Question about "earth-shine"

I think it's down to the way the brain re-interprets what's actually there. I took a snap yesterday, in twilight, of the moon (small crescent, as you'll have observed, but clearly showing the earth-lit region), and a couple of contrails. (HP417 camera).

I've blown it up and played with the contrast etc. for ages, but I can't find any trace of a moon in my picture (sunlit or earthlit). Contrails are clearly visible, as are some whispy clouds I don't remember seeing when I took the shot. (They do show up in another shot of the sunset - so they weren't just artifacts).

Hi John,

I don't understand how you can't see the crescent moon in your photos when you can see contrails (= much lower contrast than the (sunlit) crescent moon, I would assume)

Strange..

-RF_G

Neither can I!

The sky was still pretty light - the sun had only just dipped below the horizon.

I've now cleaned my glasses - and found the moon!

Still can't see the earthshine, though .

Better chances at night when the contrast with the surrounding dark area is higher.

Good answer.

I think if the air stays stable as it is, we could have another good earth-shine night today but not sure. Never sure in the UK.

With regards to the sensitivity of the eyes I don't think that is the limiting factor here. We can only see down to magnitude 5.5 or 6 if all conditions favour good viewing but even at low magnification the sky seems to explode with tiny dots we cannot see with the naked eye.

I think it is down to the contrast difference in the image and the way the pixels react to the light difference between them. I cannot believe their is anything automatically adjusted in my frames as I shoot raw *.fts files without any manipulation until I come to stack them with registax4. Even when I play with all the settings at that stage, the earth-shine seems to have completely disappeared already. Tonight I may have a go again and totally over expose the crescent just to see if it does come out at all. CCD's are very sensitive and if exposed long enough and stacked afterwards it should be able to bring out light strengths down to magnitude 17 or more. My telescopes limit is about 14 I think so it should theoretically be possible.

All I can do is try.

Thanks for replies so far.

"...it should theoretically be possible..."

Indeed. But there are SO many things that are possible in theory and impossible in practice. I think you are on the right track with the surmise about the CCD pixelation. Do report back on the results of your empirical method investigation! Inquiring minds want to know...

"The dynamic range of our eyes far exceeds that of any film"

I think that is only somewhat true. Our eyes' dynamic range isn't really the case here, but our brains actually do the processing to give you the illusion of large dynamic range.

Case491, Another possibility is that you, like most humans have what biologists call "persistence of vision". That is what allows humans to view a CRT (Television, Computer screen etc.)

The brain processes the dimly lit image and "fills in the gaps" so to speak. Cameras, unless they are highly sophisticated (or mimic the eye/brain connection like a motion picture camera) don't fill in the gaps and take a nearly instantaneous snapshot.

Just a thought.

Dragon

Hi guys,

I have not had much luck since last but I have investigated more on the old web and found many nice pics which proofs it must be possible.

Not only theoretically but also practically shown in the following:

All these are beautiful and is exactly what I am after just because I like to.

If you want to learn more about earth shine you can go here for very clear description and graphics.

I will be trying again in about a week from now as the moon will be too large and bright for any shine until then.

See you all later.

I think that maybe I can see what is happening, you can probably only shoot earthshine properly when the bright (sunlight) part is very small or the camera adjusts the exposure for the brightly light part only......

Many I suggest a camera with a very small "spot" exposure meter only (most are switchable) and center on the earthshine part with the spot (also some camera allow you to define the "spot" position in the frame as well......

Does the cleanliness of the atmosphere locally influence things? While in Botswana a few years ago, a country not exactly renowned for air particulate levels, the non-sunlit part of the moon was visible as an almost-black disc to the naked eye, and clearly visible as a different colour as compared to the space beyond it. It's more difficult to see this in the UK.

Comments, please? _{<Subscribes to discussion>}

I'm quite sure it does. The colors seen in sunsets (and sunrises), after all, are due to dust and water vapor in the air near the horizon (and sometimes pretty far above it). I'll try to keep this in mind and see what I see in the near future.

As the atmosphere will undoubtedly have an effect just like it does with the lunar eclipses, It does not account for the "black disc" you describe when you were in Africa. I think that is more attributable to the fact that maybe there is less light from that part of the earth and ergo there is less to reflect back from the moon. You can look at one of my previous links to see how that would result in a darker moon.

The atmosphere does change the colours as we know from eclipses. The eclipses are normally coppery red as the light that hits the moon is actually refracted by our atmosphere as it passes the earth on its way to the moon. The long traveled distance through our air, gives the moon its red hue.

Pollution in the air is normally a problem in hot climates and well lit urban densely populated areas. England is not polluted enough to have a real effect on how well you can see the dark side of the moon but it gets adversely affected by light pollution. We need darker skies.

All of this is purely accademic as we now have a rotten cloud filled sky for the 3rd night running.