Hubble Observations, Home-brew colour images from ESO Archive Options

[djellison]

68 Colour observations of Mars that I've been able to make into reasonable images - the job of putting these into order, adding the ACS images into the chronological sequence and annotating them is 1) long and 2) saved for later...however

http://www.unmannedspaceflight.com/doug_im..._wfpc2_contact/

12 contact sheets ( 6 to a page ) outlining all of them at a browser-worthy res.

Doug

[tedstryk]

68 Colour observations of Mars that I've been able to make into reasonable images - the job of putting these into order, adding the ACS images into the chronological sequence and annotating them is 1) long and 2) saved for later...however

http://www.unmannedspaceflight.com/doug_im..._wfpc2_contact/

12 contact sheets ( 6 to a page ) outlining all of them at a browser-worthy res.

Doug

Doug, I was wondering your thoughts about that pervasive green. In my earlier WPFC1 work, I did everything I could to get rid of it, which nearly wiped out the color varations in the images. It seems like it shouldn't be there, but keeps poping up.

[djellison]

I figure it's because of using filter sets that are not particularly faithful to 'rgb' - it's more like the MER equiv of using L257 (and infact, that can come out a little green as well). Also - I'm not 100% confident when using the FITS Liberator - which high and low end value to use. I tried to use identical values for all of them but it varied a lot - and arguably the exposure is in the mix there somewhere.

Doug

[tedstryk]

So far, this is the best luck I have had. It is from Jan 2, 1991 with WFPC 1.



And the improved version...

[dvandorn]

Hmmm... I've seen Mars directly, with my own eye, through a 3-inch reflector and a 10-inch reflector. In both cases, the dark markings I could make out really looked distinctly greenish. No filters involved, and I don't think the mirrors in question failed to reflect any given wavelengths, or emphasized any others.

Is it possible that there *is* a certain greenish tinge to the dark-colored regions of Mars?

-the other Doug

[David]

Hmmm... I've seen Mars directly, with my own eye, through a 3-inch reflector and a 10-inch reflector. In both cases, the dark markings I could make out really looked distinctly greenish. No filters involved, and I don't think the mirrors in question failed to reflect any given wavelengths, or emphasized any others.

Is it possible that there *is* a certain greenish tinge to the dark-colored regions of Mars?

-the other Doug

I think that the greenish tint has been reported since the 19th century. I've often seen it put down to a trick of the eye, looking for a contrast with the reddish tint of the rest of Mars; but it certainly looks real enough on those Hubble images.

The greenishness was one of the things that convinced some early astronomers that there must be life on Mars -- they were interpreting the patches as vegetation! Seasonal changes (due to wind transport and deposition) were interpreted as seasonal growth and retreat of whatever it was (lichens?) that was thought to form the green bits.

And of course earlier they were thought to be seas, and still have Mare... names in albedo maps. The idea that they were seas was dropped when Lowell thought he saw canals running through them -- an example of the right conclusion being drawn for the wrong reasons. This was then transformed into the concept that Mars had had seas, but then lost them -- a concept that we are still struggling with today, though hopefully on a sounder basis. Once an idea takes hold and captures the imagination, it can be very difficult to eradicate!

[djellison]

ut it certainly looks real enough on those Hubble images.

You're assuming that the Hubble images are right, given my processing so far, I'd wager they're more wrong that right.

Doug

[David]

You're assuming that the Hubble images are right, given my processing so far, I'd wager they're more wrong that right.

I've got all kinds of assumptions, but with regard to the large-scale dark patches on Mars my assumption is that the "real" color is something like what we saw at El Dorado. I simply meant that in the Hubble images you processed the color looks to be really greenish, and not just an optical effect; but I assume that's an artifact of how the images are put together. So I can't take your wager, as I'd be betting against myself.

[djellison]

I'd be betting against myself.

But think of the odd's you could give yourself

Doug