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
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
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
Friday, November 22, 2013
Comet 2P/Enke in STEREO, 19 November 2013
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| Comet 2P/Enke seen in the STEREO H1A imager on November 19. The two brighest objects are Mercury (left) and Erth (right). Enke is below Mercury. Click to embiggen | Animation of the images. Images stacked, registered then differenced using ImageJ. Click to embiggen to see some nice tail action. |
While waiting of comet ISO to turn up in the high resolution STEREO H1A images (as opposed to the low resolution beacon images) here's a nice image of 2P/Enke in H1A. Comet Al gave me his ImageJ macro for using image differencing to really pull out the detail in the comet. You can see some great motion in the tail of the comet this way, better than the raw images.
Labels: 2P Encke, comet, Stereo Satellite
Monday, November 18, 2013
STEREO catches Comet C/2012 S1 ISON firing up.
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| Comet C/2012 S1 ISON imaged in the STEREO satellites H2A instrument from 13 November to 14 November. 3 comets, Mercury and a variable star are labelled so you know where to look in the animation.Click to embiggen | 19 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 clearly. |
My Earth based ISON campaign is over, ISON is too deep in the twilight for me to see from Adelaide (despite trying very hard), and it is now below the lower limit of travel of the iTelescopes.
But STEREO still delivers. ISON is currently visible in the H2A instrument of STEREO, along with C/2013 R1 Lovejoy, 2P/Enke and 2013 V3 Nevski (there's also a variable star winking on and off).
An enlarged, inverted version of the above animation is to the left. Comet Al does a much better version where you can see the tail clearly.
Labels: 2P Encke, C/2012 S1 ISON, C/2013 R1, Comet Al, Stereo Satellite
Wednesday, May 09, 2007
Comet 2P Encke visible in binoculars
The eastern horizon at nautical twilight (and hor and a half before sunrise) as seen from the southern hemisphere (click on chart to enlarge it).Comet 2P Encke is a short period comet that returns every 3.3 years. It was the second comet to be determined to be a returning comet.
Comet Encke's return isn't particlularly favorable this year, you can now see it in 10x50 binoculars, low on the eastern horizon at astronomical twilight. Unfortunately, while the comet is relatively bright, the Moon is also fairly bright, and may make spotting the fuzzy dot of Encke rather more difficult than it should be. By the time the Moon goes, the comet will be close to the threshold of binocular visibilty (mag 8). Still, its worth a try.
Labels: 2P Encke, Astronomy, binocular, comets
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