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Posted by Paul A Brierley at 18:52 on 2011 Mar 30
I’d like to ask members of the BAA and particularly members of the UK Nova Supernova search program. For some advice please. Myself together with another local astronomer, want to begin searching for Supernovae. And we’d like some advice on how to get started.Before I continue, I will give you a break down of our equipment.I use a 200mm F4 Newtonian with a focal length of 800mm, and a Atik 16ic camera.And my colleague uses a 200mm telescope, a Celestron SCT with a focal length of 2032mm and a SXV-H18 camera.The questions which I would like answers to, are in know particular order.1. How many galaxies do people search. Is fifty a good number to begin with?2. Is it a good idea to build up a set of reference image’s first. Or can these be sourced on the internet?3. What should you do if you think you have a suspect?4. What exposure time’s are we looking at during a patrol. 30s/60s?Thank you.
Posted by Callum Potter at 12:15 on 2011 Apr 01
Hi Paul,i’m not a supernova patroller, but have been to a few talks on the topic, so here are my thoughts…1. How many galaxies do people search. Is fifty a good number to begin with?I don’t know – you have to think a bit about your ‘pipeline’ – telescope slew, aquire short image, check field right, aquire long image, aquire second image slew to next target How long all this takes will dictate to some extent how many you can image per hour. You and your partner should choose different target lists to maximise your imaging time. You should try to minimise your slewing time – by choosing targets nearto each other in RA or DEC (ie. going in a pattern up-down, or right-left. I suspect up-down is better as new objects will start to appearfrom the east).If you have a very accurate mount, you may not need to check you have got hte right field – but you probably need a paramount for that…2. Is it a good idea to build up a set of reference image’s first. Or can these be sourced on the internet?It is best to use your own references, as you won’t need to worry about image scale & orientation. But you should check your first images against internet (DSS perhaps) frames. If you get a suspect, then check agains internet frames then too.3. What should you do if you think you have a suspect?First check your second image – is the object still there? (avoids hotspots / cosmic rays, other random effects). Get another image some time later, to check if its an asteroid (it will have moved).Then get your partner to check. If that confirms it, then get in touch with Guy Hurst, who’d be able to advise on best next steps.Guy acts as a clearing house, and will be able to get other independent observations, if needed.4. What exposure time’s are we looking at during a patrol. 30s/60s?Depends on how deep you want to go – i think 60s is fairly common amongst the patrolers. Hope this helps, Callum
Posted by Paul A Brierley at 18:02 on 2011 Apr 01
Thank you Callum.I will forward a copy of this message to my colleague.
Posted by Gary Poyner at 20:23 on 2011 Apr 01
A check should also be made to ensure that your suspect hasn’t already been announced. This page is useful…http://www.rochesterastronomy.org/snimages/and I’m sure there are a number of other sites which give recent discovery details too.This happens quite a lot in Cataclysmic Variables, where someone thinks they have detected an outburst and reports it to various lists only to find it was picked up two nights earlier. Pretty frustrating all round when that happens.Speaking with my UK Nova Patrol hat on, it would be nice if anyone out there would take up a dedicated search for Novae. It’s been 10 years since a Nova was discovered photographically from the UK (Mike Collins), and 20 years for a visual discovery (George Alcock’s amazing discovery of Nova Her 1991). I think were due one. Maybe someone who is reading this forum?Gary
Posted by Paul A Brierley at 06:33 on 2011 Apr 02
Good idea, and thank you Gary.I will suggest this also.How does one go about, a CCD Nova search? And is there any free software that you can use, to help with searching for Novae?
Posted by Gary Poyner at 11:28 on 2011 Apr 02
Hi Paul,Usually (?) telescopes and CCD’s are used to search for Novae in M31 & possibly M33. For Novae in our own galaxy, the usual method is to use a DSLR. This gives you much more sky coverage in one shot (possible 10d in an 85mm lens?). Keeping in general to the Galactic Plane, one would take short exposures of the sky (depending on your local light pollution) then blink that image with your master. You will see stars blink, that’s for sure. These will be Variables, so you’ll need something to check these against (something like GUIDE 8 which has excellent VS catalogues). Checking images to a possible limit of magnitude ~10 or 12 isn’t easy, and requires great care. Like SNe hunting, you must be prepared for hundreds of negative results – maybe even thousands, depending on how productive you are. I visually observed four fields every clear and partially clear night for over 20 years without any luck! Generally people get a bit more excited when a Nova is discovered than a Supernova (unless it’s really bright) for a number of reasons. More observers get to see it for one thing, and depending on type a Nova can stick around for years and can also reach very bright magnitudes. Professionals also get excited as there is a lot to study in a Nova (shell, dust, WD mass, secondary, accretion rates, possible disc reforming after event etc.) Novae also seem to be rarer than SNe, but this just might be that more people are looking for the latter (or Tom bags them all). Guy and I are convinced that many Novae go unobserved every year, simply because not enough people are looking for them.If you would like more information on this, contact me off list and we can talk further.Gary
Posted by Paul A Brierley at 17:28 on 2011 Apr 02
Thanks Gary,I like the idea of using my Nikon D40 and 55-200 zoom lens for Novae searching.I will experiment using 10 second exposures at 1600iso using a fixed tripod. I don’t have a portable motorised EQ mount.Myself and Paul use a dark site in Derbyshire where this sort of work can be carried out. I will of cause try from home, but that will be difficult, because of the increase in light pollution.Do you, or does anybody on here, know of any free software that I can use to blink my image’s?
Posted by Gary Poyner at 19:47 on 2011 Apr 02
I use AIP4WIN for my remotely taken CCD images. You can certainly ‘blink’ with that software. I’m sure there are lots of others too which someone on this forum will recommend.Cheers,Gary
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