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The Reality of Planetary Amateur Telescopes

Started by mcneely_dupe_5262, 01/24/2009 07:20PM
Posted 01/24/2009 07:20PM Opening Post
Interesting link:

http://www.spacealberta.com/articles/seeing.htm


Michael Aaron McNeely
TeleVue Forum Moderator
Astromart.com
Posted 01/25/2009 05:37PM | Edited 01/25/2009 06:58PM #1
Amateurs will argue about the benefits of aperture forever, but I have concluded, based on my experience, that aperture is a valuable attribute for planetary observing. My first real telescope was an 8" f/8 Newtonian with a superb mirror, and it provided planetary views I have never seen matched in any 4" refractor.

The article's author complains about the brightness with larger apertures. This makes me think of some of Harold Hill's comments in his "A Portfolio of Luna Drawings," where he opined that the eye/brain has to get used to a certain brightness level, and it takes time to be able to wring out all that a new aperture will show.

I spent several nights with my wife's 14.5" f/6 when Saturn were well placed. I used it with and without a 6.5" off-axis mask. Although it was most certainly seeing limited at full aperture, the better color rendition and larger exit pupil (at the same magnification) were appreciated, and there were often moments when more detail was visible. The mask went in the trash.

Clear skies, Alan
Posted 01/26/2009 12:07AM | Edited 01/26/2009 02:38AM #2
Curious article by someone with perpetually poor
seeing.

My 11" Dob shows Io in full transit as tiny disk
with a dark equatorial band, sailing over Jupiter's
swirling cloud tops. My 4" APO can't even find
Io in full transit.

Their argument about "Wave Front Interference" is
incorrect. They argue that reflectors are inferior
because the light path is folded back on itself,
and "interfer with the incoming waves", and
hence degrades the wavefront. I promise you the
incoming waves couldn't care less about the
reflected wavefront passing by. They care no
more than the wavefront from Stephen's Quintet
cares about their ~billion mile trip through the
Suns full daylight brilliance.
Posted 01/26/2009 07:59AM #3
david goldman said:

long f/ratios improves contrast and definition more than anything else.

Why?

Clear skies, Alan


Posted 02/02/2009 06:08PM #4
1/8th wave with a ronchi?

"Don't sweat the petty things and don't pet the sweaty things" 8O