APM APO Barlow > Coma-correcting design
Posted 19 January 2013 - 05:26 AM
come see and testing this superlative Barlow in February at the Winterstarparty in Florida
Designed by Gerd Duering / Germany
Due Forum discussions pushed, Gerd Duering in Germany designed a new, improved coma corrected ED-Apochromatic Barlowlens, optimized for parabolic mirrors with f-ratio f/4. But it works also as a super high quality Apo Barlow in any other normal Telescope.
This Barlow uses as ED-element the Chinese ED glas FK61 (similar to Ohara FPL51), the lenses are soft cemented and applied on both sides with a broadband multicoating with over 99 % transmission for wavelength from 400 nm to 700 nm.
The optimal backfocus is 105 mm from center of the last lens. The focal length of the barlow is - 62.9 mm, the clear aperture 22 mm.
This barlow offers with its 22 mm aperture in secondary focus a 100 % illuminated photo-visual field of 30 mm diameter when used with 105 mm backfocus.
The 2-part adapter is photo-visual optimized, visual with the optimal backfocus of 105 mm with the new APM-Deluxe Centering Brass-Clamp. This top Deluxe adapter has a length of 55 mm and can be unscrewed, than you get a photographic T2 thread (M42 x 0.75 mm) for use with DSLR with T2 adapter ring.
This Barlow increase the diffraction limited field of view and imaging circle of your fast newtonian and dobsion very much. Observe the planets in your eyepiece at a off axis position with identical image quality as in center of the eyepiece. Observe Double Stars at the edge of your eyepiece Field with same resolution as in center. Observe Galaxies and Planetary Nebulae and galaxie fields all over the eyepiece field with same sharpness. If you have a fast Dobsonian in which Gobuar clusters like M13 or Omega Centauri cover the full eyepiece field, see with this barlow the globular resolution towards the eyepiece edge with same sharpenss as in center.
The edge distorion even in modern Tele Vue eyepieces is reduced to a level you will not see in even 2,3,4 times more expensive barlowlenses.
To my knowledge it is worldwide the only 1 Barlowlens using a expensive ED Glas to archieve apochromatic correction.
First results with the ED-Barlow has been amazing!
1 1/4" ED-Barlow Element
Barlow-Element in screw in housing US $ 95 > in stock
Barlow with nice 2 pc eyepieceholder US $ 149 > in stock
we ship worldwide for $ 20 include insurance
Posted 19 January 2013 - 01:46 PM
Sounds impressive! How does it translate to magnification (2x, 3x, ??)?
Posted 19 January 2013 - 06:00 PM
But it works also as a super high quality Apo Barlow in any other normal Telescope.
Posted 20 January 2013 - 01:37 PM
Is Soft Cementing of lenses durable ?
Also, is the barlow both Barlow and Coma corrector at the same time or is there a barlow optical part which can be separated from the coma corrector optical part.
Is the Two pc eyepiece holder to enable using the barlow with both 1.25" and 2" eyepieces ?
Posted 22 January 2013 - 02:07 AM
the glas is a barlow and coma correcting lens at once, the doublet does both fuctions.
the dual adapter is dual because you can use it with 1.25" eyepieces or with DSLR or any other camera which has the T2 connection