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How to discover a comet using only your computer!

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How to discover a comet using only your computer!

by Dave Evans

It's amazing but true... Images taken with the SOHO Space Telescope can be used by amateur astronomers to find hundreds of new comets each year.

I created "Dave's Virtual Sungrazer Observatory" (DVSO) as a one-stop observational portal that offers everything you need to make your own comet discovery.

To begin to understand how DVSO works you will need to first open the portal via this link -


Now let us look at the layout of the screen. To the left is the main menu, at the centre we have an 'information area' and to the right two sets of image files. These files list images from SOHO which are ready to be downloaded to your hard drive.

The C2 camera aboard SOHO provides high magnification of the region of space surrounding the Sun. The C3 camera operates at a lower magnification and so provides a more wide field of view.

Here's how to discover your first comet:

Step 1:

Let's first download about 6 images from both sets of cameras, then store them on your hard drive in appropriate folders labelled C2 and C3. You may have already noticed that the name of these files is based on the date and time the photograph was taken. This means files can be stored on your computer in the correct order ready to view.

Step 2:

Now we have the images, we will need a way to view them quickly in sequence - just like watching a movie for instance. Our eyes will then be able to perceive even the slightest movement of any cometary object that comes into view.

I have found a good way to accomplish this is to use the 'slideshow' feature that is offered within the freeware program called XnView. You can download it here -


Before we use XnView, we should familiarise ourselves with a very important link in the main menu of DVSO - "View the paths of Kreutz, Meyer, Marsden & Kracht comets". It is found in the 'Reference Section'. Click the link and it will open a page which shows you the various type of families of comets which each follow predictable paths in the C2 and C3 images throughout the year. These charts will show you the approximate area where you should look in the images to discover a new comet.

Step 3:

If you believe you have found something new you will need a way to tell others where to look in the image. Some comets are tiny and starlike. Each picture is built up from pixels, 1024 pixels from left to right and 1024 pixels from top to bottom and this information provides an ideal way to accurately locate the position of any pixel within the image by refering to its X and Y coordinates. X will mean the new find is located so many pixels from the left-hand side of the image and Y means so many pixels down from the top.

If you 'mouse-over' the image, XnView will automatically give you the X and Y coordinates of any pixel that your cursor is pointing to. To enable this automation, open the View tab in XnView and make sure 'Display Colour Information' is ticked. Then when you move your cursor over the image note how the X and Y coordinates change. Ideally you should determine the X/Y position of your moving object in at least four images.

Step 4:

Armed with your four sets of X and Y's and the time stamp of each image to which they refer, you are now ready to report your discovery. To do this, click the link "Found Something New? The Official Comet Report Form" which can be found in the main menu. Carefully fill in the details of your 'new find' and then click the 'Submit' button to post your report direct to the SOHO website.

Step 5:

If you happen to be first to report a new comet, credit will be given to you for its discovery and the object will be named SOHOxxxx, the xxxx being represented by a sequential number in which all new finds are recorded. However, if the object was reported earlier by someone else do not dispair. The X/Y measurements you have submitted will still prove very useful indeed to help confirm the earlier discovery.


By following the above steps, I have been fortunate to discover 19 sungrazing comets. I still remember my first 'find' and how my heart pounded while filling in details on the official form and even more so when the discovery was confirmed! In addition I have also found 2 X-comets. These are objects which are most likely comets but as yet they remain unconfirmed.

In closing, the very best advice I can offer all new comet seekers is to examine at few of the most recent discoveries (open the link "Read the latest Discovery posts"). Download the same images and then try to replicate the X/Y measurements reported by the discoverer.

Here is a list of my 19 SOHO comet discoveries:

IAU refers to the International Astronomical Union Circular which transmitted details of the discovery to the astronomical community. The first in the list refers to IAU 7930 which can be found here http://cfa-www.harvard.edu/iauc/07900/07930.html

MPEC refers to the designation which can be used to find the orbital elements of the comet in the Minor Planet Electronic Circulars. For instance, the first in the list can be found at http://cfa-www.harvard.edu/mpec/K02/K02M22.html - K02 referring to the year 2002.

All of the below discoveries belong to the 'Kreutz Group' family of comets with discovery details shown in the following shorthand format -


462: 2002/06/13: C/2002 L7: C2: 7930: 2002-M22: 2002/06/13

492: 2002/06/16: C/2002 M8: C2: 7948: 2002-P08: 2002/07/24

493: 2002/04/23: C/2002: H7: C2: 7948: 2002-P08: 2002/07/28

496: 2002/05/30: C/2002: K10: C2: 7951: 2002-P17: 2002/08/04

506: 2002/08/29: C/2002: Q14: C3: 7969: 2002-R34: 2002/08/29

509: 2002/08/18: C/2002: Q12: C3: 7969: 2002-R34: 2002/09/01

510: 2002/08/27: C/2002: Q13: C3: 7969: 2002-R34: 2002/09/01

523: 2002/09/21: C/2002: S8: C3: 7991: 2002-T75: 2002/09/21

539: 2002/11/09: C/2002: V3: C2: 8073: 2003-B42: 2002/11/09

551: 2002/11/21: C/2002: W7: C2: 8106: 2003-G07: 2002/11/21

553: 2002/11/22: C/2002: W9: C3: 8263: 2004-A03: 2002/11/22

584: 2003/02/08: C/2003: C2: C3: 8278: 2004-B34: 2003/02/09

589: 2003/03/04: C/2003: E2: C3: 8283: 2004-C31: 2003/03/04

616: 2003/05/22: C/2003: K8: C2: 8309: 2004-F29: 2003/05/24

640: 2003/05/23: C/2003: K13: C2: 8333: 2004-H49: 2003/06/28

692: 2003/11/21: C/2003: W4: C2: 8356: 2004-K54: 2003/11/21

788: 2004/05/14: C/2004: J19: C2: 8367: 2004-N16: 2004/05/23

823: 2004/08/05: C/2004: P2: C3: 8398: 2004-R02: 2004/08/05

827: 2002/05/26: C/2002: K11: C2: 8398: 2004-Q11: 2002/08/11

X-Comet 2002/06/13: C2

X-Comet 2003/05/19; C2

You may have noticed that my last discovery was made August 2004. Since then, with my workload in the office increasing, this has not permitted me sufficient time to study the C2 and C3 SOHO images in depth. However, I do gain great enjoyment from seeing other amateur astronomers using DVSO to discover new comets of their own.

I hope you find the DVSO Portal easy to use... and may I wish you good fortune with your searches!

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Thanks Dave for sharing this with us - you've done a great job on making this available to amateur astronomers.



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Thank you Dave for posting this and explaining it so clearly.

With all this cloud around, a bit of comet-crunching sounds worthwhile.


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I am trying to report my observations regarding the comet, but "sungrazer.nrl.navy.mil" site is not loading at all.

I have tried it many time, but it says the server isnt working.

Is there any other site where I can report my comet discovery. And if so then how to report it.

Thanks a lot!!!! :smiley:

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