Starship Asterisk*

Comet Lemmon near the South Celestial Pole

Explanation: Currently sweeping through southern skies, Comet Lemmon (C/2012 F6) was named for its discovery last year as part of the Mount Lemmon (Arizona) Survey. Brighter than expected but still just below naked-eye visibility, Comet Lemmon sports a stunning lime green coma and faint divided tail in this telescopic image from February 4. The greenish tint comes from the coma's diatomic C2 gas fluorescing in sunlight. Captured from an observatory near Sydney, Australia, the color composite is constructed from a series of individual exposures registered on the comet. Across the 1 degree wide field of view, the star trails are a consequence of the comet's relatively rapid motion against the background of stars near the South Celestial Pole. Moving north, the comet should grow brighter, reaching a peak (3rd magnitude or so) when it is closest to the Sun in late March. By early April it should be visible from the northern hemisphere. Of course, this year Comet Lemmon may be just another pretty comet as skygazers on planet Earth also eagerly anticipate views of Comet PANSTARRS and Comet ISON.

<< Previous APOD

This Day in APOD

Next APOD >>

[/b]

Well... looks this year is going to be rather cometizing. Maybe I'll even get to see one.

I'd never heard of C2 before. Fun! Perhaps it should be a Wikipedia link in the text, though.

Very nice picture: I like the coloured star trails left by the long exposures with filters.
Excellent job!

PDB11 wrote:I'd never heard of C2 before. Fun! Perhaps it should be a Wikipedia link in the text, though.

http://en.m.wikipedia.org/wiki/Diatomic ... #section_1

Diatomic carbon is a diatomic molecule of carbon (C2), which occurs in carbon vapor, for example in electric arcs; in comets, stellar atmospheres and the interstellar medium; and in blue hydrocarbon flames.

Margarita

fausto.lubatti wrote:Very nice picture: I like the coloured star trails left by the long exposures with filters.
Excellent job!

THANK YOU for explaining that, Fausto - I was just about to ask what caused those coloured trails!

Margarita

A typo at 2.7.13 issue... in the fourth row, second sentence... "Moving north, the comet should >grower< brighter, ... it should be grow?... please fix it.

MargaritaMc wrote:

PDB11 wrote:
I'd never heard of C2 before. Fun! Perhaps it should be a Wikipedia link in the text, though.

http://en.m.wikipedia.org/wiki/Diatomic_carbon#section_1 wrote:
diatomic Carbon is a diatomic molecule of carbon (C2), which occurs in carbon vapor, for example in electric arcs; in comets, stellar atmospheres and the interstellar medium; and in blue hydrocarbon flames.

• Why Comet Lemmon is lime:

http://en.wikipedia.org/wiki/Comet_%28cleanser%29 wrote:

<<Comet is a powdered cleaning product introduced in 1956 by Procter & Gamble. Scratch Free Comet with Bleach Disinfectant Cleanser contains 1.2% sodium diChloro-s-triazinetrione dihydrate (a derivative of cyanuric acid) and 98.8% "other" ingredients. The only clues about the [98.8%] are disclaimers on the label that mention that the surfactants are biodegradable and that it contains no phosphate. Mixing Comet with other cleaners, specifically dish soap, toilet bowl cleaners and products that contain ammonia, is dangerous. Comet was known for a series of popular television ads featuring the character of "Josephine the Plumber" (played by actress Jane Withers).

A children's song about Comet is sung to the tune of the Colonel Bogey March:

• Comet, it makes your face turn green
  Comet, it tastes like gasoline
  Comet, it makes you vomit,
  So get some Comet, and vomit today!

Neufer - how ever do you FIND these edifying morsels of information?!
M

MargaritaMc wrote:
Neufer - how ever do you FIND these edifying morsels of information?!

• I'm quite Mad you know.

MargaritaMc wrote:Neufer - how ever do you FIND these edifying morsels of information?!
M

He uses his Quotidian Quotationist Zen, to become the Abstruse Allusion Artificer, through which he can personally relate to the subject of his post. AND, he really is quite "Mad", you know. Geniusly so.

neufer wrote:

MargaritaMc wrote:
Neufer - how ever do you FIND these edifying morsels of information?!

• I'm quite Mad you know.

... It takes me back to my younger days (creak of joints - go figure ). Is MAD still published? Or is this forum the one remaining outpost?

MargaritaMc wrote:... It takes me back to my younger days (creak of joints - go figure ). Is MAD still published? Or is this forum the one remaining outpost?

As a parttime bookseller at B&N (though my wife calls it my "paid hobby") I can tell you MAD is still available on the Newsstand.

I wonder if NASA has rockets ready on short notice to launch probes to the vicinity of cometary orbits with cameras and other sensors to study these objects close up ( maybe even bring back materials from such pristine origins ) Or does austerity measures prevent such bold moves ?

Keyman wrote:

MargaritaMc wrote:... It takes me back to my younger days (creak of joints - go figure ). Is MAD still published? Or is this forum the one remaining outpost?

As a parttime bookseller at B&N (though my wife calls it my "paid hobby") I can tell you MAD is still available on the Newsstand.

How SPLENDID!!

Margarita - the Limey...

And I have found the WEBSITE!
http://www.madmagazine.com/

Oh! Frabjous day

Looks more like a LIME drop, than a Lemon Drop.

:---[===] *

fausto.lubatti wrote:Very nice picture: I like the coloured star trails left by the long exposures with filters.
Excellent job!

Regarding the startrails coloured segments, was half of the exposure taken without filters?

moontrail wrote:Regarding the startrails coloured segments, was half of the exposure taken without filters?

If you look closely at the star trails, you'll see that the image was made with 24 equal length subexposures, 12 through a clear filter, and 4 each through red, green, and blue filters. LRGB imaging is a standard approach to achieving high signal-to-noise color images with a minimum of total exposure time.

Chris Peterson wrote:

moontrail wrote:Regarding the startrails coloured segments, was half of the exposure taken without filters?

If you look closely at the star trails, you'll see that the image was made with 24 equal length subexposures, 12 through a clear filter, and 4 each through red, green, and blue filters. LRGB imaging is a standard approach to achieving high signal-to-noise color images with a minimum of total exposure time.

I am re-visiting this thread as today's Apod is also about comet Lemmon.

So, in this image, which filters would have been used first? I should be able to work it out from the image, but I can't. (It would be less difficult if coordinates for the comet had been given.)

Margarita

MargaritaMc wrote:So, in this image, which filters would have been used first? I should be able to work it out from the image, but I can't. (It would be less difficult if coordinates for the comet had been given.)

There's no way to tell which filter was used first without knowing something of the starfield and the motion of the comet. We can determine the sequence: L, R, G, B, but not the direction (it could as easily be B, G, R, L).

As a rule, most imagers collect their L data first, since if the weather goes south on them during the session, they still end up with a usable B&W image.

Chris Peterson wrote:

MargaritaMc wrote: There's no way to tell which filter was used first without knowing something of the starfield and the motion of the comet. We can determine the sequence: L, R, G, B, but not the direction (it could as easily be B, G, R, L).

As a rule, most imagers collect their L data first, since if the weather goes south on them during the session, they still end up with a usable B&W image.

Thanks - I thought that I was being dim in not being able to work out where the comet was! I'm interested to see your use of "go south" - my Londoner Mum would say of something that has broken or worn out that it "had gone west". The UK's prevailing (wet) weather comes from the west. Does yours come from the south?

MargaritaMc wrote:I'm interested to see your use of "go south" - my Londoner Mum would say of something that has broken or worn out that it "had gone west". The UK's prevailing (wet) weather comes from the west. Does yours come from the south?

No. The term is unrelated to weather, so far as I know. I think it comes from our association between "south" and "down" on maps. "Going south" is the same as "going downhill".

MargaritaMc wrote: Thanks - I thought that I was being dim in not being able to work out where the comet was! I'm interested to see your use of "go south" - my Londoner Mum would say of something that has broken or worn out that it "had gone west". The UK's prevailing (wet) weather comes from the west. Does yours come from the south?

I would have thought "going west" was a polite jab in reference to the ungrateful colonists who founded the U.S.

stephen63 wrote:

MargaritaMc wrote: Thanks - I thought that I was being dim in not being able to work out where the comet was! I'm interested to see your use of "go south" - my Londoner Mum would say of something that has broken or worn out that it "had gone west". The UK's prevailing (wet) weather comes from the west. Does yours come from the south?

I would have thought "going west" was a polite jab in reference to the ungrateful colonists who founded the U.S.

Mmm. Possibly....

I googled the phrase and (after getting rid of Go West Young Man and music group called Go West) I found some information on http://users.tinyonline.co.uk/gswithenbank/sayingsg.htm. The site doesn't permit select and copy (I'm on an Android with no separate keypad, so can't do the usual work-rounds) so I'll have to summarise.

1. The saying was made common during the First World War, when a British soldier 'going west' meant leaving the scene of fighting - often thru death or injury.
2. But the notion of West being the direction of death is an old one and is related to the setting sun
3. In LONDON, Tyburn, the place of public execution from the 12th century until 1783, is near Marble Arch, which was then far too the west of the rest of London. My Mum is from the area of the London Docklands, well to the east of the City of London. Bye the way,"Going Up west" in our family language means "getting all dolled-up and going out on the town"! (To the West End, where all the theatres were/are).

Margarita