I bought a Bintel Crayford type focuser last week which is currently on special and took a punt that it would be a close fit to upgrade my vintage 4"/f15 refractor focuser. The stepped flange as supplied is 112mm O.D. and I machined it down to 108mm to suit the tube's I.D. and drilled the five mounting holes which also suited the holes already in the tube. The beauty of this upgrade is that the old focuser can be refitted as no modification was done to the tube.
With the focuser duly fitted and tested last night it performed flawlessly. Every eyepiece I tried came to focus within the 75mm focuser range. The 13mm Ethos in combination with the 2" diagonal came to focus at the 50mm mark. The focuser is super smooth and certainly can hold a load. I tried my Meade 30mm UWA Series 5000 which is larger and heavier than the Televue Nagler 31mm grenade and it lifted it up from a near vertical position with ease.
The new focuser in combination with the 1.25"/2" modern eyepieces has breathed life into my old scope. The views through this scope come close to my Tak TOA-130, showing almost no colour and pinpoint stars with perfect diffraction rings. Jupiter looked stunning with the 13mm Ethos which equated to around 115X. An added benefit of long focal length scopes is their smaller exit pupil at the eyepiece which means I don't have to wear my glasses. Most eyepieces exhibit greater clarity towards the edge of the field than faster scopes.
Cheers everybody, hope this little article has been of interest.
Ian, I wouldn't mind a pair of the 20 X 80's but haven't come across them. Unitron's became too expensive in the mid 1980's and had to compete with the up and coming SCT's, the orange tubed Celestrons to name but one.
To answer your question Brian, the mount shown is the Unitron Alt/Az mount know as the model 134. It is a very strong mount and is quick to set up for an evening of visual observation. It is also a fantastic landscape telescope. The model 132 has an equatorial mount and was a great deal more expensive however it still had the same 4" OTA as the model 134. I have attached a pic of the 4" equatorial model for your interest.
Ian, I wouldn't mind a pair of the 20 X 80's but haven't come across them. Unitron's became too expensive in the mid 1980's and had to compete with the up and coming SCT's, the orange tubed Celestrons to name but one.
To answer your question Brian, the mount shown is the Unitron Alt/Az mount know as the model 134. It is a very strong mount and is quick to set up for an evening of visual observation. It is also a fantastic landscape telescope. The model 132 has an equatorial mount and was a great deal more expensive however it still had the same 4" OTA as the model 134. I have attached a pic of the 4" equatorial model for your interest.
Cheers, Steve.
I really craved a Unitron 4" model 132 when I was a teenager (in 1970s).
AOS had one on display in Crowe's Nest at the time.
Alan Elliot had a 4" model 134 and it was "IMPRESSIVE".
Unitron really knew how to make first rate refractors.
I've a pair of 20x80 Unitron binos that are superb.
Ashame they bit the bullet.
Unitron are still around, and they still sell telescopes going by their webpage: http://www.unitronusa.com/
As a note - Unitron also never made any telescopes, Unitron are an importing company. The classic Unitron scopes were made in Japan by Nihon Seiko, who subcontraced the optics out of various optics shops in Japan. Some of the 4",5" & 6" lenses came from A. Jaegers. As such quality varied alot between different scopes.
To quote Roland Christen "Unitron refractors were quite nice mechanically, and can be quite nice optically, if you get the right one".
Nowdays companies like Astro-Physics make first rate telescopes & mounts, and there is no 'hit and miss' on their quality!
BTW, great looking mod Stephen, keepin the scope both original (with a switch back), with improved functionality and better eyepiece range. I'm sure this will breathe new life into this wonderful scope!
Thanks for sharing the pictures Steve. The Unitron 4" f15 looks great.
I have one of these focusers on my 90mm f16.7 achromat and think it is great value.
Unitron are still around, and they still sell telescopes going by their webpage: http://www.unitronusa.com/
As a note - Unitron also never made any telescopes, Unitron are an importing company. The classic Unitron scopes were made in Japan by Nihon Seiko, who subcontraced the optics out of various optics shops in Japan. Some of the 4",5" & 6" lenses came from A. Jaegers. As such quality varied alot between different scopes.
To quote Roland Christen "Unitron refractors were quite nice mechanically, and can be quite nice optically, if you get the right one".
Nowdays companies like Astro-Physics make first rate telescopes & mounts, and there is no 'hit and miss' on their quality!
BTW, great looking mod Stephen, keepin the scope both original (with a switch back), with improved functionality and better eyepiece range. I'm sure this will breathe new life into this wonderful scope!
Last I heard Unitron's original owners went into recievorship or sold out (back in the late 90s).
In answer to a few comments, firstly, the unihex is a must have from a collectors point of view. Polarex/Unitron made three different sizes, the most common catered for 5 x 1" EP's and 1 x 1.25" EP. The second type which is fairly rare holds 6 x 1.25" EP's and lastly there is the super unihex (very large) which holds 1 x 2" EP, 1 x 1.25" EP and 4 x 1" EP's. In Europe, Asia and Australia the unihex is known as a rotary eyepiece selector. I have a few unihex's and contrary to popular belief, they do not soak up lots of light as they still have the same single diagonal prism as a standard right angle star diagonal. Yes, they are quite expensive to buy, especially in the US.
Kal is quite right that Unitron (United Trading Company) never produced scopes themselves although they had a huge influence on the types and sizes sold in the US. I have owned many Polarex/Unitron scopes over the years and have had found that the optics have been consistently excellent. Ian, apparently Nihon Seiko Kenkyusho was a family owned company and closed its doors in the 1990's as you mentioned.
Even though I don't use my Polarex/Unitron scopes much these days, they are just fantastic to look at on display.
Pardon my ignorance, but what is the alt-az mount in the photo? It looks impressive.
Cheers,
Brian.
The Unitron Altaz mounts, both the altaz mount on their 3 inch refractor and also the larger altaz mount on their 4 inch refractor, were quite lightweight, but they are very stable and very precise instruments, and the microscrew controls enable very smooth and small movements of the mount.
I (last year) searched high and low for a lightweight altaz mount suitable for 3-5 inch refractors, and there does not seem to be much currently on the market that measures up to these old unitron mounts.
(The new mounts are mostly cheapies that are made to a low price )
These Unitron refractors were very expensive and beautifully machined instruments , and schoolboy astronomers used to lust after them in the 1960s and 1970s, particularly the four inch Unitron refractor;
as for the optics, well my three inch Unitron refractor bought in 1975 had goodish but far from perfect optics.
The Unitron Altaz mounts, both the altaz mount on their 3 inch refractor and also the larger altaz mount on their 4 inch refractor, were quite lightweight, but they are very stable and very precise instruments, and the microscrew controls enable very smooth and small movements of the mount.
I (last year) searched high and low for a lightweight altaz mount suitable for 3-5 inch refractors, and there does not seem to be much currently on the market that measures up to these old unitron mounts.
(The new mounts are mostly cheapies that are made to a low price )
These Unitron refractors were very expensive and beautifully machined instruments , and schoolboy astronomers used to lust after them in the 1960s and 1970s, particularly the four inch Unitron refractor;
as for the optics, well my three inch Unitron refractor bought in 1975 had goodish but far from perfect optics.
i wonder if your three inch Unitron refractor bought in 1975 had goodish but far from perfect optics could match the optics of my royal astro 76mm fl 1200mm refractor.
