Ok, just a matter of vocabulary :)
Le 16/10/2013 23:31, Darren Addy a écrit :
I knew what "flats" were, but the "flat field images" made me wonder
if you might be referring to something else.
Thank you Stéphane!
On Wed, Oct 16, 2013 at 3:58 PM, poirierstephane
<poiriersteph...@free.fr> wrote:
And I precise I don't always do the axis calibration the same order, it's
totally random ;-)
Also you asked me a few days ago (on pentaxforum if I'm right) what I mean
by: "Otherwise you need to add your own flat field images in the pp."
Flat fields images are used to correct images from optical aberrations (like
vignetting) and sensor sensitivity variations accross the frame.
Usually flat fields images are taken by shooting a uniform field (like a
portion of the sky just before sun rise) at "normal" shutter speed.
Then the flat field is used in the image processing by the application of
this formula :
corrected_image = (raw_image - dark) / FlatField * const
const ~= FlatField average value
DSS lets you choose and add flat field images in the whole stacking process
In my case I consider the Lightroom corrections for my lens do a satisfying
job, so I drop this step.
Stéphane
Le 16/10/2013 22:17, Darren Addy a écrit :
Hi Stéphane,
Your work is my inspiration and I have shared the link to your
K-5/O-GPS1 work in many, many places. (We have corresponded via email
in the past).
Thanks for your link to your procedure.
I was wondering if you could describe the way you do the "precise
calibration". For example, do you proceed slowly? Do you always do the
three axis calibration in the same order (if so, what order)? I was a
little disappointed that with my 135mm lens I could only do 45 second
exposures before I got some trailing. The camera told me I should be
able to do a lot more.
-Darren
On Wed, Oct 16, 2013 at 2:45 PM, poirierstephane
<poiriersteph...@free.fr> wrote:
Very cool result :) But I suspect you benefit of good sky conditions,
isn't
it ?
I also use DSS and I got a very similar result (although with the a K-5 &
DA*200): poirierstephane.free.fr/photos/picture.php?/3542/category/132
<http://poirierstephane.free.fr/photos/picture.php?/3542/category/132>
For this picture I stacked 8 good images (30s each @1600 ISO) together
with
a dark frame (but I consider now that dark frames are useless with the
latest camera sensors). The way I procede is described here:
poirierstephane.free.fr/photos/index.php?/page/astrophotography_without_equatorial_mount
<http://poirierstephane.free.fr/photos/index.php?/page/astrophotography_without_equatorial_mount>
Stéphane
Le 16/10/2013 01:00, Darren Addy a écrit :
Y'all may recall
(hey, that rhymes!)
the m31 (Andromeda galaxy) image I shared a few days ago. It was a
single 45 second exposure and made from a single in-camera JPEG (not
even the RAW file).
Refresher link: http://www.flickr.com/photos/pixelsmithy/10181475554/
Well, I finally got to attempt my first use of the freeware
DeepSkyStacker (version 3.3.3 beta 51) and with it I stacked the 11
"good" RAW images that I had taken that evening. Added together, they
represent a 6 minute "integrated" exposure time.
The latest versions of DSS also let you work with the histogram (in R,
G, & B), luminance, and saturation, along with the curves. I then
applied a few Photoshop astrophotography-related actions and adjusted
the color-balance, which seemed a bit green to my eye. Here is the
result:
http://www.flickr.com/photos/pixelsmithy/10299785464/
This is still not even doing everything "right" because I was working
with no "dark frames", "bias frames", or "flats" which would make for
an even better stacked image (especially where noise is concerned).
Still I'm pretty pleased with the result, for my "maiden DSS voyage".
K-5ii, O-GPS1, ISO 800 K135mm f2.5 @ f4
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