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Monday, 16 December 2013

20131216 - ISON - Search and Rescue appears to have failed.

For the past few weeks, very much like when a yacht has been reporting missing, search and rescue have been out looking for this comet in distress.

At the beginning dozens, if not hundreds, of telescopes and binoculars swept the area of sky where the deathly remains of ISON hopefully could be found - but only if the remains were either large or dense enough to be seen.

There were a number of potential sightings by very experienced observers, though these potential sightings were always accompanied with health warnings. There was even a "sighting" report being circulated where someone had misunderstood the date format of a report which was of an earlier observation of the comet.

Everyone of these sightings needed to be followed up .... just in case someone has actually found the wreckage. Like most, I prefer for observers to post potential sightings, than for them to be sat on because of a concern of being wrong. There is always the danger though that they will get picked up by the media and misinterpreted - as is often the case, but we should never allow that to stop us making reports.

One of the good things about amateur observations are that they are distributed as soon as possible. Amateurs know that by putting out these possible sightings they may be able to be confirmed by someone in another Time Zone, before the object(s) have completely left, or are in the vicinity of that field of view.

Soon I expect the obituaries will start to be published telling us as much as possible about the life and death of ISON with the coroners verdict of Lost at Sea - sorry Lost in Space. As with all celebrities, much more will be written and published as more facts are discovered about ISON's life.

We only got to know her in her final years of life and know little of her childhood spent somewhere in the little know Oort cloud.  Someday in the distant future a little of what remains may arrive back at her original home.

                               -------------------------------------------------

I suspect that on posting this, within a day or two there will be more reports of seeing it, but as in real life there will be less suitable resources available to check.

From now on my time will be split, with Exoplanet Transits taking priority, but there will still be plenty of time for comets and other objects :) . This means that future Blogs will cover more subjects, including progress on a new SON observatory.

Wednesday, 11 December 2013

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