Borg
Astrographic
Systems
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One of the fundamental cornerstones of Borg's
scope designs has been excellence in performance
as astrographs - high-performance objectives
combined with uniquely high-performance flattener/reducer
elements, specially designed for imaging.
The latest in
this line of astrographs are a family of five systems optimized
for digital imaging:
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- 45EDII F4.7 (Mini Borg)
- 60ED F3.8 (Mini Borg)
- 77EDF4.3
- 101EDF4.1
- 125SDF3.9
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The 77/101/125mm Borg astrographs utilize the new
4-element ED super reducer (components shown at left),
which is optimized for full 35mm-sized digital imagers.
These astrographs also include built-in filter holders as well
as a camera rotator for flexible image composition.
Borg helical focusers are standard, but motorizable Feather
Touch focusers are an option. |
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The Mini Borg astrographs incorporate the 0.66x Triplet
Super Reducer [7866],
optimized for APS-sized sensors.
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Focal reducers are optimized for specific distances
between the optical components and the image plane.
For the F4 focal reducer, these are accomplished through
the use of calibrated spacers for specific focal lengths.
Two 63mm diameter spacers are provided for the front (between
focuser and front reducer lens assembly), and two 58mm diameter
spacers for the rear (between the rear reducer lens assembly
and the camera adapter):
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Scope |
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Front Spacer |
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Rear Spacer |
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Borg 76ED/77ED/77EDII or equiv. 500mm FL scope |
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(None) |
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2mm thick |
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Borg 100ED/101ED or equiv. 640mm FL scope |
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(none) |
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1mm thick |
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Borg 125EDF6.4 or equiv. 800mm FL scope |
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2mm thick |
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(none) |
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Borg 150ED or equiv. 1000mm FL scope |
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4mm thick |
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(none) |
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Camera Configurations (attached to F4 reducer):
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SLR cameras: [Borg camera adapter*] - [SLR camera body]
* The following camera mounts are not compatible with
the F4 reducer because of insufficient internal diameter:
Pentax S (#5001), Minolta MD (#5006), Olympus OM (#5008) and
Four Thirds (#5010)
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SBIG STL Cameras: [M49.8-STL] - [STL Series Camera]
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Starlight Express Cameras:
[7920] -
[7601]* -
[7601]* -
[7522] -
[SX Series Camera]
* Two 7601 parts are required to reach the required distance
for Starlight Express cameras
Contact Hutech for configurations with other camera systems.
Filter Attachment
Provision for the attachment of filters is via a a 55mm diameter
filter thread on the front reducer lens assembly (for semi-permanent
filter installation) and via an easily removed filter holders
which accomodate 52mm or 48mm filters.
A camera shutter cable can be attached to the focal reducer assembly
to make removal of the filter holder a simple operation which does
not disturb the optical train. Additional filter holders
[7518] are
available for quick changes between filters.
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Optical Performance Plots:
Click on images to enlarge
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Mini Borg 45EDII F4.7 |
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Borg 77EDF4.3 |
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Borg 101EDF4.1 |
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Borg 125SDF3.9 |
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Physical Data:
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45ED F4.7
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60ED F3.8
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77ED F4.3
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101ED F4.1
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125SD F3.9
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| F.L. (mm) |
210
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230
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330
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410
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490
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| Weight (kg) |
0.6
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0.8
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1.7
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2.3
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4.5
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| Length (mm) |
230
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270
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350
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520
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680
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Samples:Click on images to enlarge
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Borg 101EDF4.1: Veil Nebula shot with Canon 5D full-frame DSLR
with LPS-V3-52 nebula filter - 8 x 10 minutes @
ISO 800 |
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Full size (4368x2912) unprocessed Canon 5D frame
of Veil shot [2.7MB jpeg]
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Borg 77EDF4.3: IC1848 and IC1805 shot with Canon 5D full-frame DSLR
with LPS-V3-52 nebula filter - 8 x 10 minutes @
ISO 800. |
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Borg 101EDF4.1: Witch Head nebula shot with Canon 5D full-frame (cropped) DSLR
with Type Ia fiter - 16 x 10 minutes @ ISO 800. |
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Borg 101EDF4.1: NGC1333 region photographed with SBIG ST11000 - 8 x 10 min. luminance and 5 x 6 min. for each color (RGB). |
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