From: Alan Friedman <alan@greatarrow.com>

Date: July 31, 2006 11:33:51 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Transit of Io 16 June 2006

Hi Cal -

That's a fine first image. Great to record the transit and you can just make out oval BA (aka red jr) to the lower right of the GRS. Color is very nice.

There is some debate on how to record the seeing quality - all of the methods will become more meaningful with experience. I use a simple "report card" method now - poor (would have been better to go back to sleep), fair (4-5 Pickering), good (6-7 Pickering), excellent (pinch myself to make sure it's not a dream). Needless to say fair/good covers 99% of the conditions at my location when it is worthwhile to image.

Gamma at 1.6 seems high to me - I usually use 1.0 to a max of 1.3 with my B&W DMK camera (not sure if the settings have the same meaning with your camera). But the image quality doesn't indicate a problem to my eye and I think there may be an advantage to stacking to increase the contrast in the frames. I usually use a lower pixel matching tolerance too but it seems that most of the selected frames were stacked so it doesn't seem to have been a problem at this image scale.

Look forward to seeing more of your images.

Alan

ps - no apologies needed, but thanks for the reference! 8^)

On Jul 31, 2006, at 11:50 AM, k.logg wrote:

Hi all

This is my first ever image. It was only meant to be an exercise in

familiarising myself with Astro IIDC. It was pure luck that I captured

the transit of Io on the 16 June.

http://groups.yahoo.com/group/Astro_IIDC/files/Planetary/Transit of Io

16 June 2006.jpg

As I'm new to this I don't know how to quantify the seeing,

transparency. It was clear but not very dark this close to the

Solstice and the atmosphere was pretty turbulent, particular as

Jupiter was so low in the sky. Hence so few frames captured using a

Unibrain Fire-i colour webcam at f10 on a friend's 8" LX200 (altaz)

Below are the logs from Astro IIDC, any comments will be gratefully

received, as I really have no idea what I'm doing.

Settings for Astro IIDC image capture were as follows;

Gamma: 1.64

Saturation: 36

Blue Gain: 115

Red Gain: 69

Brightness: 102

Black Point: 248

Exposure: 133.33 ms

Settings for Astro IIDC stacking and processing:

Stacking : 8 Bit Movie

CI Cutoff: 60 %

Aligned Using:Luma Channel

Gross Alignment: Planetary

Pixel Alignment: Horizontal and Vertical Separate

Pixel Alignment Block Size: 32 x 32 pixels

Pixel Matching Tolerance : High

Scale Frames by: 1 x

Frame Sharpening: Medium

HighQuality Bayer: Off

Auto Clip Area: On

Averaging Images

Sharpness Statistics: Min 0.759031 , Max 0.833257 ,

STD0.013007 , Mean 0.795522 , Median 0.795564 , Mode

0.793824, CutOff Value 0.802748

Pixel Noise Percentage: 0.392157

Main Image Centroid X:243.7, Y:205.8

Pixel Area One Centroid X:270.7, Y:189.8

Pixel Area Two Centroid X:234.7, Y:227.8

Stacked 198 out of 680 frames

Final processing using Photoshop.

Best wishes

Cal

PS Apologies to Alan Friedman as I've pretty much copied your method

of presenting the image.

__._,_.___

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