Mars Magnification

The image I see in the EP is probably 4 or 5 mm in diameter at some 200 X's
magnification...does this sound right irrespective of the type of scope?

What size are you expecting to see when you look through your scope?

Why the concern with visual size at that magnification?

The visual size you see will be the same in any scope if you compare at the
same magnifications. The only differences seen will be resolution and colour
corresponding to the different scope sizes.


Todd

http://www.backyardastronomy.com
http://www.skynewsmagazine.com
http://www.simpleastrophotography.com

"Mick" wrote in message ...
The image I see in the EP is probably 4 or 5 mm in diameter at some 200 X's
magnification...does this sound right irrespective
of the type of scope?

Actually, your statement is meaningless (unless you really mean to say
that Mars is as microscopic as what Harald calculated). How big does
5 mm look? If i hold a 5 mm bead 50 cm in front of my face, it looks
the same size as a 20 mm grape does 2 meters away.

Unless you plan to hold a *very* long tape measure against the dusty
red Martian surface, you can't talk about linear units such as
millimeters. Angular size is the only meaningful measure in this
context.

Actually, you might get a better idea of apparent sizes with that 5 mm
bead than with your TP rolls. Mars (actual size, 6,794,000,000 mm)
subtends 22.3" across the sky tonight. Magnify that 200x and you get
an image 74' across, irrespective of the type of scope. This is what
the bead looks like if you hold it 0.23 meter away. The naked-eye
Moon should appear the same size as the bead at 0.54 meter. Try it,
see if it answers your question.

(As always, since this is a sci.* newsgroup, please feel free to
falsify my math.)


Clear skies!

--
------------------- Richard Callwood III --------------------
~ U.S. Virgin Islands ~ USDA zone 11 ~ 18.3N, 64.9W ~
~ eastern Massachusetts ~ USDA zone 6 (1992-95) ~
--------------- http://cac.uvi.edu/staff/rc3/ ---------------

The other night when I was out viewing Mars in pretty steady conditions, I was
mostly using 260x and 470x... the image size of Mars was large enough with
either of these magnifications to make out excellent detail with my C9.25",
though I found the best image at 260x was with with using a "moon filter"
neutral density filter to cut down on the brightness. As someone pointed out,
the same magnification will give the same apparent image size with any
telescope, but will differ mainly in brightness and resolution.

Mike Simmons wrote:
OBRiley wrote:

On 01 Aug 2003 01:08:45 GMT, (CHASLX200) wrote:


*******************
I start with 300x and up to 1200x on Mars, when seeing allows! The bigger the
better, if the optics and seeing are excellent...

Chas P.

1200x???? Methinks the aroma of bull**** is in the air.

-- OBR


You better check your pants. I've used that kind of power and higher
many times. I observe from a location with great seeing, though.

Mike Simmons


Yes, I agree with Mike...I've had the 30" up to 1350 X on Saturn,
but you have to have one of those near-perfect steady nights, seeing
wise, to push it that heavy.
Clear Skies,
Tom W.

Subject: Mars Magnification
From: (OBRiley)
Date: 7/31/03 6:48 PM Pacific Daylight Time
Message-id:



1200x???? Methinks the aroma of bull**** is in the air.

-- OBR
*******************
Me thinks ya need to come look thru some Starmaster Dobs, here in Tampa FL,
when many summer nites have seeing above 8+!

Buddy i've forgot about more scopes that i've owned, than you will ever have...

Chas P.

On Thu, 31 Jul 2003 19:46:49 GMT, "Mick" wrote:

The image I see in the EP is probably 4 or 5 mm in diameter at some 200 X's
magnification...does this sound right irrespective
of the type of scope?

No. A linear dimension like 4 or 5 mm has no meaning at all for the
virtual image seen through the eyepiece. Only angular dimensions are
meaningful for eyepiece views.

To get a real image of mars 5 mm across with its current angular size
of 22 arc seconds takes a telescope with a focal length of 4.6 meters.

At its largest apparent size, Mars is tiny as seen through the
telescope. This throws off people used to seeing photographs from
spacecraft or large observatory telescopes.