Seeing Mercury, Finding it in Earth's sky Options

[ugordan]

The point of a gamma function is not to convey the entire dynamic range of what is probably a huge starting dynamic range in the first place. Your analogy with the Uranian system makes it seem that gamma correction doesn't have any place here on Earth, as you say a monitor can't cope with the huge dynamic range of our world down here. Yet it doesn't prevent anyone from watching TV here or using digital cameras on Earth and having reasonably good colors and contrast, albeit not as bright as the real thing.

Even if gamma destroys whites (and it's not exactly true, it's those white levels being close in brightness in the first place, also the Cassini image was overexposed by me accidentally), I can come up with a counterargumet that no gamma correction destroys darks - check out the terminator region in the rightmost image, it's gone. Either way - you lose detail somewhere, the question is which one is preferred.

Shoving linear data onto a computer screen has many advantages and don't get me wrong, I actually use very little to no gamma manipulation in my composites of most Saturnian system moons because they're bland as hell, but every once and again I like seeing the amount of contrast and color saturation an object would actually have in real life. Yes, the eye can make out a surprising amount of detail even in such cases especially on closer scrutiny, but having an accurate display on a screen is one step closer to what reality looks (at first glance at least, before your eye adapts to lower contrast of the real thing) than an inaccurate display.

Of all the solar system bodies, Mercury, Earth, the Moon and Mars are the places where I'd want to see gamma corrected imagery in addition to the usual processings just so I can visualize what they'd look like through a scope or simply naked eye. In case of Mercury, up until now all I saw were Mariner composites with very saturated brown colors yet observers said it just has a touch of a soft coppery hue.

[nprev]

...observers said it just has a touch of a soft coppery hue.

Maybe so. It's really hard to get a view of Mercury without a whole lot of sunset/sunrise skyglow, though (very favorable elongations aren't that common), and that's often reddish; might be predispositioning the observer's impressions. The last good look I had through a scope against a reasonably dark sky seemed brownish-gray to me; darker then the Moon, anyhow. Your colors seem reasonable, Gordan.

[ilbasso]

The first time I saw Mercury was during the May 9, 1970 transit. (That was a great year for my amateur astronomy! I also got to see the March 7, 1970 total solar eclipse!) I have seen Mercury 6 or 7 times since then, never telescopically, but usually when driving just after sunset and when there is a clear view of the western horizon. It is brighter than one would expect.

[JRehling]

Another bit of luck was when I arrived home near sunset one fine November day in Indiana, noticed that the Sun was, unusually, not setting into clouds, set up my solar projection and witnessed the transit that I knew was occurring but was too pessimistic to have expected clear skies for.

I think the unstated factor that truly makes Mercury challenging is that the near-horizon sky is statistically more likely to be cloudy, because of the longer lines of sight. Otherwise, even in a big city, it's just a matter of timing. It's one of the five brightest sky objects (sometimes) and it appears several degrees above the horizon at least a couple of times a year. Clouds are the only real enemy. In a continental climate, this may favor morning observations over evening (?). I used to think of Mercury as easy pickings on a winter morning. Assuming you're willing to go outside when it's cold and an indecent hour for being out of bed.