This comment on the current answer to Why is this telescope so short? How hard is it to make such a fast primary? says

In this forum topic Borisov appears to call it an f/1.5 Hamiltonian.

Wikipedia's Catadioptric system; Catadioptric dialytes) says:

Catadioptric dialytes are the earliest type of catadioptric telescope. They consist of a single-element refracting telescope objective combined with a silver-backed negative lens (similar to a Mangin mirror). The first of these was the Hamiltonian telescope patented by W. F. Hamilton in 1814. The Schupmann medial telescope designed by German optician Ludwig Schupmann near the end of the 19th century placed the catadioptric mirror beyond the focus of the refractor primary and added a third correcting/focusing lens to the system.

The image of the telescope in the linked question shows a very short and squat telescope with a 65 cm aperture that does not appear to have a "single-element refracting telescope objective", so I am confutes!


  1. What (the heck) is and is not a proper Hamiltonian telescope?
  2. Is the Gennady Borisov telescope in the linked question (and shown here) one?
  • $\begingroup$ potentially helpful: ceravolo.com/hamilton.html $\endgroup$ – uhoh Nov 5 '20 at 22:46
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    $\begingroup$ A Hamiltonian telescope is a telescope that visits each vertex of a graph exactly once. $\endgroup$ – Mark Nov 6 '20 at 2:56
  • $\begingroup$ Question: Is this telescope still used today? or has it become obsolete? I think that since it is 19th century technology, it is easily replaced by digital telescopes. $\endgroup$ – Nilay Ghosh Nov 6 '20 at 5:15
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    $\begingroup$ @NilayGhosh according to information here and in the answer below, Gennady Borisov discovered comet G Borisov in 2019 with one, so I would say yes, it is still being used! $\endgroup$ – uhoh Nov 6 '20 at 9:01

Gennady Borisov wrote on the astronomy.ru forum:

The first observations of the object were made in the morning of August 30 with a 650 mm telescope, F / 1.5 Hamilton

Первые наблюдения объекта были сделаны под утро 30 августа на телескопе 650 мм, F/1.5 Гамильтоне

Yes, this is Hamilton. All surfaces are spheres. Has a 3-lens corrector. Good image quality, high aperture ratio. Large field of view: on FLI ML16803 FOV: 2.1 х 2.1 deg 1.87"/pixel

Да, это Гамильтон. Все поверхности сферы. Имеет 3-х линзовый корректор. Хорошее качество изображения, высокая светосила. Большое поле зрения: на матрице FLI ML16803 FOV: 2.1 х 2.1 deg 1.87"/pixel enter image description here

  • $\begingroup$ Thanks for the speedy answer! I'd like to try to read further (with google translate's assistance). I tried searching the page for "Гамильтон" or "гамильтон" or "поверхности" but no success. It's not easy making a 65 cm lens with a big hole in the center; the backstory on how this was done must be interesting! Actually I will ask about how that's done in a separate question so don't answer that here :-) $\endgroup$ – uhoh Nov 6 '20 at 4:05
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    $\begingroup$ @uhoh He's not really an amateur. He is an observatory employee who builds and repairs telescopes. The optical system is made on professional equipment. $\endgroup$ – A. Rumlin Nov 6 '20 at 12:13
  • $\begingroup$ Oh I see what you mean, got it. Nonetheless it will be interesting to see how such a "holy lens" (pardon the pun) can be made. $\endgroup$ – uhoh Nov 6 '20 at 12:50

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