Re: [ATM] First telescope

["Eric S. Johansson" <esj@harvee.org>]

Jean-François B. wrote:
> Thanks everyone for all your answers...this list is really useful for a 
> beginner and I'm confident that I'd get help through the entire process
> 
> The application of the telescope at first would be for moon + planets but 
> after deep-sky would also interest me...I understand that with a bigger 
> diameter we can expect to see more objetcs in deep-sky observation but what 
> would it change for the moon (for example)...? could it help getting more 
> details about it?

as you increase the diameter of the telescope, you increase the amount of light 
gathered, the resolution and increase sensitivity to atmospheric turbulence.

in New England, I would say the most useful diameter telescope is around 10 to 
12 inches if you are observing planets.

But the resolution you increase is not always useful.  I remember using the 
six-inch shupmann  on Saturn and I could see very nice detail on the body of the 
planet and a fair amount of detail on the rings.  I went over to a friends 25 
inch dob and Saturn was brighter, had more detail in the rings but nothing was 
visible on the planet except a few major bands.  I suspect if I had a 10 inch 
schupmann, I would have seen more detail overall albeit still fainter.

This difference was explained by an optical is a something pertaining to MTF ( 
which I'm ashamed to say I haven't learned much about). 
http://www.skyscientific.com/opticalprimer.htm

as far as I understand things, the larger telescope has overall higher 
resolution just by virtue of its aperture but the lack of central obstruction in 
the shupmann with its adjustable components, frequently gives planetary images 
that show more detail than a scope almost twice its size.  Personally, I think 
that a significant amount of the detail could be restored to an ordinary 
telescope by some sort of color correction device analogous to the one in the 
schupmann and possibly some method of throwing away light near the eyepiece so 
you don't overwhelm the eye but don't lose the image detail.


-- 
Speech-recognition in use.  It makes mistakes, I correct some.
_______________________________________________
ATM mailing list http://www.atmlist.net/