Pentax 75 EDHF


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Brand and Model:Pentax 75 EDHF
Price ($USD):no longer availa
Type:Apochromatic Refractor
Attributes: un-checked Go-To un-checked PEC
Aperture:75mm (3")
f Ratio:f/6.7
Focal Length:500mm
Finder:6x30
Electric Power:
Mount:German
Tripod:
Weight (lbs):lbs.
Dimensions (w/h/d):
Description:

Vote Highlights Vote
Pentax 75 EDHF
The 75 EDHF was designed in the mid '80's and was an advanced optical design for that time. I bought one new in '86 for $870 with mount (and still have it).

OTA:
The OTA is 75mm x 500mm at f/6.7 containing three elements. An objective consisting of an air-spaced ED doublet and a rear "field flattener/reducer" mounted in front of the focuser. It was conceived with flat-field photography in mind. It is compact, lightweight (5.5 lbs/2.5kg) and solidly built. The optics are sharp, with good contrast, quite apochromatic and stand up well against some of today's small APO's that I have used (Taki, TMB) which is impressive for a design over fifteen years old.

FOCUSER:
The focuser is multi-segmented with a rather large ID for a small scope and quite smooth in operation. The draw-tube has a solid bat-handle locking clamp, three inches of focus travel, and is 60mm (2.37") inside diameter with lock screw for slip fit adapters. Into this goes an adapter, one end threaded for 58mm filters, the other terminating in 50mm inside threads. Into this screws an adapter which takes it down to 38mm/1.5" slip fit with locking screw. Into this fits the original high quality prism diagonal or straight-through eyepiece holder which take 0.96" eyepieces directly or Pentax Rear converters (Barlow's). The eyepiece holders are friction slip-fit without locking screws and not very convenient for changing eyepieces without jostling the mount. The straight-through eyepiece adapter also unscrew to attach directly to Pentax screw mount cameras. Both 2" and 1.25" adapters are currently available.

MOUNT:
The mount is solid and quite portable at 6kg/13lb. The tripod is a bit short, but not unreasonable for use by a normal sized person (over six-foot).
The mount has a unique polar alignment scope (with optional illuminator) that rotates with a date/time index. When set to the current sidereal date/time, a small circle indicates where Polaris should be for precise alignment.

ACCESSORIES:
A large assortment of adapters and accessories were available from Pentax.
Two optional RA only tracking drives were available, an AC powered synchronous unit without controller, and a 12vdc unit with hand controller and rechargeable 12vdc battery pack. The hand controller has 4x 8x and 16x forward and reverse RA speeds.
The Pentax 1.4x and 2x Rear Converters are high quality Barlow like multipliers designed for photographic (or visual) use and have 1.5" slip fit on both ends to work with the eyepiece holder, diagonal or adapters.
Numerous 35mm camera adapters were available as well as an adapter for the Pentax 645 and eyepiece projection adapters.
A 0.72 focal reducer to yield 360mm f/4.8 optics for 35mm photography.
Mounting plates and piggy-back adapters for OTA's and camera combinations.

Overall Rating: 8
Weight: 10 (Trustworthy Vote)
Date:
By: Anonymous (xxx.xxx.155.62)
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=40098


Pentax 75 EDHF
Exceptionally compact. Exquisite optics. Smooth focuser. Very well built overall. Series of focuser adapters required to use is not convenient for those in the USA as there is no importer. In spite of that, any competent, or half way competent, machinist can make a 1.5” to 1.25” adapter on a lathe in 15 minutes. The superb optics in such a compact package make it all worth while. Shortness of mount legs doesn’t bother me (I’m 6’ 1” tall) as I usually observe sitting down anyway. The mount legs are extremely stiff for aluminum legs. The equatorial mount itself is a tiny thing of beauty, and well sized to the small tube. An excellent combination of stability, weight, and size in an equatorial mount for a tube the size of the 75 EDHF, but will also handle longer tubes quite well. If you ever get a chance to buy one, don’t pass it up.

Overall Rating: 9
Optics:10 Mount:9 Ease of Use:9 Value:8
Weight: 5 (Veritable Vote)
Date:
By: dbledsoe
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=310875


Pentax 75 EDHF
EQUIPMENT: OTA ~5lbs. Length ~19" (dewshield retracted, w/out diagonal. EQ mount ~25lbs. RA drive (AC; no controller). Polar-align scope (no illum). 6x30 finder (simple crosshair; no illum; short-ish e.r.). Scope is ca. mid/late '80s. Replaced by SDHF (super-low disp. ED); overall design same. Purchased mine used in '94, (w/mount, RA drive, & 6mm Ortho) for ~$800. Not easy to find.
SCOPE CATEGORY: very portable high-quality semi- or true APOs in 3" range (TV Pronto, Oracle; Tak 76-78mm; Vixen/Celestron 70-80mm flourites; Brandon 80mm).
Formats: 2.37"-1.5"-.965". Adapted mine with machined aluminum insert (1.5"-1.25"). APM-Markus Ludes sells adapters; I've not seen/used any.
Standard prism diagonal (1.5" to .965"): fully coated; no degradation seen; uses slip-fit at eyepiece. Retro-fitted mine with 1.25" Lumicon.
OPTICS: Fully-MC (3 elements w/field flattener ahead of focuser). Not expert, but star test in 1/6-1/7 wave range AT EYEPIECE with or without diagonal (Pentax 6mm Ortho or Clave 10mm/Ultima barlow). Only slight overcorrection noted with confidence. Exc. contrast/sharpness. In good seeing, in focus, it IS an APO (even on lunar limb); but not as corrected as current APs or Taks.
Focuser: rack/pinion; collar clamp; 7+" backfocus; may not be enough forward travel for 2" diag. to focus. Will try to test & add comment at later date.
Mount: well executed design/machining/tolerances; smooth & sturdy, but smaller (it's Japanese; not designed for U.S. market). I estimate load capacity at ~12lbs. Damping time ~2 sec. max. NOT tall when extended. Aluminum legs ala Vixen GP-DX (not GP); seamless hexagonal cross-section; very rigid.
SAMPLE PLANETARY PERFORMANCE: Juptier: transits (discs with Jovian background, not just shadows), GRS, mult. belts/bands, festoons, mottling, limb darkening. Saturn: Cassini, banding, polar darkening, four moons. Mars: ice caps, polar hood, larger features. Exc. images up to 167x w/current eps & good seeing. Higher mags begin to dim; maybe due to eyepiece/barlow combo limits.
DEEP SKY: as expected for excellent 3" aperture; one note: Rigel split clean.
SCOPE CATEGORY: extreme portable high-qual ~3" APO/semi-APO (TV Pronto, Oracle; Tak 76-78mm; Vixen/Celestron 70-80mm flourites; Brandon 80mm).
OVERALL IMPRESSIONS: Hardware/refinement=9. Convenience=7. Optics=10.

Overall Rating: 9
Weight: 3 (Unreliable Vote)
Date:
By: Anonymous (xxx.xxx.153.240)
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=40094


Pentax 75 EDHF
Bought my EDHF used at a flea market two years ago for a measly $300.
The mount head was damaged ( vertical adjustment treads ripped out and knob/axle missing)
Also have a slightly worn focuser rack, and a fairly scatched front lens.
Anyhow, the scope is performing very well, but I haver never achieved any superb results yet on Jupiter & Saturn.
The major reason might be that I'm living in a valley where the heat from industy & housing cauces a lot of air disturbance in the autum/spring/winter time (In Norway, where I live, the summernights are to "bright" ).
My major grumble against the set-up is the physical shortness of the mount, which makes you have to go down on your knees to catch anything above 50 degrees.
Anyhow, at $ 300 this APO was a ripp-off, and still is !

Overall Rating: 8
Optics:9 Mount:7 Ease of Use:7 Value:10
Weight: 1 (Unreliable Vote)
Date:
By: Anonymous (xxx.xxx.98.34)
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=144973

>Bought my EDHF used at a flea market two years ago for a measly $300. 
>The mount  head was damaged ( vertical adjustment treads ripped out and knob/axle missing)
>Also  have a slightly worn focuser rack, and  a fairly scatched front lens.
>Anyhow, the scope is performing very well, but I haver never achieved any superb results yet on Jupiter & Saturn. 
>The major reason might be that I'm living in a valley where the heat from industy & housing cauces a lot of air disturbance in the autum/spring/winter time (In Norway, where I live, the summernights are to  "bright" ). 
>My major grumble against the set-up is the  physical shortness of the mount, which makes you have to go down on your knees to catch anything above 50 degrees. 
>Anyhow, at $ 300 this APO was a ripp-off, and still is !

Pentax 75 EDHF
Exceptionally sharp and contrasty up til 150 x magnification, and usable even up at 250x. Tripod is to short for people over 5 feet tall.

Overall Rating: 9
Weight: 1 (Unreliable Vote)
Date:
By: Anonymous (xxx.xxx.40.2)
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=40097


Pentax 75 EDHF
ADDITIONAL COMMENTS/CORRECTIONS TO REVIEW:
Back-focus is NOT 7+" as noted; call it 5".
Max. damping time (2 secs) is with tripod fully extended and a good/hard thump.
Finder reticle includes ~1 degree circle.
Clean split of Trapezium @ 16-17x in average seeing (30mm Ultrascopic).
Different grey-tones on floor of Plato easy.
WILL TEST/COMMENT IN FUTURE (hopefully):
Craterlets in Plato. Sure of 1-2; need to re-test/confirm (damn floaters!).
In-focus capability with 2" diagonal.
More deep-sky impressions.
Magnification limits (alternate eyepieces/barlows).

Overall Rating: No Vote
Weight: <none>
Date:
By: Anonymous (xxx.xxx.153.240)
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=40095

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