Comet Mcnaught Jan 17th

[Big V]

Well this is turning out to be a real winner, even though the cloud was around, it was still an awesome sight...should be similiar thurs and fri evening. Get out and have a go!!! at least have a look at this once in a life time event - for most of us anyway..

[colin_12]

#1 is your best yet Big V. It gives a sense of size.
Rgards Colin

[Steffen]

Wow, it's turning out to be a real cracker! Great shots! Will have another go at it tonight...

Cheers
Steffen.

[Steffen]

And yes, go out and see it, even if you're not photographing it. A daylight comet doesn't pass by too often!

Cheers
Steffen.

[Steffen]

And a question for Gordon: why is it that comet tails are often curved? Is it because the matter ejected by sunwind gets pulled back to the sun? Or is it an illusion?

Cheers
Steffen.

[Big V]

I can answer that: The Sun's radiation pressure and solar wind accelerate materials away from the comet's head at differing velocities according to the size and mass of the materials. This means relatively massive dust tails are accelerated slowly and tend to be curved as the comet moves past the sun. The ion tail is much less massive, and is accelerated quickly,so that is why it appears as a nearly straight line extending away from the comet opposite the Sun. This comet does not have an obvious ion tale..

[wendellt]

very cool and historical

that last one is is really nice

[Steffen]

Thanks Big V, that makes sense. It would also explain why some comets have a split tail (or two tails). Like a mass-spectrometer.

Cheers
Steffen.

[Gordon]

I'm just back after several days with no working power supply for my laptop... As BigV says, its to do with the solar wind and particle sizes.
The dust tail behaves just like a hose that is moved side to side- you get a curved jet of water- the amount of curvature is dependent on how fast the water is squirting out and how fast the source is moving/rotating. C/McNaught being very close to the Sun and moving very fast showed very strong curvature of the dust tail, but that is reducing now. Also complicating things is the viewing angle, we are looking at a foreshortened view because the tails are pointing away from us as the comet recedes from the Sun.
Unfortunately I have had thick bushfire smoke and cloud eveny night this week and no chance to see it at all since perihelion, just a couple of daytime views through a telescope on the 9th: http://msowww.anu.edu.au/~rmn/C2006P1.htm
and again on the 12th.
Whilst there is no obvious gas tail at the moment, I suspect this is partly due to the amount of atmosphere we are looking through to see the comet- most of the blue gas tail light is scattered by the atmosphere, whilst the longer wavelength sunlight (reflected of tail dust particles) passes through relatively unimpeded. This is the same reason we have red sunsets.

[Gordon]

You can see the ion(gas) tail here on the left of the dust tail:

http://antwrp.gsfc.nasa.gov/apod/ap070117.html

[garlino]

#1 one is definitely the best. Although the others a good but the first as colin said gives a sense of size.

Very nice

[Big V]

Yes, it is a large one and will continue to delight, although we have total cloud cover here at the moment...might have to go for a long drive to see it tonight, hope others are more fortunate. Gordon I saw that pic of you looking through the big scope during daylight - you did not look too comfortable at that angle , on Sunday we were viewing it naked eye during the day with ease!!!

[mikephotog]

Love the sense of scale/environment in the first one.
I might try a shot her in Melb tonight (Thurs), what is the best time?
Earlier in the week it was obscured by bushfire smoke haze here in Melb.

[Gordon]

Gordon I saw that pic of you looking through the big scope during daylight - you did not look too comfortable at that angle , on Sunday we were viewing it naked eye during the day with ease!!!

It was very uncomfy, no choice though- we cant move it as its part of the overall scope balance.



Mike, the best time is any time you can clearly see it So, any time from about 15 mins after sunset is good, but before it sinks into the horizon murkiness.

[Big V]

Gordon, figured it would have been something like that, reminded me of David Malin sitting up in the cage of the AAT, suffering for 3 hours at a time

[Gordon]

I've been up in the cage for half a night a coupe of times before- once with 90km/hr winds howling by the dome slit. I took 10X50s with me and leaned back and looked around at wherever the scope was pointed at the time- like a spacewalk I was up there to rotate the filter wheel which isn't automated at Prime focus.
We were using a CCD filled with liquid Nitrogen- so when they moved the scope around the sky I had to drive the cage one way or the other to keep up with the slewing, otherwise I may have ended up with a lap full of LN2!
I'd probably be speaking with a very high pitched voice if that happened

[Big V]

Man that is doing it tough, you have to admire that sort of dedication. I complain when I have to manually rotate the dome which mena getting out of my nice comfy chair and away from the screen!!

[frink]

Dammit... I knew I should've gone out last night
Went out monday night and was pretty disappointed.
Nice shots Big V
and thanks for your tips on stacking in that other thread
Here's hoping it will still be around and reasonably bright when this weather clears.

[MattC]

Impressive shots.

Now damnit, if this solid overcast cleared, I might actually get to see the thing for myself!

Cheers

[christiand]

Great captures,

no such luck in Canberra.
We wen't up Black Montain Tower on Tuesday - clouds
Yesterday and today we have clouds again but this time with some very welcomed rain.

Cheers,
CD

[Big V]

I feel your pain - it is raining here, well I think that is what these wet things are falling from the sky, have not seen too much of it over the last 10 months..