Latest on Comet ISON

M.T. Cranium

As you may have heard, Comet ISON is rapidly approaching the Sun and will have a very close encounter with the south polar regions of the Sun on 28 November -- after that, it could rapidly brighten in our pre-dawn morning skies and then after about 4-5 December it could be visible at almost all times of the night.

Before that happens, we apparently have a chance to see the brightening comet through binoculars this week, before it gets too close to the Sun to be seen. You would need to be in a dark (non urban) environment with binoculars to catch it between now and about the 22nd.

If anyone happens to read this today (Friday) before first light, check out the ESE horizon after 5:45 a.m., if you can find Spica (a first magnitude blue-white star) near the horizon, and reddish Mars well above it, then look for the brightest star between them (closer to Spica) and ISON should be between that star and Spica (or in less complicated terms, above Spica in the pre-dawn east-southeastern sky). By Monday 18th, the comet has moved enough that its tail would be obscuring Spica from our view. Mercury and Saturn are also visible in this part of the sky, but they rise into view around 6 to 6:30 a.m.

The best time to look if you have clear skies would probably be around 7 a.m. when the objects in question are higher, but the Sun's first pre-dawn glow has not yet begun. I have clear skies here although it's only 7 p.m. Thursday evening, so I will try to find ISON around 0630h and report back. I would expect it to be borderline naked eye visible around 4-6 mag like some of the fainter stars in that part of the sky. It won't be as bright as the guide star that I mentioned which I think is Gamma Virgionis, an optical double in the second and third magnitude range (together about second magnitude, Spica is the standard for first magnitude at 0.97).

If you're not familiar with the concept of magnitude, brighter than first magnitude would be zero magnitude, then minus one, etc, and the scale is logarithmic so that minus fourth magnitude Venus or minus second magnitude Jupiter are a lot brighter than Spica. An example of a zero magnitude star would be Canopus which is visible most of the night well above Orion, Sirius is midway between minus first and second magnitude, but Aldebaran, Rigel and Betelgeuse are all between zero and first magnitude, as is Procyon (in Canis Minor, above Sirius) -- the twins of Gemini, Castor and Pollux, and Regulus, are other first magnitude stars in the winter sky. There's some chance that Comet ISON will become almost this bright in a few days before the larger spectacle in December when it could be as bright as Venus.

Let us know if you spot ISON. My report will be around 1500h due to the eight hour time difference (all of the above is valid for any time zones with slight timing differences for when Spica would be obscured by the comet's tail).

By Saturday morning the position should be about one-quarter of the separation between Spica and Gamma Virgionis. It would be about one-tenth of the separation of Spica and Mars (closer to Spica in both cases). One good thing is that the angle of the ecliptic plane in the pre-dawn sky is almost at right angles to the horizon and objects will rise quickly as a result.

shedweller

Had a look there and the cloud cover is too much. I'll keep an eye on it over the next while. Cheers for the heads up.

RobertKK

Yeah it was too cloudy this morning, was going to look for it, then saw this thread.

I hope it really flares up as it gets closer to the sun, it will be hard for any comet to rival Hale Bopp, which was a privilege to see back in 1997 I think.

M.T. Cranium

I was clouded out too, clear at 10 pm but overcast at 0100 so I didn't set the alarm. My next chance looks like being Tuesday ... make a note that 25th to 29th there may be no sighting possible so that next week is our chance for the pre-encounter sighting (which may be all we get if the thing comes apart).

StompToWork

Clear skies over west cork this morning, but by the time I got up at 7am, dawn had sprung a little too much. No observation.

Rikand

Perfect clear skies here but too many high buildings around me - i did get to see 2 very big bright shooting stars away to the west while admiring my snow covered lawn though

Dharnam

clear skies, up at 0525 UT, ditch is currently obstructing the view, heading out again just before 0700 UT... lets hope to get a glimpse of this :-)

Squidvicious

As I understand it, the comet is visible only in the mornings, low down to the horizon and will become harder to see as it approaches the sun(even as it brightens). But what happens when it begins to move away from the sun? Will it only be visible in the daytime after sunrise ?

shedweller

Squidvicious wrote: »

As I understand it, the comet is visible only in the mornings, low down to the horizon and will become harder to see as it approaches the sun(even as it brightens). But what happens when it begins to move away from the sun? Will it only be visible in the daytime after sunrise ?

In the evening after sunset. And it will be further and further away as the days go on so we'll have a better chance of seeing it. Once it's not cloudy of course.

BBC Horizon special on the comet, this sat

http://www.bbc.co.uk/news/science-environment-25001732

Squidvicious

shedweller wrote: »

In the evening after sunset. And it will be further and further away as the days go on so we'll have a better chance of seeing it. Once it's not cloudy of course.

Thanks - obvious when explained to me of course, but I hadn't thought of the fact that if it's near the sun, it'll be visible in the evenings too!!

shedweller

Squidvicious wrote: »

Thanks - obvious when explained to me of course, but I hadn't thought of the fact that if it's near the sun, it'll be visible in the evenings too!!

You're welcome. It did take bit of mental imaging to be sure of it though! Exhausted after that!!

M.T. Cranium

I believe it will be more visible in the morning than the evening, if you visualize the Sun at mid-day going dark so you could see the comet at noon, it would be off to the right now but coming in from the far side of the solar system too (it recently passed Mars which is generally speaking on the far side of the solar system from us). When it approaches the Sun it will pass under the Sun's south pole but then will recurve away towards us and somewhat ahead of us so that once again it will be to the right of the Sun although now much closer and with an activated tail if it stays intact. So the spectacular portion of this event, if it happens, will also be visible pre-dawn, but it gets high enough in the sky within a week or two that it should then be visible most of the night as it will not set with the evening Sun but will move across the northern sky to its pre-dawn rising position. This means that at some point the tail will be visible in the evening although the comet head will be below the horizon.

shedweller

Well that just made a complete mockery of my thoughts on this!! I hadn't thought about its orbit coming back between us and the sun. Wouldn't it be nice if its tail washed over us as it passed! Well, not passed i know but ya know what i mean.

M.T. Cranium

I'm going to have my chance on Wednesday morning, as we have clear skies that look set to remain clear most of the night.

what about from the southern hemisphere? the same applies?

Squidvicious

M.T. Cranium wrote: »

I believe it will be more visible in the morning than the evening, if you visualize the Sun at mid-day going dark so you could see the comet at noon, it would be off to the right now but coming in from the far side of the solar system too (it recently passed Mars which is generally speaking on the far side of the solar system from us). When it approaches the Sun it will pass under the Sun's south pole but then will recurve away towards us and somewhat ahead of us so that once again it will be to the right of the Sun although now much closer and with an activated tail if it stays intact. So the spectacular portion of this event, if it happens, will also be visible pre-dawn, but it gets high enough in the sky within a week or two that it should then be visible most of the night as it will not set with the evening Sun but will move across the northern sky to its pre-dawn rising position. This means that at some point the tail will be visible in the evening although the comet head will be below the horizon.

Bloody complicated stuff;). Either way, it's good news to know that we should get a good look at it, if it doesn't break up and becomes sufficiently bright.

M.T. Cranium

On-line reports are indicating that the comet has brightened rapidly this past week and was at the thresh-hold of naked eye visibility (in dark rural skies) of mag 4 as of early 19th. So I was optimistic that I might find it before sunrise here given clear skies, but found that even in binoculars the glare of the nearly full moon (high in the west) was washing out objects any fainter than mag 3 around Spica to Mars and even worse towards the horizon, was able to spot Mercury rising (approx mag 0.5) but no clear view of either comet or tail which is said to be 16 million km long at this point, as ISON hurtles in towards the Sun (currently it is about 0.4 AU from the Sun, about equal to Mercury's distance.

So I feel that I could say that the comet did not reach mag 3.0 since last published reports from about 24h previous and is probably no brighter than 3.5.

Your chances of seeing it would absolutely depend on being in the darkest possible location, mine was somewhat urban although I do have a large park nearby and can get out of range of any streetlights there. I also tried getting into the shadow (relative to moonlight) of a large tree, but the higher Spica and the comet get, the more pre-dawn glow works against your chances. I thought 0615h was about the best combination of darkness and elevation, after 0630h you start to lose visibility for Spica. Checking my astronomy program, my local times are 12 minutes earlier than yours would be, so would recommend being in position at 0620h with Spica found, and each morning from now to 24th the comet would make considerable progress towards Mercury which was just rising around then. After 25th the tail may still be visible but the nucleus will be past Saturn as seen from earth and into the dawn glare of the Sun.

We shall live in Hope

M.T. Cranium

If anyone does give it a try on Thursday morning, note that the position is not just below Spica and approaching Mercury in the east-south-east, it is also off to the right of the line that joins them -- in the complicated orbit of the comet, it is now at its lowest point relative to our orbital plane, and that takes it off to the right of the "ecliptic" which the two planets happen to be slightly above. To find it, you need to sweep down to the horizon from Spica in a direction to the right or south of where Mercury is rising, about two-thirds to three-quarters of the way to the horizon at 6:20 or half-way by 7:00.

The tail should be pointing almost straight up but slightly to the right.

Chances look better for viewing in the west and as I found, you need to block out the glare of the Moon if at all possible to give your eyes a better chance. You'll notice that the Moon is approaching Jupiter and is crossing the Milky Way.

Just for reference, I think Friday morning would be the last real chance to spot the comet before the week after 29th, and by then it will be moving past Mercury which will be acquiring Saturn as a close companion (they were separated by enough sky on Wednesday morning that I never observed Saturn's faint rising but 2-3 days on, it will be more visible as it currently emerges out of the dawn glare of sunrise. So for Friday and possibly Saturday mornings, the comet would be rising with these two planets and off to their right (lower right by Saturday). Part of the tail might still be visible by as late as Monday 25th and the major brightening could then begin later in the week but only the tail would be seen until perhaps as early as morning of 30th. When and if the comet emerges, it will be coming back out on that same side of the Sun but considerably higher than Saturn and Spica so off to their left as it makes progress away from the Sun.

Also just for reference, the various objects are rising at about a 60 degree angle to the eastern horizon, not straight up.

Good luck, I may give it one more try myself especially if I read anything very encouraging on the updates.

M.T. Cranium

Deleted User wrote: »

what about from the southern hemisphere? the same applies?

As it would be approaching summer and the sky is mirror image for anything solar-related, what they would see is the various objects rising in the ENE although at a less favourable angle to the horizon as is the csae for us in late May, but with the comet at a higher elevation in the sky off to the right (south towards right) than it would appear on our side this week -- but in the possible brighter episode to follow, it would come out on the horizon side of the ecliptic or left of already low-hanging Saturn and later Spica, so we get the better of the situation eventually in the northern hemisphere. However they get the better of this week's view and also don't need gloves and three layers of clothing in most cases. It would be a lot earlier in the day of course.

All of these factoids are similar for various longitudes too, but when the motion is large per day, your time zone would have a bearing on where exactly the objects would appear. For lunar conjunctions with planets in the sky, time zone is often quite significant as the Moon can move a considerable distance in the eight hours between our two time zones, for example.

shedweller

Is that the iss passing overhead?

readytosnap

when i stand with my back to my front door i am facing south, where should i be looking to try and see this comet?, I know nothing about astronomy, so in your best laymans terms can you tell me where to look please.

shedweller

readytosnap wrote: »

when i stand with my back to my front door i am facing south, where should i be looking to try and see this comet?, I know nothing about astronomy, so in your best laymans terms can you tell me where to look please.

At the moment it is almost at the sun. MTC summarised it beautifully above so just read what he wrote so i dont have to embarrass myself!

readytosnap

Yeah I tried that and got lost in the mercury rising, (i thought that was a film) and spica and saturn talk???????????, thats why I displayed my ignorance by asking a dumb question was hoping for a simple "look left" response :rolleyes: or "look south east just above the horizon", looks like i'll have to send the missus out all night till she finds it.

shedweller

readytosnap wrote: »

when i stand with my back to my front door i am facing south, where should i be looking to try and see this comet?, I know nothing about astronomy, so in your best laymans terms can you tell me where to look please.

At the moment it is almost at the sun. MTC summarised it beautifully above so just read what he wrote so i dont have to embarrass myself!

readytosnap

ok i just spent the last 2 hrs in the garden and i cannot for the life of me find the sun.

readytosnap

readytosnap wrote: »

Yeah I tried that and got lost in the mercury rising, (i thought that was a film) and spica and saturn talk???????????, thats why I displayed my ignorance by asking a dumb question was hoping for a simple "look left" response :rolleyes: or "look south east just above the horizon", looks like i'll have to send the missus out all night till she finds it.

your poor missus

You could download Stellarium, it will give you a great idea of whats in the sky and can help you easily identify where you need to be looking. May be easier than any one here trying to explain, as its all laid out for you on the Stellarium site

http://www.stellarium.org/

Elmer Blooker

BBC2 at 9.15, a Horizon special called...... wait for it...
COMET OF THE CENTURY
This better be good :rolleyes:

shedweller

Elmer Blooker wrote: »

BBC2 at 9.15, a Horizon special called...... wait for it...
COMET OF THE CENTURY
This better be good :rolleyes:

It might be the only time i see it because its always cloudy here!

Rikand

I take it the comet is rounding the sun at the moment, based on the lack of talk about it. When does it come back into our view ?