Orpington Astronomical Society

Astronomy => Alerts! Questions? Discussions... => Topic started by: spendrey on Apr 20, 2004, 16:23:00

Title: Comet question
Post by: spendrey on Apr 20, 2004, 16:23:00
Hello,

Are any of the 3 comets that are currently putting in an appearance (Neat, Linear and Bradfield) visible from our skies?

Title: Comet question
Post by: Mike on Apr 21, 2004, 01:40:00
Not really at the moment as they are too far south. One of them will become visible in the next few months, but by then it will be very dim.
Title: Comet question
Post by: Whitters on Apr 21, 2004, 16:26:00
See http://news.bbc.co.uk/1/hi/sci/tech/3642725.stm
Title: Comet question
Post by: Rocket Pooch on Apr 21, 2004, 18:03:00
Hi,

Comet c/2001 Q4 (NEAT) should be very visable from about th 10th May for a month or so going from Canis Major to Ursor Major.  Apparently it could get to Mag1.

see http://www.ast.cam.ac.uk/~jds for details.
Title: Comet question
Post by: Mike on Apr 21, 2004, 18:57:00
Yup. missed that one. Ran it through Starry Night and it looks like it should be quite spectacular !
Title: Comet question
Post by: spendrey on Apr 21, 2004, 21:37:00
Interesting. In fact May's edition of Astronomy Now gives a nice little chart showing where it will be on certain nights.
I assume that to be able to image it you would need a modified webcam for long exposures?
What magnitude would it need to get to so that you could image it with an unmodified webcam? Or would you then miss out on capturing some of the finer details such as the tail?
Title: Comet question
Post by: Mike on Apr 21, 2004, 23:14:00
I should imagine you would get the head and possibly a bit of fuzz if it gets bright enough, but you would definately need a longish exposure to capture the tail properly. Paul would be your best man to ask that as he has a few comet pics.

Title: Comet question
Post by: Whitters on Apr 22, 2004, 04:53:00
Don't know about a modified webcam, but these can be bright. I would probably try using good old film, and a 15-30 second exposure, about the longest you can give with a 50mm lens.
Title: Comet question
Post by: Ian on Apr 22, 2004, 18:48:00
well if that doesn't sound like a challenge, I don't know what does... :grin:
Title: Comet question
Post by: Rocket Pooch on Apr 22, 2004, 18:55:00
Ok glove down I'm up to see what we can do with an SLR, shall we compair results :smile:


But wait, does a digital camera fall into this category?

Title: Comet question
Post by: Rick on Apr 22, 2004, 19:22:00
The latest BAA printed circular seems to have had some missing negative signs on positions. The versions of the comet section website should be correct though....
QuoteThe printed Circular sent to members contains the following errors ...

Comet C/2002 T7 (LINEAR)
The signs indicating whether the declination of the comet is north or south of the celestial equator have been accidentally stripped during the Circular's production. From May 4 the comet is at a southerly
declination during the period of the ephemeris given on page 4. A minus sign in front of the declination value should have indicated this.

Comet C/2001 Q4 (NEAT)
A similar error has occurred in the ephemeris for this comet on page 6. From the start date to May 10, this comet is at a southerly declination.

The cause of this error is still being investigated!

[ This Message was edited by: Rick on 2004-04-22 13:42 ]
Title: Comet question
Post by: Mike on Apr 22, 2004, 19:41:00
Chris, an SLR is an SLR. Whether the light falls onto film or a CCD chip is irrelevant so count me in :wink:

Looks like Paula nd Ian have unwittingly started a photo competition (hey that's an idea!).

[ This Message was edited by: Mike on 2004-04-22 11:42 ]
Title: Comet question
Post by: Rocket Pooch on Apr 22, 2004, 20:10:00
Why don't you mention it tonight and see if you can get any other takers then maybe we can look at the results during the June meeting?

I'm positive Malcom, Jim and others would join in.  Maybe even Rick?
Title: Comet question
Post by: Mike on Apr 22, 2004, 20:23:00
Chris i've already PM'ed Paul about it and we will discuss it with the committee tonight. Seems like a good idea to me. Why not make it a regular monthly feature of the meetings whereby the 'photo of the month' is displayed on the projector with the other contenders also?!
Title: Comet question
Post by: Mike on Apr 22, 2004, 20:25:00
Does Rick's post mean the comets ARE south of the equator and not visible?
Title: Comet question
Post by: Rick on Apr 22, 2004, 21:54:00
Bookmark the BAA Comet Section Ephemeides (http://www.ast.cam.ac.uk/~jds/#ephems) that Chris S posted earlier.

C/2004 F4 Bradfield and C/2003 K4 LINEAR are both observable at present, though not necessarily at sociable times, and LINEAR is rather faint. C/2001 Q4 NEAT will become observable second week in May. Theoretically...

[ This Message was edited by: Rick on 2004-04-22 14:00 ]
Title: Comet question
Post by: malcolm on Apr 26, 2004, 04:47:00
Is the 15 - 30 seconds exposure with a 50 mm lens an undriven exposure? I'd have a go, but it seems we'll be shooting below the horizon.
Title: Comet question
Post by: Whitters on Apr 26, 2004, 05:11:00
Yes it is unguided on a tripod and a 50mm lens you could go for between 20 and 40 seconds, best to take several shots giving an extra five seconds each time and you should get an image.
Title: Comet question
Post by: Rocket Pooch on Apr 27, 2004, 21:15:00
Hi,

That orion shot was taken using a 90 second exposure with a 28mm lens, I also took some photo's with 2 minute exposures and they are also fine.  

So I'd think you should be able to get about 1:30 from a 50mm lens.  

I did some reading last week about taking pictures of comets and a lot of people we're using iso400 or 800 film and 45 second exposures.