553 replies to this topic

[William Frogge]

If correct this will be a show for the ages.  -2 to -6 brightness would be crazy.  Brightest will be during daylight (and close to our sun) but a -2 at sunset in mid October would be spectacular 

https://skyandtelesc...ne-predictions/

Edited by William Frogge, 12 September 2024 - 02:31 PM.

[Octans]

That article is wrong, and confused the stated forward scattering brightness enhancement for the actual magnitude.

[jupiter122]

That article is wrong, and confused the stated forward scattering brightness enhancement for the actual magnitude.

For those of us who are not comet experts, maybe you could explain your comment further. The article referred to visual magnitude, not actual magnitude. I thought they were not the same. Isn’t the forward scattered brightness what we would see? 

 

Tim

[Octans]

The article misinterpreted the original CBET: http://www.cbat.eps..../CBET005445.txt

The magnitudes quoted in the article are the ones the CBET describes as "the modeled brightness increase in visual magnitude, relative to that viewed from (normalized to) a 90-degree scattering angle"; in other words, how many magnitudes brighter forward scattering is making the comet compared to if we were looking at it from the side, not the brightness compared to Vega. The real brightness peak described in the CBET is between -4 and -5 (a more accurate extreme forward scattering model bumps it up to something more like -5 to -6); however, that's a very brief daytime peak, and it will have faded to zeroth magnitude by the time it moves more than ~10-15 degrees from the Sun. That should still make it very bright and impressive, and probably visible in daylight during its brief peak on October 9, but will fall far short of the level implied by the article which really describes a comet surpassing any seen in the past century.

 

Update: Looks like they updated the article to correct this mistake right after I posted this, and it now correctly describes the very large negative magnitudes are the magnitude enhancement, not the actual expected magnitude of the comet. The image captions are still wrong though.

 

Update again: Looks like the captions were fixed too.

Edited by Octans, 12 September 2024 - 08:19 PM.

[beggarly]

Other websites with information about comets:

 

https://www.alpo-ast.../Home/Blog?pg=1

 

http://www.aerith.ne...3A3/2023A3.html

 

https://cobs.si/

 

https://people.ast.cam.ac.uk/~jds/

[yuzameh]

I'm afraid that after seeing one or two articles by s&t on upcoming phenomena which were just press releases or misunderstandings of press releases by the same author (one calling Sekanina's stuff on this object a "publication" which it wasn't, I think that was him anyway, and the repeat expounding of the schaeffer prediction of t crb outburst) I now take everything he writes with a pinch of large areas of subterranean Cheshire.

 

I did not read that article until the above mentioned corrections were made (although I did read it before I saw this thread).  More properly, I scan read it.  I thought it would be the usual misquote when others caught on (I saw the original source, the cbet, the day it was posted) where noises of "comet brighter than Venus" would appear in the more popular press.  He DOES remember to mention the miniscule solar elongation, but I didn't notice (again, I scan read) any major warnings about accidentally viewing the Sun with optical aid, they should always be in bold and on colour pages started with the word warning in red capitals.  Remember, even eclipse glasses aren't always recommended for looking at the full unobstructed disc.  Visually -4 or brighter mag at 4 degrees around UT noon (9.4 UT = 10:24 BST) is going to need eye protection too.

 

I'd disagree that -4 at 4 degrees from the Sun is feasible.  I don't remember seeing people mention seeing Venus visually in day time around the third week of June this year when it was -4 at around 4 degrees Solar Elongation.

 

I remember reading the CBET and not finding it completely clear what was being mentioned, remember the pseudonucleus will be a lot brighter than the whole, the inner coma bright but less so, and the tail will be much less bright, so is he talking integrated mag -4?  I can't remember.  This object will be an extended object and -4 isn't the same as pinpoint -4 for those (I used to, pre LED street lighting, be able to see M31 readily averted vision and sometimes naked eye, but didn't even get a hint of M33 even with finder scopes or binoculars for example, first is ~ mag 4 and t'second is ~ mag 6).

 

I don't know what the field of view of the wider lasco field is on SOHO, might not just be enough for 4 degrees, but it might look interesting in that.  Dunno whether solar orbiter and parker solar probe have that sort of imaging capabilities, and SDO occultation images seem to be relatively low resolution.

 

Do not take S&T as authoritative, check it's source (preferably via direct link to source professional astronomy paper/announcement) and read between the lines even for that.

 

Of course you'll know what's happening in reality on the day, but keep yer eyeballs safe from the Sun!!!

[Octans]

The magnitude of a comet given without any context commonly refers to the brightness of just the coma, unless the coma is too small to be resolved in which case it usually refers to the brightness of the coma + inner part of the tail whose brightness can't easily be separated from the coma (which is often the entire tail for very distant comets, which is not the case here). The tail for a comet of this sort is often several magnitudes brighter, but tough to precisely measure, which is tail magnitudes are rarely reported.

Magnitude -4 is tough to see naked eye so close to the Sun, but may be possible from somewhere like Maunakea/Loa and Haleakala in Hawaii where the atmosphere is clean enough that sky brightness often remains essentially constant all the way to the limb of the Sun. It'll be a tall order under anything less.

 

I think the peak is more likely to be closer to -6 though, as the commonly used forward scattering corrections aren't calibrated for comets at >170 degrees elongation and underestimate the degree of brightening there, and also don't take into account that the tail will be pointed toward Earth and along the line of sight of the coma, further adding to the brightness. These factors have not previously come into play as no comet of remotely similar brightness has been observed at as high a phase angle in recent decades (most recent instance was the 1948 eclipse comet, and the only other one I know of with reliable observations was Skjellerup-Maristany of 1927), but will be important for this comet. At magnitude -6, it may be marginally naked eye visible from typical continental sites. (This difference of course, is only relevant to the peak brightness, and does not significantly affect twilight visibility)

Edited by Octans, 13 September 2024 - 01:50 PM.

[BrooksObs]

I'm afraid that after seeing one or two articles by s&t on upcoming phenomena which were just press releases or misunderstandings of press releases by the same author (one calling Sekanina's stuff on this object a "publication" which it wasn't, I think that was him anyway, and the repeat expounding of the schaeffer prediction of t crb outburst) I now take everything he writes with a pinch of large areas of subterranean Cheshire.

 

I did not read that article until the above mentioned corrections were made (although I did read it before I saw this thread).  More properly, I scan read it.  I thought it would be the usual misquote when others caught on (I saw the original source, the cbet, the day it was posted) where noises of "comet brighter than Venus" would appear in the more popular press.  He DOES remember to mention the miniscule solar elongation, but I didn't notice (again, I scan read) any major warnings about accidentally viewing the Sun with optical aid, they should always be in bold and on colour pages started with the word warning in red capitals.  Remember, even eclipse glasses aren't always recommended for looking at the full unobstructed disc.  Visually -4 or brighter mag at 4 degrees around UT noon (9.4 UT = 10:24 BST) is going to need eye protection too.

 

I'd disagree that -4 at 4 degrees from the Sun is feasible.  I don't remember seeing people mention seeing Venus visually in day time around the third week of June this year when it was -4 at around 4 degrees Solar Elongation.

 

I remember reading the CBET and not finding it completely clear what was being mentioned, remember the pseudonucleus will be a lot brighter than the whole, the inner coma bright but less so, and the tail will be much less bright, so is he talking integrated mag -4?  I can't remember.  This object will be an extended object and -4 isn't the same as pinpoint -4 for those (I used to, pre LED street lighting, be able to see M31 readily averted vision and sometimes naked eye, but didn't even get a hint of M33 even with finder scopes or binoculars for example, first is ~ mag 4 and t'second is ~ mag 6).

 

I don't know what the field of view of the wider lasco field is on SOHO, might not just be enough for 4 degrees, but it might look interesting in that.  Dunno whether solar orbiter and parker solar probe have that sort of imaging capabilities, and SDO occultation images seem to be relatively low resolution.

 

Do not take S&T as authoritative, check it's source (preferably via direct link to source professional astronomy paper/announcement) and read between the lines even for that.

 

Of course you'll know what's happening in reality on the day, but keep yer eyeballs safe from the Sun!!!

 

In fact, Yuzameth, spotting an object, even a slightly diffuse one, 4-degrees from the Sun presents no real challenge ONCE THE OBSERVER HAS GAINED THE KNOWLEDGE OF HOW TO APPROACH THIS TYPE OF OBSERVING. I've seen a defocused Venus at -4.0 when only 39' from the solar limb (November 2, 1982), while noting that I could have done much better if the opportunatey were presented. Likewise, I've seen Mercury, at -2.0 , 62' removed from the limb (September 30, 1978) at noonday employing only the simplest of optical means (while naturally using great care in the setup of my gear) as part of a program of extended observations for just that purpose of spotting near-Sun objects.

 

I would further mention that I've clearly observed Comets West and McNaught in full daylight at about magnitude -4.0 complete with short tails (!) with just ordinary handheld binoculars, likewise also spotting both with just the naked eye prior to sunset at an elongation of about 7 degrees..

 

BrooksObs

Edited by BrooksObs, 13 September 2024 - 09:55 PM.

[yuzameh]

In fact, Yuzameth, spotting an object, even a slightly diffuse one, 4-degrees from the Sun presents no real challenge ONCE THE OBSERVER HAS GAINED THE KNOWLEDGE OF HOW TO APPROACH THIS TYPE OF OBSERVING. I've seen a defocused Venus at -4.0 when only 39' from the solar limb (November 2, 1982), while noting that I could have done much better if the opportunatey were presented. Likewise, I've seen Mercury, at -2.0 , 62' removed from the limb (September 30, 1978) at noonday employing only the simplest of optical means (while naturally using great care in the setup of my gear) as part of a program of extended observations for just that purpose of spotting near-Sun objects.

 

I would further mention that I've clearly observed Comets West and McNaught in full daylight at about magnitude -4.0 complete with short tails (!) with just ordinary handheld binoculars, likewise also spotting both with just the naked eye prior to sunset at an elongation of about 7 degrees..

 

BrooksObs

Well, that's more promising then.  Folk still be careful of that Sun though.  NB you hve better than usual skies?  The dates are a long while ago, I remember far crisper skies in those days, not just due to nostalgia, more regular westerlies and barely any easterlies, which has been emulated this year for the first time in a long while (albeit whilst also giving much cloud).

 

Still not yer hale-bopp in dark skies though, we'll see how the more popular media pick up on the details nearer the time, as it's an announcement made for hype.

 

ONCE they've gained the experience, as you point out.  It's rarer than you'd think, especially with current younger folk, as urban skies are hard places to pick such stuff up nowadays, let alone experienced daytime observers.

Edited by yuzameh, 14 September 2024 - 12:09 PM.

[cometguy]

It's certainly looking promising at the moment.  From a few hours ago (Sep 14.795, 2024 UT) I was able to image it with a stationary mounted camera and 135 f1.8 lens.   Although visible on individual 1.3 second exposures, stacking is still required to get an acceptable signal.  The image attached is a combination of 60 x 1 sec and 60x1.3sec, cropped to 1.5 degrees square.  Extracting the green channel, I did a magnitude comparison with nearby mag 6.65 star HIP51784 and a 6' diameter measurement aperture and the magnitude is estimated at 4.8.   I tried visually with small binoculars with no success, but the skies were a little hazy.

Attached Thumbnails

• 

[adlibitum]

It's certainly looking promising at the moment.  From a few hours ago (Sep 14.795, 2024 UT) I was able to image it with a stationary mounted camera and 135 f1.8 lens.   Although visible on individual 1.3 second exposures, stacking is still required to get an acceptable signal.  The image attached is a combination of 60 x 1 sec and 60x1.3sec, cropped to 1.5 degrees square.  Extracting the green channel, I did a magnitude comparison with nearby mag 6.65 star HIP51784 and a 6' diameter measurement aperture and the magnitude is estimated at 4.8.   I tried visually with small binoculars with no success, but the skies were a little hazy.

Thank you for this, looking forward to any more reports you are able to give us! 

[PEterW]

If would be great if it could be visible nearly in he daytime, I’m not going to forget seeing n naught with binos from a window at work just after the sun had set….

Peter

[cometguy]

C/2023 A3 (Tsuchinshan–ATLAS) Sep 16.793, 2024.  Unfortunately a large cumulus cloud deck obscured the horizon, so I had to wait for the comet to clear the top deep into twilight.  So no visual observation through small binoculars, although I it should have been possible.  m1 = 4.4 estimated by comparison with Delta Sextans and HIP 51784 using the green channel of a 30 second exposure (stack of 1sec) and a 6' diameter measurement aperture in Maxim DL.  Camera Sony A7iii and 135/1.8 lens.  Location Wellington Point, QLD, Australia.  This is a 3 degree square crop using t3 x 1.6sec ISO640 exposures with the previously mentioned camera combination.  Clearly brighter than 2 mornings ago.

Attached Thumbnails

• 

Edited by cometguy, 17 September 2024 - 05:01 AM.

[emflocater]

Living in the Northern Hemisphere, I'll just sit back and wait until the 2nd week of October 2024 and check the progress of this comet as it rounds the Sun and comes into better view in the Northern Hemisphere in the evening...if it survives perihelion with the Sun! Recent updates show the comet appears so far to be in good health.

 

Cheers

Don

Edited by emflocater, 17 September 2024 - 10:51 AM.

[cometguy]

Latest observation from this morning.

 

C/2023 A3 (Tsuchinshan–ATLAS) : Sep 18.780, 2024. 2.5sec exposure Sony A7iii + 135/1.8 lens over North Stradbroke Island, QLD, Australia.  FOV is 10 degrees squared.

 

Observation:  Sep 18.785, 2024.  m1 = 4.0 estimated by comparison with Delta Sextans using the green channel of a 75 second exposure (stack of 30x2.5sec) and a 6' diameter measurement aperture in Maxim DL.  Camera Sony A7iii and 135/1.8 lens.  Visible dimly in 10x42 Binoculars as a fuzzy star with a hint of tail.  Low altitude, twilight and full moon severely impacted observation.  Location Wellington Point, QLD, Australia.

Attached Thumbnails

• 

Edited by cometguy, 18 September 2024 - 05:58 PM.

[D.H.3.14]

Latest observation from this morning.

 

C/2023 A3 (Tsuchinshan–ATLAS) : Sep 17.780, 2024. 2.5sec exposure Sony A7iii + 135/1.8 lens over North Stradbroke Island, QLD, Australia.  FOV is 10 degrees squared.

 

Observation:  Sep 18.785, 2024.  m1 = 4.0 estimated by comparison with Delta Sextans using the green channel of a 75 second exposure (stack of 30x2.5sec) and a 6' diameter measurement aperture in Maxim DL.  Camera Sony A7iii and 135/1.8 lens.  Visible dimly in 10x42 Binoculars as a fuzzy star with a hint of tail.  Low altitude, twilight and full moon severely impacted observation.  Location Wellington Point, QLD, Australia.

Very nice! I'm going to try and spot it from ~42 degrees north on the 22nd. I have... really low hopes for this attempt, but hopes nonetheless!

 

Good luck,

Dom

[triviniu]

 

Morning of 2024-09-20 from Chile. Decent, but to be frank not exactly the great comet one was hoping for.

Edited by triviniu, 20 September 2024 - 08:35 AM.

[Aquarellia]

Very nice! I'm going to try and spot it from ~42 degrees north on the 22nd. I have... really low hopes for this attempt, but hopes nonetheless!

 

Good luck,

Dom

I try this morning from 43°42'N with a cooperative horizon but no success.

Michel

[MEE]

Morning of 2024-09-20 from Chile. Decent, but to be frank not exactly the great comet one was hoping for.

Are you really making the judgement call on this comet just from this one observation?

Edited by MEE, 20 September 2024 - 01:41 PM.

[William Frogge]

Wow

 

https://www.space.co...inick-iss-photo

[triviniu]

Are you really making the judgement call on this comet just from this one observation?

Yep. It's close to perihelion, it'll remain extremely close to the sun while it's in forward scattering enhancement, and it will be closest to earth soon (and not much closer than now). I doubt the general public will register even a trace of it, which the very least I think would be needed to be considered "great". Much less impressive than Leonard 2021 at a similar stage. If this was to go big while it still has the possibility to do so (up to mid-October, more or less), it would already be.

[Octans]

The comet will be *much* closer to Earth than it is now, while also brightened by forward scattering, and will moreover be angular farther from the Sun at that time. Few comets that could be considered great had viewing geometry as poor as the one it has right now on the other side of the Sun, but that will very rapidly change. In fact, it's been doing well enough that I'd say it has decent odds of at least matching the peak display of Hale-Bopp, albeit for a much shorter period.

Edited by Octans, 21 September 2024 - 06:59 PM.

[MichaelJB]

The comet will be *much* closer to Earth than it is now, while also brightened by forward scattering, and will moreover be angular farther from the Sun at that time. Few comets that could be considered great had viewing geometry as poor as the one it has right now on the other side of the Sun, but that will very rapidly change. In fact, it's been doing well enough that I'd say it has decent odds of at least matching the peak display of Hale-Bopp, albeit for a much shorter period.

You are stating this for when it comes into the Northern Hemisphere? I assume?

[Octans]

Yes, after it re-emerges into evening twilight starting maybe around October 12-13 (it might actually start to be visible as early as October 10-11, but won't look like much yet) and for the following week or so. Should be visible from most of the Southern Hemisphere around then too, as it'll only be slightly north of the Sun.

 

It could actually have already started to develop a fairly long (10+ deg) tail in morning twilight before conjunction in the first week of October prior to conjunction (October 9), and there could be a period just before conjunction where the tail might remain visible after the head has dived too deep into twilight to see, but the viewing geometry is better after conjunction.

Edited by Octans, 21 September 2024 - 07:18 PM.

[joshman]

It's got potential. that tail is getting longer. Based on what I've seen in my images, it's at least 1.5-2 degrees long.

 

Hopefully it gets brighter.