Re: [APML] Rising Emu

[Axel Mellinger <axm2@canopus.physik.uni-potsdam.de>]

On Mon, 20 May 2002, Volker Wendel wrote:

> this is a great shot! How did you get the background color so neutral?

Volker,

the images were "flat-fielded" by subtracting an unsharp mask consisting
of a Gaussian-blurred version of the original image. Of course, I had to
remove the Milky Way star clouds from the mask by hand; otherwise, they
would have been "flat-fielded", too.

> Another question (because I´m in Namibia in July too): how do you plan such
> mosaic shots? Do you look for the center of the area for every shot and how
> much do you overlap the frames?

In the text below the mosaic, there is a hyperlink titled "4-frame mosaic"
that will open a little JPEG file with the four raw images. As you can
see, I try to get about 20% overlap. Sometimes this is not trivial to
achieve, especially in areas with few bright stars (when it is hard to see
anything at all in the viewfinder). It is always a good idea to sketch the
frames in a star chart, especially when your exposures are several nights
apart.

Clear skies,

Axel

-- 
Axel Mellinger  <http://canopus.physik.uni-potsdam.de/~axm/astrophot.html>


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