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Re: (IAAC) Obj: M1 - Inst: MEADE ETX 3.5" MAK



>Lew,
>
>I beg to differ on your binocular take of M1. You should try it some time!
>I find M1 to be much much better in bino views than scope views. This must
>be due to it's low surface brightness, which is spread out over a large
>area.  As with some fainter objects, such at the Helix Nebula, sometimes
>less is more :)
>
>Happy observing!
>
Hi Penny,

This illustrates Roger CLARK's statement of the Optimum Magnification
Visual Angle (described in his book "visual astronomy of the deep sky").
The author says that the optimal size of detection for a faint object
(using averted vision) is between 1 and 2 degrees. That's why the 8' of M1
(and Helix is also around 8') are better seen with 12x than 50x or 100x.
The formula giving the OMVA is
OMVA=90/S
where S is the size of the object in arcminutes and OMVA is in x.
For S=8', OMVA=11,25 that is the typical magnification of a binocular.

Of course, this is the magnification to be used for detection of the
object. In order to search for details (wisps and things), you will have to
use higher magnification (eg. 140x for 40" wisps).

clear skies, Yann.


Yann Pothier	tel: 01 43 41 43 29
11 impasse Canart, 75012 PARIS, FRANCE
Email: ypothier@abi.snv.jussieu.fr
Site : http://pegase.unice.fr/~skylink/publi/cielextreme



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