[APML] Scorpius, Sagittarius, and the Milky Way

[Wei-Hao Wang <whwang@gmail.com>]

ALOHA,

A new image is in 
http://www.ifa.hawaii.edu/~wang/gallery/picutres/sco_sgi_milkyway.htm

To correct the vignetting pattern, I used a little crappy but quick
flat field method.

As I introduced my flat field technique to you about half year ago, I
took several
images of daytime sky and average them to make a flat image.  The old way is
to nonlinearly match this flat with the sky background in a real
astronomical image
and then divide the image with the matched flat image.  This method works quite
well.  I had showed the results on my Orion mosaic to you.  However,
this technique
may be a little difficult for most people since it requires some computer
programming.

In order to see if things could be more simple, I divide the image with the flat
directly (without any background matching).  The result is the image above.
I have to say, this flat fielding is not perfect but the residual
vignettign pattern
can be so easily fixed in PhotoShop.  I think this is worth trying. 
You don't need
to write a C++ program.  All you need is to take a picture of daytime sky and 
find a image processing software that does division (PhotoShop doesn't).

Cheers,

Wei-Hao

-- 
________________________________________________________________
Wei-Hao Wang  :)

Institute for Astronomy at University of Hawaii

Address:                       
2680 Woodlawn Drive         Personal Website:
Honolulu, HI 96822             http://www.ifa.hawaii.edu/~wang
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