Comments on: How do you calculate FWHM of the primary beam of the telescope from wavelength and dish size? http://www.telescopebuyingguide.com/blog/how-do-you-calculate-fwhm-of-the-primary-beam-of-the-telescope-from-wavelength-and-dish-size/ Thu, 17 May 2012 20:15:50 +0000 http://wordpress.org/?v=2.7 hourly 1 By: c http://www.telescopebuyingguide.com/blog/how-do-you-calculate-fwhm-of-the-primary-beam-of-the-telescope-from-wavelength-and-dish-size/comment-page-1/#comment-2648 c Wed, 21 Jul 2010 01:19:19 +0000 http://www.telescopebuyingguide.com/blog/how-do-you-calculate-fwhm-of-the-primary-beam-of-the-telescope-from-wavelength-and-dish-size/#comment-2648 It's not "field of view" it's "full-width at half maximum" beam size. The field of view is set by aberrations and field curvature.<a href="http://www.resumeminers.com/home-business.htm"> c</a> It’s not “field of view” it’s “full-width at half maximum” beam size.

The field of view is set by aberrations and field curvature. c

]]> By: jonal http://www.telescopebuyingguide.com/blog/how-do-you-calculate-fwhm-of-the-primary-beam-of-the-telescope-from-wavelength-and-dish-size/comment-page-1/#comment-2647 jonal Sat, 17 Jul 2010 16:41:04 +0000 http://www.telescopebuyingguide.com/blog/how-do-you-calculate-fwhm-of-the-primary-beam-of-the-telescope-from-wavelength-and-dish-size/#comment-2647 Resolution angle Theta = 1.22 Lamda over D Lamda = wavelength D = diameter Use the same units for Lamda and for D For very small angles...Theta = sin Theta...see trig books Read down for variants of the formula . . . . . The usable field of view varies with the quality and size of the collecting surface and for very large telescopes is only a few minutes of arc. For visual telescopes the Dawes Limit is 4.56"/D in inches = 114"/D mm Where " = seconds of arc. A mirror or lens 4.56 inches in diameter resolves 1" That is for a specific set of criteria...two close 2nd magnitude stars in a dark sky background with good seeing.<a href="http://www.ecohomefashion.com/holiday-decor-76"> jonal</a> Resolution angle
Theta = 1.22 Lamda over D
Lamda = wavelength
D = diameter
Use the same units for Lamda and for D
For very small angles…Theta = sin Theta…see trig books
Read down for variants of the formula . . . . .
The usable field of view varies with the quality and size of the collecting surface and for very large telescopes is only a few minutes of arc.
For visual telescopes the Dawes Limit is 4.56″/D in inches = 114″/D mm
Where ” = seconds of arc.
A mirror or lens 4.56 inches in diameter resolves 1″
That is for a specific set of criteria…two close 2nd magnitude stars in a dark sky background with good seeing. jonal

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