From: "milton_aupperle" <milton@outcastsoft.com>

Date: October 13, 2009 4:52:40 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Normal versus Binned 2x2 while stacking


Hi Folks;


Here is an example of what binning 2x2 when stacking can do you you.


Here is Messier 71, a faint compact Globular cluster shot with my Grasshopper camera using LRGB filters and in 16 bit monochrome.


This first image is generated using normal stacking of the 4 LRGB movies:


http://www.outcastsoft.com/AstroImages/M71_20090927_MJA.jpg


And here are the same movies processed with 2x2 binning while stacking:


http://www.outcastsoft.com/AstroImages/M71Bin2x2_20090927_MJA.jpg


That's basically just check marking the "Bin Frames 2x2 and auto subtract background before stacking." in the "Stacking Options.." window.


To use 2x2 effectively binning, you must have applied Flat Frame Correction and also Dark Frame Subtraction. If you don't you will get odd discolorations in your images, as shows up in my Veil Nebula image:


http://www.outcastsoft.com/AstroImages/NGC6960_20090722_MJA.jpg


which has bright red in the upper left corner and bluish green in the bottom right. I was not collecting proper darks and flats images when I shot it, and that's the end result.


Another place that 2x2 binning does not not work really well is with close to saturated images, like Messier 15 which has a very bright central core:


http://www.outcastsoft.com/AstroImages/M15_20090725_MJA.jpg


as all you wind up with is a big white central blob and scattering of stars on the edges.


HTH..


PS:


Calgary set a new record temperature on Monday morning of -16.1`°C, which is 25 to 30°C below seasonal normal temperatures. Sort of weird seeing trees with green leaves all over the place (we went summer to winter in 24 hours) and 10+ cm of snow everywhere. I sure hope this global warming kicks in soon before we all freeze to death.


Milton Aupperle