3 replies to this topic

[rmorein]

The objective is masked off to 10 or 15mm, depending on the source, to mitigate the defects. The focal length is close to a meter, the speed about F100. The power is about 20X, the field of view tiny. And Galileo was not a master optician.

 

I wonder if I'd see any Jovian moons.

Edited by rmorein, 02 February 2025 - 01:21 AM.

[RichA]

The objective is masked off to 10 or 15mm, depending on the source, to mitigate the defects. The focal length is close to a meter, the speed about F100. The power is about 20X, the field of view tiny. And Galileo was not a master optician.

 

I wonder if I'd see any Jovian moons.

Stop down a telescope you have now, use the eye lens of a Huygen's microscope eyepiece and you can approximate what he saw.  It just won't be as colourful as a singlet. 

[triplemon]

Sure, I build one for that purpose.The moons are no problem, once you got Jupiter in the view you need to point that scope in the direction of the belts - the moons not always fit the same field of view !

Actually, its a "Super Galilean ™". The eyepiece can be exchanged for a very futuristic one, a Keplerian, sortof the UWA back then. Heck, the two are even parfocal .... so with hat one you get the moons and Jupter all into the same view.

 

But I would not say this was because Galileo wasn't good at making lenses. Mind you, before that no one on earth had any use for a lens more accurate than a dozen lambda. As they only ones in use were for spectacles ... so Galileo was a master back then, the world leading expert in high magnification lenses and telescopes.

 

And Galileo surely didn't want to wait until he had a 0.99 strehl lens. He used what he had, learned that stopping down helps and "optimized" it for max magnification.  He did later make more - for both terrestrial use as well as astronomy. Some of those could be used at much bigger apertures.

Edited by triplemon, 02 February 2025 - 04:58 AM.

[Sketcher]

About the closest that I've come to Galileo's telescopes would be a 42mm singlet refractor when used stopped down to a 1/2-inch (12.7mm) aperture:

 

https://www.cloudyni...-all-that-much/

 

The eyepieces I used had much wider apparent fields of view than Galileo's eyepieces -- which consisted of just a single negative (concave) lens.

 

At the time, I wasn't trying to match Galileo's telescopes.  I just wanted to see what I could see with a dirt-cheap singlet refractor.