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Comet C/2015 V2 (Johnson)

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#51 vakulenko_sergiy

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Posted 05 May 2017 - 05:48 PM

Yesterday I have checked that C/2015 V2 still present smile.gif

ED80, OSC QHY8, 14x300s

C/2015 V2 05/05/17 ed80 osc qhy8 14x300s

Edited by vakulenko_sergiy, 05 May 2017 - 05:51 PM.

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#52 canukLX90

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Posted 08 May 2017 - 02:22 AM

Finally a somewhat clear night and a chance to do some imaging.  C/2015 V2 was 60 degrees from the almost full moon.

The sky transparency was not good and the SQM-L was 19.4 with the comet about 50 deg. above the horizon.  I could not

see the comet with my 66mm refractor.  I am not sure what the ? is in the image.  I stacked on the comet so it appears to be

stationary relative to the comet.

 

PJ

 

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#53 Tonk

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Posted 08 May 2017 - 07:25 AM

I'd investigate the "?" as its downstream from the direction of the dust tail. It could be a comet fragment that is starting to brighten as the comet nears perihelion



#54 Aquarellia

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Posted 08 May 2017 - 12:04 PM

I'd investigate the "?" as its downstream from the direction of the dust tail. It could be a comet fragment that is starting to brighten as the comet nears perihelion

Indeed that's a possibility but another explanation is that this is an artefact, a material reflection, I think about that because of the symmetric position vis-a-vis the pseudo-nucleus and also because I don't see yet any other picture showing that.  If you look carefully there is another very faint point like the first one.   Also I have a question : what is this very small vertical line toward bottom on the zoomed image?

Anyway this is an interesting question mark, I like that!

Michel



#55 canukLX90

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Posted 08 May 2017 - 02:07 PM

If I could get consecutive clear nights I would be able to confirm whether artifact or ?.  Maybe someone else

can image and confirm.  I had several satellites pass thru the image field and that would be the vertical line.

I did notice several other faint ? in and behind the comet tail but the bright ? drew my immediate attention.

 

PJ

 



#56 canukLX90

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Posted 08 May 2017 - 04:45 PM

I did another stack and this time on the stars.  It appears to be an artifact of some sort as the ? did not blur which it should

have if it had any motion associated with it.  Still a nice comet to image and watch.  Sorry for the false ?

 

PJ

 



#57 galazie

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Posted 11 May 2017 - 08:39 PM

On 29 April, using my 16-inch dob, C/2015 V2 Johnson looked as good as a B&W photo at 60x.



#58 Augustus

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Posted 13 May 2017 - 08:53 PM

I literally forgot entirely about this one.

 

Going to observe it this week.



#59 mightymouse

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Posted 14 May 2017 - 01:30 AM

I went looking for Comet Johnson last night.  According to LiveSky, it was near Mu Bootis (SAO 64687).  Using my goto, I slewed to Mu Bootis and scanned around the area.  I found a fuzzy object nearby....but could not see a tail.  Unfortunately the clouds came in so I don't have an opportunity to go out later in the night to see if it has moved.  Is the tail apparent with the telescopic view? (i.e. does the tail become apparent with stacking?)   My telescope is a SCT-8; eyepiece used was a 40 mm.   Thanks from a novice.

 



#60 Aquarellia

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Posted 14 May 2017 - 02:28 AM

I went looking for Comet Johnson last night.  According to LiveSky, it was near Mu Bootis (SAO 64687).  Using my goto, I slewed to Mu Bootis and scanned around the area.  I found a fuzzy object nearby....but could not see a tail.  Unfortunately the clouds came in so I don't have an opportunity to go out later in the night to see if it has moved.  Is the tail apparent with the telescopic view? (i.e. does the tail become apparent with stacking?)   My telescope is a SCT-8; eyepiece used was a 40 mm.   Thanks from a novice.

The dust tail is easy to find but not very long, it looks like an elongated coma, the ion one is much more difficult to detect, maybe a SWAN filter can help, I try with my 6" refractor but without success yet. With my 12"DOB it's much more easy.

The apparent size of this comet is quite small, I suggest you to use more magnification while on the target, a good 10mm could be a better choice with your material.

Hope to see another observation from you here soon!

Michel


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#61 caheaton

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Posted 14 May 2017 - 09:02 AM

Also observed it for a bit last night.  It looked like an elongated gray patch of light in the 120ST and a 12.5mm plossl.  Sky conditions weren't the best as there was considerable sky glow from the moon (in addition to the normal local lp).  Looking forward to observing this one at the upcoming Calhoun star party.


Edited by caheaton, 14 May 2017 - 08:10 PM.

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#62 Dave Mitsky

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Posted 15 May 2017 - 02:21 PM

The conditions weren't the best but I showed Comet C/2015 V2 (Johnson) to visitors at 216x using the ASH 17" f/15 classical Cassegrain during our public observing session at the Naylor Observatory last night.  Another ASH member had it in view with our 12.5" f/6.5 Cave Astrola Newtonian.

 

The short dust tail showed up as an asymmetric elongation of the comet's coma. The pseudonucleus was definitely noticeable.

 

Dave Mitsky


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#63 LivingNDixie

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Posted 15 May 2017 - 08:50 PM

Caught it last night before the Moon came up, it was easy to find and clearly visible in the 8X50 finder. Nice views on my 8in.
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#64 Special Ed

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Posted 16 May 2017 - 06:57 AM

I had my first sighting of C/2015 V2 (Johnson) last night (0300 16 April UT) under beautiful clear skies--been clouds and rain here for 3 weeks.  It took me a while to find it because I had to reorient myself to the constellation positions--it's been that long.  Sure was nice being out under the stars.  smile.gif

 

Comet Johnson is in the "ice cream" part of the "ice cream cone" asterism of Bootes and of course, Arcturus was easy to spot but I had the "cone" stretching off to the NW instead of the NE (there are plenty of stars out there so you can make pretty much any pattern you want).

 

After about a half hour wondering why the stars in my 12x36 binocular FOV didn't match the charts I finally realized my mistake.  tongue2.gif   Looking in the right place with the image stabilized binoculars I saw Comet Johnson immediately ~1.5* SW of Alkalurops.  It appeared as a fairly large smudge with the 12x36's, not well condensed and with a hint of elongation.  I estimated the magnitude using the defocused star method.

 

At first I thought I could see a stellar pseudonucleus winking in and out but I was skeptical it could be that with such small binoculars.  Checking my chart, Johnson was passing in front of a 10th magnitude star which created the illusion.

 

C/2015 V2 (Johnson) 2017 05 16.13 UT  m1= 7.5  DC= 4  Dia= 10'  12x36B

Alt: 65*  Transparency: 5/6  SQM-L: 21.63 mpsas  No Moon


Edited by Special Ed, 16 May 2017 - 06:59 AM.

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#65 astrocy

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Posted 16 May 2017 - 03:57 PM

I found C/2015 V2 (Johnson) this evening of 16th May using 20x80 binoculars about 2.5 degrees from Delta Bootis and 2 degrees from Mu Bootis. It appeared as a large fan-shaped nebulous object with a slightly brighter coma and a fainter dust tail pointing NW. I estimated its brightness around +8 magnitude.


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#66 Chopin

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Posted 16 May 2017 - 08:25 PM

I had my first sighting of C/2015 V2 (Johnson) last night (0300 16 April UT) under beautiful clear skies--been clouds and rain here for 3 weeks.  It took me a while to find it because I had to reorient myself to the constellation positions--it's been that long.  Sure was nice being out under the stars.  smile.gif

 

 

Michael, I know exactly how you feel. If the weatherman even mentions drought I'm calling bs on that one! lol.gif

 

Last night was my first opportunity to do any viewing in months, and the evening clouds moved out along with the atmospheric moisture right around midnight. Just enough time to enjoy the dark before the moon began to hamper the view. Took the 10" 4.5 dob out, threw in an eyepiece for a 27x and 2.3º TFOV. Spotted the little comet immediately. My CSC was predicting crummy seeing, but I have to say, it was soooooo clear when I walked outside. I was gobsmacked by how easy Johnson was to see. Clear fan shape, and brightly condensed head. First comet I've seen in a while, and a very satisfying object on a first-in-a-long-time outing!


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#67 andrew hampton

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Posted 17 May 2017 - 06:34 PM

Had another look tonight, although it's not dark here in the UK till near midnight. It was a nice clear view in 10x50s around 7th magnitude estimate. Getting brighter toward the June approach.

 

andrew



#68 Special Ed

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Posted 17 May 2017 - 08:56 PM

Took another look this AM, first with the binoculars and then with the big CAT (local midnight).  Not much to see in the binoculars but with the telescope at 71x, 98x, and ultimately 122x, the comet revealed itself to have a large round coma and a short, stubby fan shaped tail (much like what Jason reported).  The coma was moderately condensed with a fairly bright pseudonucleus (as Dave Mitsky reported).

 

This comet is not a fast mover and I did not really detect much motion during the session.  I moved the comet in and out of the FOV to get a sense of the size, extent, and direction of the coma and tail.  Conditions were good and the SQM-L reading was 21.61 mpsas.

 

I tried looking with my new Lumicon SWAN Band filter which showed a much larger coma but no ion tail.  I don't have any experience with a SWAN filter so any guidance is appreciated.

 

C_2015_V2_2017.05.17.composite.v1.JPG


Edited by Special Ed, 17 May 2017 - 09:14 PM.

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#69 MarioJumanji

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Posted 17 May 2017 - 11:07 PM

I wanted to find a comet tonight, so I Googled this one up and found it pretty easily. :) Can't really discern the tail visually in my 5", but it's a pretty cool sight.

#70 Aquarellia

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Posted 18 May 2017 - 01:27 AM

I had the very similar view than the Michael's one but just one night before.

Sorry I have not a lot of cloudynights to post,... or to sleep wink.gif

 

Here my sketch, this is the 6th one I did about this slow motion comet since the end november last year.  I did two sketches, one with and another without the SWAN filter, both sketches are very similars, maybe the one with the filter shows a bit bigger coma but the tail was the same and the ion tail was sadly but really not visible.

 

20170515_l.jpg

 

Easy to catch with 10x70 bino but the sketch was made with my 12" Dobson 40x and 150x.

C/2015 V2 (Johnson) 2017 05 15 20:35 UT  m1= 7.5  DC= 5  Coma Dia= 5' Tail 11' tail direction 050°

Transparency: 5/6  SQM: 20.74 No Moon

 

Michel


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#71 Tonk

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Posted 18 May 2017 - 03:01 AM

Michael, Swan band filters pass a couple of green light lines from C2 molecule fluorescence emissions. These are predominately in the coma as they are neutral molecules. If any one (or filter manufacturer ) says its from cyanogen they are 100% wrong. In fact to date cyanogen (CN)2 has never been detected in comets despite various websites quoting the green colour of comets is cyanogen!!

 

You would need a different filter to pick out the blue light emissions in ion tails.

 

The nitrile radical (CN) strongly fluoresces in comet comas in the far violet right on the border with UV so is probably only visible to young peoples eyes. In a spectroscope this emission is often bright compared to C2 but our eyes are far more sensitive to green so that latter source dominates in visual observations.


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#72 Special Ed

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Posted 18 May 2017 - 07:06 AM

Michael, Swan band filters pass a couple of green light lines from C2 molecule fluorescence emissions. These are predominately in the coma as they are neutral molecules. If any one (or filter manufacturer ) says its from cyanogen they are 100% wrong. In fact to date cyanogen (CN)2 has never been detected in comets despite various websites quoting the green colour of comets is cyanogen!!

 

You would need a different filter to pick out the blue light emissions in ion tails.

 

The nitrile radical (CN) strongly fluoresces in comet comas in the far violet right on the border with UV so is probably only visible to young peoples eyes. In a spectroscope this emission is often bright compared to C2 but our eyes are far more sensitive to green so that latter source dominates in visual observations.

Thanks for the info, Tony.  I remember the thread a couple of years back where you and others discussed how (CN)2 is not present in the coma and made efforts to get websites like Spaceweather to make corrections.

 

I didn't realize that the SWAN filter would not enhance the ion tail--I knew it didn't help with the dust tail.  So it's just for looking at the coma of "gassy" comets?

 

This was my first look through a SWAN filter--the view was greenish (with very dark sky background), dimmer stars, and an almost eerie visual appearance with the coma edge wavering (fluorescing?).

 

Lumicon never mentions cyanogen.  The info from Lumicon says that the filter passes the OIII line (501nm) and two C2 lines (511nm and 514nm).  They say that the filter helps determine the difference between gaseous comets and dusty comets and "the high contrast of the filter reveals the delicate ion tail of gaseous comets".  Would that be the OIII line?

 

@ Michel--nice sketches and good mutual confirmation of our visual observations.  waytogo.gif 


Edited by Special Ed, 18 May 2017 - 07:08 AM.

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#73 Tonk

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Posted 18 May 2017 - 07:40 AM

Michael - Looks like Lumicon have recently corrected their filter description (HORRAY!). You can still see the old description on vendor sites where they have copied the old Lumicon description.  E.g.

 

http://www.astroshop...er-1-25-/p,6750

 

 

The Lumicon Comet filter, A narrow band-pass filter system (25nm), isolates the 501nm OIII line and both Cyanogen lines 511nm and 514nm. The high contrast gain of the filters reveals the delicate ionized tail of gaseous comets, allowing you ton lake their full extent. The Comet filter thus helps you tons more better distinguish gaseous comets from dusty comets which normally show little contrast gain.


My bible of comet spectra lines is the paper "A High Spectral Resolution Atlas of Comet 122P/de Vico" (https://arxiv.org/pd...-ph/0202038.pdf) plus citations within (sorry - its heavy going for the detail explanations - unless you have taken detailed courses in spectroscopy - however the sections for each species is useful as the main spectral band regions and comet feature that they occur in are listed).

The principle ion tail emission species CO+ (ionised carbon monoxide) which has a number of lines spread throughout the visible region - brightest group are in the blue/violet region.

Update: Re-reading the the Lumicon description - the filter is a single bandpass 25nm wide that is open to OIII and the two main C2 bands @ 501nm, 511nm, 514nm. If you can see anything of the CO+ lines in the tail it would have to be a line within this band pass region. Looking at Figure 3 in the paper "A High Spectral Resolution Atlas ..." shows that none of the main ionised species found in the ion tail H2O+, CH+, CO+ have lines that coincide with the Swan filter window. So I'm now puzzled why Lumicon claim that their filter enhances tails. Its not an optimal filter for ion tails!


Edited by Tonk, 18 May 2017 - 08:31 AM.

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#74 Dave Mitsky

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Posted 18 May 2017 - 01:34 PM

I observed Comet C/2015 V2 (Johnson) through the ASH 17" f/15 classical Cassegrain late Monday night when it was quite high in altitude.  This time I could detect its short dust tail to some degree.  I used magnifications of 116, 162, 216, and 259x to view the comet.

 

Dave Mitsky



#75 Uwe Pilz

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Posted 18 May 2017 - 11:35 PM

> 25nm wide that is open to OIII and the two main C2 bands @ 501nm, 511nm, 514nm. If you can see anything of the CO+ lines in the tail

 

The Swand band doen't come from CO, but from carbon gas (C2). This is mentioned in the paper "A High Spectral Resolution Atlas...":

 

 

3.1 C2
There are two principal band systems of C2 which are observed in the optical in the spectra of comets. These are the Swan, or d 3Πg – a 3Πu, system...



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