155mm f7 STARFIRE EDF APOCHROMATIC REFRACTOR ASTROGRAPH
WITH 4" FOCUSER AND 4" FIELD FLATTENER LENS
This 155mm f7 StarFire EDF (6.1" aperture) was designed to be the
ultimate astrograph while providing uncompromising visual performance.
Outstanding photographs published in Sky & Telescope, Astronomy and
various international astronomy magazines can only hint at the detail
of the original prints and negatives. The 30" x 40" prints of the Lagoon/
Trifid and Horsehead Nebulas that are on display in our showroom show
incredible pinpoint star images from one side of the print to the other with
no sign of image degradation. Truly amazing! Photographic spot
diameters measure 15-20 microns over a 5 degree field (4" circle). The
fast f7 focal ratio captures elusive and faint deep-sky objects easily with
incredible detail. This lens has outperformed mirror type astrographs
twice its size, as we had predicted.
The EDF is superb as a visual instrument as well. It is easily capable
of high-power observations of the moon and planets. Secondary
spectrum is nearly absent at any power. Deep-sky views are equally
impressive due to the very high transmission of the three glass types.
In the astrographic configuration, the lens is a 5-element design in 2
groups (3 elements in front, 2 in rear). The heart of the front triplet
apochromatic lens is an ED glass and 2 crowns. This combination
totally eliminates all secondary spectrum, coma and spherical
aberration. The rear lens is a 2ement field flattener that eliminates
astigmatism and field curvature. In the visual configuration, the rear
2-element lens is removed and replaced with a standard visual
adapter. This adapter allows all our usual accessories to be
attached, as well as all standard 2" and 1.25" oculars.
The tube assembly comes fully baffled for a 5 degree 4" field. The
giant 4" focuser is silky smooth and can be locked for long
time-exposure astrophotography. Although it is possible to attach
your own custom-made film holder, we have determined that the
most practical camera back is the Pentax 6 x 7cm medium format
camera. Field coverage is 3 x 3.5 degrees. After 4 years of field
research, we've chosen this camera because it holds the film
critically flat without the use of special vacuum attachments. This is
not the case with other, less expensive film backs; the Pentax
allows the user to critically focus directly on the ground glass with a
high-power magnifier, assuring the highest possible resolution.
Another feature is the extra large opening and minimum back
distance to the film plane which minimizes the inevitable vignetting
of the light in the extreme corners of the format. All the important
color and black/ white films are available in the 120 format, which is
not the case with large formats. It is for these reasons that we have
standardized on the Pentax 6 x 7 and offer all the attachments
necessary to use with the 155mm EDF.
The Astro-Physics giant 4" focuser is truly versatile. The 4" ID of the
drawtube will allow maximum coverage of the Pentax 6 x 7 cm
negative for medium format photography. The inside of the
drawtube has a series of knife-edge baffles for maximum contrast.
When you wish to use your 35mm camera with the Astro-Physics
telecompressor for even faster exposures (f5.2), you can attach the
2.7" reducer and you are ready to go. The 2" and 1.25" adapters will
allow you to use all of our standard accessories to maximize your
visual and photographic applications.
||Less than 0.01% focus variation from 405nm to 706nm (r to h
||1085mm (43") efl
||0.74 arc second
||Multi-layer, overall transmission greater than 97% in peak
visual wavelengths see table at right
||20x to 600x
||White, 6.5" aluminum tube, baffled, flat black interior,
engraved push-pull lens cell
||4.0" I.D. Astro-Physics rack & pinion focuser, 4.5" travel,
2.7", 2" and 1.25" adapters, 2.5"
||41" (1,040mm) with dewcap fully retracted
||27 lbs. (12.3 kg)
||4" diameter 2-element with multi-coatings
||Foam-fitted, vinyl-covered plywood case
|Carrying Case dimensions:
||44-1/2 x 10.5 x 10.5 inches
|Carrying Case weight:
||15.5 lbs (7 kg)
|35mm Photographic field at prime focus:
||1.3 x 1.8 degrees @ f7
|35mm Photographic field with Telecompressor:
||1.7 x 2.4 degrees @ f5.2
|35mm Photographic field with 2x Barlow:
||0.6 x 0.9 degrees @ fl4
|6 x 7 cm Photographic field at prime focus:
||3.2 x 3.7 degrees @ f7
|Maximum Photographic Field:
||5 degrees, 4 inch circle
Left: Color correction of the Astro-Physics 155 mm EDF Apo telescope (69,285 bytes).
Click on image for higher quality, enlarged view (178,123 bytes).