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What was the surface brightness of the green comet on the fifth.

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#1 UnityLover

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Posted 06 February 2023 - 01:13 PM

I want to know what it was so I can get a general baseline for what to expect from the messier galaxies.


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#2 Sketcher

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Posted 06 February 2023 - 02:44 PM

I can't supply numbers.  Besides, different parts of the comet have very different brightness levels; and the same goes for many galaxies.

 

But when I observed the comet on January 31st, I also took a quick a look at two Messier galaxies, M81 and M82, all 3 with 25x100 binoculars.  And those two galaxies are among the brightest, and easiest Messier galaxies to see.  There was a huge difference between the galaxies and the comet.  The comet appeared to be much larger and much brighter.  The comet was bright enough for the eye to easily see the greenish color.  I don't recall noticing any color in the galaxies.

 

That observation was from a seriously dark sky, in the absence of moon light, etc.  Under the light polluted skies (and bright moonlight) that many others observed the comet under, the comet and galaxies would appear to be considerably fainter, with the comet appearing to be considerably smaller (than it appeared in a darker sky); but the relative visibility of the comet and galaxies would likely remain essentially the same -- the comet being much brighter;  and I doubt that the date difference would make any meaningful difference in the above comparisons.


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#3 sevenofnine

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Posted 06 February 2023 - 10:15 PM

The estimated mag. is 8.37. This will tell you all about the comet:   borg.gif

 

https://theskylive.c...here-is-c2022e3.


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#4 David Knisely

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Posted 06 February 2023 - 10:48 PM

The estimated mag. is 8.37. This will tell you all about the comet:   borg.gif

 

https://theskylive.c...here-is-c2022e3.

Well, currently, I did pick it up in my 12x70 binoculars, and while it wasn't exactly easy, it was definitely brighter than 8th magnitude.  I gave it a total integrated magnitude estimate of 6.2 on Monday night February 6th (7th UT) with a diameter of around 15 arc minutes, so it is definitely getting fainter.  Clear skies to you.


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#5 Dave Mitsky

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Posted 07 February 2023 - 02:09 AM

Magnitude estimates on COBS for February 6th range from 5.3 to 5.9.

 

    06.45, 5.9, 10' (C. Wyatt, 15x70 Binoculars);

    06.74, 5.3, 15' (M. Paradowski, 7x50 Binoculars);
    06.78, 5.4, 15' (G. van Buitenen, Dordrecht, NL (G06), 10x50 Binoculars);
    06.78, 5.7, 15' (J. Konecny, Medlov - Hlivice, 25x100 Binoculars);
    06.82, 5.6, 18' (C. Harder, Jeersdorf h, 8x44.0 Binoculars);
    06.85, 5.9, 30.46' (N. James, 0.072-m Refractor + CCD);
    06.97, 5.6, 8' (M. Goiato, 20x100 Binoculars);

I observed the comet tonight from the orange-zone Naylor Observatory using my Canon 15x50 IS binocular, an 80mm finder scope, a 5" finder scope, an 8" Hardin Dob, a 12.5" Cave Astrola, and a 17" classical Cassegrain.  With the bright moonlight, it was a bit difficult to see with the 15x50 and I was not able to detect the comet at all using one of the observatory's 8x40s.
 


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#6 UnityLover

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Posted 07 February 2023 - 11:21 AM

BTW, by surface brightness I mean like Mag/arc sec. Not the total combined magnitude.


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#7 Jon Isaacs

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Posted 07 February 2023 - 12:08 PM

BTW, by surface brightness I mean like Mag/arc sec. Not the total combined magnitude.

 

Surface brightness is typical stated as the average surface brightness for an object:

 

SB = Vb + 2.5 x log (area)  where Vb = Visual brightness and the Area is in the units of choice. The sky is usually measured in magnitudes per square arc seconds, mpsas.  Magnitudes per square arc minutes are also used. To convert mpsam to mpsas, add 8.89.

 

Comets have a small very bright nucleus with fainter coma and tails. Averaging the surface brightness for a comet does not characterize a comet's visibility because you may only be seeing the brightness regions of the comet.  I've been observing the comet during this full moon period from my urban backyard and I've seen it each night with 10x42 binoculars. I doubt there are any galaxies I could have seen in 10x binoculars during the full moon.

 

Surface brightness is really a point by point function. 

 

M31 has an average surface brightness of about 22 mpsas, more than 3 magnitudes dimmer than an urban sky but the bright core can be seen in 7x35 binoculars from most urban backyards.

 

Viewing the comet, I was only seeing the bright nucleus. From a moonless, dark site, I was seeing much more and it was visible as a small faint spot naked eye.

 

Jon


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#8 sevenofnine

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Posted 07 February 2023 - 12:21 PM

I found it pretty easily in Auriga with mounted 12x60 binoculars. The only tough part is it's almost straight overhead. The Sky Live link states the observed mag. is around 5.8  borg.gif


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#9 Dave Mitsky

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Posted 07 February 2023 - 11:29 PM

I want to know what it was so I can get a general baseline for what to expect from the messier galaxies.

Trying to use surface brightness in this case would be akin to comparing apples and oranges, as Jon explained.


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#10 UnityLover

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Posted 08 February 2023 - 08:02 AM

Also, is the comet ion tail visually possible? 


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#11 Nankins

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Posted 08 February 2023 - 08:52 AM

Surface brightness on diffuse objects is not like surface brightness on compact objects.  For instance, you can have a star whose surface brightness is 5.0, and it will be very obvious in your eyepiece.  On the other hand, a galaxy or comet whose surface brightness is the same, will be more spread out and look dimmer in the same eyepiece.  The comet's appearance and brightness is actually a bit similar to some of the brightest Messier galaxies (excluding the obvious ones, M33 and M31).  Obviously the nucleus is a lot brighter than the rest of the comet, like a stellar point.  This is exactly what you should see when looking at M51's core.  But the fainter areas are a bit brighter than many of the Messier galaxies will appear.  I use M51 as an example because if you see it, it will indeed look a lot like a fainter version of the comet.  It's outer areas will be fainter and its core will be almost stellar. 

 

I think the comet's ion tail is possible visually.  Thought I saw it in my telescope once.


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#12 Tony Flanders

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Posted 08 February 2023 - 09:18 PM

Surface brightness on diffuse objects is not like surface brightness on compact objects.  For instance, you can have a star whose surface brightness is 5.0, and it will be very obvious in your eyepiece.  On the other hand, a galaxy or comet whose surface brightness is the same, will be more spread out and look dimmer in the same eyepiece.


I think you're confusing surface brightness and total brightness. Surface brightness is total brightness divided by area. A star, being a point source, has no area, and therefore no surface brightness, properly speaking.

You could, I suppose, consider the star's area to be the size that its actual disk would have if there were no atmosphere and if you had a telescope big enough to actually see the star's disk. In that case, any G-type star has a surface brightness roughly the same as the Sun's -- namely, some trillions of times brighter than any galaxy.

Or you could consider the star's area to be the apparent size of its diffraction disk. In that case the star's surface brightness would only be billions times higher than a galaxy.
 

The comet's appearance and brightness is actually a bit similar to some of the brightest Messier galaxies.


Having seen it for the first time this evening (from densely populated Cambridge, MA), I would agree with this. The comet is considerably more prominent than M51 but probably not as prominent as M81 or M82.

I actually think it looks a lot more like a globular cluster -- one of the middling ones. Nowhere near as bright as M13, maybe more like M9.
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#13 Oregon-raybender

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Posted 09 February 2023 - 03:05 AM

The comet was visible tonight, getting close to Mars (this Saturday)

I saw it with 11X80 and my 6 inch GSO with a 26mm. I used a 9mm to look for

the center, it was there. The shape is still a Fuzz Ball, nothing more, the Moon

is still interfering, plus the local lights (lite fog) 

 

Starry Nightswaytogo.gif


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#14 Tony Flanders

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Posted 09 February 2023 - 04:19 AM

Comets have a small very bright nucleus with fainter coma and tails. Averaging the surface brightness for a comet does not characterize a comet's visibility because you may only be seeing the brightness regions of the comet.


Sure, but exactly the same thing is true of essentially all deep-sky objects. I do think it's reasonable to compare the surface brightness of comets to the surface brightness of deep-sky objects -- especially globular clusters. I think it's no accident that Messier the comet hunter included each and every bright globular cluster visible from Paris in his list, whereas he missed quite a number of bright galaxies.
 

I've been observing the comet during this full moon period from my urban backyard and I've seen it each night with 10x42 binoculars. I doubt there are any galaxies I could have seen in 10x binoculars during the full moon.


You might be surprised. M31 is easy to spot through my 10x30 binoculars at full Moon, and I bet that M81 is, too, though I don't have any recorded observations to vouch for that.

 

You also have to be careful about the phrase "full Moon period." The Moon's brightness varies hugely during the four or five night surrounding the full phase.

 

Having said all that, I'd say that the inner part of the comet has very high surface brightness compared to most galaxies, but not as high as (say) M32 or M94. Sorry I can't put a number on it.



#15 Jon Isaacs

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Posted 09 February 2023 - 05:57 AM

Sure, but exactly the same thing is true of essentially all deep-sky objects. I do think it's reasonable to compare the surface brightness of comets to the surface brightness of deep-sky objects -- especially globular clusters. I think it's no accident that Messier the comet hunter included each and every bright globular cluster visible from Paris in his list, whereas he missed quite a number of bright galaxies.
 


You might be surprised. M31 is easy to spot through my 10x30 binoculars at full Moon, and I bet that M81 is, too, though I don't have any recorded observations to vouch for that.

 

You also have to be careful about the phrase "full Moon period." The Moon's brightness varies hugely during the four or five night surrounding the full phase.

 

Having said all that, I'd say that the inner part of the comet has very high surface brightness compared to most galaxies, but not as high as (say) M32 or M94. Sorry I can't put a number on it.

 

scratchhead2.gif

 

I used the example of M31 to explain why average surface brightness is a poor way to characterize galaxies. I think it's even poorer for comets because of the diffuse tail(s) that make up much of the area but contribute little of the visible light. 

 

Regarding the full moon period, I've observed this particular comet all but 4 nights since January 17th. I'm sharing my experiences.. I saw it naked eye three nights, I've seen it in every thing from 6 x30 binoculars to my 22 inch.. 

 

Surface brightness in an important concept but for most objects that are visible visually, total integrated brightness is a better measure of visibility than average surface brightness.  Total integrated brightness provides a better explanation of why I saw C/ 2023 E3 in 6x30 binoculars with a magnitude -11.6 moon. Seeing M32 or M94 in 6x30s under such conditions is most unlikely.

 

Both surface brightness and total integrated brightness are important but in my experience, the visibility of the nearly all comets and galaxies is better characterized by total integrated brightness than by average surface brightness.

 

Jon


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#16 AmraanAmjad

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Posted 09 February 2023 - 06:20 PM

Surface brightness is typical stated as the average surface brightness for an object:

 

SB = Vb + 2.5 x log (area)  where Vb = Visual brightness and the Area is in the units of choice. The sky is usually measured in magnitudes per square arc seconds, mpsas.  Magnitudes per square arc minutes are also used. To convert mpsam to mpsas, add 8.89.

 

Comets have a small very bright nucleus with fainter coma and tails. Averaging the surface brightness for a comet does not characterize a comet's visibility because you may only be seeing the brightness regions of the comet.  I've been observing the comet during this full moon period from my urban backyard and I've seen it each night with 10x42 binoculars. I doubt there are any galaxies I could have seen in 10x binoculars during the full moon.

 

Surface brightness is really a point by point function. 

 

M31 has an average surface brightness of about 22 mpsas, more than 3 magnitudes dimmer than an urban sky but the bright core can be seen in 7x35 binoculars from most urban backyards.

 

Viewing the comet, I was only seeing the bright nucleus. From a moonless, dark site, I was seeing much more and it was visible as a small faint spot naked eye.

 

Jon

So, Would a Celestron UpClose 7x35 work 

 

Please say yesunsure.png


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#17 UnityLover

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Posted 09 February 2023 - 07:56 PM

So, Would a Celestron UpClose 7x35 work 

 

Please say yesunsure.png

for what? the comet is too dim now, but m31 is low here. Might be fine for you though.



#18 Tony Flanders

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Posted 10 February 2023 - 06:17 AM

Surface brightness in an important concept but for most objects that are visible visually, total integrated brightness is a better measure of visibility than average surface brightness.


I agree, though there are plenty of obvious exceptions, such as M33, M101, and M110, which are among the brightest of all Messier galaxies by integrated magnitude and among the hardest to spot from typical suburban skies. The brighter your skies, the more likely low surface brightness is to be the limiting factor.
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#19 Tony Flanders

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Posted 10 February 2023 - 06:21 AM

So, Would a Celestron UpClose 7x35 work


That depends how bright your skies are. I would be able to see the comet through 7x35 binoculars from my local park, but I have lots of experience viewing faint objects under bright skies. I think the chances of a newbie doing so are essentially zero.

Under truly dark skies I imagine an experienced observer will be able to see the comet without optical aid for quite some time to come, and it should stick out like a sore thumb through 7x35 binoculars.
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#20 UnityLover

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Posted 10 February 2023 - 07:57 AM

It dimmed by at least one magnitude, and is still dimming. Be fast if you want to spot it with the 7x35



#21 WillR

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Posted 10 February 2023 - 09:03 AM

I want to know what it was so I can get a general baseline for what to expect from the messier galaxies.

I look at it the other way round. For me I use what else I can see to judge the comet. This is also more reliable than surface brightness. For example the other night I could just see the comet (in 10x50 bins) with a full moon and very poor transparency, while I could not see M38, M36, or M37 nearby. These are considerably brighter than all Messier galaxies except M31. Of course all I saw was a concentrated small core of the comet.

 

So for the two weeks I have been observing it, the comet has been far brighter than almost all of the Messier galaxies.

 

I feel bad for people who are buying their first binocular or telescope because of the hype around this comet, people like Amraan, who has been trying to determine what binocular to buy. I don't want to see them turned off to astronomy. The comet is interesting to see because it is a comet, like M1 is interesting to see because it is a supernova remnant. But if you did a list of the top 100 or 200 targets to observe for interest, the comet wouldn't be included.

 

And as has been mentioned, we can't ignore experience. When I started out not that long ago, I used binocular guides to determine what I could see in my telescope. I was amazed at what people could see in binoculars that I couldn't. Now I can see far more.


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#22 UnityLover

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Posted 10 February 2023 - 09:18 AM

I believe I saw the ion tail, is that possible.



#23 Oregon-raybender

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Posted 10 February 2023 - 02:24 PM

The comet will be close to Mars tonight (Friday, not Saturday like I mention), so it may be easier to find

for a newbie. I am using 11x80, for a 7X50 in the city area may have a hard time seeing it.

It is a faint fuzz ball, looks like a small cotton ball.

 

https://www.heavens-...ed&alt=0&tz=UCT

 

 

Starry Nightswaytogo.gif


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#24 Dave Mitsky

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Posted 10 February 2023 - 02:30 PM

Has anyone ever seen published figures for the surface brightnesses of comets?  I haven't.


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#25 Dave Mitsky

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Posted 10 February 2023 - 02:32 PM

There's an article on the various methods of estimating cometary visual (integrated) magnitudes at https://skyandtelesc...ets-brightness/


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