Kasai Astroplan eyepieces?
Posted 27 December 2010 - 02:09 PM
Posted 27 December 2010 - 02:31 PM
Posted 27 December 2010 - 02:58 PM
I'm not sure by any means, but to me these look like perhaps the same design as the Tak LEs in 5mm, 7.5mm, and 10mm. Anyway, I always assumed these simply clones of the Tak LEs in the shorter focal lengths.
They can't be the same as the 7.5mm and 5mm Tak LEs because those two Taks are negative-positive designs that get longer (physically) with shorter focal length. My guess, rather, is that these were formerly the Celestron Ultimas of the same focal lengths.
Posted 27 December 2010 - 05:11 PM
Do you have a diagram of the Tak LE design? I've looked and looked and have never been able to find one.
Posted 27 December 2010 - 06:15 PM
At any rate, search anywhere for photos of the 5mm and 7.5mm Ultimas (was there a 10mm Ultima?) and compare to these Kasai eyepieces.
Posted 27 December 2010 - 06:48 PM
From telescope to eye, a negative doublet, a 10mm internal field stop, a plano-convex doublet (i.e. plano facing the field end), and a convex-plano (i.e. convex facing the field end) singlet. The eye lens surface seems to be very slightly convex, so the eye lens might be DCX, but that top surface is relatively flat. Appears to be fully multi-coated and the coatings look first rate (very black when looking straight on with a cap on the other end). The upper two elements were spaced by about, 3-4mm or so at the edge (less in the middle, obviously). Didn't measure the height of the spacer. The field stop is not very close to the positive group's field lens surface, and the upper retaining ring is beveled.
Roland mentioned that the design was basically a three element Ortho followed by a Barlow.
I emailed you your pics if you'd like to re-post them here.
Posted 27 December 2010 - 07:20 PM
Posted 27 December 2010 - 11:44 PM
Posted 28 December 2010 - 01:43 AM
Astroplan. Very similar to
"astroplanokular", the Zeiss-designed 5-element design also called "Super Plossl" by some, and made by Masuyama for years.
Since all those eyepieces come/came from Japan and most came from Kasai, I'm betting these are merely the same eyepieces without the familiar brand names:
Parks Gold Series
Tuthill Super Plossls
Meade Series 4000 Super Plossls
Posted 28 December 2010 - 09:54 AM
I can state they are not the same as meade 4000 super plossl. The plossl have a much tigher eye-relief.
Posted 01 January 2011 - 03:46 PM
The 5mm Celestron Ultima, like the 5mm Masuyama, but unlike the 5mm LE, 5mm Ultrascopic, etc., is a short, stubby eyepiece.
The 5mm Ultrascopic, for example, has 7 elements. The 5mm Ultima, in contrast, has 5. The pictured 5mm looks like the stubby Ultima and unlike the taller Ultrascopic and clones.
The 5mm Ultima is pictured in front:
The Orion is much taller, as is the Parks Gold Series version.
Posted 01 January 2011 - 05:45 PM
That meant you essentially got two eyepieces in one--a 10/5 couple or a 7.5/3.8 couple.
A few years later they started cementing them together so the barlow couldn't be removed from the eyepiece.
I had a complete set, and the barlow lens could be inserted in several of the eyepieces, not just the 10 and 7.5.
Most of the companies selling these eyepieces didn't have the shorter focal lengths as separate, 5-element, eyepieces because of the extremely short eye reliefs. Adding the internal barlows made the shorter focal lengths with the eye reliefs of the longer eyepieces, which were, in their own rights, already extremely short.
Posted 03 January 2011 - 06:10 PM
The eye-relief is a bit tight (stated as 8.5mm), but increased to a fairly comfortable level when the eyepiece was barlowed 2x.
This eyepiece gave wonderful views of Jupiter at 160x with a TSA-102. The image of the planet was sharp, even at the edge, but the planet suffered visible "stretching". Like and ellipse.
The eyepiece was tested as well, on two tight doubles - Alnitak and Eta Orionis. Both stars were split even at the edge of the field.
Overall, I feel this eyepiece is very good value.
Currently they sell in Europe for 100€, a +30€ premium over a 9mm volcano top kasai ortho.