Previous in Forum: hydraulic oil   Next in Forum: What are the Most Dangerous Technologies, and Why?
Close
Close
Close
23 comments
Guru

Join Date: Sep 2007
Posts: 1817
Good Answers: 7

Question about "earth-shine"

02/10/2008 1:58 PM

Hi folk,

I have noticed that when I image the moon with my CCD on the telescope, the earth-shine disappears.

When you look at a new or old moon, often the light reflected from the earth bounces back to the moon, showing the "dark" outline of what is not directly lit up by the sun. This looks spectacular when viewed with the naked eye or low powered bino's but in the telescope it completely goes away.

Is there a way, other than to grotesquely over expose the crescent moon itself, to mimic the low powered bino view with the CCD? I would like to image the "dawn" and the view beyond it without loosing the detail of the moonscape on the other side of the dawn.

Probably not possible but you have to ask

Register to Reply
Pathfinder Tags: ccd earth shine earthshine Moon
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 467
#1

Re: Question about "earth-shine"

02/10/2008 4:49 PM

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).

__________________
"Love justice, you who rule the world" - Dante Alighieri
Register to Reply
Power-User

Join Date: Apr 2007
Location: n. Switzerland
Posts: 133
Good Answers: 6
#2
In reply to #1

Re: Question about "earth-shine"

02/11/2008 3:54 AM

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

__________________
Regards, RF_guy
Register to Reply
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 467
#3
In reply to #2

Re: Question about "earth-shine"

02/11/2008 4:11 AM

Neither can I!

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

__________________
"Love justice, you who rule the world" - Dante Alighieri
Register to Reply
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 467
#7
In reply to #2

Re: Question about "earth-shine"

02/11/2008 8:50 AM

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

Still can't see the earthshine, though .

__________________
"Love justice, you who rule the world" - Dante Alighieri
Register to Reply
Guru

Join Date: Sep 2007
Posts: 1817
Good Answers: 7
#9
In reply to #7

Re: Question about "earth-shine"

02/11/2008 1:25 PM

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

Register to Reply
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 467
#10
In reply to #9

Re: Question about "earth-shine"

02/11/2008 5:29 PM

Agreed, but my poxy snapshot camera (HP M417) won't let me override the fancy settings & get into Manual. Once it gets a bit too dark, you have to use Nighttime mode - flash then wait about ½ second to soak up a bit of the stuff the flash didn't reach. I keep trying to fool it - get a bit of something in the (peripheral) foreground, so the flash is happy, then hope something comes out from the "long" exposure bit.

I fooled it once by taking a 'normal' shot with a sodium streetlamp at the edge - the only time I've got anywhere near a decent shot of the moon:

One day I'll splash out on a digital SLR ...

__________________
"Love justice, you who rule the world" - Dante Alighieri
Register to Reply Off Topic (Score 5)
Guru
United States - US - Statue of Liberty - New Member Hobbies - Fishing - New Member

Join Date: Nov 2007
Location: Gone to Alabama with my banjo on my knee...
Posts: 5595
Good Answers: 20
#11
In reply to #10

Re: Question about "earth-shine"

02/11/2008 5:36 PM

See, they add on all these fancy features to make the use of the thing as idiot-proof as possible for people who've not got a clue. The folks who DO have a clue are then forced to put up with all of the crapola that makes life difficult instead. Ought to be able to turn the fool flash off though, dern it!

__________________
Veni, vidi, video - I came, I saw, I got it on film.
Register to Reply Off Topic (Score 5)
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 467
#12
In reply to #11

Re: Question about "earth-shine"

02/11/2008 5:45 PM

You can turn the flash off - but then you can't get the 'long' exposure .

Another thing I wanted to do was use it to make time-lapse movies. I asked HP if the camera could be controlled via the USB - they thought about it for a week or so, then said "No, sorry - use a webcam". .

__________________
"Love justice, you who rule the world" - Dante Alighieri
Register to Reply Off Topic (Score 5)
2
Power-User

Join Date: Apr 2007
Location: n. Switzerland
Posts: 133
Good Answers: 6
#4

Re: Question about "earth-shine"

02/11/2008 4:19 AM

Hi case

as I'm sure you're aware, our senses are...sensitive. Incredibly, in fact. The dynamic range of our eyes far exceeds that of any film, let alone CCD sensors.

My guess is that the moon lit by earthshine isn't bright enough in comparison to the sky background to show up on the CCD...and/or there's automatic exposure compensation happening which is 'compressing' the eartshine. Can you force it to overexpose by a couple of stops?

I've done a fair amount of (amateur, obervational) astronomy, worked in a planetarium for many years, etc. Earthshine continues to fascinate me (one of those simple things..), but it's a pretty low-contrast phenonemon. Many times I've observed a 'perfect' crescent moon which should have exhibited very fine earthshine effect, but it remained invisible because of haze & humidity in the evening (or morning) resulting in high background sky illumination.

The recent crescent moon we're all watching and talking about has indeed been spectacular, especially here in Europe. We're presently experiencing a very powerful high-pressure area across Europe, whose corresponding reduced humidity leads to quite high-contrast skyies at sunset. However, the (solar-illuminated) crescent is growing fast so in order to observe earthshine under favorable conditions again we're going to have to wait at least 20 days or so...

-RF_G

__________________
Regards, RF_guy
Register to Reply Good Answer (Score 2)
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#5
In reply to #4

Re: Question about "earth-shine"

02/11/2008 6:53 AM

Good answer.

__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply
Guru

Join Date: Sep 2007
Posts: 1817
Good Answers: 7
#6
In reply to #4

Re: Question about "earth-shine"

02/11/2008 8:29 AM

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.

Register to Reply
Guru
United States - US - Statue of Liberty - New Member Hobbies - Fishing - New Member

Join Date: Nov 2007
Location: Gone to Alabama with my banjo on my knee...
Posts: 5595
Good Answers: 20
#8
In reply to #6

Re: Question about "earth-shine"

02/11/2008 12:19 PM

"...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...

__________________
Veni, vidi, video - I came, I saw, I got it on film.
Register to Reply
Guru
Popular Science - Evolution - New Member Popular Science - Weaponology - New Member

Join Date: May 2006
Location: The 'Space Coast', USA
Posts: 11109
Good Answers: 918
#13
In reply to #4

Re: Question about "earth-shine"

02/11/2008 8:57 PM

"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.

Register to Reply
Guru
Popular Science - Cosmology - New Member Popular Science - Paleontology - New Member Popular Science - Weaponology - New Member Popular Science - Evolution - New Member Popular Science - Genetics - New Member Popular Science - Biology - New Member

Join Date: Nov 2007
Location: The Nevernever as much as possible, Earth when I have no choice.
Posts: 665
Good Answers: 11
#14

Re: Question about "earth-shine"

02/11/2008 9:50 PM

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

__________________
Ignorance is the beginning of knowledge. Heresy is the beginning of wisdom. The ignorant heretic is the wisest of all.
Register to Reply
Guru

Join Date: Sep 2007
Posts: 1817
Good Answers: 7
#15

Re: Question about "earth-shine"

02/13/2008 1:34 PM

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.

Register to Reply
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 467
#16
In reply to #15

Re: Question about "earth-shine"

02/13/2008 4:51 PM

Did these come with info. about the optics/imaging system?

As I think I've already said, I'd dearly love a decent digital SLR, but there's too much other stuff to get and/or pay for first.

My ancient Acer laptop's on it's last legs - & I need one for service work etc.

Small has just got through an audition to be in a performance of High School Musical. Show fees, costumes etc follow - then the sting: we'll have to buy tickets to watch her perform!

See you later, SLR!

__________________
"Love justice, you who rule the world" - Dante Alighieri
Register to Reply Off Topic (Score 5)
Guru

Join Date: Sep 2007
Posts: 1817
Good Answers: 7
#17
In reply to #16

Re: Question about "earth-shine"

02/13/2008 5:02 PM

No unfortunately not much in the way of "here is how we did it, now go and do it yourself"

All without exeption are from astronomical websites and done with high end dslr cameras. No further details about iso, stops, shutter speeds etc, etc.

I have asked my brother to do some experiments as he has a canon fancy digi thing but he did not manage good results on the first night either. He is however going to do some more and also is waiting for delivery of a nice 200 mm vivitar lens which he reckons will be able to show craters. I need to see them before I believe as my bino is 7x and very light sensitive and craters are difficult to determine by hand. Maybe better on tripod.

Go buy tickets for offspring concert, you chose to have kids, you need to teach them culture. I am in the same boat here, trust me, if bringing up is done right, you'll love them forever

Register to Reply Off Topic (Score 5)
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 467
#18
In reply to #17

Re: Question about "earth-shine"

02/13/2008 5:27 PM

Looking forward to results. Tripod essential for any serious observation (scope, bins or camera).

Culcha? culcha? dont tork to me abat fu'in culcha - im up to the fu'in ereoles wiv it. an weev gotta pay for anuver 5 fu'in ars a week for the brats to get more fu'in culcha!

__________________
"Love justice, you who rule the world" - Dante Alighieri
Register to Reply Off Topic (Score 5)
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#19
In reply to #15

Re: Question about "earth-shine"

02/14/2008 4:36 AM

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......

__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 30581
Good Answers: 822
#23
In reply to #15

Re: Question about "earth-shine"

02/15/2008 7:04 AM

Beautiful images. Music album covers, perhaps?

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply Off Topic (Score 5)
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 30581
Good Answers: 822
#20

Re: Question about "earth-shine"

02/14/2008 8:39 AM

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>

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru
United States - US - Statue of Liberty - New Member Hobbies - Fishing - New Member

Join Date: Nov 2007
Location: Gone to Alabama with my banjo on my knee...
Posts: 5595
Good Answers: 20
#21
In reply to #20

Re: Question about "earth-shine"

02/14/2008 9:21 AM

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.

__________________
Veni, vidi, video - I came, I saw, I got it on film.
Register to Reply
Guru

Join Date: Sep 2007
Posts: 1817
Good Answers: 7
#22
In reply to #20

Re: Question about "earth-shine"

02/14/2008 2:45 PM

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.

Register to Reply
Register to Reply 23 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".
Copy to Clipboard

Users who posted comments:

Andy Germany (2); Anonymous Hero (1); case491 (5); Dragonsfarm (1); EnviroMan (3); JohnDG (7); PWSlack (2); RF_guy (2)

Previous in Forum: hydraulic oil   Next in Forum: What are the Most Dangerous Technologies, and Why?
You might be interested in: CCD Cameras, CCD Image Sensors, Telescopes

Advertisement