Saturnseeing reloaded

The updated Saturnseeing page is up on
http://astronomy.trilobytes.com.au/m...turnseeing.htm

Thanks for all suggestions.

Jupiter's next...

Martin Lewicki

Martin Lewicki wrote in message ...
The updated Saturnseeing page is up on
http://astronomy.trilobytes.com.au/m...turnseeing.htm

Thanks for all suggestions.

Jupiter's next...

Martin Lewicki

Martin,

You did an excellent job with the update. The images in your 3.5" and
6" simulations are very close to what I see in my TV85 and 6" Dob on
good nights at the respective powers. Bravo.

Clyde

Martin Lewicki wrote in message ...
The updated Saturnseeing page is up on
http://astronomy.trilobytes.com.au/m...turnseeing.htm

Thanks for all suggestions.

Jupiter's next...

Martin Lewicki

Well thank you Martin...
A beautiful site, my 60 mm agrees well,
a big improvement, (and a beautiful sight).
The magnification is a nice touch.

I sit in my office and peer threw a double
glaze window in any temperature and find
no viewing difference compared to being
outside.
Anyone else do this with larger instruments?

I've read that refractors are superior to
reflectors of equal aperature in viewing and
resolving planetary detail, presumeably because
high power (magnification) works better for
refractors. Is this a rumor? Is there any
supporting science?
Because of instrument quality/price variation
I presume refractors are more carefully
constructed.(?).

Regards Ken S. Tucker

PS: Looking forward to seeing your Jupiter
images. You should toss a sponsor on this
fine site you a developing, makes me want
to move up!

(Ken S. Tucker) wrote in
om:

Martin Lewicki wrote in message
...
The updated Saturnseeing page is up on
http://astronomy.trilobytes.com.au/m...turnseeing.htm

Thanks for all suggestions.

Jupiter's next...

Martin Lewicki

Well thank you Martin...
A beautiful site, my 60 mm agrees well,
a big improvement, (and a beautiful sight).
The magnification is a nice touch.

I sit in my office and peer threw a double
glaze window in any temperature and find
no viewing difference compared to being
outside.
Anyone else do this with larger instruments?

A larger aperture through windows will surely give a degraded image because
it is likely to include more inhomogenities in the glass than a smaller
aperture.

I've read that refractors are superior to
reflectors of equal aperature in viewing and
resolving planetary detail, presumeably because
high power (magnification) works better for
refractors. Is this a rumor? Is there any
supporting science?

Refractors are said to be superior mainly for the fact that they do not
have a secondary mirror obstruction like reflectors that reduce contrast
and and light throughput. So image *contrast* not resolution, is better
than for the same aperture in a reflector.

Appart from these, reflectors are superior in that they have no chromatic
abberation whereas refractors have some false color residues.

Aperture determines resolution irrespective of scope type. It's the laws of
optics! Eg resolution in arcseconds = 4.5/aperture.

Because of instrument quality/price variation
I presume refractors are more carefully
constructed.(?).

Price variation has little to do with qaulity of construction. Refractors
are more expensive because they actually cost more to manufacture.

Regards Ken S. Tucker

PS: Looking forward to seeing your Jupiter
images. You should toss a sponsor on this
fine site you a developing, makes me want
to move up!

Thanks. BTW my Saturnseeing page is residing on the host website.
http://astronomy.trilobytes.com.au
I'll pass your suggestion on :-)

Martin Lewicki

"Martin Lewicki" schrieb im Newsbeitrag ...
Refractors are said to be superior mainly for the fact that they do not
have a secondary mirror obstruction like reflectors that reduce contrast
and and light throughput. So image *contrast* not resolution, is better
than for the same aperture in a reflector.
So, we can make better lenses than mirrors? (in terms of contrast
and losses)

Greetings!
Volker

In article ,
Volker Hetzer wrote:
Refractors are said to be superior mainly for the fact that they do not
have a secondary mirror obstruction like reflectors that reduce contrast
and and light throughput. So image *contrast* not resolution, is better
than for the same aperture in a reflector.

So, we can make better lenses than mirrors? (in terms of contrast
and losses)

No, the issue is not the quality of the optical elements, but the
compromises inherent in the usual way they are used. Any system with a
central obstruction will have reduced contrast and increased losses. It's
just that such an obstruction is typically unnecessary with lenses, while
with mirrors, avoiding it involves considerable extra trouble.

(Lenses inherently pass light onward, so if we think of the telescope as
pointed upward, the next lens is located below the first one. Mirrors, on
the other hand, inherently reflect light *back*, so the obvious layout
puts the second mirror *above* the first one, blocking some of the first
one's light. As others have noted, there are ways around that, but they
have their own complications.)
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

"Henry Spencer" schrieb im Newsbeitrag ...
In article ,
Volker Hetzer wrote:
Refractors are said to be superior mainly for the fact that they do not
have a secondary mirror obstruction like reflectors that reduce contrast
and and light throughput. So image *contrast* not resolution, is better
than for the same aperture in a reflector.

So, we can make better lenses than mirrors? (in terms of contrast
and losses)

No, the issue is not the quality of the optical elements, but the
compromises inherent in the usual way they are used. Any system with a
central obstruction will have reduced contrast and increased losses.
Ok. Understood.

Thanks a lot!
Volker

"Ken S. Tucker" wrote:

I've read that refractors are superior to
reflectors of equal aperature in viewing and
resolving planetary detail, presumeably because
high power (magnification) works better for
refractors. Is this a rumor? Is there any
supporting science.

As Martin pointed out, the secondary mirror obstruction decreases
contrast in most reflector designs. But a reflector design such as the
off-axis Newtonian avoids the obstruction, and you do have the best
of both worlds. However, off-axis primary mirrors are difficult and
expensive to make. For the same effort and expense you can make a
much larger mirror. :-)
--
Judson McClendon (remove zero)
Sun Valley Systems http://sunvaley.com
"For God so loved the world that He gave His only begotten Son, that
whoever believes in Him should not perish but have everlasting life."

And who was God's Mother and Father?

"Judson McClendon" wrote in message
...
"Ken S. Tucker" wrote:

"For God so loved the world that He gave His only begotten Son, that
whoever believes in Him should not perish but have everlasting life."

"Peter Gennaro" wrote:
And who was God's Mother and Father?

Not sure if you're kidding or expect a serious answer. I prefer not to
get into serious discussions of religious issues in OT newsgroup posts,
because they can generate lots of hostility. :-)
--
Judson McClendon (remove zero)
Sun Valley Systems http://sunvaley.com
"For God so loved the world that He gave His only begotten Son, that
whoever believes in Him should not perish but have everlasting life."