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 <[email protected]> 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 >> <[email protected]> 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 >>>> >>> >>> -- >>> PDML Pentax-Discuss Mail List >>> [email protected] >>> http://pdml.net/mailman/listinfo/pdml_pdml.net >>> to UNSUBSCRIBE from the PDML, please visit the link directly above and >>> follow the directions. >> >> >> > > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and > follow the directions. -- Nothing is sure but death and Pentaxes. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
