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25” f4.0 (100" FL) Dobsonian with Perforated Primary Mirror For Sale

Price - $9,800.00

Ad Number: 175493

Posted: 28 Jun 2019

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This is a 25” f4.0 (100” FL) Dobsonian, with a perforated 2.8” diameter Primary Mirror Core, that was built in the 1990’s by Joe Castoro.

Joe advised me of the Optician’s name (but unfortunately I cannot remember it now) and that he is a well-known Optician to some of the largest & finest Telescopes at the Professional / Research level.

Like all of Joe’s Telescope or Binoscope work, they are all outstanding, and this Dobsonian is no exception.

What is unique about this Telescope is the Primary Mirror was designed with a perforated 2.8” diameter Core. As a result, instead of supporting the Primary with a strap, it is securely held in place at the center of the Mirror as shown in one of the photos.

For those of you who are always looking for something that not only meets your immediate needs, but also has HUGE upside potential, then it definitely does not get any better than having this Primary with all of its specs. As a result, if you ever have the inclination to go nuclear with this Primary, you would be able to use the Primary to build a Classical Cassegrain that is easily worth 6, 7, or 8 times the amount that is being asked for this entire Dobsonian - - not to mention the sky gazing power that will be at your fingertips.

For those that are interested, I can reply back with Joe’s greater detailed commentary on this Telescope.

The condition of the Primary Mirror is excellent, and it’s coating can be described as very brilliant, with zero indication that a recoating is needed - - all Thanks to the ingenius Mirror cover that Joe designed that does an excellent job of protecting & sealing the Mirror’s Primary surface when not in use.

Please keep in mind that the Telescope may need some minor cosmetic touchups.

The last photo shows Joe Castoro in the 1990’s with this (his) beloved Dobsonian.

I will be moving in the not too distant future and unfortunately, my new residence will likely not accommodate this magnificently designed & engineered Telescope.

The $9,800 amount includes the Black Shroud, large Secondary Mirror, and Dual Speed Crayford 2” Focuser. Also, a 2” Howie Glatter Laser Collimator is available for an additional $200.

This is a pickup only sale, and the location is in the Northern suburbs of the Greater Metro-Detroit area.


  • Condition Very Good
  • Location Greater Metro-Detroit Area

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