*** CONTRAST vs RESOLUTION for Telescopes REFRACTORS vs REFLECTORS ***

Hello all,

How would you rate the Contrast verses the Resolution of telescopes having
the same total light gathering capacity and are either REFRACTORS or
REFLECTORS.

Clear Skies to all.

Mohib..

I see you are making progress, at least you are asking an Astronomical
question Sir.
I will let others try to make a stab at it.

Clear Skies

P. Edward Murray

In sci.physics Dr.Mohib.N.Durrani wrote:
Hello all,

How would you rate the Contrast verses the Resolution of telescopes having
the same total light gathering capacity and are either REFRACTORS or
REFLECTORS.

Clear Skies to all.

Mohib..

I wouldn't unless you introduce something else, i.e. a camera, into the
system.

--
Jim Pennino

Remove .spam.sux to reply.

Dr.Mohib.N.Durrani wrote:

Hello all,

How would you rate the Contrast verses the Resolution of telescopes having
the same total light gathering capacity and are either REFRACTORS or
REFLECTORS.

I'd rate IT as A troll.

Dr.Mohib.N.Durrani wrote:
Hello all,

How would you rate the Contrast verses the Resolution of telescopes having
the same total light gathering capacity and are either REFRACTORS or
REFLECTORS.

Greg Crinklaw:
I'd rate IT as A troll.

I believe that you would be rating it wrongly. Dr. Durrani is a
distinguished lunar observer and computer scientist.

I further believe that the question means "Given the same light
gathering capacity, which has higher contrast and resolution -- a
refractor or a reflector?"

Davoud

--
usenet *at* davidillig dawt com

"Davoud" wrote in message
...
Dr.Mohib.N.Durrani wrote:
Hello all,

How would you rate the Contrast verses the Resolution of telescopes
having
the same total light gathering capacity and are either REFRACTORS or
REFLECTORS.

Greg Crinklaw:
I'd rate IT as A troll.

I believe that you would be rating it wrongly. Dr. Durrani is a
distinguished lunar observer and computer scientist.

I further believe that the question means "Given the same light
gathering capacity, which has higher contrast and resolution -- a
refractor or a reflector?"

Davoud

--
usenet *at* davidillig dawt com

Well? Don't leave us in the dark. which is it?

I'd rate IT as A troll.

Are you sure Greg? That name sounds familiar but I can't quite
place it. Has he trolled here before? I was going to answer it
until I saw the comments labeling it a troll. But then, I've
been had before.

Clear Skies

Chuck Taylor
Do you observe the moon? If so, try
http://groups.yahoo.com/group/lunar-observing/

If you enjoy optics, try
http://groups.yahoo.com/group/ATM_Optics_Software/
*********************************************

Dr.Mohib.N.Durrani wrote:
How would you rate the Contrast verses the Resolution of telescopes having
the same total light gathering capacity and are either REFRACTORS or
REFLECTORS.

This really doesn't belong in either sci.astro or even sci.physics. I'm
trimming those groups out in the expectation that you'll still see my
response.

There are two ways to answer this, based on what you mean by "same total
light gathering capacity." It either means same aperture, which is not
quite the same thing, but might be what you mean; or else it means same
total light throughput.

If both telescopes are the same aperture, then a premium refractor will
have better contrast than a premium reflector. The difference will be
noticeable, though not earth-shattering (in my opinion). Both will have
about the same resolution (in terms of, say, ability to split tight
doubles). If you're comparing run-of-the-mill telescopes, the
differences will be somewhat smaller.

However, reflectors pass less light than refractors of the same size.
This is in part because reflective coatings reflect less light than
lenses pass, and in part because reflectors generally have a central
obstruction that typically blocks out anywhere from 4 percent (for a
typical slow Newtonian) to 15 percent (for a small SCT) of the light
entering the scope. The upshot is that in order to match the
light-gathering power of a refractor, a reflector typically has to be
maybe 10 or 15 percent larger by diameter.

In that case, the reflector will have marginally better resolution
(because of the greater aperture), and contrast might be just about the
same between the two--possibly still a nod to the refractor, but it will
be difficult to tell, at least.

--
Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Chuck Taylor wrote:
Are you sure Greg? That name sounds familiar but I can't quite
place it. Has he trolled here before? I was going to answer it
until I saw the comments labeling it a troll. But then, I've
been had before.

It's a legitimate question. I gave my own answer in a separate message
in this thread.

Dr. Durrani is the same fellow who posts young Moon sightings, chiefly
to mark the beginning of the next month in the Islamic calendar, which
is purely lunar. I wouldn't call it trolling, necessarily, but I must
think that Dr. Durrani knows exactly what he is going to get each time
he posts one of those reports (some minor vitriol from Uncle Al et, err,
al, and a few defenses from Chris Peterson, etc). You can all draw your
own conclusions.

I suspect some of the vitriol is drawn by the benediction to Allah at
the beginning of each post.

--
Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Brian Tung:
Dr. Durrani is the same fellow who posts young Moon sightings, chiefly
to mark the beginning of the next month in the Islamic calendar, which
is purely lunar. I wouldn't call it trolling, necessarily, but I must
think that Dr. Durrani knows exactly what he is going to get each time
he posts one of those reports (some minor vitriol from Uncle Al et, err,
al, and a few defenses from Chris Peterson, etc). You can all draw your
own conclusions.

My conclusion is that since the sighting of the Crescent Moon ("Hilal"
in Arabic) is very important to about 1-1/2 million Americans because
it marks the beginning of the month in the Islamic calendar, and since
Dr. Durrani is North American Coordinator for Astronomical Information
of the Islamic Society of North America, and since the information that
Dr. Durrani occasionally posts on this astronomy newsgroup is
astronomical information, he is not a troll.

So what if that information is not of interest to most readers here?
This NG gets a lot of esoteric posts that are of little interest to the
majority. And did not John Stuart Mill caution us about the tyranny of
the majority in his Essay on Liberty?

One doesn't have to troll to catch a few rotten fish like "Uncle Al."
Just being on the river is enough.

I suspect some of the vitriol is drawn by the benediction to Allah at
the beginning of each post.

Indubitably. Dr. Durrani is required to preface his writings and his
formal speeches with that benediction. If a few bigots have a problem
with that, that's the bigots' problem, not Dr. Durrani's problem.

Davoud

--
usenet *at* davidillig dawt com