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The new Leica ASPH zoom 17.6-8.8mm

Started by andydj5xp, 03/23/2009 02:18AM
Posted 03/23/2009 02:18AM | Edited 03/23/2009 02:53AM Opening Post
Two weeks ago I took delivery of my long (VERY long) awaited new zoom: Leica 25x-50x ASPH. The designation "25x-50x" refers to the available magnifications together with the Leica spotting scope's focal length of 440mm. I will call it 17.6-8.8mm. The designation "ASPH" refers to the aspheric lens(es?) employed. It is used with my TEC140 (f/7).

General:
- Body dimensions: 59mm/2.3" diameter, 89mm/3.5" body length (without barrel)
- weight approx. 400g/14oz
- twist-up eyecup (3 positions, 9mm difference)
- comfortable eye relief (18mm)
- smooth zoom-ring movement

Having been a fan of my Leica zoom 22-7.3mm for quite some years my expectations were rather high. My benchmark was this:

http://www.cloudynights.com/ubbthreads/showflat.php?Cat=&Board=Eyepieces&Number=2742856&Forum=,,,,,,All_Forums,,,,,,&Words=&Searchpage=3&Limit=25&Main=2742856&Search=true&where=&Name=3690&daterange=&newerval=&newertype=&olderval=&oldertype=&bodyprev=#Post2742856

Fortunately the skies were cooperative at the very first evening showing a 12 day's moon with fairly good seeing conditions. I did compare the new zoom against the ZAOII's and the old zoom at different focal lengths of 16mm, 10mm, 8mm, 6mm, and 5mm. The main target for the higher mags was crater Gassendi. As reported in the given link the old zoom and the ZAOII's again were so close that it wasn't possible to see differences. The new zoom instantly could be seen as being on par with both. But after the comparisons had been performed for more than one hour it even seemed to excede both for coming slightly better into focus, not by a large margin but repeatedly so. It kind of looked a tad "sharper" which I did interpret as being may be even more contrasty. At any rate: it can easily compete for contrast, definition, and absence of stray light. And of course it substantially surpasses the ZAOII's for its huge AFOV and its generous eye relief.

Last week the sun made for a very tough test target for stray light and ghosting. With a filtering of ND5 (100 000 times) the apparent brightness of the solar disk is still 1.6 magnitudes brighter than the full moon. Putting the sun just outside the field stop there could not be seen even the faintest glow. This is equal to the ZAOII's where the approaching solar disk can be seen already through the triangular cuttings without generating stray light within the field of view.

Saturn gave a very pleasing view with natural colors slowly drifting through the large field of view without the necessity to refocus. To conclude this little report: the double cluster looked magnificent at different magnifications displaying pinpoint stars up to the field stop. Finally, the E and F stars within M42 could equally easily be observed with both Leica ASPH zoom and the ZAOII's.

Pros:
- wide AFOV: 58.5° at 17.6mm up to 79.5° at 8.8mm
- virtually flat field (within my measurement uncertainty of 0.05mm)
- no astigmatism up to the field stop
- extremely sharp
- extremely high contrast due to complete absence of straylight and ghosting
- no eyeball reflections
- neutral color rendition
- parfocal
- no kidney beaning
- replaces three high quality eyepieces (even more with barlowing)
- barlows very well
- with a quality barlow lens element and extension rings it covers all focal lengths

Cons:
- expensive (800 Euros/1080 USD)
- 2"-adapter not yet available (I'm using a modified Baader adapter T2-#16)
- no click-stops (I don't need it: see below)

Summary:
Is it the "ultimate" eyepiece? For me: YES. For others as always: YMMV (or better: YMWV). Together with a premium barlow lens (Baader VIP Modular) and a two-stage scheme of adding extension rings I have 3 barlow factors of 1.5x, 2x, and 2.5x. Thus a focal range of 17.6mm down to 3.5mm gives me everything I would need. For widest TFOV I'm keeping my WO UWAN28 which gives incredible views with my TEC140 for having the same field curvature (approx. –380mm).

My UWAN16 and the old Leica 22-7.3mm zoom have been sold already, and eventually I will even sell my ZAOII's since I don't think them to be used often any more after – of course – much more comparisons. I haven't noticed any differences between them and my old Leica 22-7.3mm zoom within a period of 5 months – see link above - and again no differences between the ZAOII's and the new Leica zoom under favourable seeing conditions. OTOH due to the ease of use with this new zoom with its 18mm eye relief, large AFOV's and – most noticeable advantage – the possibility to zoom in and out it is vastly superior to fixed focal length eyepieces of narrow AFOV's and fairly short eye reliefs.

Another thought for observing no differences came from thoroughly reading the famous "6 mm Lunar/Planetary Eyepiece Comparison" by Bill Paolini. Paragraph 3 of his conclusions goes like this:
"3. Larger aperture instruments or brighter celestial objects are required to show significant differences between eyepieces. Many observing sessions demonstrated this, as reported in results sections of this comparison. This leads to the following sub-conclusions:

a. Planetary observations can yield significantly improved details using the highest ranked eyepieces in larger aperture instruments.
b. Lunar observations can yield significantly improved results using the highest ranked eyepieces even in moderate aperture instruments."

My 140mm aperture is way too small to comply with letter "a". But with lunar observations my scope should be able to yield different results – if there are any. As a final thought: may be my northern lattitude of 52.3° will make the neccessary seeing conditions rather unlikely. Anyway, I'm strongly tending to see no future use for the ZAOII's.


The attached picture gives an impression. From left: Zoom with 2"-barrel, barlow lens for 1.5x, 30mm T2-extension for 2x, 32mm T2-extension for 2.5x. The two combos 1.5x and 2x fit within the 2" eyepiece holder of my Baader Maxbright diagonal, the second extension will be placed outside the eyepiece holder. The white markings on the eyepiece body are little pieces cut from a nylon cable binder and glued onto small strips of transparent selfadhesive tape. They enable "feeling" the chosen magnification and are placed such that they give with my TEC140 mags of 60x, 80x, and 100x unbarlowed and the corresponding magnifications multiplied with the barlow factors.

Andreas



Attached Image:

andydj5xp's attachment for post 46187
Posted 03/23/2009 09:30AM #1
Hi Andreas

I used the same eyepiece at WSP 2009, but I have had to order as a Leica Dealer the eyepiece with the expensive Apo-Spotting scope, I was told by Leica they will not sell the eyepiece alone right now.

Did you have had to buy also the spotting scope or could you really buy the eyepiece standalone ? If yes in Germany ?

thanks
Markus

clear skies

Markus Ludes
APM-Telescopes/Germany
Posted 03/25/2009 05:36PM #2
BH Photo video shows it as "accepting orders", at 1100 bux.

http://www.bhphotovideo.com/c/product/597338-REG/Leica_41019_25_50x_WW_Aspherical_Eyepiece.html

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