Tuesday, January 14, 2014
Will We See Meteors for Comet ISON on January 15 and 16 (Not Likely)
Once again we are seeing claims of a possible meteor shower from the long departed Comet C/2012 S1 ISON. Comet ISON broke up as it rounded the Sun, a rapidly fading cloud of dust was seen exiting the STEREO H1 A imager, but despite repeated attempts, no on has been able to observe the remnants of ISON since.
The meteor claims come from three different sources. Each with a different likelihood of happening, all either non-existent or remote.
1) Debris from the breakup of ISON back in late November - early December.
Nope, not happening. When comets break up they don't go all explody like in Hollywood. The debris remains fairly close to the original orbit of the comet (we have numerous examples where we have seen this). Also, the comet passed its closest approach to Earth back on December 26th (at our closest we were a bit under half the distance from Earth to the Sun).
The nominal position of ISON is now well above Earth's plane of orbit, between the orbit of Earth and Mars. Any remnants of the comet are close to this position so, no, no meteors from the pile of gravel and dust formerly known as ISON.
Around November 2 the comet passed 0.0227128 AU above the plane of Earth's orbit (this is 10 times the distance from the Earth to the Moon). On the 15th and 16th (AEDST, 14th and 15th Universal Time) Earth will be close to where ISON passed.
BUT, what will be passing is dust that was released two and a half months earlier (EDIT Jakub Cerny points out that orbital and solar wind/light pressure issues means that it is likely the dust will have been released mor tha 2.5 months earlier), when the comet was far less active, also the comet was passing above Earth's plane of orbit, so the solar wind will have been pushing any dust away from Earth (although larger particles will keep to the original orbit). As well, ISON turned out to be relatively dust poor compared to other comets.
So it is very unlikely we will get an meteors from ISON this way (see my previous post on this for more detail).
However, if we do get meteors, they should be originating from the sickle of Leo (see this post from Rob Lunsford at the American Meteor Society, his dates are for America though). The image above (click to embiggen) shows the view at 2 am ACDST as seen from Adelaide on 16 January. Similar views will be seen elsewhere in Australia (and other Southern hemisphere locations) at a similar local time.
Given the low likelihood of meteors in the first place, and the full Moon close by, I will be surprised if anyone sees any meteors.
3) Dust blown back from ISON when it was closer to the Sun.
Despite the title of the article, this wasn't about meteors (the NASA PR department should hang its head in shame). Meteor researcher Paul Wiegert suggested that ultra-fine dust particles from ISON might be blown back onto Earth by the solar wind, forming noctilucent clouds (NOT meteors).
However, as ISON turned out to be smaller than we thought, and less dusty than average, this scenario is also much less likely now.
Summary
Meteors from ISON, not likely, but going out on the early mornings of the 15th and 16th could be possibly pick up one or two meteors per hour that may be from ISON (or none).
Labels: C/2012 S1 ISON, Meteors
Friday, December 13, 2013
Earth will NOT be hit by a "Wave of Killer ISON Debris"
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| Chart showing the predicted position of ISON as seen from STEREO H1A on 1 December 00:09 UT (click to embiggen). The Pleaides is the cluster at centre left in both images. | Image showing the actual position of ISON as seen from STEREO H1A on 1 December 00:09 UT (click to embiggen). The STEREO image has Earth and Mercury in the centre, these are not plotted on the star chart. |
Now that Comet C/2012 S1 ISON has fallen apart into a sad pile of gravel and dust, the fear merchants are at it again. With headlines like "COMET ISON'S KILLER Debris Wave Heading for EARTH" (I'm not going to link to the various pages and give them the page views, but you can google it yourself if you want to kill a few brain cells) the fear merchants are trying to scare people into thinkg a massive strom of rocks is headed our way.
But it isn't.
ISON's predicted orbit takes it well away from us, the nearest the pile of gravel formerly known as ISON comes to us is 0.43 AU (64,000,000 km), that's a bit under half the distance form Earth to the Sun, or the distance from Earth to Venus's Orbit.
i.e. Nowhere near us. I have previously checked ISON's orbit as it came out from its close approach to the Sun in the SOHO LASCO C3 images, it was right on track. I've done it again for ISON is the high resolution STEREO H1A imager images. This is more tricky as STEREO-A does not have the same field of view as Earth, so I needed to make a special ephemeris using JPL horizons based on the STEREO-A spacecraft's position.
They match to within 8 arc seconds. This means that ISON is on track in it's predicted orbit, and will come no closer to Earth than 0.43 AU. The rather compact debris trail will be high above Earth's orbit heading out to space. Oh yes, and the leftover material will not be "city sized". ISON itself was less than 1 Km in diameter (more like 600 meters), the biggest bits in the leftover gravel will be meter sized, at the outside as big as the Chelyabinsk meteor. If the debris cloud did come near us, we would get a pretty meteor display, but nothing more.
But of course, they will not come anywhere near us.
Labels: C/2012 S1 ISON, Meteors, Pseudoscience, Stereo Satellite
Wednesday, December 04, 2013
A Bit of a Comet ISON Wrap-up.
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| Comet C/2012 S1 ISON (indicated) has survived its passage around the Sun. It is much faded, and is probably no more than a pile of rubble gently dissipating into space. image from 30 Nov 2013 | Animation of 20 images from 30 November to 1 December 2013 showing ISONs progressive fading |
Being off at a conference and away from my astronomy software I have not been able to blog ISONs going saga. After initially recovering from its beating as it passed perihelion, it has continued to fade as it passed from the LASCO C3 imager to the STEREO H1A imager.
While still visible in H1A up until the time it passed out of the H1A field of view, it is very much faded, and it is uncertain if the remnants will be visible in amateur instruments when it gets high enough in dark sky several days from now.
I've done a quick image and animation of the high resolution H1A images available now, this give a more realistic view than the medium resolution highly enhanced images that have been available until now.
Labels: C/2012 S1 ISON, Soho, Stereo Satellite
Saturday, November 30, 2013
Comet C/2012 S1 ISON Keeps On Keeping On (29 November UT)
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| Comet C/2012 S1 ISON seen in the SOHO LASCO C3 instrument from 12:30 UT 29 November.It is 0.107AU from the Sun by the end. | C/2011 W3 Lovejoy in SOHO C3 (16 December 2011 UT). Lovejoy is 0.08 AU from the Sun here. Image credit NASA/SOHO |
Comet ISON keeps on going, despite several news reports suggesting its demise, the comet still looks more or less comet like over 24 hours from perihelion (for views of what it looked like then see here, and its subsequent return here and here). For comparison I show the other great survivor, comet C/2011 W3 Lovejoy.
Lovejoy was brighter, and continued to brighten developing a spectacular tail before its ultimate demise. ISON is fading slowly, although what is probably the synchronic tail is developing nicely.
It is still too early to write ISON off yet, but it is also still too early to determine if we can see it in the skies in the next few days.
A nice ABC article immediately post perihelion, which quotes me, is here.
Labels: C/2012 S1 ISON, comet lovejoy, Soho
Friday, November 29, 2013
Comet C/2012 S1 ISON stays on track (29 November UT)
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| Comet C/2012 S1 ISON seen in the SOHO LASCO C3 instrument at 06:18 UT 29 November. Stars indicated for comparison with chart. Click to embiggen | Chart of the predicted position of ISON at 06:18 UT 29 November.Click to embiggen |
In the wake of the dramatic breakup and revival of comet ISON as it rounded the Sun, once again there has been speculation that it is significantly off track.
Here I show one of the latest SOHO images together with the predicted position of ISON at the same time, using old orbit parameters. ISON is exactly where it should be, between Chi Ophiuchus and the dim star TYC-6210-254-1. Measuring their positions I find the present position of ISON is within 6" of teh predicted poition, well within the measurement error from the images.
Pre-perihelion track positions diagram and predictions are here.
Note the broad fan shape of comet ISON at the moment, comet ISON seems to be reviving, a bit. But it is still not clear what we are seeing is a pile of gravel with attitude, or a substantial chunk of comet remnant. Karl Battams and the STEREO team think it likely that there is a substantial chunk of material, Terry Lovejoy and Jacub Cerny think it likely there is not.
All I can say is keep on watching, even if it is just gravel with attitude, it is still beautiful and we can still learn a lot.
Labels: C/2012 S1 ISON, Soho
Comet ISON, It's Not Dead Yet! (it may go for a little walk)
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| Latest 12 images from the SOHO LASCO C3instrument animated. Comet ISON breaks up, but some comet-looking material comes out the other side. You can see the remnants of the old tail on the other side of the Sun. | Latest 30 low resolution beacon images from the STEREO COR2B instrument animated. As for LASCO C3 you can see a big bright blob of material coming out. |
C/2012 S1 ISON continues to amaze. After fizzing out, it seems to have turned on again. Whether this is just a bunch of gravel fizzing out or a fragment of nucleus turning on again, as happened with comet Lovejoy is not clear. Because of the orientation of the comet and it's orbit in COR2B it looks like it is spinning, but this is just a line of sight effect. However, looking carefully at the image it may be that we are seeing the beginning of new tail production. Only time will tell, so we need to keep on watching.
Monty Python: "I'm not dead yet!".
Labels: C/2012 S1 ISON, Soho, Stereo Satellite
Is Comet C/2012 ISON channelling comet Lovejoy? (post perihelion, 28 November 2013)
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| Latest 30 images from the SOHO LASCO C2 instrument animated. Comet ISON breaks up, but some material comes out the other side. | Latest 30 low resolution beacon images from the STEREO COR2A instrument animated. The Big blob is Venus. As for LASCO C2 you can see the breakup, but something continues on. |
C/2012 S1 ISON reached perihelion. And then broke up, and then something continues on. It might be just gravel and dust, or there might be a chunk big enough to be comet like. This is not unlike what happened to comet Lovejoy. Only time will tell if there is a chunk big enough to turn on again.
Insert favourite Monty Python or Princess Bride Quote here.
Labels: C/2012 S1 ISON, Soho, Stereo Satellite
Thursday, November 28, 2013
Comet C/2012 S1 ISON Brightens More, Prospectes for Perihelion (28 November 2013)
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| Latest 30 images from the SOHO LASCO C3 instrument animated. Comet ISON skims past delta Scorpii. | Latest 30 low resolution beacon images from the STEREO COR2A instrument animated. The Big blob is Venus. |
We are just over 7 hours away from comet C/2012 S1 ISON reaching perihelion. What an amazing trip it has been, with the comet defying all expectations, stops and starts in brightness increase, dramatic outbursts and fades.
Now on the last leg of its long journey, which began around a million years ago in the Oort cloud at the edge of the solar system, in a few short hours it will skim around a solar diameter from the surface of the sun, being exposed to almost unimaginable heart wich will vaporize the very dust on its surface.
Will it survive is the question on everyone's lips? How bright will it get?
Currently it is outperforming C/2011 W3 Lovejoy, latest brightness estimates put it at around magnitude -3 (a bit dimmer than Venus ), quite a bit above Lovejoy at the same time, and ISON has a more complex tail. The twin tails you see in the LASCO C3 instrument are a broad dust tail and a synchronic dust streamer. No ion tail can be seen in the LASCO C3 image at the moment (info from the latest CBET via Jakub Cerny).
So, what happenes next? Will it disintegrate? For typical Kreutz sungrazer comets with radii under 100 meters, they tend to disintegrate at 10 solar radii from the Sun. ISON is much larger than 100 meteres (somewhere between 1 Km and 2.4 Km in radius), but the 10 Solar radii checkpoint is at around 12:00 UT in a half an hour from now as I type. If it passes this check point, then there is a good chance it will get to perihelion. After that, it's all still up in the air. Karl Battams of the STEREO mission is enthusiastic but cautious. Jakub Cerny has a detailed post here were he expects it not to survive.
How bright will it get? Jakub Cerny reports J. N. Marcus as saying it will not get too much brighter, as the heat from the Sun begins to vaporise the dust grains.
If it survives perihelion, it's grazing approach to the Sun, what happens then? Will it be like Lovejoy and disintegrate a few days later, leaving us with a pale and impressive tail? Perhaps the best analogs will be two sungrazers of around 1 Km radius, the great Southern Comet of 1880 and C/1970 K1, which survived and were reasonably bright with decently long tails for a short time.
So if ISON survies we might expect it to not be as bright as C/2006 P1 McNaught, but brighter than Lovejoy.
The best we can say is "don't count your comets before they are hatched". As the excitement mounts you can watch the comet in various spacecraft instruments (links here) . No matter what happens, this is the first sungrazing comet from the Oort cloud, so the show will be well worth watching.
So happy comet watching folks.
Labels: C/2006 P1 McNaught, C/2012 S1 ISON, comet lovejoy, Soho
Is Comet C/2012 S1 ISON on Track?
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| Comet C/2012 S1 ISON seen in the SOHO LASCO C3 instrument at 05:06 UT 28 November. Stars indicated for comparison with chart. | Chart of the predicted position of ISON at 05:06 UT 28 November |
There has been some rumination on the interwebs that comet ISON is off course. Here I show one of the latest SOHO images with the predicted position of ISON, using an old orbit. ISON is exactly where it should be; right next to delta Scorpii.
Labels: C/2012 S1 ISON, Soho
Comet C/2012 S1 ISON Brightens, comparison with Lovejoy (28 November 2013)
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| Comet C/2012 S1 ISON in the SOHO Lasco C3 imager at 00:30 UT 28 November 2013 | Comet C/2011 w3 Lovejoy in the SOHO Lasco C3 imager at 09:30 UT 15 December 2011 | Overlay of the two images |
Comet ISON continues to brighten, its head is now brighter than comet Lovejoy at a similar distance from the Sun in the STEREO imager (ISON was at 0.084 AU from the Sun in this image, Lovejoy was closer at 0.079 AU). ISON's tail is a bit wimpier though.
What does this all mean for ISON's chances of survival? Who knows, we just have to keep watching.
Labels: C/2012 S1 ISON, comet lovejoy, comets, Soho
How Bright is ISON? Comparing Comet ISON to Lovejoy
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How bright is comet C/2012 S1 ISON now? It's pretty hard to tell with the images we have, as we don't really have high resolution images with good comparison stars at the moment. So I've compared ISON as it looks now to C/2011 W3 Lovejoy as it looked when it just entered the SOHO LASCO C3 imager and STEREO COR2B imager.
Both comets look roughly the same in the SOHO images, but Lovejoy looks brighter in the COR2B images. Unfortunately I don't know where Lovejoy was with respect to COr2B, so I don't know if this is due to the comet being closer to the camera.ISON looks around the same brightness as
Still, overall it is looking similar to Lovejoy at the moment, perhaps it will perform like Lovejoy?
Labels: C/2012 S1 ISON, comet lovejoy, Soho, Stereo Satellite
Wednesday, November 27, 2013
Comet ISON Reaches Perihelion Tomorrow (28 November 2013)
At this time it is a mere degree (that's one fingerwith) form the Sun (see here for diagrams). If you are not an experienced solar observer DO NOT look for it in daylight, your eyes can be severely damaged by exposure to the Suns glare.
However, a bevy of spacecraft will be observing, and you can watch from the safety of your computer screens.
These times are taken from Karl Battams info sheet.
November 28, 0400UT: Enters STEREO/SECCHI COR-2A (15:00 AEDST)
November 28, 1300UT: Enters SOHO/LASCO C2 (24:00 AEDST)
November 28, use links above for everything except the SDO.
~1600 - 2300UT: Transits STEREO/SECCHI COR-1B (10:00 29th AEDST)
~1700 - 2200UT: Transits STEREO/SECCHI COR-1A (15:00 AEDST)
~1720 - 1920UT: Transits SOHO/SUMER (15:00 AEDST)
~1810 – 2010UT: Transits STEREO/SECCHI EUVI-B (15:00 AEDST)
~1820UT +/- ?? hr: Transits SDO/AIA! (15:00 AEDST)
Post-Perihelion: November 28 2300UT: Exits SOHO/LASCO C2 (10:00 29th AEDST)
November 29 1400UT: Exits STEREO/SECCHI COR-2A (01:00 30th AEDST)
November 29 2000UT: Exits STEREO/SECCHI COR-2B (07:00 30th AEDST)
November 30 2300UT: Exits SOHO/LASCO C3 (10:00 31st AEDST)
November 31 0000UT: Enters STEREO/SECCHI HI-1A (to Dec 7) (11:00 AEDST)
There is always some lag in transmission from the spacecraft to Earth, so you won't actually be watching live, but it will be pretty close.
Labels: C/2012 S1 ISON, Soho, Stereo Satellite
Comet C/2012 S1 ISON meets a Coronal Mass Ejection (or does It?) 27 November 2013
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| Comet C/2012 S1 ISON in the field of view of the STEREO COR2B imager (lower left). Jupiter is the bright dot center left. Animation of 30 STEREO images. Click to embiggen. | Comet C/2012 S1 ISON in the field of view of the SOHOLASCO C3 imager (lower left). Animation of 30 SOHO images. Click to embiggen. |
Comet ISON may not have reached unaided eye visibility, but it is certainly putting on a show in the bevy of spacecraft observing it. Today ISON entered the field of view of the STEREO COR2B imager and the SOHO LASCO C3 imager. We only have the low resolution images from the STEREO COR2B imager at the moment, but it appears to have caught a dramatic moment.
When a Coronal Mass Ejection blasts out of the Sun and slams into the comet, causing great disruption to the tail.
As you can see, at the time the time (around 4:40 UT) when the CME apparently slams into the comet in COR2B, it is nowhere near the comet in LASCO C3.
If you look at the image to the left, this is the NASA Goddard solar wind/CME model, you may need to click on it and embiggen to see in detail, but the CME blasts out bottom right and misses ISON (top right) by a great distance.
The apparent CME impact is just a line of sight effect.
As ISON makes its final plumet into the Sun tomorrow, it may encounter, or appear to encounter, other CME's. Interpreting these will require a good understanding of where the CME actually is, and avoid confounding by line of sight effects.
Labels: C/2012 S1 ISON, Soho, Solar flare, Stereo Satellite
Tuesday, November 26, 2013
Comet C/2012 S1 ISON in STEREO H1A (23 November 2013)
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| Comet C/2012 S1 ISON imaged in the STEREO satellites H1A instrument on 23 November. 2P/Enke is to the top right and ISON is the big bright thing to the centre. 13 images stacked in ImageJ and aligned then the images differenced to cancel out stars. The vertical lines are imaging artefacts from Earth being too bright (off screen).Click to embiggen | Comet C/2012 S1 ISON imaged in the STEREO satellites H1A instrument on 21 November. 2P/Enke is to the top right and ISON is the big bright thing to the bottom left. 26 Images stacked in ImageJ, then the images differenced to cancel out stars and assembled into an animation. The vertical lines are imaging artefacts from Earth being too bright (off screen).Click to embiggenYou will need to click on the image to embiggen it. |
Comparison of Comet ISON on the 21st and 23rd in high resolution stereo H1A fits images. While there is a lot of debate over ISON's fate, I think these images show the comet is still in play.
In the images above I have used Comet Al's ImageJ macro for using image differencing to really pull out the detail in the comet.
Although to the same scale comet ISON looks a trace dimmer on the 23rd vs the 21st, however this is basically image brightness scaling issues. You can see the comet apparently change significantly in brightness, but comet 2P Enke does the same in parallel. ISON has an extensive tail with what looks like knots of material moving down it, just as in the 21st.
In the images below I have taken a different approach, using a log transform to try and bring out some of the detail in the comets tail. It gives a somewhat different view of the knots moving down the tail, and extensive billows of material in the tail.
I have not had a chance to do calibrated estimates of the comets. However, I think the imminent demise of ISON is less likely from these images and the medium resolution images from the 25th.
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| Comet C/2012 S1 ISON imaged in the STEREO satellites H1A instrument on 23 November. 2P/Enke is to the right and ISON is the big bright thing in the centre. 13 images stacked in ImageJ and aligned then LOG processed to enhance dim details. Click to embiggen. Asteroid Kleopatra is towards the bottom of the image. | Comet C/2012 S1 ISON imaged in the STEREO satellites H1A instrument on 21 November. All 26 Images stacked in ImageJ, then the images LOGed to enhance detail and assembled into an animation. You will need to click on the image to embiggen it. |
Labels: 2P Encke, C/2012 S1 ISON, Stereo Satellite
Has Comet ISON disintedgrated? (or is it disintedgrating)
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| Comet C/2012 S1 ISON in the medium resolution PNG images from H1A on 23 November. If you click the image you can see a bright "knot" in the tail. | Comet C/2012 S1 ISON in the medium resolution PNG images from H1A on 25 November. The comet still apears to be healthy, but looks can be decieveing |
There has been a lot of buzz in the astronomy community over the last 8 hours of so over news that comet C/2012 S1 ISON may be breaking up/ has already broken up. There are several elements to this.
A CalTech team using the IRAM millimeter telescope in Spain has reported a 20 fold fall in molecular emission lines from 21 November to 25 November. They interpret this as a disintegration of the comet. The TRAPPIST team reports a fall in dust production rates by a factor of 3, AfRho measurements by the CARA team suggest nuclear erosion. Terry Lovejoy has measured strong non-gravitational forces which may suggest a breakup. Dan Fishers notes an alternate view of the CalTech results.
Against this the comet looks healthy and brightening in the STEREO images. This could be due to the comet being an expanding cloud of reflective dust though.
Labels: C/2012 S1 ISON, Stereo Satellite
Comet C/2012 S1 ISON, more tail action in H1A (23 November, 2013)
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| Comet C/2012 S1 ISON in medium resolution PNG images from STEREO H1A on 23 November. No processing. Click to embiggen | 25 images stacked and animated using ImageJ, no other processing. Click to embiggen (warning about 14 Mb file). If you look hard you can see 2P/Enke. |
Comet ISON in medium resolution PNG images from STEREO H1A,while more detailed than the beacon images, they are somewhat limited for analysis, using 38Ari, Lambda Ceti, Mu Ceti and Xi Tau (O Tau that I used for the images from the 21st is behind the label), the comet stars of around magnitude 2.7 (this is probably fainter than it actually is due to the CCD response of H1A and pixel saturation in the processed PNG), and the comet brightening by 0.5 magnitudes over the course of the day.
Labels: 2P Encke, C/2012 S1 ISON, Stereo Satellite
Monday, November 25, 2013
Comet C/2012 S1 ISON in STEREO H1A, great tail action (21 November 2013)
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| Comet C/2012 S1 ISON imaged in the STEREO satellites H1A instrument on 21 November. 2P/Enke is to the top right and ISON is the big bright thing to the bottom left. Single frame of 26 images stacked in ImageJ and aligned then the images differenced to cancel out stars. The vertical lines are imaging artefacts from Earth being too bright (off screen).Click to embiggen | All 26 Images stacked in ImageJ, then the images differenced to cancel out stars and assembled into an animation. You will need to click on the image to embiggen it. |
Comet ISON has moved further into the field of view of the STEREO H1 inager, and it looks quite stunning.
In the images above I have used Comet Al's ImageJ macro for using image differencing to really pull out the detail in the comet. Comet ISON shows amazing detail in it's tail, there may be some tail rotation, and you can see knots of material moving down the comets tail. In contrast Enke's tail is quite thin, but whips around a fair bit.
In the images below I have taken a differnt approach, using a log transform to try and bring out some of the detail in the comets tail. It gives a somewhat differnt view of the knots moving down the tail.
It tried estimating the magnitude of the comet using the reference stars Rho Ari (5.56), 38 Ari (5.18), Lambda Ceti (4.69), Mu ceti (4.28) and O Tau (3.61). It get the comet starting at magnitude 5 at the begining of the day, and magnitude 4.5 by the end of the day. This is probably an underestimate due to the spectral response of the H1A CCD camera. My estimate of the magnitude of Enke was 5.5, a full magnitude less than predicted.
However, the key point is irrepective of the absolute magnitude, the comet is steadily brightening. An analysis of the brightening of images from the 23rd.
Certainly, whatever happens in the next few days, ISON is giving us a pretty good show.
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| Comet C/2012 S1 ISON imaged in the STEREO satellites H1A instrument on 21 November. 2P/Enke is to the right and ISON is the big bright thing to the bottom left. Single frame of 26 images stacked in ImageJ and aligned then LOG processed to enhance dim details. Click to embiggen | All 26 Images stacked in ImageJ, then the images LOGed to enhance detail and assembled into an animation. You will need to click on the image to embiggen it. |
Labels: 2P Encke, C/2012 S1 ISON, Stereo Satellite
Readers Images of comets ISON and Lovejoy
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| S1 ISON: EOD 5D MK III, Sigma 120-300mm f/2.8 @ 300mm f/2.8, ISO 2000, 13 x 0.6s light frames (RAW), 13 darks and 13 bias stacked in deep sky stacker. Levels and curves in photoshop, create master flat frame and subtract from original image to eliminate light pollution and lens vignetting. Then another levels and curves adjustment, denoise to remove colour noise and adjust contrast slightly. The bright star is Spica. Time was between 3.31am and 3.34am on November 19. Click to embiggen. | R1 Lovejoy: EOD 5D MK III, Sigma 120-300mm f/2.8 @ 120mm f/2.8, ISO 2000, 8 x 2.5s light frames (RAW), 10 darks and 10 bias stacked in deep sky stacker. Levels and curves in photoshop, create master flat frame and subtract from original image to eliminate light pollution and lens vignetting. Then another levels and curves adjustment, denoise to remove colour noise and adjust contrast slightly. Time was between 3.33am and 3.35am on November 19. Click to embiggen. |
Reader Krishan Kara sent me these marvellous shots of comet C/2012 S1 ISON and C/2013 R1 Lovejoy, taken on November 19 in Brisbane (note that he holds the copyright on these images, so please ask if you want to copy or use them). The most amazing thing about these shots is that they are unguided! Great work Krishan..
Labels: astrophotography, C/2012 S1 ISON, C/2013 R1
Sunday, November 24, 2013
Comet C/2012 S1 ISON enters STEREO H1A (20 November, 2013)
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| Comet C/2012 S1 ISON imaged in the STEREO satellites H1A instrument on 20 November. 2P/Enke is to the right and ISON is the big bright thing to the bottom left. 13 images stacked in ImageJ and aligned . Click to embiggen | 12 Images stacked in ImageJ, then the images differenced to cancel out stars and assembled into an animation. You will need to click on the image to embiggen it, The process crops out ISON, but you can see the movement of Enke's tail. |
Comets ISON has finally entered the field of view of the STEREO H1A instrument. The left-hand image was processed in ImageJ as usual, The right-hand image was processed using a difference macro in ImageJ which subtracts out non moving pixels to bring out more details with the comets. Enke and ISON have active tails (which you can't see for ISOn as it just enters in the last few frames), but you may wish to compare the 20th in H1A with the comets appearance on the 20th in H2A.
Labels: 2P Encke, C/2012 S1 ISON, Stereo Satellite
Saturday, November 23, 2013
Comet C/2012 S1 ISON, good tail action in STEREO (20 November, 2013)
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| Comet C/2012 S1 ISON imaged in the STEREO satellites H2A instrument on 20 November to 14 November. 3 comets, Mercury and the Pleiades are labelled so you know where to look in the animation. 12 images stacked in ImageJ, aligned then the imges differenced to cancel out stars. Click to embiggen | 12 Images stacked in ImageJ and assembled into an animation. You will need to click on the image to embiggen it, so that you can see ISON, Lovejoy and 2P/Enke and their tails at their best. |
The latest images of comets ISON, Lovejoy and Enke in the STEREO H2A instrument. The data was processed using a difference macro in ImageJ which subtracts out non moving pixels to bring out more details with the comets. Enke and ISON have active tails, and I may have caught the edge of a tail disconnection event with ISON.
You can clearly see the active tail now, and the brightness jump when the out burst occurs is still readily seen.
ISON is very obviously brighter on the 20th, have to do some astrometry to determine how bright.
I have lots of images to download and process, this may take a while. But clearly the plotting of tail and brigness evolution is well worth it.
Labels: 2P Encke, C/2012 S1 ISON, Stereo Satellite
Click to read about or order
Click to read about or order
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