The objectives for aerial telescopes sometimes had very long focal lengths.

Aerial telescopes were employed by several other astronomers.

For example, this could result in extremely long telescopes such as the very long aerial telescopes of the 17th century.

In 1684, he published Astroscopia Compendiaria on his new tubeless aerial telescope.

These were consequently termed aerial telescopes.

This may have been the longest "tubed" telescope before the advent of the tubeless aerial telescope.

Hartsoeker also came up with contrivances for aiming very large aerial telescopes originally popularized by Huygens.

The Huygens contrived some ingenious arrangements for aiming these "aerial telescopes" at an object visible in the night sky.

Constantijn continued to make larger and longer focal length telescope objectives culminating in the very large tubeless aerial telescopes.

As long as these were, they were actually much shorter than the longest singlet refractors in aerial telescopes.

Cassini found Dione using a large aerial telescope he set up on the grounds of the Paris Observatory.

The Royal Society also has two other very long focal length aerial telescope objectives acquired in 1725, both made by Constantijn.

In 1684 he used one of his aerial telescopes to find Dione and Tethys, two satellites of Saturn.

His deduction of the rotational period of Venus was based on the observation of its surface using a 2.6" (66mm) 100 foot focal length aerial telescope.

His brother, Matteo Campani-Alimenis, and he were experts in grinding and polishing lenses, especially for very long focal length aerial telescope objectives.

An aerial telescope is a type of very long focal length refracting telescope, built in the second half of the 17th century, that did not use a tube.

Telescopium was introduced in 1751-52 by Nicolas Louis de Lacaille with the French name le Telescope, depicting an aerial telescope.

On this tower he mounted long tubed telescopes and the objectives of aerial telescopes made for him by the Italian optician Giuseppe Campani.

These eyepieces work well with the very long focal length telescopes (in Huygens day they were used with single element long focal length non-achromatic refracting telescopes, including very long focal length aerial telescopes).

He made many observations with large aerial telescopes and he is noted for briefly considering the construction of a huge aerial telescope 1,000 feet in length that he would use to observe animals on the Moon.

He became a member of French Academy of Sciences in 1678, and subsequently became active as an astronomer, calculating tables of the movements of the Sun, Moon, and planets and designing contrivances for aiming aerial telescopes.

The instrument was examined by Society members James Pound and James Bradley who compared its performance to the 7.5 inch (190 mm) diameter aerial telescope built by Constantijn Huygens, Jr. that the Society had in their collection.

Considerably higher magnifications can be reached with this design but to overcome aberrations the simple objective lens needs to have a very high f-ratio (Johannes Hevelius built one with a 45 m (150 ft) focal length and even longer tubeless "aerial telescopes" were constructed).

Christiaan Huygens published designs for these tubeless "aerial telescopes" in his 1684 book Astroscopia Compendiaria, and their invention has been attributed to him and his brother Constantijn, although similar designs were also used by Adrien Auzout; the idea is even sometimes attributed to Christopher Wren.

In the comparison they noted that the Hadley reflector "will bear such a charge as to make it magnify the object as many times as the latter with its due charge", and that it represented objects as distinct, though not altogether so clear and bright as the Huygens aerial telescope.