Clyde Tombaugh discovered Pluto in early 1930 after taking two exposures of the same section of the sky 6 days apart. It was not by accident that he found the 9th planet for his job was to systematically image the area of the sky around the ecliptic in the hopes of finding the long sought and elusive Planet X. When he was not photographing, he was comparing pairs of plates to find a star that moved between them. Clyde took 60 minutes exposures using a 13-inch (3 lens element) f/5.3 refractor called an astrograph (an astrograph is a telescope that has a wide field of view). The Lowell Observatory does not have any information about the film speed of the original 14x17 inch glass plates used, but after seeing copies of the original discovery plates, I estimate that the film speed was no higher than 50, probably 25 or lower.

In honor of Clyde¹s discovery, I imaged Pluto on emulsion, using ISO400 negative film, with a 4-inch refractor
(TV NP101) working at f/10.8. My Astro-Physics 155 F7 Starfire EDF served as the guidescope with an attached
ST-4 autoguider. The biggest advantage I had over Clyde was knowing exactly where Pluto is located and I obtained this information from the Astronomical Calendar 2003 by Guy Ottewell. Pluto was around magnitude 13.8 at the time I
took these pictures. The 13-inch astrograph had 10 times more light gathering capability than my 4-inch refractor but today¹s modern films far surpass those of 1930 so I was able to easily image our smallest planet in
20 minutes.

The above images of Pluto were autoguided with a ST-4, with the FMF+XYF Combo. This is a special autoguiding accessory for the ST4. The FMF+XYF Combo is a totally intergrated unit that has a Flip-Mirror-Focuser with The XY Finder bolted into the Flip-Mirror-Focuser.

The picture on the left shows the ST4 attached to the FMF+XYF Combo. And the ST4 FMF+XYF Combo is attached to a telescope. The FMF with the 3 axis adjustable reticle easily focuses for the ST4 and the XY Finder makes finding and centering guidestars a breeze. It's fast, easy and very intuitive to use. No awkward 3 point positioning with guidescope rings. No worry about damaging the guidescope tubing, no flexture concerns either. The guidescope can remain securred and parallel with the main telescope.

For a complete description of the Flip-Mirror-Focuser for the ST4 please click HERE

For a complete description of the XY Finder please click HERE

The ST4 FMF+XYF Combo is cnc milled from Aluminium, deburred and black anodized, to give it a matte like finish. Light weight, and compact it only takes up about 2.5" of back focus, which is suitable for short focul length refractors.

Price is only $449.00
Please contact Tau Ceti Co. for availability and deliver schedules.

Please click here to view a cad rendering of the ST4 FMF-XYF Combo. This will have some basic dimensions.

The image to the right shows the FMF+XYF Combo being used on the main telescope, an AP 155. The ease of using the FMF+XYF Combo means that one can use it on any scope, go from one scope to another. This offers the user much more flexability for the types of images one wishes to take. Whatever the form of imaging one wishes to take, the unused scope will serve as the guidescope. And which ever scope is used for image acquisition, the FMF+XYF Combo offers one more important advantage, image composition. Centering and framing the object to be imaged is important. Finding a guidestar thru the guidescope shouldn't hinder that effort. The FMF+XYF Combo will allow finding guidestars, that will facilitate a satisfactory image composition.

All images on these pages are copyrighted by Tau Ceti Co.
Photos of the FMF+XYF Combo attached to telescope [AP155] are courtesy Ken Graun, [Copy Right Ken Graun]
Image of Pluto is courtesy Ken Graun, [Copy Right Ken Graun]