Highest theoretical magnification?

What does a highest theoretical mag. of 720X mean? What would one be able
to see with a telescope with that level of magnification?

Chuck

Highland wrote:
What does a highest theoretical mag. of 720X mean? What would one be able
to see with a telescope with that level of magnification?

Chuck




Talk about excellent questions.............

Divide the focal length of your primary lens (or mirror) by the focal length
of your highest powered eyepiece, for example a typical 6 inch reflector
might have a focal length of 900mm and come with three eyepieces, 6mm, 12mm
and 25mm. This would give you a highest theoretical magnification of 150X
(900 / 6). Get a 2X barlow lens and now your highest theoretical
magnification is 300X, but ( and this is a huge BUT), there are several
practical factors that make the theoretical maximum of any scope
"practically" un-attainable.

1. atmospheric seeing (the steadiness of the air column you are looking
through)
2. the resolving power of your telescope (mostly a function of the
aperture).
3. the quality of the optics in your telescope.
4. the collimation of your scope.

With the example above, of 300x, Jupiter would look about 5 times bigger in
your telescope than the moon looks with the naked eye, but it would be very
"shaky" most of the time (because of poor atmospheric seeing) and possibly
grainy looking if you are using a small aperture scope (less than 4 inches).

IP


"Highland" wrote in message
news:Y2%Lc.142980$a24.46611@attbi_s03...
What does a highest theoretical mag. of 720X mean? What would one be able
to see with a telescope with that level of magnification?

Chuck

In article Y2%Lc.142980$a24.46611@attbi_s03,
"Highland" wrote:

What does a highest theoretical mag. of 720X mean? What would one be able
to see with a telescope with that level of magnification?

Chuck

The following formulas should help:

ta = Telescope Aperture in millimeters

Minimum useful magnification = ta * 0.13
Maximum useful magnification = ta * 2.00
Magnification for Best Visual Acuity = ta * 0.25

Dawes Limit can be calculated = 115.8/ta (answer in arc seconds)

Hope this helps,
tom

Excellent. Thank you all.


Chuck




"tom" wrote in message
...
In article Y2%Lc.142980$a24.46611@attbi_s03,
"Highland" wrote:

What does a highest theoretical mag. of 720X mean? What would one be
able
to see with a telescope with that level of magnification?

Chuck

The following formulas should help:

ta = Telescope Aperture in millimeters

Minimum useful magnification = ta * 0.13
Maximum useful magnification = ta * 2.00
Magnification for Best Visual Acuity = ta * 0.25

Dawes Limit can be calculated = 115.8/ta (answer in arc seconds)

Hope this helps,
tom

"Highland" wrote in message
news:Y2%Lc.142980$a24.46611@attbi_s03...
What does a highest theoretical mag. of 720X mean? What would one be
able
to see with a telescope with that level of magnification?

Chuck
Almost certainly, that the scope is crap!...
'Highest magnification' claims, are common on cheap 'department store'
scopes, and rare on better kit. To really have a useable magnification
this high, would require around a 14" aperture. All you will see at this
magnification, is probably the optical defects of the scope, and the
atmospheric blur, showing very large...
If the scope is 14" in aperture, then the claim is 'reasonable', and for
bright objects (the planets), on nights of very good seeing, a
magnification at this sort of level, might be used to show as much as
possible, in the odd moments of good seeing.

Best Wishes

I know people in this group are very able but to answer the question from a
novice like myself [who is aware that some of us know very little!] the
theoretical bit applies to max magnification but it means very little when
applied to smaller telescopes and so the number is meaningless!

Keith

Hello,

To know the real magnification for any scope, multiply 50 by inch
of apperture (primary mirror), so for 3 inch, the maximum available is 150x,
but it's in the very best air condition, that mean, perfect darkness,
perfect seeing, no atmospheric turbulence, etc... The real practical
maximum, is more like 30x to 40x by inch. This equation is true for all
kind of scope.

And if you whan know what is your magnification, you take focal lenght (not
the diameter lenght, usualy, it's write on the scope, like D=xxxmm F=xxxmm,
the F is the Focal lenght), divide by the ocular focal (usually, the number
is write in mm and it's write on the ocular), i.e. if F=800, and you use
your 25mm ocular, the magnification will be 800/25 = 32x.

I hope this little information help you! Clear sky
Eric

"Keithbcook" a écrit dans le message de
...
I know people in this group are very able but to answer the question from
a
novice like myself [who is aware that some of us know very little!] the
theoretical bit applies to max magnification but it means very little when
applied to smaller telescopes and so the number is meaningless!

Keith


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Keithbcook wrote:

I know people in this group are very able but to answer the question from a
novice like myself [who is aware that some of us know very little!] the
theoretical bit applies to max magnification but it means very little when
applied to smaller telescopes and so the number is meaningless!

Generally, the maximum power that a telescope is capable of is often quoted to
be around 50x per inch of aperture (2x per millimeter of aperture). The
aperture of the telescope is the diameter of the main lens or mirror. If the
telescope is 3 inches in aperture, the maximum power will be around 150x or
so. This is not exactly a hard and fast rule, but more of a general "rule of
thumb" kind of guide for how much power might be employed. However, for
larger telescopes, the Earth's atmosphere comes into play, as it frequently
will disturb the path of incoming light, causing the variable blurring known
as "seeing" and preventing the full magnification of a telescope from being
used all the time. Usually, most observers will only be using half to perhaps
2/3rds of that maximum power, and for fainter and larger objects, the power
used might be less than 1/4 of the maximum. I hope this helps a little.
Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

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