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Posted by Michael Foylan at 18:04 on 2012 Jun 26
Hi,Just wondering if any other amateur astronomer here on the forum has undertaken work or is strongly thinking of completing work in the area of photometry of comets? Any advice and pointers would be appreciated.Best wishes and clear skiesMikeCherryvalley Observatory (IAU Code: I83)
Posted by Denis Buczynski at 14:45 on 2012 Jun 28
Hi Mike,Good question. Yes there are other amateurs in the BAA Comet Section who are interested in undertaking this type of CCD observing. We are going to cover this subject at a Comet section meeting in the Spring 2013. At present I know that Roger Dymock one of our regular contributors does submit comet photometry to both the CARA (Italian group) project and to Mark Kidger’s Spanish group. Also that Nick James is currently looking at the details of setting up such an observing project for the BAA Comet Section. You may want to look at both these groups webpages: http://cara.uai.it/ http://www.eso.org/~hukaufl/DI_TALKS/kidger_amateur_photom.pdfSo in conclusion, yes we are interested as a group in becoming involved with this type of CCD comet observing and would welcome anyone interested in letting us know of that interest.Denis BuczynskiSecretary BAA Comet Section
Posted by Martin Mobberley at 15:22 on 2012 Jun 28
Hi Mike,I’m always reluctant to blatantly plug a book I’ve written, but asCallum wondered if I’d like to comment, well, Chapter 14 in my book’Hunting and Imaging Comets’ does cover this topic…..However, Denis has already pretty much answered your questionalready….. To go into great detail, well, it’s a bit of a minefieldto be honest, but, as Denis says, CARA (Italians) and Mark Kidger’sSpanish group are the experts…..However, their techniques varyconsiderably, with the Italian group requiring mainly precise, filteredwork and Mark’s group using a more user-friendly approach which lessadvanced amateurs will prefer……Hope this is of some use…..Regards,Martin
Posted by Michael Foylan at 21:38 on 2012 Jun 29
Many thanks Denis and Martin for the advice and the website links. Certainly seems to be an interesting area of research that amateur astronomers could be involved in and contribute valuable scientific data.I certainly know a number of amateur astronomers that would be interested in getting involved in this area of research and willing to cooperate with our fellow British amateur astronomers on specific comets. I wouldnt think such work is fundamentally different from asteroid photometry, arguably somewhat more tricky, the main differences I guess is that comets themselves maybe diffuse and extended in nature and perhaps an amateur may need to learn new software and techniques for worthy end results.Like other amateur astronomers undertaking asteroid astrometric and photometric measurements a variety of software can be utilised, I find MPO Canopus, Mira-Pro, Astrometrica and TheSky6 Pro / CCDSoft combo very useful in this regard, I guess software such as listed may be used by many an astronomer on this forum. Such work would indeed challenge those amateurs that wish to bring their astronomy to the next level. When I first took on the challenge of obtaining an observatory code I thought this is too difficult, but perseverance and some help ended in a positive result, I had the same thoughts about measuring asteroid light curves but that too proved to be a very positive and indeed enjoyable experience (I must give credit to Mr. Roger Dymocks book; Asteroids and Dwarf Planets and How to Observe Them that really sparked me into doing such work). I guess what I am trying to say is that such undertakings is achievable by many amateur astronomers here that are keen to take on a challenge but is all the more easier because of the knowledge and help on offer by the BAA. Best wishes and clear skiesMikeCherryvalley Observatory (IAU Code: I83)PS; thanks Martin, I have just ordered your book!
Posted by Richard Miles at 12:02 on 2012 Jun 30
Good-day Mike – Nice to see the interest in photometry of comets – Martin’s book although not dealing with the intricacies of photometry is nonetheless well worth having. I’m sure you’ll find it a very stimulating read.Since asteroids and comets both wander the skies, their photometry share some common issues most notably selection of comparison stars having accurate magnitudes and known colours. Here we are at a watershed in that the AAVSO APASS survey is now reaching fruition with an excellent online source of data at:http://www.aavso.org/download-apass-dataSoon these data will be added to the catalogues used by astrometry / photometry software.There are a few key differences between comets and asteroids. The main one stems from one being essentially a point source of light whereas the other is an extended object. However, an important issue with comets is that there is a whole zoo of comet types out there for which no single photometric approach suits all types of object. You can look at a comet as comprising 3 components; (a) the nucleus acting as a point source and reflecting sunlight directly; (b) the dust coma also reflecting sunlight but which has a diffuse distribution, more concentrated towards the nucleus but which is asymmetric once a tail appears; and (c) a gas coma / ion tail which emits light by chemiluminescence towards the blue-green end of the spectrum. Even the same type of comet will behave differently depending on its heliocentric distance and so observing the same object far from perihelion may require different observing methodology than if it is at say 1 AU from the Sun. Having dedicated observing campaigns on particular objects is a good way forward.I should also mention that a joint BAA Section meeting is taking place on Saturday 6 October at The Open University, Milton Keynes on the subject of Comet-Asteroid Connections during which several talks will refer to the topic of photometry comparing and contrasting the two types of object. We also have Luca Buzzi planning giving a talk on the T3 project, which aims to identify comet-like asteroids: multi-aperture photometry is one tool that can be used to confirm cometary nature, for example.Richard Miles
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