Re: [APML] OT: New M106 Composite

[Wei-Hao Wang <wang@IfA.Hawaii.Edu>]

Great image, Rob!

One thing I'm wondering is if it's really necessary to use F9 to 
obtain the details.  I believe that your F6 has the same image 
details as F9 (and a wider field), unless the seeing is subarcsec.

At F6, your focal length is about 1.9m.  With 1".5 seeing (I assume),
the FWHM of an unsaturated star on the focal plane is 14 um.  The 
diffraction of the telescope at F6 will add another 4 um to this FWHM.
So the FWHM of stars is at least 18 um, corresponding to 2.6 pixels 
on ST10.  In other words, at F6, with 1".5 seeing, you already reach
Nyquist sampling.  Increasing the focal length will make you 
over-sample the stars (and therefore all the details in the image)
without actually increasing the resolution.  This is not true only 
when the seeing is less than 1".  In this case, F9 will give you
a higher resolution.

Cheers,

Wei-Hao


______________________________________________________________________
Wei-Hao Wang  :)

Institute for Astronomy at University of Hawaii

Address:                       Phone: 808-956-9867                  
2680 Woodlawn Drive            Personal Website:
Honolulu, HI 96822             http://www.ifa.hawaii.edu/~wang
______________________________________________________________________



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