APM 2 inch coma-correcting telecentric 1.5x Barlow
by the well known physicist and optic designer Philipp Keller
About 2 years ago APM Telescopes introduced the coma-correcting 2.7 times Barlow designed by Gerd Duering, which enjoys great popularity.
When our customers asked for a 2 inch version with a smaller magnification factor APM Teleslescopes let the well known physicist and optical designer Philipp Keller calculate a new 1.6x Barlow.
All of today's knowledge was incorporated to optimize the optical design. The telecentric design prevents that the distance has to be individually adjusted for each eyepice. Just insert the eyepiece into the optional 2-inch adapter sleeve and automatically have the optimum distance. The other special of this Model is again the same super high quality as the 2.7 model, the manufactur is the same specialist optical company. So expect a worldclass high end opticla quality.
As already for the Barlow by G. Duering the design was calculated to yield a large back focus, in order that it can be used as an optical glass path corrector with coma-correcting effect combined with binocular viewers.
The large back focus allows the use of an off-axis guider + filter + CCD to take photographs with full format chips.
magnification 1.5 x
M54 x 0.75 male thread and M48 x 0.75 female thread (eyepiece/CCD side)
telecentric design with 4 lenses
works as optical path corrector 1.6 x for bino-viewers
large imaging field for full format chips
outward focus shift: 96 mm
Optical design:2 achromatic lenses ( 2 + 2 lenses = 4 lenses )
Backfocus:105 mm (from centre last lense)
Fully corrected field:44 mm
Fully illuminated field:44 mm
2 inch eyepiece holder
Our asking price for excport is Euro 370 include shipping which equals to about US $ 400
for those who want the very best of 2 worlds, we had Howie Glatter designed a 2" paralizer adapter, made by Starlight Instruments for APM, cost additional $ 100
by using my Tele Vue eyepieces , the backfocus changes only about 10 mm inwards against without use of the telezentric.
I have tested this Telezentric also at my 16" F/10 Mak, my LZOS 6"F/8 triplet Apo and my Takahashi FC100D and it works here also great without noticing degratation of performance at the edge, so it is a kind of allround performer