From: Mark Gaffney <markgaffney@me.com>
Date: November 11, 2009 4:09:57 PM MST
To: Astro_IIDC@yahoogroups.com
Subject: Re: [Astro_IIDC] a comparison of two stacks
Hi Howard, Milton & Alan,
I`m getting "document not found" for Howard`s comparison-has the file since been removed? I tried Registax at the time of the initial new version. Apart from the difficulty of converting from Astro IIDC`s native de-bayered QT movies to .avi (Registax can`t be used for image acquisition like Astro IIDC) I found it to be impossibly complex. I had little patience with it at the time because I had only Virtual PC for Mac & had the problem that the green Registax logo kept getting stuck in the middle of things & stopping any progress! I have it on my PC now but haven`t returned to use it as I pestered Milton in the meantime `til he disclosed in more layman`s terms how to use "stacking & aligning" etc. in Astro IIDC. I usually find with my PGR cameras that I can find quite easily 21 or so selection areas with a pixel variance over 10.0 & this is a figure I usually stick to (21 areas). I know that many more are perhaps viable but am usually stacking so many movies that it keeps me up the rest of the night spent imaging & much of the following day just using 21! By the way I did a spring clean of my Mac Mini G4`s desktop yesterday & dragged (I thought!) my folder with my movies from the 5th November with the Scorpion to my Lacie external HD. It hasn`t turned up there though, anywhere & I`ve done a quite extensive search to see if I doubled it up somewhere else!? It`ll teach me to check that important folders like this are saved (which I usually do!) before trashing the originals. I spent another frustrating hour or so attempting polar alignment last night but found that my south placement by compass left no room for adjustment in the right direction by the mount control knobs! I was using Sirius for "All Star" alignment which was perhaps too easterly (although I wasn`t getting a warning this time).I`ve set the tripod now so it was pointing at the Large Magellenic Cloud which was directly on the meridian at the time according to TheSky X & will try again anon...
Mark.
On 12/11/2009, at 8:39 AM, Milton Aupperle wrote:
Howard;
You have 3 alignment points in Astro IIDC and 250 in Registax - so what are you comparing here? Although you can't find them anymore due to Yahoos' broken search engine, I've shown in the past the difference between one and using 82 MAP points for Stacking (see "SingleVersuMultipleMAP.jpg " file in the "Others" folder).
Stacking in Astro IIDC does very little image manipulation of the frames during the stacking process, while Registax appears to be doing quite a bit. In my opinion, that's a post stacking process that can best be done interactively in Astro IIDC or other Apps like PhotoShop.
Also read how %CI works on page 31, as Quoted below:
The "Only stack frames whose sharpness exceeds the" slider allows you to select the statistical percentage of frames that will be stacked. Each frame in the movie will be analyzed
and assigned a sharpness value. Based on your specified percentage (0 to 100) Confidence Interval, the frames will be included or excluded from stacking. The lower the slider value the
less selective it is and the more frames are included.
The key to understanding it is highlighted in bold above. The higher the CI percentage, the fewer the frames that are to be stacked. If you use the Histogram sheet Astro IIDC displays, you'll see that hoe manipulating the slider affects how many frames are to be included for stacking.
HTH..
Milton Aupperle
On 11-Nov-09, at 2:02 PM, Howard wrote:
The images are cropped from the originals and enlarged 200%. They use the same source movie, converted to avi for Registax at no compression, best frame rate and millions of colors. The AstroIIDC image retained more of the original width. The Registax stack had one big hole and some ragged edges. The Registax has artifacts introduced; a bunch of parallel lines. It's sharper but darker. The astro is a bit softer but the color is better. It also responds to the levels control in photoshop more smoothly. Setting levels from the registax result never gave me the long shadow of a mountain just on the terminator without blowing out everything else, while the astro lets me control the contrast of the mountain shadow while retaining contrast of the rest.
The image I submitted yesterday was only 3 seconds long, and every frame was 90%. These exposures are a minute long and only 6 frames made it to 90% CI. These were both stacked at 80% CI.
Howard Fink
