APOD: Sunshine, Earthshine (2015 Mar 20)

Comments and questions about the APOD on the main view screen.
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APOD: Sunshine, Earthshine (2015 Mar 20)

Post by APOD Robot » Fri Mar 20, 2015 4:07 am

Image Sunshine, Earthshine

Explanation: Today's date marks an Equinox and a New Moon. Remarkably, while the exact timing of both geocentric events occur within a span of only 13 hours, the moon also reaches its new phase only 14 hours after perigee, the closest point in its orbit. That makes the Equinox New Moon the largest New Moon of 2015, though hard to see since that lunar phase presents the Moon's dark, night side to planet Earth. Still, in this well composed image of a young lunar phase from late January you can glimpse both night and day on the lunar surface, the night side faintly illuminated by Earthshine next to the day side's brightly sunlit crescent. But some will see today's Equinox New Moon in silhouette! The Equinox Solar Eclipse will be total across stretches of the Arctic Ocean, visible in partial phases from Europe, northern Africa and western Asia.

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by alter-ego » Fri Mar 20, 2015 5:08 am

Speaking about focal reducers ...
A pessimist is nothing more than an experienced optimist

roger roger gilmour

Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by roger roger gilmour » Fri Mar 20, 2015 5:32 am

Matter of fact, it's all dark.

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by Boomer12k » Fri Mar 20, 2015 7:45 am

Guess it too is all relative to where you are....

Got out the binocs tonight.... Need to use my tripod more... :D

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by R. Loeppky » Fri Mar 20, 2015 12:41 pm

Error in last sentence; I think it should be North Atlantic Ocean, not Arctic Ocean.

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by Chris Peterson » Fri Mar 20, 2015 2:14 pm

R. Loeppky wrote:Error in last sentence; I think it should be North Atlantic Ocean, not Arctic Ocean.
Arctic Ocean is certainly correct. The North Atlantic should also be included, as the eclipse was visible there, too.
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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by firstmagnitude » Fri Mar 20, 2015 3:37 pm

No "lunar wave?!" :lol2:

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by MarkBour » Fri Mar 20, 2015 4:07 pm

In today's APOD, why does the dark portion of the moon get darker as one approaches the terminator ?
Mark Goldfain

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by JohnD » Fri Mar 20, 2015 5:19 pm

This is supposed to be a megamoon, at the time of the Eclipse, so apparently big Moon.

Will this deprive observers in the line of totality of Bailey's Beads, as the rim of the Sun shines between the Mountains of the Moon?
They should still see the Diamond Ring, though.

JOhn

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by Chris Peterson » Fri Mar 20, 2015 5:21 pm

MarkBour wrote:In today's APOD, why does the dark portion of the moon get darker as one approaches the terminator ?
You need to consider how to make an image like this. The dynamic range of the actual Earthshine lit Moon is much to wide to display on a monitor in a linear fashion. Indeed, it is too wide to effectively capture in a single image with a typical electronic detector. So you need to use images made at several exposures, and composite them using something like an HDR technique. But the images exposed for the dark region will have a large amount of scatter and glare from the massively overexposed lit region, which will largely be near the terminator. So in combining the images, it's necessary to create some sort of gradient mask to reduce that glare. But that mask will also darken the zone just inside the terminator on the dark side. It would be extremely tricky to eliminate this effect entirely.

In other words, what we're seeing is a residual processing artifact.
Chris

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by Ron-Astro Pharmacist » Sat Mar 21, 2015 3:29 am

The senses play their role in painting our total life experience. “What” light and its shadows reveal - instantly sights the now. Sound waves touch our emotional “why”. “When” feels like it helps us analyze past experiences and smell hints to “where” we’re heading and “how” feeds on our taste for the future.

So who's hungry for tomorrow but wondered why we loved how a food smelled tonight when we heard the cork pop for what looked so good on the table now.

Where's the crescents :?:
Make Mars not Wars

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by DavidLeodis » Sat Mar 21, 2015 1:34 pm

I like the image but it's a shame that the date it was taken in "late January" is not given in the information about the image in Dylan's website. There is a date January 31 2015 but that seems to be when the image was published and is not necessarily also that when it was taken. Knowing the date when images were taken adds a lot to my pleasure of seeing APODs but the date is often not available (or readily available). The Exif data I was able to find for this APOD did not give the date taken.

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by Nitpicker » Sat Mar 21, 2015 1:46 pm

DavidLeodis wrote:I like the image but it's a shame that the date it was taken in "late January" is not given in the information about the image in Dylan's website. There is a date January 31 2015 but that seems to be when the image was published and is not necessarily also that when it was taken. Knowing the date when images were taken adds a lot to my pleasure of seeing APODs but the date is often not available (or readily available). The Exif data I was able to find for this APOD did not give the date taken.
It was January 24, 2015.

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by DavidLeodis » Sat Mar 21, 2015 6:29 pm

Nitpicker wrote:
DavidLeodis wrote:I like the image but it's a shame that the date it was taken in "late January" is not given in the information about the image in Dylan's website. There is a date January 31 2015 but that seems to be when the image was published and is not necessarily also that when it was taken. Knowing the date when images were taken adds a lot to my pleasure of seeing APODs but the date is often not available (or readily available). The Exif data I was able to find for this APOD did not give the date taken.
It was January 24, 2015.
Thanks Nitpicker for that information which is appreciated :). I wonder how you managed to obtain it and so quickly :?:

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by Chris Peterson » Sat Mar 21, 2015 7:42 pm

DavidLeodis wrote:
Nitpicker wrote:It was January 24, 2015.
Thanks Nitpicker for that information which is appreciated :). I wonder how you managed to obtain it and so quickly :?:
Just use a program that shows the Moon given the date. Set yourself at Brisbane (or even the exact coordinates of Byron Bay, if you want). Go to the end of January. You can estimate the time the image was taken to within an hour or two.
Chris

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by DavidLeodis » Sat Mar 21, 2015 9:50 pm

Chris Peterson wrote:
DavidLeodis wrote:
Nitpicker wrote:It was January 24, 2015.
Thanks Nitpicker for that information which is appreciated :). I wonder how you managed to obtain it and so quickly :?:
Just use a program that shows the Moon given the date. Set yourself at Brisbane (or even the exact coordinates of Byron Bay, if you want). Go to the end of January. You can estimate the time the image was taken to within an hour or two.
Thanks for your help Chris.

Do you have a program that you recommend as I've just had a look at a few and I got very confused. One site indicated that the image (based on its APOD orientation) would have been taken on about January 15 whereas others indicated about January 25. I think my confusion may be to do with the orientation of the Moon apparently differing when viewed in the northern and southern hemispheres (well that's my excuse :wink: ).

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by Nitpicker » Sat Mar 21, 2015 10:24 pm

DavidLeodis wrote: Thanks for your help Chris.

Do you have a program that you recommend as I've just had a look at a few and I got very confused. One site indicated that the image (based on its APOD orientation) would have been taken on about January 15 whereas others indicated about January 25. I think my confusion may be to do with the orientation of the Moon apparently differing when viewed in the northern and southern hemispheres (well that's my excuse :wink: ).
Hi David,

This APOD was presented with the Moon's North pole up, which is perhaps a more natural orientation for northerners, than for southerners. As for a software recommendation, I use Stellarium a lot. It is free, it is easy and it is good.

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by Chris Peterson » Sun Mar 22, 2015 12:21 am

DavidLeodis wrote:Do you have a program that you recommend as I've just had a look at a few and I got very confused.
I normally use TheSky, but it's overkill for simple planetarium purposes (for me, it's what I use to control my telescope and conduct remote control sessions).
Chris

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by DavidLeodis » Sun Mar 22, 2015 12:23 am

Thanks again Nitpicker for your help :).

On a separate note I get very confused with the differing orientation of astronomical objects when they are presented as seen in the southern hemisphere (Orion is one in APODs that is a good example). I have Stellarium and use it to check my local area at that date/time but I never realised that it could be used to check back to see things at earlier dates.

I was just about to send this when I found that Chris has posted so thanks Chris for your suggestion :).

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Re: APOD: Sunshine, Earthshine (2015 Mar 20)

Post by NGC3314 » Mon Mar 23, 2015 1:30 pm

[
Chris Peterson wrote:
MarkBour wrote:In today's APOD, why does the dark portion of the moon get darker as one approaches the terminator ?
You need to consider how to make an image like this. The dynamic range of the actual Earthshine lit Moon is much to wide to display on a monitor in a linear fashion. Indeed, it is too wide to effectively capture in a single image with a typical electronic detector. So you need to use images made at several exposures, and composite them using something like an HDR technique. But the images exposed for the dark region will have a large amount of scatter and glare from the massively overexposed lit region, which will largely be near the terminator. So in combining the images, it's necessary to create some sort of gradient mask to reduce that glare. But that mask will also darken the zone just inside the terminator on the dark side. It would be extremely tricky to eliminate this effect entirely.

In other words, what we're seeing is a residual processing artifact.
Indeed, all that. I pretty much got rid of these problems in this image of the Moon in front of the Pleiades, which includes data from 18 CCD images of various exposure times and center locations. Even so, I had to get some scattering information and fill in some saturated regions near the terminator using an image of the full Moon, warped to compensate for the difference in libration. After all that, it is about 5000x7600 pixels, so it was sort of worth the messing around over a couple of months to get.
M45Moon.jpg
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