Comet McNaught (2006/P1) - discussions - Page 6

tornado33 · #**101** 11-01-2007, 11:06 PM

This makes prospects VERY exciting
http://www.shopplaza.nl/astro/C2006P1.doc
Talks about the foward scattering, brightness may peak on Jan 14 UT at a whopping mag -5.2!

Also says
"In the forecast with forward scattering and n = 4, the comet’s brightness would exceed that of Venus over Jan. 13 and 14. The comet would be visible in daylight by binoculars and probably to the shielded naked eye in very clear skies. But if n = 3, the comet may be only marginally visible in daylight binoculars, if at all. If the comet can be located in daylight, visible/infrared photometry would be possible if the telescope and detectors can be shielded from direct sunlight. Between Jan. 12.3 UT and Jan. 15.7 UT, the comet will be at 8 deg or less elongation and visible in the SOHO C3 coronograph field at brightness levels likely to greatly saturate the central pixels unless precautions for shorter exposures are planned in advance."

erick (Eric) · #**102** 11-01-2007, 11:59 PM

(Not sure which Comet McNaught thread is best for this question - I'll try this one)

Everything (being weather, diary, work, family, health!) permitting, I'll be imaging to 400ASA slide film. I'll be using my Pentax KX and alternating my 55mm/f1.8 and my (thanks Terry

) 135mm/f3.5 lenses. Maybe also my 28mm/f2.8, but I doubt it. I'd like to try pre-dawn and post-sunset.

Would you experienced astrophotographers please suggest some aperture/shutter settings I can bracket? I'm guessing aperture fully open or maybe shut down one stop. But I really don't have a feel for shutter speed. I could see what the meter suggests and use that as a maximum speed?? Or can we guess now? - are we talking bracketing, say 1/60 second or 1 second? What is the ball-park? Many thanks in advance.

Of course, being way behind the times, I've no way of knowing how I went until the slides come back! Could I get the comet to do an encore if I stuff it up?

iceman (Mike) · #**103** 12-01-2007, 07:10 AM

I need to find a clear western horizon for sun->wed!

OneOfOne (Trevor) · #**104** 12-01-2007, 07:39 AM

I am planning on going to Brighton beach in the coming evenings. I should get a clear view over the bay to the horizon.

Fingers crossed...

h0ughy (David) · #**105** 12-01-2007, 07:39 AM

Quote:

Originally Posted by iceman

I need to find a clear western horizon for sun->wed!

Yes and we need some clear skies then as well.

erick (Eric) · #**106** 12-01-2007, 09:37 AM

Quote:

Originally Posted by OneOfOne

I am planning on going to Brighton beach in the coming evenings. I should get a clear view over the bay to the horizon.

Fingers crossed...

I was thinking the same, OneofOne - from the eastern side of Port Philip Bay. Might be able to get a few sailing boats silouetted? Anyone see a problem with photographing the comet over a vast expanse of water?

dcnicholls · #**107** 12-01-2007, 10:55 AM

Quote:

Originally Posted by erick

I'll be imaging to 400ASA slide film. I'll be using my Pentax KX and alternating my 55mm/f1.8 and my (thanks Terry

) 135mm/f3.5 lenses. Maybe also my 28mm/f2.8, but I doubt it. I'd like to try pre-dawn and post-sunset.

Would you experienced astrophotographers please suggest some aperture/shutter settings I can bracket?

In the absence of someone with more recent experience, I'll hazard an answer. (Last one I photographed was Comet Bennett in 1970!)

Unless you mount the camera on a tracking mount, you want to avoid trailing. That limits you to an exposure of somethng like a second. However, this applies more in a dark sky context.

In the twilight, I'd trust your exposure meter and bracket one or two stops either way.

DN

erick (Eric) · #**108** 12-01-2007, 12:12 PM

Quote:

Originally Posted by dcnicholls

In the absence of someone with more recent experience, I'll hazard an answer. (Last one I photographed was Comet Bennett in 1970!)

Unless you mount the camera on a tracking mount, you want to avoid trailing. That limits you to an exposure of somethng like a second. However, this applies more in a dark sky context.

In the twilight, I'd trust your exposure meter and bracket one or two stops either way.

DN

Thanks DN.

I'll go with the exposure meter reading and bracket around that.

I won't be tracking, but I would have thought I could go up to 15 sec without trailing with the 55mm lens, probably less than 10 seconds for the 135mm lens. But I'm not anticipating having to expose for more than a few seconds??

dcnicholls · #**109** 12-01-2007, 12:34 PM

Got it!!!

Easily seen in my 25x100 Oberwerks. All it needed was an extended shade to reduce the glare from the sun.

I can see a vestigial tail (not sure how long as I can't remember how big the field is in the Oberwerks) like a pair of fuzzy "horns" below the fat-ish nucleus - probably 10 arc minutes or so.

Not as bright as Venus, by very easily seen.

Canberra, 12.25 AEDT, 12 Jan.

DN

dcnicholls · #**110** 12-01-2007, 12:38 PM

Quote:

Originally Posted by erick

Thanks DN.

I'll go with the exposure meter reading and bracket around that.

I won't be tracking, but I would have thought I could go up to 15 sec without trailing with the 55mm lens, probably less than 10 seconds for the 135mm lens. But I'm not anticipating having to expose for more than a few seconds??

You could be right. It depends on how far north or south the comet is, and thus its movement per second. The way did it last time was to work out the grain size of the emulsion (using Ilford HPS and Kodak Tri-X) and worked out how long the trail would take to traverse one grain. However, with slide film, that's not so easy.

DN

tornado33 · #**111** 12-01-2007, 01:00 PM

Just saw and imaged it today, (just after noon) sky brighter, hazier then yesterday but still readily visible in the 10 inch.
Scott

tornado33 · #**112** 12-01-2007, 01:37 PM

Update, after comet passed the meridian I swung the tube on the other side of the mount, its more favouravle as less reflected light bouncing around. Comet definately looks a little brighter than yesterday, and despite the very bright sky I could see the start of the tail, a noticable lee of the sun wide fan like tail.

I recommend using a uv/ir filter to view as the sky was uncomfortable bright to look at being close to the sun.

Not recommended for viewing now with short tube scopes as focussed sunlight could well do damage both to ones eyes and the tube assembly.

Its noticably closer to the Sun than yesterday
Scott

fringe_dweller · #**113** 12-01-2007, 01:55 PM

some latest pics from various soucres

STEREO image!! yikes! http://secchi.nrl.navy.mil/images/hi1b_comet.jpg

and youtube videos - never seen a comet caught on video before!!

http://www.youtube.com/watch?v=v9xhQeNiL2o

check out sidebar for more!!!

I see Spaceweather is calling it a Great comet!

Satchmo · #**114** 12-01-2007, 02:07 PM

Wow, this comet is going to be bright

I have a pair of 62 X 305mm binoculars loaned to me for Lostock with 1.1 degree true field ( 24 Panoptics ) which will be superb for viewing the coma region . Bring on the good weather.

Mark

fringe_dweller · #**115** 12-01-2007, 02:08 PM

Erick with the 55mm you can go up to even 10-15 sec's without much trailing i would think - but I would go for all the ones between 1 and 10 sec do all different random ones, thats what would i do - one has got to be the one! i simply lock the shutter release cable in bulb mode and count the sec's 'missippi one' ect. i would think 4 sec's would be a nice figure.
with the 135mm you have less time before trailing begins, and it will be darker due to being not as fast a lens - keep them too 1-5? secs' and the
28 i think you could go for up to 20 secs before trailing begins.
i would stop the 55 down one stop as well as some wide open.
the 135,, as Terry said is best wide open (I have the same lens- see my avatar for an example from it- and that is stopped down a stop!!) this is all on a nice sturdy tripod i assume?

iceman (Mike) · #**116** 12-01-2007, 02:32 PM

The sky will still be reasonably bright.. 15 seconds will give you a completely white picture I imagine

At dusk, I'd say 3-6s exposure.

erick (Eric) · #**117** 12-01-2007, 02:36 PM

Quote:

Originally Posted by fringe_dweller

Erick with the 55mm you can go up to even 10-15 sec's without much trailing i would think - but I would go for all the ones between 1 and 10 sec do all different random ones, thats what would i do - one has got to be the one! i simply lock the shutter release cable in bulb mode and count the sec's 'missippi one' ect. i would think 4 sec's would be a nice figure.
with the 135mm you have less time before trailing begins, and it will be darker due to being not as fast a lens - keep them too 1-5? secs' and the
28 i think you could go for up to 20 secs before trailing begins.
i would stop the 55 down one stop as well as some wide open.
the 135,, as Terry said is best wide open (I have the same lens- see my avatar for an example from it- and that is stopped down a stop!!) this is all on a nice sturdy tripod i assume?

Yes, on a pretty solid Velbon. I can lock the mirror up before I open the shutter, to reduce shake. I'll be using a cable release.

I've been thinking as much about composition of the photos as exposure and actually getting the comet onto film. I've some "weird" ideas I want to try - probably won't come off!

Thanks, Eric

fringe_dweller · #**118** 12-01-2007, 02:45 PM

hehe yes those figures are for darker skies i admit - but we are talking about 400 speed film here - nowhere as sensitive as digital Mike - but myself and friends have done a bit of tripod/400 film work in strong twilight before and have done wonders with 4 secs

I have never locked up a mirror Erick - and never will - not with widefield anywayz

fringe_dweller · #**119** 12-01-2007, 02:55 PM

here's a nice example 4 sec 400 speed film shot on tripod stewart took

http://southern-x.org/g-trio/gallery-pic3.html

EDIT: and by the mid-end of the week those figures might come into play? and specially if you stop it down a bit, it will be even better again

tornado33 · #**120** 12-01-2007, 03:20 PM

Just for something different I installed my Baader 7 Nm Ha filter (not intended for visual use) and could see the comet through it on the 10 inch newtonian! The field was a deep red almost dark, with a bright red central condensation.
Scott