Martian Sky, What's it look like? Options

[nasaman58]

What I'm about to write could go equally well under the Opportunity section, but I had to put it somewhere. (Doug, maybe this ties to the post I wrote earlier in reply to your reorganization scheme about lumping oppy and spirit together).

Now, onto business...

I'm curious what the whole sky of Mars looks like. Whenever we get color pans, we only see a little strip of the sky (with the nice exception I believe Doug did of the sun above Eagle crater). Sure, the sky looks bright and maybe a tad bluish near the Sun, but what about up high near the zenith but away from the sun? Is it a dark brownish color? Or close to black?

On Sol 178 (July 4 for us Americans )when Spirit was climbing toward West Spur, the PanCam was pointed up, so we got to see some darker, higher altitude sky than we normally see. But I'd like to see basically a whole-sky or near whole-sky "pan" to see the color gradients. Consider this a challenge for you people with the right Photoshop/software hook-ups and mad skillz!

Attached thumbnail(s)

 

[Deimos]

I'm curious what the whole sky of Mars looks like. Whenever we get color pans, we only see a little strip of the sky (with the nice exception I believe Doug did of the sun above Eagle crater). Sure, the sky looks bright and maybe a tad bluish near the Sun, but what about up high near the zenith but away from the sun? Is it a dark brownish color? Or close to black?

On Sol 178 (July 4 for us Americans  )when Spirit was climbing toward West Spur, the PanCam was pointed up, so we got to see some darker, higher altitude sky than we normally see. But I'd like to see basically a whole-sky or near whole-sky "pan" to see the color gradients. Consider this a challenge for you people with the right Photoshop/software hook-ups and mad skillz!

There are lots of images. A further challenge would be to compare sol 178-ish with recent images, since there was much less dust way back then. The dust storms hit about sol 350 for Spirit, around our Ney Year. Dust was also high for the 50-100 sols after landing.

[Nirgal]

one problem is that for a reliable "true color" view, only the radiance calibrated composites obtained from the PDS archive should be considered.
(up to sol 180 so far, as of April 22, up to sol 270)
Such as posted, e.g. on http://www.lyle.org/~markoff/

Those pictures actually suggest a pinkish-bluish sky during dust-clear conditions.
At least for the strip of sky relatively near to the horizon.
However, I too have yet to see a real radiance calibrated near-true color
image where the visible strip of sky extends to more than, say 40 degrees above the horizon.

Many Navcam-pictures (due to the wider lens angle) do show considerably more of the sky towards the Zenit: many of them even up to near the "black" region
(and I simply can't belive that, due to the thin atmosphere, the color of the sky *near the Zenit* can't be anything other than nearly black)

The interesting thing would be the color just of the transition/gradient from the
sky to this "black" area.

[nasaman58]

one problem is that for a reliable "true color" view, only the radiance calibrated composites obtained from the PDS archive should be considered.
(up to sol 180 so far, as of April 22, up to sol 270)
Such as posted, e.g. on http://www.lyle.org/~markoff/

Those pictures actually suggest a pinkish-bluish sky during dust-clear conditions.
At least for the strip of sky relatively near to the horizon.
However, I too have yet to see a real radiance calibrated near-true color
image where the visible strip of sky extends to more than, say 40 degrees above the horizon.

Many Navcam-pictures (due to the wider lens angle) do show considerably more of the sky towards the Zenit: many of them even up to near the "black" region
(and I simply can't belive that, due to the thin atmosphere, the color of the sky *near the Zenit* can't be anything other than nearly black)

The interesting thing would be the color just of the transition/gradient from the
sky to this "black" area.

Yeah, that gradient would be great to see. I'd rather not consider NavCam pix, given their monochromatic nature and their seeming lack of a variable f-stop. That, in my opinion would exagerate the presumed blackness near 70 degrees or so above the horizon.

[Bubbinski]

Thanks for the link to lyle.org - I look forward to seeing more images there as they're calibrated.

I'm also curious as to what the night sky would look like and how the stars and planets would look from Mars. I assume that the night sky would look the same as on earth, as there'd be no light to illuminate the atmospheric dust. When Spirit took its images of Earth in the night sky near Bonneville crater on or about Sol 66(?) I had hoped to see a color image, but alas the image was from the Navcam. (Was the scene simply too dark for the Pancam?). Anyway, tonight I fiddled around with the image in Paint Shop Pro 7 and changed the histogram to Red 44, Green 54, Blue 94 just because it looked to me like a night sky should (totally unscientific), and I colored in the dot representing earth with what looked like a good shade of blue-green to me. (Again, a SWAG).

Here it is, a colorized image of Earth taken from Mars by Spirit. Does it look plausible?

Attached thumbnail(s)

 

[Nirgal]

Thanks for the link to lyle.org - I look forward to seeing more images there as they're calibrated.

I'm also curious as to what the night sky would look like and how the stars and planets would look from Mars.  I assume that the night sky would look the same as on earth, as there'd be no light to illuminate the atmospheric dust.  When Spirit took its images of Earth in the night sky near Bonneville crater on or about Sol 66(?) I had hoped to see a color image, but alas the image was from the Navcam.  (Was the scene simply too dark for the Pancam?).  Anyway, tonight I fiddled around with the image in Paint Shop Pro 7 and changed the histogram to Red 44, Green 54, Blue 94 just because it looked to me like a night sky should (totally unscientific), and I colored in the dot representing earth with what looked like a good shade of blue-green to me.  (Again, a SWAG). 

Here it is, a colorized image of Earth taken from Mars by Spirit.  Does it look plausible?

very well done !

also matches the impression of other pre-sunset views seen e.g. from the pathfinder mission.

However, if I remember correctly (?), wasn't the actual "dot" of the earth as a star not really visible in that original Spirit photo, so the people at JPL
inserted the earth for the press release image ?
Anyway: does anyone know if there are other earth-from-mars images
taken by one of the rovers ?

[Jeff7]

very well done !

also matches the impression of other pre-sunset views seen e.g. from the pathfinder mission.

However, if I remember correctly (?), wasn't the actual "dot" of the earth as a star not really visible in that original Spirit photo, so the people at JPL
inserted the earth for the press release image ?
Anyway: does anyone know if there are other earth-from-mars images
taken by one of the rovers ?

Link to the press release.

Seems like the Navcam didn't see Earth, but the Pancam did. Sol 63.
Looks like they made a mosaic then with the the Navcam image as the backdrop, and the image of Earth from the Pancam. And yes, they did take the Pancam photos in a variety of filters.

[Bubbinski]

very well done !

also matches the impression of other pre-sunset views seen e.g. from the pathfinder mission.

Thanks, Nirgal.

The pics by Spirit were taken one hour before sunrise....I assume the same blue halo around the sun would show then too, right? I'm wondering if maybe I used too much blue in my rendition to be realistic, but I like how it looks artistically, and it'll end up being my computer wallpaper.

In any case, using the Paint Shop Pro histogram function is merely adding a single, uniform color tone to an image. I'm a rank, and I do mean rank, amateur at image manipulation, a lot of the stuff I've seen on this board just blows my mind. For example, that Hazcam B&W image someone colorized was just awesome, I wish I had that kind of talent.

[4th rock from th...]

very well done !

also matches the impression of other pre-sunset views seen e.g. from the pathfinder mission.

Thanks, Nirgal.

The pics by Spirit were taken one hour before sunrise....I assume the same blue halo around the sun would show then too, right? I'm wondering if maybe I used too much blue in my rendition to be realistic, but I like how it looks artistically, and it'll end up being my computer wallpaper.

In any case, using the Paint Shop Pro histogram function is merely adding a single, uniform color tone to an image. I'm a rank, and I do mean rank, amateur at image manipulation, a lot of the stuff I've seen on this board just blows my mind. For example, that Hazcam B&W image someone colorized was just awesome, I wish I had that kind of talent.

Hi,

On my page http://www.astrosurf.com/nunes/explor/explor_vik.htm you can see a sequence of sunrise images from Viking 1. I've calibrated so that the surface maintains the same basic color as in daylight if you brighten the images. On the original data blue levels are very high, but I think the human eye should compensate for that, as it does on earth. Overall brightness levels seem to be acurate.

So I think your colorization is very close to the original data, but if you were there the saturation whould appear lower.

[Nirgal]

On my page http://www.astrosurf.com/nunes/explor/explor_vik.htm you can see a sequence of sunrise images from Viking 1. I've calibrated so that the surface maintains the same basic color as in daylight if you brighten the images. On the original data blue levels are very high, but I think the human eye should compensate for that, as it does on earth. Overall brightness levels seem to be acurate.

Hi forth_rock !

the color images on your site are absolutely awsome !
(Don Davis himself could not have made it better

Also your MGS wide angle color composites...

What I especially like, is that your colors seem accurate *and*
very aesthetically pleasant at the same time.

Do you allow me to pose just two questions about your MGS images ?

The MGS Wide Angle camera has only two filters (red & blue) so
I suppose that you synthesize the green channel as a mixture of red&blue,
right ?

From the MGS/MSSS site raw images, do you use the "processed" i.e contrast stretched (GIf,IMG) versions or the unprocessed (IMQ) versions as
starting point for your RGB-color composites ?

BTW.: recently, there are also wunderful MGS color wide angles posted here
by djellison (lovely Olympus Mons & Limb pictures

[djellison]

I made green by simply have a 50% transparent red image over the blue image. - I used the GIF's most of the time, but where an image was particularly dark, or light, or non-contrasting, I used the IMG instead

Doug

[Nirgal]

I made green by simply have a 50% transparent red image over the blue image. - I used the GIF's most of the time, but where an image was particularly dark, or light, or non-contrasting, I used the IMG instead

Doug

Thanks a lot for the info Doug ... always appreciated !

I tried several combinations for the green-channel
(+ saturation/contrast stretching)
but with little success so far ...
Colors still not nearly as vivid as in your or 4throck's pictures.
So I guess it's going to be also a lot of additional fine-tuning with histograms,
color correction etc. after the initial RGB-composition ...
Havn't spent too much time on it yet ... still too obsessed with those
single-band colorizations

[4th rock from th...]

On my page http://www.astrosurf.com/nunes/explor/explor_vik.htm you can see a sequence of sunrise images from Viking 1. I've calibrated so that the surface maintains the same basic color as in daylight if you brighten the images. On the original data blue levels are very high, but I think the human eye should compensate for that, as it does on earth. Overall brightness levels seem to be acurate.

Hi forth_rock !

the color images on your site are absolutely awsome !
(Don Davis himself could not have made it better

Also your MGS wide angle color composites...

What I especially like, is that your colors seem accurate *and*
very aesthetically pleasant at the same time.

Do you allow me to pose just two questions about your MGS images ?

The MGS Wide Angle camera has only two filters (red & blue) so
I suppose that you synthesize the green channel as a mixture of red&blue,
right ?

From the MGS/MSSS site raw images, do you use the "processed" i.e contrast stretched (GIf,IMG) versions or the unprocessed (IMQ) versions as
starting point for your RGB-color composites ?

BTW.: recently, there are also wunderful MGS color wide angles posted here
by djellison (lovely Olympus Mons & Limb pictures

Thankyou for your kind words.

For the MGS i used the Gif images, scaled the histograms using Mars Express and MER rover images as a guide for surface and sky colors and then created a green channel by mixing red and blue.
It isn't very accurate but the results are pleasing.

If you were in orbit the color might look different because of the atmosphere.
Light goes twice through the atmosphere on orbital images (sun - > down, reflected by the surface, up - > sensor).
By using surface images for reference I'm eliminating half of this effect, but i get more color variation and contrast. Otherwise it whould be "mars through red dust" type images.

Look at earth from space images and this effect is visible (lots of blue).

I'll put this explanations on my site some time in the future, as I did for the Viking stuff.

I like djellison images, great work there!

4throck