APOD: Moon, Venus, and Planet Earth (2013 Sep 19)

[Cousin Ricky]

Having the dark side of the Moon appear darker than the surrounding sky is distracting. It makes the Moon look as if it's in front of the clouds.

It seems to me that artistic license was stretched to the breaking point in this composite.

[Anthony Barreiro]

Interesting discussion of the technique through which this image was made and the aesthetic and scientific pros and cons of the choices the photographer made. It occurs to me that a human observer without a camera could have seen this scene perfectly well. The human visual system has evolved to see the world around us and to make sense of what we see. To an observer the Moon would not have appeared oversaturated and would have appeared the correct angular size. Imaging technology can show us astronomical wonders we couldn't otherwise perceive -- distant galaxies, colorful nebulosity, details on the surfaces of planets -- but sometimes the best thing to do is to go outside and look at the sky.

[BDanielMayfield]

In this image, the Moon appears 230 arcminutes in diameter, more than seven times its actual size.

How did you figure that out? Just curious.

When the image was made, Spica and Venus were 216 arcminutes apart. Since they are 66 pixels apart in the image, scale is 3.27 arcmin/pixel. The apparent diameter of the Moon is 70 pixels, which at this scale is 229 arcminutes. At the time, the angular diameter of the Moon was 31.4 arcminutes. So the lunar image is scaled up by 7.3 times compared with the astrometric background.

That’s what I like, an answer that can be backed up with a solid mathematical proof.

[JohnD]

Strange.

The APOD, the Astronomy Picture Of the Day and it's cousin site, the ESPOD, the Earth Science PoD, seem to be exchanging remits.
Today's APOD is wholly and completely Earthbound, a rocky sea shore that happens to include some night sky objects.
Today's ESPOD is the view from as high as you can get without a rocket. A black sky and the distant Earth with a strongly curved horizon, as 32 miles above Greece, a helium balloon explodes and the camera package begins its long drop home. http://epod.usra.edu/blog/

John

[FloridaMike]

In this image, the Moon appears 230 arcminutes in diameter, more than seven times its actual size.

I just figured it was taken during one of the "Super Moons" the media gets all worked up about.....

When the image was made, Spica and Venus were 216 arcminutes apart. Since they are 66 pixels apart in the image, scale is 3.27 arcmin/pixel. The apparent diameter of the Moon is 70 pixels, which at this scale is 229 arcminutes. At the time, the angular diameter of the Moon was 31.4 arcminutes. So the lunar image is scaled up by 7.3 times compared with the astrometric background.

Check out the Big Brain on Brad! ...er... Chris! ....

(best quote from THE best movie ever)

Do you have software that does the measuring or are you actually counting pixels?

[Beyond]

Check out the Big Brain on Brad! ...er... Chris! ....

(best quote from THE best movie ever)

[Chris Peterson]

Do you have software that does the measuring or are you actually counting pixels?

I just opened the image in Photoshop and used the ruler tool.

[FloridaMike]

Check out the Big Brain on Brad! ...er... Chris! ....

(best quote from THE best movie ever)

Pulp Fiction

[Beyond]

Check out the Big Brain on Brad! ...er... Chris! ....

(best quote from THE best movie ever)

Pulp Fiction

Ah, i haven't seen that movie. No wonder it made no cents.

[Boomer12k]

Nice photo....but I can see FOUR stars and Venus...there is a very faint one further to the left.

And no mention of the Lunar Corona...

LOVE the Mysterious Island in the distance...

:---[===) *

[Nitpicker]

In this image, the Moon appears 230 arcminutes in diameter, more than seven times its actual size.

How did you figure that out? Just curious.

When the image was made, Spica and Venus were 216 arcminutes apart. Since they are 66 pixels apart in the image, scale is 3.27 arcmin/pixel. The apparent diameter of the Moon is 70 pixels, which at this scale is 229 arcminutes. At the time, the angular diameter of the Moon was 31.4 arcminutes. So the lunar image is scaled up by 7.3 times compared with the astrometric background.

The only problem with Chris' method, is that his scaling is based on a measurement between Spica and Venus, and these two objects are not from the same exposure, and hence the distance between them is not likely to be that meaningful.

If one instead measures the distance in the photo between Spica and Beta Corvi (both from the same exposure) -- which is known to be about 1034 arcmin in the sky -- one can estimate (with a ruler or however you like) that this distance is about 6.2 times greater than the apparent size of the moon in the photo. So, the Moon actually appears in the photo with a diameter closer to 167 arcmin (1034/6.2), which is only 5.3 times bigger than it should be (but still too big to avoid criticism from lovers of science and aesthetics alike).

Incidentally, from my backyard in Brisbane, about fourteen and a half hours before this photo was taken, I took an 8 second exposure (just one) which includes the overexposed Crescent Moon (with Earthshine), Venus, Spica and the International Space Station streaking past. The image is only 215kB and ain't that pretty. It also includes labels, which makes it even less pretty than this APOD. But on the plus side, the scaling is certainly realistic. Pity is, this is my first ever post to this (excellent) forum, and so I am unable to attach an image, and I have otherwise no particular skill in uploading images to the web such that I could provide a link. So, you'll just have to imagine it.

Cheers,
Nitpicker.

P.S. Now that I have pointed out the problem in Chris' method (normally his posts are flawless, and I have learned a lot from them), I expect that someone will point out some obvious error I've made too.

[Chris Peterson]

The only problem with Chris' method, is that his scaling is based on a measurement between Spica and Venus, and these two objects are not from the same exposure, and hence the distance between them is not likely to be that meaningful.

Agreed. I assumed (you know what they say about that...) that the images were stacked with reference to Venus. Apparently not. The astrometric solution using only stars is clearly the right way to do it.

[geckzilla]

Pity is, this is my first ever post to this (excellent) forum, and so I am unable to attach an image, and I have otherwise no particular skill in uploading images to the web such that I could provide a link.

Make an account and you can upload images directly to the forum. Otherwise, http://www.imgur.com requires no particular skill.

[Nitpicker]

I'm going to guess that the original, longer exposure left a rather large halo around the Moon (or at least the crescent part). To insert the shorter exposure of the Moon at the correct location and scale may have required too much jiggery-pokery in Photoshop to remove the halo remnants easily. So, instead, the decision was made to mask the halo by increasing the size of the Moon. This approach has the added benefit of "exaggerating the young Moon's slender crescent shape", which appears to be a non-technical way of saying it is not to scale.

Nitpicker.

P.S. Thanks for the info geckzilla. Will investigate.

[Nitpicker]

Well geckzilla, that was easier than I thought. This is the image to which I referred earlier:

Click to view full size image

Nitpicker.

[Beyond]

Why is the ISS labled (Zarya)

[Nitpicker]

Why is the ISS labled (Zarya)

Zarya (Russian for "Dawn" apparently [thank you Wikipedia]) was the name given to the first (main) module of the ISS to be launched. I originally labelled the image for the benefit of my own memory. One of the reasons I became interested in astronomy was to learn the history and reasoning behind the names of objects in the sky.

[Beyond]

ha-ha, i set my Bing translator Russian to English and typed in Zarya. What came out was zarya.

[JohnD]

заря

[Beyond]

заря

By George (and anybody else) you're right I wasn't thinking Zarya was English. I just did it the right way and it comes out 3ap-with a sdrawkab->r.

[Nitpicker]

Thanks John. But now I'm a little confused. Is "Zarya" the phonetic spelling of the Russian "заря" in the English (Roman/Latin) alphabet? If so, at least backward, mono-lingual Antipodeans like me can get a hint on how to pronounce it.

Perhaps I should re-label my little photo to say "International Space Station (Zarya [заря])", but by the time I get through all that, it would streak out of shot.

(Apologies for the topic hijack by the way.)

[Beyond]

(Apologies for the topic hijack by the way.)

Think nothing of it. BTW, you have a 2 degree thumb. Mine is about 98.6 degrees.

[Nitpicker]

BTW, you have a 2 degree thumb. Mine is about 98.6 degrees.

Hey short-arms, I'll thank you not to make fun of my narrow thumb!

[JohnD]

In Old Country, "В огоро́де бузина́, а в Ки́еве дя́дька."

[Beyond]

In Old Country, "В огоро́де бузина́, а в Ки́еве дя́дька."

I ran that through BING and got this-->"In ogoróde buziná, and Kíeve dấd′ka."
It's still 'Greek' to me.