From: Milton Aupperle <milton@outcastsoft.com>
Date: January 31, 2008 9:55:00 AM MST
To: Astro_IIDC@yahoogroups.com
Subject: Re: [Astro_IIDC] Feature Request
Dear Jeff;
On 31-Jan-08, at 8:50 AM, Jeff Phillips wrote:
Would it be possible to incorporate a waveform monitor into Astro IIDC? The histogram doesn't seem to provide useful info for planetary imaging (unless I'm missing something).
What the issue is that the number of back ground pixels over whelm the number of pixels for the planetary object.
For example, assume a 30 pixel radius Mars disk in a 640x480 image. Mars would occupy 2827 pixels out of 307200 pixels in the image. Even if there were 2 colors in the image (background black and Mars a single red shade), mars only accounts for 0.92% of the histogram values. If you actually spread Mars over the actual range of pixel brightnesses it has (say 40 to 160), then your dealing with around 0.078% of the pixels for each color above the background.
Or if I could use this program to monitor the incoming video, that'd be OK, too.
<http://www.bigmugsoftware.com/monitor/help/>
That product requires QuickTime which Astro IIDC doesn't use and would still be subject to the same issue as above (unless it does "spot" measurements, which I didn't notice in my quick look).
What you really need is to be able to crop the image until only Mars / Saturn etc. nearly fills the frame, and then the histogram would have more image than background. With other cameras that's possible but not the TIS cameras because they don't support hardware cropping. The problem with this approach is that with long focal lengths if you have any image drift because your alignment is off, your target could slide outside the field of view.
It's too late to do it in Version 4 (the features for it are set in stone), however it's possible that in a future release we can allow you to set up a "Live Spot Histogram". Basically you would select a pixel width for the size of square you want to measure (i.e. 16, 32, 48, 64, 96, 128 pixels etc.) and then Astro IIDC will do a live centroid track of the object to keep the box centered around the target. Then it could generate the histogram from whatever is inside the boxed area.
As an available cheap solution, you might want to also want to explore using the "DigitalColor Meter" application (it's in your Applications/Utilities Folder ). It has the ability to measure the RGB color pixel values of a single or block of pixels under the cursor in real time (for real time, you need to set this in it's Preferences)..I've used it in the past for color balancing planets and also determining how much actual image brightness I'm getting too. I like to keep my target brightness around 50 to 65% of the maximum pixel range (i.e. 125 to 165 for 8 bit cameras) to so that my white areas don't get over saturated or set too low. I find that when I'm looking at the LapTop screen in the dark I grossly underestimate the brightness of the target.
Hope That Helps..
Milton J. Aupperle
President
ASC - Aupperle Services and Contracting
Mac Software (Drivers, Components and Application) Specialist
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