No longer part of the collection
Focal length: 560 mm
Objective diameter: 100mm
Effective aperture: 96 mm (acc. to spec)
IPD: 50 – 80 mm
Focus type: IF
Focal ratio: f/5.6
Weight (measured, w/o eyepieces, with eyepiece cover and objective caps): 5‘670g
Made in: China
In 2018, Oberwerk of Dayton, Ohio, brought out two new instruments to the binocular telescope market: first a 100mm, followed a bit later by an 82mm BT, see separate post https://binocular.ch/oberwerk-bt-82xl-ed/ (and still a bit later, Oberwerk followed up with a slightly smaller 70mm model). Both feature ED glass, are available in grey or pearl white, are beautifully finished, and they compete head-on with similar instruments already in the market, e.g. from APM. Hobby astronomers will welcome this further offering. The 100XL is a bit lighter than the same size competitor from APM. Initial reviews in the astro communities are positive. The 100XL can easily be used with magnifications up to 80x; in very good seeing conditions, perhaps even higher magnifications can be used with good results. More recently, Oberwerk has added an “SD” version of this BT, which is more expensive, but offers supposedly even better CA performance and contrast.
Initial inspection: beautifully finished, mechanically impeccable. The BT came with two Oberwerk 14mm 70 degree eyepieces, providing 40x magnification (the Oberwerk 100-XL ED has 560mm focal length, f/5.6.
In the initial version of this BT, not all 1.25” eyepieces could be brought to focus. It is our understanding that later versions have been modified in this respect.
Spending an hour to use the BT at night. Two targets:
– the moon. Very little CA, very nice rendition of the moon surface, with – given the current phase – staggering details of Vallis Schroeteri, the Montes Agricola and the Agricola Straits (northwest of Aristarchus), at 40x and 63x (eps of 14 and 9mm).
– Mars: an almost perfectly round little disc (no surface details at BT magnification levels), probably better than I recall having seen it in other instruments, with no flares or other light structures around it. Really good.
The BT is not free from stray-light effects, but this will have to be explored further before coming to reliable conclusions.
The initial overall impression of the Oberwerk optics and mechanics is very positive.
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