F3.5 the 10mm TV DELOS outpointed the 10mm PENTAX XW, by quite a margin. Only problem here is I don't know anyone who uses a telescope faster than F4 that it is not a large aperture Newtonian and all of the large aperture Newtonian users that I know always use a paracorr at anything faster than F4; 95% of them use a paracorr in any Newtonian faster than F5. So I rate the testing at F3.5 without a paracorr absolutely pointless. Testing at F7 and maybe F4.5 would have been much more realistic and meaningful. If we remove the test results at F3.5 the overall result of the tests are much different.

2) Lets look at some of the specific optical tests

The one which tests optical quality on axis at F7 in red light is interesting. In this test the 10MM DELOS tested at lambda/109 and rated 5/6; whereas the lowly 10mm PENTAX XW only tested at lambda/53 (what a lemon). The same on axis test in green light showed the 10mm DELOS at lambda/133 with a 6/6 rating and the lowly 10MM PENTAX XW rated 4/6 at lambda/86 (what a lemon). Lambda / 53 was the worst on axis optical performance of the 10MM Pentax XW. Dayyam dud eyepiece !!

Now this poses an interesting situation.

Is there anyone out there who can detect the difference in optical performance between either of these eyepieces, in red light and green light?
Is there anyone out there who owns a refractor with a combined optical quality of objective and diagonal in excess of lambda/53?
Is there anyone out there with a Newtonian whose combined optical quality of primary and secondary mirror is in excess of lambda/53?
Is there anyone out there with a Catadioptic Telescope whose combined optical quality of primary, secondary, corrector plate and star diagonal is in excess of lambda/53?

Most importantly is there anyone out there with an eyeball that is close to lambda/53 and also with the ability to detect optical errors at lambda/53?

Truth is unless you satisfy both the telescope criteria and the eyeball criteria you won't see a difference. I know some very skilled observers with some very high end equipment and I don't know anyone who can satisfy both criteria. Consequently, I rate that review as being worth what it cost me to read it, "ZERO". I let my own eyes and telescopes do the analysis for me.

Cheers,
John B

Are you professionally fluent in French or at least had the review read to you via someone who is professionally fluent in French?

I don't mean common conversational French or internet translations

[ausastronomer (John Bambury)]

No I am not, but why do I need to be? Please enlighten me if something in the text, or commentary makes anything I have said above, or below incorrect, or that my assessment of that review, as being pretty useless from the point of view of an amateur astronomer, incorrect.

Having spent quite a bit of time with both the 10mm Delos and the 10mm Pentax XW and with the 6mm DELOS and the 7mm Pentax XW, in several different telescopes, I have had enough time to form a pretty accurate assessment on how both series of eyepieces perform in the real world, under the stars, in an amateur astronomers telescope, as perceived by an experienced amateur astronomy. I do own both. The differences between them are very subtle at best. In some criteria the Delos is best, in some others the 10mm Pentax XW is best. One is not a 16/20 eyepiece and the other a 12/20 eyepiece. You can take that to the bank and cash it in.

50% of the testing was done at F3.5. Less than 5% of the telescopes in use by the amateur astronomical community are faster than F4. So why test at F3.5 when 95% of the amateur astronomical community don't go there and never will.

The optical differences were differentiated at > lambda / 50. I don't know anyone with telescopes, eyeballs, or ability good enough to take advantage of that, or to pick a difference at an accuracy > lambda / 50.

Cheers,
John B

[PlanetMan]

Originally Posted by ausastronomer

No I am not, but why do I need to be? Please enlighten me if something in the text, or commentary makes anything I have said above, or below incorrect, or that my assessment of that review, as being pretty useless from the point of view of an amateur astronomer, incorrect.

Having spent quite a bit of time with both the 10mm Delos and the 10mm Pentax XW and with the 6mm DELOS and the 7mm Pentax XW, in several different telescopes, I have had enough time to form a pretty accurate assessment on how both series of eyepieces perform in the real world, under the stars, in an amateur astronomers telescope, as perceived by an experienced amateur astronomy. I do own both. The differences between them are very subtle at best. In some criteria the Delos is best, in some others the 10mm Pentax XW is best. One is not a 16/20 eyepiece and the other a 12/20 eyepiece. You can take that to the bank and cash it in.

50% of the testing was done at F3.5. Less than 5% of the telescopes in use by the amateur astronomical community are faster than F4. So why test at F3.5 when 95% of the amateur astronomical community don't go there and never will.

The optical differences were differentiated at > lambda / 50. I don't know anyone with telescopes, eyeballs, or ability good enough to take advantage of that, or to pick a difference at an accuracy > lambda / 50.

Cheers,
John B

Thanks Ausastronomer - Just wanted to confirm your level of French literacy

[ausastronomer (John Bambury)]

My French Literacy is actually pretty poor.

My ability to use google translate is pretty good. Good enough to know what criteria was being assessed. I don't need to know French to assess the numbers.

My ability to assess the optical quality of telescopes and eyepieces is very good. Over a lot of years I have used and owned some of the best of both that money can buy. I would say a lot more than most. That includes refractors up to 15" aperture and Newtonians to 36" aperture. Looking at the number of eyepieces and other pieces of astronomy equipment you have sold, or wanted to buy on icetrades over the past few months, you seem to spend more time buying and selling it than you do using it

And the relevance of my inability to read French fluently having regard to the comments I have made is ?


Cheers,
John B

[AG Hybrid (Adrian)]

..and in summary. If you already own a Delos or Pentax XW, don't sell them to finance DeLite's, as they are about as good as it gets. The end.

[MortonH]

Originally Posted by AG Hybrid

..and in summary. If you already own a Delos or Pentax XW, don't sell them to finance DeLite's, as they are about as good as it gets. The end.

Unless you need something that is half the weight of those two.

[SkyWatch (Dean)]

I just saw this interesting thread, and thanks Bill for your excellent review that started it all. The DeLites certainly look like a great alternative- just a pity that the exchange rate has blown their price here up so much! If purchased in Aust they are currently $100+ more than the LE's...

Reviews are by nature subjective, and even if you are using scientific measurements on an optical bench, I believe the true test is how the equipment performs in the real world. In this case direct comparison of several eyepieces in the same telescopes (3 in fact) can give a pretty good idea of real-world performance, and is I believe a very valid way of reviewing.

However, because we are all different, we like some things better than others. I remember a number of years ago trying the 19mm Panoptic after various reviews rated it as one of the best eyepieces ever made: but for me it gave poor, distorted views and I ended up swapping it for a 18mm Radian. Likewise, I much prefer a 60-70° view than a 100° where I have to move my head around to see the edges and jam my eye onto the eyepieces, whereas some of my colleagues love the 100's...

So, a review by someone else is a guide, and can be a very good one- especially if that person has no axe to grind for a particular manufacturer.

Having said that, can I make a plea for polite, well-considered responses? I don't think it is ever appropriate in a forum like this to make denigrating comments about someone else's efforts. We can disagree without impolite put-downs.

Thanks again Bill for taking the time and effort to help the rest of us make better informed decisions about a not-inexpensive piece of equipment.

- Dean

[WilliamPaolini]

However, because we are all different, we like some things better than others. ... So, a review by someone else is a guide, and can be a very good one- especially if that person has no axe to grind for a particular manufacturer.

Dean,

You are 100% correct in what you say. There is a personal preference component to all equipment we use. As a result one person can think it is the cat's meow and another hate it. So that aspect of any review one just can't tell. For me, I try to get to know the reviewer by reading between the lines of their writing to glean out their personal preferences on things...it is usually not so hard to tell. So then I can determine how close that reviewer may be to me in personal preferences...then I can give a review more or less weight as it may apply to me. But there are aspects of these field tests that are not personally driven, especially how sharp the off-axis performs in various scopes. So they in the end are a mix of performance facts and performance preferences. More up to the reader to dissect it properly, separate items, keep what is relevant and discard what they don't care or agree with. So the reviewer only gets us half way there, up to the reader to finish the analysis based on what was presented. At least this is how I proceed when readying reviews. Always have a grain of salt handy too

[SkyWatch (Dean)]

Thanks for the thoughts Bill, - and well said.

[Profiler (Profiler)]

Originally Posted by AG Hybrid

..and in summary. If you already own a Delos or Pentax XW, don't sell them to finance DeLite's, as they are about as good as it gets. The end.

Its amazing all the different directions this thread has gone.

To me I thought this and the other DeLite thread originally stemmed from a comment about good quality orthos and when the variables of AFOV and ER are excluded most orthos can outperform most Televue eyepieces and yet will cost a 3rd of the price.

[bytor666]

Won't be selling off my XW's for these.

Nope.

[WilliamPaolini]

Originally Posted by bytor666

Won't be selling off my XW's for these.

Nope.

Neither will I. But I sure will be purchasing some when the shorter focal lengths come out to supplement my XWs with improved planetary capability.

[bytor666]

"Improved planetary performance"

Well, first this has to be proved. I've been told other certain eyepieces do this as well, and tried them. Can't say I saw any improved performance at all, plus 62 degrees compared to 70 won't be cutting it for me.

[WilliamPaolini]

Originally Posted by bytor666

"Improved planetary performance"

Well, first this has to be proved. I've been told other certain eyepieces do this as well, and tried them. Can't say I saw any improved performance at all, plus 62 degrees compared to 70 won't be cutting it for me.

Definitely not a "replace" option for me...why I specified it as a supplement. As far as proving, well each of us needs to prove it individually. The reason is that we all have different optical chains and the optical chain will very much affect whether planetary performance of a particular component, like an eyepiece, will be of impact. So a complete optical chain is like any complex multivariate system, and different components will have different sensitivities to the outcome depending on the exact contribution/specifications of individual components.

In my case, I optimize my optical chains as much as possible specifically for planetary observing, and for me I have very much proven the DeLites best the XWs. XWs are good in this respect, but it is not difficult to best best them on planetary IMO. A good quality Ortho will and a top tier Ortho does it with ease (i.e., ZAO level). So in my optical chain, the DeLites were performing as good if not a touch better than the "good quality Ortho" level, so I want them on hand as a comfortable alternative to a level better performance than my XWs on planetary. But for DSO work noting trumps AFOV IMO so XWs are going no place...just having a few friends added when the come off the production line

[Profiler (Profiler)]

Personally I think people get carried away far too much in debating supposed inferiority/superiority of different eyepieces/eyepiece designs and overlook the obvious confounding variable to everything which is the significant variance in the performance of the human eye and individual differing eyes we all have.

From a medical perspective a lot of the supposed benefits/improvements are seldom tangible (non-significant) due to this issue. So, in essence everyone should work on "the lowest common denominator" principle. This is why I agree with the proposition that reasonably good ortho eyepiece will be just as good or better than most Televue eyepiece and will cost about a third of the price.

However, I must stress that this tenet -does not - does not - account for the benefits Televue eyepieces do provide in terms of AFOV and ER

[WilliamPaolini]

Originally Posted by Profiler

However, I must stress that this tenet -does not - does not - account for the benefits Televue eyepieces do provide in terms of AFOV and ER

I agree. This is very true. If all one looks at is the central 40 degrees of AFOV than a *good* Abbe Ortho is as good as just about anything out there...excepting a better Abbe of course But I think this trivializes the importance of AFOV and ER. IMO Optical Performance, ER, and AFOV all come bundled like three legs of a stool. Cut any one leg off and you potentially have a "specialty" stool. So when people ask advice or there are discussions, all three really have to be considered and weighed together as it is the whole package that is required for observing.

I have wide fields with nice ER, and I have *good* Orthos. When I try to observe with just the Orthos, after a few sessions I try a wide field and realize well why I would not want to be stuck with just Orthos as my observing eyepieces. Then when I observe with just wide fields, after a few sessions that involve lunar and planetary, then I realize why I would not want to be stuck with just wide fields. In my course I have realized that for me, they compliment each other rather than compete. The DeLites though, are IMO the first eyepiece that seemingly *starts* to bridge that gap.

[N1 (Mirko)]

Originally Posted by WilliamPaolini

I agree. This is very true. If all one looks at is the central 40 degrees of AFOV than a *good* Abbe Ortho is as good as just about anything out there...excepting a better Abbe of course But I think this trivializes the importance of AFOV and ER. IMO Optical Performance, ER, and AFOV all come bundled like three legs of a stool. Cut any one leg off and you potentially have a "specialty" stool. So when people ask advice or there are discussions, all three really have to be considered and weighed together as it is the whole package that is required for observing.

I have wide fields with nice ER, and I have *good* Orthos. When I try to observe with just the Orthos, after a few sessions I try a wide field and realize well why I would not want to be stuck with just Orthos as my observing eyepieces. Then when I observe with just wide fields, after a few sessions that involve lunar and planetary, then I realize why I would not want to be stuck with just wide fields. In my course I have realized that for me, they compliment each other rather than compete. The DeLites though, are IMO the first eyepiece that seemingly *starts* to bridge that gap.

Bill, while I quite like your review and would consider it valuable to anyone considering these EPs, I respectfully disagree with your chair/stool analogy. I can't see how ER and AFOV could possibly be of the same importance as optical performance. Rather, I'd class the latter as the legs and seat of the chair, with eye relief and apparent field of view corresponding to things like armrests, padding, heating coils in the seat, social media connectivity of the seat and so on - you get the idea. Omit optical performance - the legs and the seat - and the whole thing is all but useless. The same is not true for the other two things.