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

Date: August 20, 2009 9:09:49 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: confidence intervals & frame selection

Hi Willie;

You have a "Type B - Single unskewed symmetric hump", as described on page 41 of the Astro IIDC manual and I copied the relevant section out of the manual:

--------- Start Quote

Type B - Single unskewed symmetric hump with a narrow range of sharpness values and a  small STD96 value of probably 0.05 and lower,as shown below. This is the curve you get on good imaging nights or if you take lots of sample under consistent skies. With this you should select a Confidence Interval percentage that is to the right of the central hump in around the 50 to 75% range, depending on how many frames you want to use in your stack. 

--------- End Quote

Your STD96 value is higher than I mention, but you also have a much higher sharpness value range than I typically see (I'm used to 1 or 2, your getting 5), so you can expect higher STD. You likely had Jupiter filling the image?

Your Brightness / Gains were fairly high (608 out of about 1024), so you likely need 100 to 300 frames to suppress the pixel noise, depending on how much sharpening you plan on doing after stacking.

HTH..

Milton Aupperle

--- In Astro_IIDC@yahoogroups.com, Willie Strickland <cwskas@...> wrote:

I had some fairly good seeing last night and therefore most of the  

frames that I took ended up on the right half of the graph.  See the  

screen shot below for an example.  Using that example, a CI of 55%  

provides 501 frames, CI of 68% selects 194 frames, 80% selects 87  

frames and 90% selects 41 frames.  I captured 1241 frames.  Here are  

excerpts from the logs.

At this stage of my experience, it is often hard for me to tell which  

provides the best results.  Would any of you care to comment on your  

reasoning?

=================== File:20090820_045333_U.mov #frames 1241

Monochrome Camera = Model:'DMx 21AF04.AS' SerialNumber: 0xFED2BB

CCD Image Left: 0

CCD Image Top: 0

CCD Image Width: 640

CCD Image: Height 480

Gamma: 1.60

Brightness: 608

Black Point: 0

Exposure: 16.67 ms

----Processing Movie: 20090820_045333_U.mov 1 of 1

Stacking : 8 Bit Movie

CI Cutoff: 90

Aligned Using: Luma Channel

Gross Alignment: Planetary

Pixel Alignment: Horizontal and Vertical Separate

Pixel Alignment Block Size: 96 x 96 pixels

Pixel Matching Tolerance :  6.00

Scale Frames by: 2 x

Frame Sharpening: Light

Gaussian Blur sharpness and alignment frames: Off

Sharpen alignment frames: Off

Auto Histogram Expand alignment frames: Off

HighQuality Bayer:Off

Auto Clip Area: Off

Adjust Pixel Comparison Area Brightness: Off

Remove Hot & Cold Pixels: Off

Binning Frames 2x2: Off

Averaging Images

Subtracting Background: Off

Sharpness Statistics: Min 4.862712 , Max 5.163545 , STD0.046297 , Mean  

5.027537 , Median 5.027230 , Mode 5.042507, CutOff  Value 5.110049

Pixel Matching Value:  6.00

Main Image Centroid   X:641.5, Y:973.7

Pixel Area Two   X:624.5, Y:433.7

Stacked 42 out of 1241 frames