20131211 - A catch up on comet images

As I mentioned in the last post, the reaon for lack of entries it is not that nothing has been happening, but the reverse!

A comment to the previous post exclaimed surprise at the time that processing the images take.

Let us go through a simple outline processing the comet images that I now follow. I will cover an observing run another time.

OK then, I have finished and observing run and closed down the observatory. What next?

On the computer there may be as many as 500+ images from the observing run all held in a directory named after the evening before's date in reverse order. Today is the 11th December 2013, so the observing run that could have started yesterday evening and finished at daybreak today so the directory would be named 20131210.

I then create a number of subdirectories named after the objects I have imaged. Where I have imaged the same object in two different ways then I create two subdirectories. Into these subdirectories I copy the various groups of files. There could be up to a hundred or more image files in each subdirectory.

The images in each of the subdirectories need to be reduced (or calibrated). Data reduction This is to take out inconsistencies. If you want to read more about it here is a link that explains the basics. The reduced files are put into a subdirectory - we do not overwrite the original files as we need to keep these.

After this has been done what happens next depends on what type of observations have taken place on different classifications of objects.

I will now describe what I do for single framed images of comets. My starting point is a folder of reduced images of a comet. There maybe 100 images and at a quick glance you would think that they are all the same, but there are not. A comet is moving against the background of stars. If we looked at each of the images carefully you would note the comet, especially as it gets nearer to the Sun will be in a slightly different position against the stars.

We are interested in the comet - not the stars. Let us say that each of the images is a 10 seconds exposure. We have a hundred and we need to overlay each of the images so that the comet overlays itself and not the stars. A number of programmes can do this, but I have not found one better than Astrometrica . Not only can it stack the comets - called Stack and Track the programme can many other things including astrometery and photometry (where is it and how bright is it).

This exercise leaves me with a single combined image that I can save and its brightness (magnitude).

I can now load this image into another programme and prepare it for submission.

At the moment some of the images are shown here, sent to the British Astronomical Association, shown in a few Facebook groups including Comet Watch and CIOC_ISON and also shortly to the University College London.

We do not delete any of the observations because you do not know when they may be of use. A good example is the UCL where I will be going back in time to find images that meet their needs.  


Here then is a gallery of some of the images taken since the last images until the 7th December:


SON@OSC (Searchlight Observatory Network at the Observatorio Sierra Contraviesa, Granada, Spain)
Observers Tony Angel and Caisey Harlingten
4" F4 Refractor ST8 Clear bin 1x1
FOV 115.5 x 77.7 arcmin
North at top

C/2013 R1 - Lovejoy - 2nd December

C/2013 R1 - Lovejoy - 2nd December

5th December

C/2013 R1 Lovejoy - 5th December

C/2012 R1 Lovejoy - 5th December

6th December

C/2012 R1 Lovejoy - 6th December

C/2012 R1 Lovejoy - 6th December

7th December

C/2012 R1 Lovejoy - 7th December

C/2012 R1 Lovejoy - 7th December

C/2012 X1 Linear - 7th December

C/2012 X1 Linear - 7th December

C/2013 V3 Nevski - 7th December

C/2013 V3 Nevski - 7th December

2nd December morning - Comet C/2013 R1 Lovejoy and C/2013 V3 Nevski and a little on ISON

After nearly a week of cloudy skies I had a good observing run yesterday morning :)

I first went to Comet Lovejoy. I was using the wide field 4" F4 Refractor along with an ST8 CCD Camera. This comet is getting better, brighter and clearer each time I observe it. It was discovered by Terry Lovejoy in Australia, this is his 2nd Christmas Comet and I will say more about him in another post. He is most certainly an astronomer's astronomer. It is visible to the naked eye and well worth looking for.

I had decided that I wanted to image the whole of the comet, which because of its length meant that I would have to take a series of images, starting with its head and working along the tail.

I took them between UT 2013-12-02 5:00:34.063   and  2013-12-02T05:14:50.329 . Each image has an FOV of FOV 116.5 x 77.7 arcmins - north is on the left! You really need to click on the image to see it better!

I took seven images.each 1 minute exposure - no binning - and overlaid them.

Using simple trig the comet as displayed is a touch over 5 degrees in length. It was not until I processed the images that I realised that I had not captured the full length of the tale. I was not able to do a retake this morning, so fingers crossed for tomorrow, but it will need this evening's winds to drop. :( If it is clear then I will do x2 binning but keep the exposure time to 1 minute. That will bring out the furthest parts of the tail. As this will produce smaller images it will make it easier to create the overall image. The comet is moving against the back drop of stars, so I have to move onto taking the next image directly after the previous one, (partially guessing I am moving the right way :) ). so that there is no perceptible change.

As well as the above image I took a series of shorter exposures of the comet head. These exposures are between half a second and ten seconds. I also took a colour image as well. These are still to be processed. I used a series of the shorter images with Astrometrica by Herbert Raab to get a N Magnitude of 8.8

The next comet I images was C/2013 V3 Nevski. It is quite recently discovered - 6th November - by Vitali Nevsky using an 8" F1,5 reflecting telescope. Vitali is no stranger to discovering comets. He, along with Artyom Novichonok, discovered Comet C/2012 S1 ISON.  When discovered it was magnitude 15.1. Fellow CIOC_ISON member +Charles Bell  imaged it on the 14th November and its N Magnitude was 15.6. There had been reports that it had brightened to about magnitude 10 however when I imaged it yesterday morning the N  magnitude was 14.7.

Here is my image taken UT 2013-12-02 5:58:27.454 - FOV 116.5 x 77.7 arcmins - north is at the top. The comet is to the right of centre. It is still quite small, though a short tail has been observed.

I then took a few of Comet Linear and I will put these on next time. After Linear I did try for a couple of others, but my processing has not yet brought them out. They were a bit fainter.

To complete the observing run I finally I went to the the Eastern Horizon to see if I could capture the poor remains of C/2012 S1 ISON, but it was too bright - the sky that is, not ISON. If the weather is OK I will trying tomorrow morning.  Is there anything to see? We just do not know yet.

Before I finish for the night I must mention a particular hang out that you may wish to look at. It is the Comet Festival South Bend Today I watched yesterdays and today's editions. They have good astronomers on there and today's edition - hosted by +Chuck Bueter had +Pamela Gay , +Karl Battams and CIOC_ISON's +Padma Yanamandra-Fisher  (heck I hope I have the links right - if I have not - sorry!). Yesterday's edition was great as well, especially as it had my favourite astronomer, +Alex Filippenko, on.