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12mm Radian & 12mm Pentax XF

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#1 asaint

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Posted 22 April 2006 - 04:46 AM

12mm Radian & 12mm Pentax XF

#2 Patrik Iver

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Posted 22 April 2006 - 06:42 AM

This is about the most comprehensive (yet logical and easily followed) EP review I have ever seen.

I very much appreciate the test with (sun)glasses, as so many peolpe not needing eyeglasses skip this (to me) quite important aspect.

Makes me consider to get a pair of 12 mm XF's for my binoviewer.

Good job!!!

#3 suburbanskies

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Posted 22 April 2006 - 08:43 AM

Wow, this is the most thorough and credible eyepiece review I've seen! I'm convinced now that there really are differences among eyepieces on deepsky objects.

:goodjob:

Mark

#4 Starman1

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Posted 22 April 2006 - 09:10 AM

Amalia's review is quite thorough and I think she investigated just about every characteristic of these two eyepieces in order to point out their differences.
Because they are the same focal length, her resolution test had validity.
And I note that neither eyepiece had any appreciable pincushion distortion, which would make both appropriate for spotting scope use, or in panning through star fields.
I look forward to her comparisons (if she does any more, given how much time she spent on this one) of other eyepieces.
Good job.

#5 darkskyfarm

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Posted 22 April 2006 - 09:14 AM

Wonderful review! It should set a standard by which others are rated - very meticulous yet a "smooth" read.

I was hoping someone would tackle one on the Pentax XF. I had considered buying one but I couldn't find one to look through at a star party or even a review.

Thanks for the hours and effort spent. Please write some more.

John

#6 Sgt

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Posted 22 April 2006 - 10:09 AM

Amazing! Never seen such a thorough and painstaking review! Especially appreciate the effort to invent(!) your sharpness test... perhaps, we could have a standardised chart for testing sharpness so that others can use your method?

#7 Cosmosphil

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Posted 22 April 2006 - 11:19 AM

Amalia,
I think you have set up a very nice template for eyepiece reviews. Everthing was covered and yet was entertaining and informative.
I am a bit shocked at the lack of contrast you saw with the Radian. It was opposite of what you would have expected.
My guess would be that it was designed as more of a "planetary/lunar" unit rather than deep sky. Still, you would have thought the differences on that part would have been minor. The Pentax would not be so suprising as they are known for their excellent coatings and contrast.

#8 MikeRatcliff

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Posted 22 April 2006 - 12:09 PM

Amalia, that is the best eyepiece review I've seen.

I especially enjoyed the contrast portion and the drawings of M104. (How many eyepiece reviews have sketches too?)

I see Pentaxs in my future.


Mike Ratcliff

#9 miniventures

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Posted 22 April 2006 - 12:54 PM

Kudos to you, Amalia. This is a great report! Your results surprised me some. Thank you.

#10 Joe Ogiba

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Posted 22 April 2006 - 04:06 PM

Wow, what a great eyepiece review Amalia. I might have to get a pair of 12mm Pentax XF's for my binoviewer.

Joe

#11 Amalia

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Posted 22 April 2006 - 04:41 PM

Thank you, Don, Patrik, Larry and Joe! :)

Amalia

#12 dgs©

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Posted 22 April 2006 - 04:41 PM

Nice job Amalia. :waytogo:
Thank you for all the effort you put into it. Very informative.

#13 Amalia

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Posted 22 April 2006 - 04:42 PM

Wow, this is the most thorough and credible eyepiece review I've seen! I'm convinced now that there really are differences among eyepieces on deepsky objects.

:goodjob:

Mark



Mark, yes, there really are differences among eyepieces regarding
performance on deep sky objects. One question which remains open
to me is the following:
"How much are these differences among eyepieces to be noticed
under a, let's say, a sky of less than 5 mag?"
I will try to find out while doing my next eyepiece review.

Amalia

#14 Amalia

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Posted 22 April 2006 - 04:44 PM

Wonderful review! It should set a standard by which others are rated - very meticulous yet a "smooth" read.

I was hoping someone would tackle one on the Pentax XF. I had considered buying one but I couldn't find one to look through at a star party or even a review.

Thanks for the hours and effort spent. Please write some more.

John



John, I have everything ready to continue and to write a new review,
only weather is not cooperating, but that is normal here at this time
of the year. It will take me two to six months to find everything out.

Amalia

#15 Amalia

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Posted 22 April 2006 - 04:46 PM

Amazing! Never seen such a thorough and painstaking review! Especially appreciate the effort to invent(!) your sharpness test... perhaps, we could have a standardised chart for testing sharpness so that others can use your method?



Sgt,
on the review's picture of the pattern sheet you can read:
"Personal and educational use supported."
Send me a PM with your address and I will send you a laminated
copy plus one original print for your personal tests/researches.

To standardise it will be difficult, as there are many variables, such as:
- focal length of scope
- focal length of eyepiece
- distance scope - test patterns
- visual acuity of the tester

Determining sharpness was even with these patterns not really easy.
I think the pattern sheet's real advantage is the ability to measure
on-axis and off-axis sharpness and to put them into an easier
understandable relation, as I tried in the diagram.
I have chosen this procedure:
"Focus in center and measure, then measure at 50%, and at the
border of the FOV without refocusing."

German CNer Sven Wienstein proposed a probably even better procedure:
"Focus in center and measure, refocus at 50% and measure, refocus at
the border and measure"
to find out about *only the field curvature*.

Unfortunately I have not been able to try his procedure (due to an awfully
tenacious flu). But I will try during the next tests with other eyepieces.

Amalia

#16 Amalia

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Posted 22 April 2006 - 04:49 PM

Amalia,
I think you have set up a very nice template for eyepiece reviews. Everthing was covered and yet was entertaining and informative.
I am a bit shocked at the lack of contrast you saw with the Radian. It was opposite of what you would have expected.
My guess would be that it was designed as more of a "planetary/lunar" unit rather than deep sky. Still, you would have thought the differences on that part would have been minor. The Pentax would not be so suprising as they are known for their excellent coatings and contrast.



Phil,
sometimes I call the stuff I write "infotainment", by this I mean:
"Informations together with entertainment". After all this is a hobby --
and it was fun doing these researches. :)

After the first comparison with galaxies, driving home, I shook my head
in the car and exclaimed: "This can not be possible!". I have not expected
such a contrast difference myself. But I have re-tested it and re-re-tested.
Amazing, really. You are probably right, the Radian must have
been designed for planetary and lunar work.

Amalia

#17 Amalia

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Posted 22 April 2006 - 04:52 PM

Amalia, that is the best eyepiece review I've seen.

I especially enjoyed the contrast portion and the drawings of M104. (How many eyepiece reviews have sketches too?)

I see Pentaxs in my future.


Mike Ratcliff



Mike,
I think you own Celestron Ultimas and TV Plössls. I reveal you
"a secret" now: I intend to compare 2 widefield eyepieces and a Baader
Eudiascopic (same as the Celestron Ultima) and a TV Plössl.
If you are patient enough, I will be able to tell you more later. As written
before, this will take me two to six months, as I want to be as sure as
possible about my results.

Amalia

#18 Amalia

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Posted 22 April 2006 - 04:53 PM

Nice job Amalia. :waytogo:
Thank you for all the effort you put into it. Very informative.



Thank you for your nice words, David! :)


Many, many thanks to Allister and Mike of CN for all the work you had by
converting my document into a readable text. Next time I will not use
AppleWorks anymore, but as you told me, OpenOffice!
Thank you so much!

Amalia

#19 spaceydee

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Posted 22 April 2006 - 05:03 PM

Amalia, you obviously put a lot of effort into this review. Well done!

#20 Amalia

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Posted 22 April 2006 - 06:37 PM

Amalia, you obviously put a lot of effort into this review. Well done!


Thank you, Dee!

Amalia

#21 Amalia

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Posted 22 April 2006 - 06:44 PM

I have been asked in a PM about many things about eyepieces...

I thought my answer could be interesting you:

So many questions... Now that I have started to do this work so
precisely, I am hesitant to say anything which is not checked
three times...

But I will try all the same:

I like the XWs very much. To me they are the best widefield
eyepieces for galaxy/DSO observers. But the 14mm and the 20mm
XWs show some field curvature. Not the 10mm, 7mm, 5mm and 3.5mm.
Besides, the XWs are the most comfortable eyepieces around.

I think Naglers are great to give that space-walk-feeling together with
a nice corrected field of view, but they vary a lot in transmission,
depending on the type:
During my comparison I realized that, only regarding contrast on galaxies
(or transmission), the 12mm type 4 Nagler was showing a better transmission
than the 13mm type 6 -- noticeably better.

But... there is even better than XWs or Naglers: very good orthos!


I'll try to help you with these links. They are from the San Diego Astronomy Association,
two members made a lot of eyepiece shootouts -- shorter evaluations, but they made
them by two persons:

http://www.sdaa.org/...er.currentissue

Down on the page, on the left, you'll find a little box to chose the older newsletters:

May, 2002: 10mm Radian vs. 10.5mm Pentax XL
June, 2002: 12mm Radian vs. 12mm Nagler t 4
July, 2002: 18mm Meade 4000 SWA vs. 18mm Radian vs. 19mm Panoptic
August, 2002: 35mm Panoptic vs. 31mm Nagler t5
September, 2002: 27mm Panoptic vs. 26mm Nagler t5
December, 2002: 21mm Pentax XL vs. 22mm Vixen Lanthanum vs. Panoptic vs. 22mm Nagler t4
January, 2003: 24.5mm Meade 4000 SWA vs. 24mm Panoptic
February, 2003: 14mm Meade 4000 UWA vs. 13mm Nagler t6
March, 2003: 7mm Pentax XL, 7mm Nagler t6, 6.7mm Meade 4000 UWA
April, 2003: 22mm Nagler t4 vs. 20mm Nagler t2
August, 2003: 17mm Nagler t4 vs. 16mm Nagler t5
September, 2003: 8.8mm Meade 4000 UWA vs. 9mm Nagler t6
October, 2003: 5mm Radian vs. 5mm TMB Supermono
November, 2003: 15mm Panoptic vs. 14mm Pentax XL
December 2003: 22mm Nagler t4 vs. 20mm t5

More about the Pentax XWs you will find in:
-- CN's Eyepiece Forum
-- Best Of
-- (scroll down) Eyepiece Profiles
-- Pentax XW
or simply click here

Here I have collected all reviews I could find about the XWs -- but also about some
other eyepieces -- hey, I am not payed by Pentax!! ;)

Please remember that I think there is no "best eyepiece". It depends what you expect,
it depends on your favorite observation objects, personal needs (eyeglasses) etc. etc.

Have fun! :)

Amalia



#22 Psa19one

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Posted 23 April 2006 - 08:42 AM

Absolutely outstanding. Thank you, Amalia!

#23 jack45

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Posted 23 April 2006 - 09:15 AM

Amalia

I've had most of the Radian,UO eps and find the 5.2mm XL,7mm,10mm,14mm and 20mm Pentax XW to be the best for detail viewing! Now I just need to get the 40mm Pentax XW or XL if I can get it! Great information and were glad your back with us!


Clear Skies!

#24 F.Meiresonne

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Posted 23 April 2006 - 10:36 AM

Amalia,

What a great review, very complete and very thoroughly.
Never read one like that....

I am starting to look for a good 'galaxy ep'. Seems that the pentax XF could be the way to go...

#25 suburbanskies

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Posted 23 April 2006 - 01:30 PM

Wonderful, please do. For many of us, this is the more practical question. Thanks in advance for doing the hard work for us! :grin:

Mark, yes, there really are differences among eyepieces regarding
performance on deep sky objects. One question which remains open
to me is the following:
"How much are these differences among eyepieces to be noticed
under a, let's say, a sky of less than 5 mag?"
I will try to find out while doing my next eyepiece review.

Amalia




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