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Venus Full Disk -mariner 10
Guest_BruceMoomaw_*
post Sep 14 2005, 09:30 AM
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Weird story from Bruce Murray's autobiography, "Journey Into Space": Apparently James Fletcher -- the chronically deceitful NASA head appointed by Nixon (big surprise) -- asked Murray whether color views of Mercury could be reconstructed from Mariner 10's photos for public release. When Murray told him that the craft's color filters weren't right for true-color views, Fletcher asked Murray -- to his disbelief --whether he could FAKE them.
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Malmer
post Sep 14 2005, 11:46 AM
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Im not sure on what to do with the picture named "VENUS_HQ_MOSAIC.jpg"
I want it to be as natural in color as possible. Does anyone have any telescopic pictures that i can use as reference? (did hubble ever picture venus in visible light?)


I searched trough the mariner edrs and found this "minusUV" filtered image of the southern pole. it clearly shows some kind of markings/bandings.

The minus uv filter reaches from about 400 to 670nm and is centered on 511nm. So it basically covers the visible spectra. (missing out some in the reds) so whatever brightness variations that shows up in this picture should be visible to the eye. and remember that these pictures only contain 256 levels and that the screen on your computer is extremly low in dynamic range. so whatever detail shows up here would be easy to see in real life. im also not sure about the linearity of the videocons. Usually cameras are slightly logaritmic. So in reality the scene is probably more contrasty.

I also found an orange image showing the same area. they are very much alike. But since they where photographed by different cameras with unknown properties* its hard to know what colors would actually be there.

*unknown to me at least, I sure would like to find the calibration report... anyone?

Mattias
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edstrick
post Sep 14 2005, 12:10 PM
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Those are the one midrange set (if I recall) of Mariner 10 non-UV imagery. I'd have to dig through 23+ year old notebooks and stuff to find my documenatation on what was taken when.

See Mark S. Robinson's Mercury work with Mariner 10
http://cps.earth.northwestern.edu/index.html
He has done photometric work with Mariner 10 data and should be able to chase down the documents.
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Malmer
post Sep 14 2005, 01:07 PM
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I wrote a simple 3dsmax script that converted the mariner raw tape dumps into "png" files. It also created a corresponding text file with the image label info.

Then i wrote a second script that went trough all files and renamed them to YearDayGmtFDS.png so that i could sort out the FDS resets and move the files into Folders one for each FDS reset. Then i finally renamed the files to FDS.png. (and put all duplicate images in a special folder.)

I also made a log file for each folder that contains all lable data for each image.
FDS, Year, Day, GMT, Camera, Filter and Exposure.

So now I have a mariner dataset in cronological order. (makes everything way easier to handle). Its easy to find each mosaic, I just look in the log file or use photoshops File Browser to find what I need.

I will contact Mark about the calibration report. (thanks for the pointer)

Btw, I have made a bunch of other large panoramas aswell. I need to make some kind of hompage at some point to showcase them all... for now its just a folder on the internet...

take a look at :
A folder with most of my composites
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tedstryk
post Sep 14 2005, 01:10 PM
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Every telescopic photo I have seen has been basically white. That is the result that I get too.


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4th rock from th...
post Sep 14 2005, 02:06 PM
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All my webcam images of Venus, taken with a 8'' telescope show a white disk. But if I push the saturation to extreme values (like 80% or 90%) I get a orange disk with blue-white poles.

Visually I've never seen any color. But color variations through a telescope are always weak. Jupiter is almost white with some brownish dark bands. Even the Great Red Spot looks grey/brown. You see variations in brighness, but not in color, unless seeing conditions are excelent...

You can find some good telescopic images of Venus (and other planets) here:
http://www.kk-system.co.jp/Alpo/Latest/index.html

A very nice Venus in diferent wavelenghts:
http://www.kk-system.co.jp/Alpo/kk04/v041001z.htm


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Bob Shaw
post Sep 14 2005, 03:51 PM
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QUOTE (Malmer @ Sep 14 2005, 02:07 PM)
Btw, I have made a bunch of other large panoramas aswell. I need to make some kind of hompage at some point to showcase them all... for now its just a folder on the internet...

take a look at :
A folder with most of my composites
*


Great images!


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JRehling
post Sep 14 2005, 05:49 PM
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QUOTE (edstrick @ Sep 14 2005, 02:07 AM)
JRheling: "Here's an image I've created using the Clear and Blue bandpass filters. Not much details, but this is what you would see if you were there. General color balance is a  best guess."

That's the one I was talking about.
*


That was 4th Rock who created it (I quoted him); I can't take credit for his fine work.

And you join the millions who seem to prefer that I switch the order of letters in my name...
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Malmer
post Sep 17 2005, 08:08 PM
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I noticed that the mariner 10 images have nonsquare pixels. Will fix the panoramas tomorrow. Now they are slightly stretched.

The telescope has a fov of 0.48*0.36.
the raw images are 832*700 pixels and should be resized to 933*700 to be "square"

/Mattias
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tedstryk
post Sep 17 2005, 08:52 PM
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QUOTE (Malmer @ Sep 17 2005, 08:08 PM)
I noticed that the mariner 10 images have nonsquare pixels. Will fix the panoramas tomorrow. Now they are slightly stretched.

The telescope has a fov of 0.48*0.36.
the raw images are 832*700 pixels and should be resized to 933*700 to be "square"

/Mattias
*


Out of curiousity, where did you find that information. I had known they were nonsquare, but I never knew the precise measurements.


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dilo
post Sep 17 2005, 09:35 PM
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Malmer, your work is simply outstanding, congratulations!
I made a false color image starting from R/B/UV channels...
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Malmer
post Sep 18 2005, 09:15 AM
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QUOTE (tedstryk @ Sep 17 2005, 10:52 PM)
Out of curiousity, where did you find that information.  I had known they were nonsquare, but I never knew the precise measurements.
*



I was talking to Don Mitchell and he sent me a paper that had some information on the cameras. Not much but some, I still need more info on the cameras to be able to calibrate the images.

the paper

It seems to be correct information because the venus disc gets perfectly circular when i stretch the images using this data.

Mattias
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edstrick
post Sep 18 2005, 10:26 AM
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Note that in addition to any non-squareness of pixels, all planetary images taken with vidicon type cameras have other distortions as well. Mariner 6/7 and 9 were particularly bad, with pincushion distortion making the corners stick out and the real images's sides slightly concave, and small amounts of parallelogram distortion, etc. These distortions were as bad as 10-15% as I recall on the earlier missions.
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Malmer
post Sep 18 2005, 10:54 AM
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QUOTE (edstrick @ Sep 18 2005, 12:26 PM)
Note that in addition to any non-squareness of pixels, all planetary images taken with vidicon type cameras have other distortions as well.  Mariner 6/7 and 9 were particularly bad, with pincushion distortion making the corners stick out and the real images's sides slightly concave, and small amounts of parallelogram distortion, etc.  These distortions were as bad as 10-15% as I recall on the earlier missions.
*


It would be great to know the undistorted positions of the Mariner 10 reseau marks. then it would be possible to write a featuretracking software that goes trough the images, finds the marks and saves the data to file. (with a confidence rating for each mark)

this data could then easily be used to rectify the images. (just feed the data into a polygonal mesh, texture it and warp it to the rectified shape)

/M
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tedstryk
post Sep 18 2005, 12:44 PM
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QUOTE (Malmer @ Sep 18 2005, 09:15 AM)
I was talking to Don Mitchell and he sent me a paper that had some information on the cameras. Not much but some, I still need more info on the cameras to be able to calibrate the images.

the paper

It seems to be correct information because the venus disc gets perfectly circular when i stretch the images using this data.

Mattias
*



Thanks!


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