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Huge comet outburst reported, 17P/Holmes
Guest_Sunspot_*
post Oct 28 2007, 08:02 PM
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The sky has finally cleared and i've just come in from observing it with my 4.5" reflector. It does look exactly like some of the pictures i've seen. A large spherical coma with a slightly brighter annulus. Star like nucleus with a brighter patch to one side.
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Stu
post Oct 28 2007, 08:17 PM
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... and now it's cr**ping it down. Again.

(noise of fingers drumming on desktop)

Going to take up cloud-spotting if this goes on, I swear...


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NMRguy
post Oct 28 2007, 08:25 PM
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QUOTE (ugordan @ Oct 28 2007, 05:27 PM) *
A figure of say 300 m/s sounds more plausible.

I agree. Rough calculations for me yield velocities of ~360m/s and this number is more or less constant for the last three days (to within error).

I also searched the literature and found nothing in the range of 2.4km/s for comet emission velocities. Most were at or less than 0.5km/s and this also seems to be the norm for comet gas emissions. What still strikes me with this comet is that the expanding cloud is spherical in shape--the gas and dust seems to be moving from the source outward largely uninhibited. Perhaps naively, I might have expected a more directed emission of the volatiles.

Kohoutek 0.5km/s
Hale-Bopp 0.4km/s
LINEAR 1999 S4 0.5km/s
Tempel 1 >0.16km/s (projected velocity)

Anyway, more rain tonight...
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nprev
post Oct 28 2007, 08:34 PM
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Nice & clear here (finally; the damn smoke is abating as the fires come under control). Gonna give it a shot tonight naked-eye from the roof of my apartment complex. Would drive out of town, but gotta work tomorrow & as anyone who's ever been in LA for any amount of time knows you can get stuck in traffic at the drop of a hat in either direction...


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ngunn
post Oct 28 2007, 08:47 PM
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Within the last hour skies have cleared beautifully over North Wales. The comet is in full view now, and so bright that the full moonlight hardly matters. It is much bigger and fuzzier than when I saw it first and noticeably brighter too relative to the stars of Perseus. (I hope the same happens in Cumbria, Stu. Snowdonia and Cumbria often get the same weather at about the same time so keep looking out!)
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Guest_Sunspot_*
post Oct 28 2007, 08:47 PM
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The Moon is VERY bright tonight and not too far off in the sky, lets hope the comet maintains it's brightness for a few more days.
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Stu
post Oct 28 2007, 10:00 PM
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Yes!! Finally!!! The cloud cleared around 9pm and I went outside to see if I could see Perseus - and noticed right away that there was something wrong with its shape, an extra blobby "something" that isn't usually there.... Lifted the binoculars -

GOOD GRIEF!!! Someone moved the globular cluster M13 closer to Earth! It was **ridiculous**! Like a new gas giant planet had somehow appeared in the solar system. Inside for the telescope, swung it around...

Oh. My. Word.

Look at that... it filled a quarter of the eyepiece at 26x magnification, with a stellar centre and a bright core surrounded by a fainter, larger ring. I went back inside to get my girlfriend and have her take a look, and she had the same "wow..." reaction, suggesting that it looked like "a cell" or "a jellyfish".

She went back inside then, leaving me alone in the yard with my telescope and the most ridiculous comet I've ever seen. Thought I'd push my luck and try a few photos, just holding my digi camera up to the eyepiece, and this is what I got...

Attached Image


Not going to make the Gallery on Spaceweather.com but I'm pretty chuffed with it smile.gif


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nprev
post Oct 28 2007, 10:24 PM
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ohmy.gif Wow!!! You got that just from a cam-to-eyepiece shot??? Unreal!

Okay, that's it: gonna see this thing, this event. If I can't see it from home, will do the drive...too damn marvelous to miss!


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Stu
post Oct 28 2007, 10:35 PM
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That was the best out of 80 or so shots; the rest ranged from "it's just there" to "where the **** did it go?!?!" laugh.gif

Had to really push the camera to the limit to get that pic, cos it's a v simple low tech one. Settings: 400ASA, "cloudy", "centre spot metering", and lined up the camera lens with the eyepiece by pushing the lens into half a 35mm film cannister and then placing it against the eyepiece...

The view thru the eyepiece was SO much more impressive... I'll have to try simulating it with Photoshop or something.


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Del Palmer
post Oct 28 2007, 11:42 PM
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Well, if 17P/Holmes is that Saturn-like object near the Moon then I guess I've just observed my first comet. smile.gif Mind you, I almost broke my neck slipping on the wet grass as I rushed into the house to get my binos... laugh.gif


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um3k
post Oct 29 2007, 01:55 PM
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Here's my shot of it:

Attached Image
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Pertinax
post Oct 29 2007, 02:28 PM
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It's Monday, so what better time than now for a somewhat off the wall question? smile.gif

With all the (deserved) excitement over comet Holmes, I wondered (as we did here over McNaught earlier this year) if the rovers would be able to see it. My thinking is that it would likely not be as it is well above the ecliptic and the rovers are south of Mars' equator. However, I don't have my copy of Starry Night handy at all to do any tests. Can anyone help on this front? Second (and just as important), is Spirit (or either rover really) in any possition to do even very limited evening or night obs? Again, my guess would be no but I wanted to ask to be sure.

Cheers,



-- Pertinax
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Stu
post Oct 29 2007, 02:48 PM
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Great pic um3k! Makes mine look a bit pathetic, but I'm just happy I saw it given the weather here! laugh.gif


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Stu
post Oct 29 2007, 02:54 PM
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I had a quick mess about look with Starry Night to try and figure this out myself last night, and while I found that both rovers can see Comet Holmes - it appears to be in the constellation of Cassiopeia from Mars - I can't find out what magnitude it would be because obviously the outburst brightening means all the figures Starry Night generates are waaay off. However, it stands to reason that as Mars is closer to the comet than Earth, the comet should appear brighter from Mars than it does from Earth, right? And as the rovers have imaged objects like the Orion Nebula and the Magellanic Clouds, both of which are naked eye astronomical objects, they should be able to see a big naked eye comet from Mars too, right?

Would love some professional input on this...


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Stu
post Oct 29 2007, 03:38 PM
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Spirit's view...

Attached Image


and Oppy's view...

Attached Image


Both pics show the comet's highest point in the sky.

Again, no idea of brightness, sorry.


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