Comet 45P

[doug]

     Have a look at today`s APOD. Very nice image of Comet 45P etc etc.

     Doug.

[MarkS]

Yes, that's a very nice image.  Fritz Hemmerich uses a Sony A7S - the same camera as me.

I've been waiting for a clear night but now the moon is beginning to get too close.  The best opportunities have already gone.

Mark

[MarkS]

I've been waiting for a clear night but now the moon is beginning to get too close.  The best opportunities have already gone.

Looking at my planetarium software indicates it is moving very fast - 8 degrees every day.  That's 20arcsec of motion in every minute of time.  So with a focal length of 500mm I'm going to need short exposures of around 10-15seconds to prevent blur.

[MarkS]

Oh well - I set the alarm clock but the sky was full of hazy cloud at 4am this morning

Mark

[doug]

     Wish you luck, Mark

     Doug.

[MarkS]

I found it last night after midnight.  Impossible to see in binoculars.  I could only just find it in a 30sec exposure.  It's really faint and I'm sure that's not just because moonlight is drowning it out.

I took 80 x 15sec exposures that I'll attempt to process tonight.

Mark

[JohnP]

that I'll attempt to process tonight

...

Blimey I'd be in 'dog house' if I tried processing images on Valentines night Not that I've got any images to process though... Look forward to seeing it - John

[doug]

Well done Mark. If you can suss out an image. I will be very glad to put it into my Report for the meeting. I haven`t got very many images to put into there because of the awful weather; one more would be brilliant.

Cheers, Doug

[Carole]

I read a thread of some-one else who had imaged it and they also said it was very faint, also appears to have little in the way of a tail.

Carole

[Roy]

I also tried last night but gave up, the combination of the moon and some murk was too much.

Roy

[MarkS]

I hope you weren't holding your breath for this one.  It's the poorest excuse of a comet I've seen in a long while.  Really faint and no tail.  This is 20minutes of total exposure on the amazing Sony A7S and Tak Epsilon combination.  Which just goes to show how dim this thing is.  The moonlight increased the background noise by a factor of 2-2.5 so I can't even blame the moon.



Mark

[Carole]

Well done Mark, wow that is faint, I won't be attempting to get this one.

Carole

[JohnP]

Nice Mark - well done on getting it. Interesting to see the different colours of star trails. Just curious how on the trails where you can see the individual exposures different colours have been recorded - is this effectively the 'twinkling' of the stars i.e. Atmospheric Dispersion?

Great capture - John

[MarkS]

Nice Mark - well done on getting it. Interesting to see the different colours of star trails. Just curious how on the trails where you can see the individual exposures different colours have been recorded - is this effectively the 'twinkling' of the stars i.e. Atmospheric Dispersion?

No this is not atmospheric dispersion.  It is caused by dithering and the star sometimes landing on a green pixel, sometimes on a red and sometimes on a blue.  When you stack the star, it averages out to the true colour of the star.  But when you smear it you see those odd colours.

Mark

[JohnP]

Thks Mark for the explanation.