This is 7.5 hours total exposure: 5 hours from Kelling Heath and 2.5 hours from France.
Modified Canon EOS350D on Celestron C11 with F6.3 reducer. Guided with a modified Toucam on a 300mm lens with 2x converter with PhD Guiding software.
(http://gallery.orpington-astronomy.org.uk/albums/userpics/10046/normal_m51synth.jpg)
Full size is here:
http://gallery.orpington-astronomy.org.uk/albums/userpics/10046/m51synth.jpg
Mark
Stunning
Carole
let us know which magazine prints it first, won't you? ;)
Ok that was worth the trip
That is absolutely incredible, looks like a cooled CCD image, and a bloody good one at that, awesome stuff man!
Daniel
:O)
Gobsmacked Mark - Your commitment has really paid off..! The extra 5hrs worth of data has really let you push the curves (pull up the brightness) without introducing noise & keeping the background nice & smooth - That m51 really stands out...! Another top notch image. I ;ove the extra background galaxies as well.
Out of interest do you think there is a 'diminishing limit on returns' type rule with taking images i.e. do you think 3hrs is better than 2, 5 better than 3, 7 better than 5....etc. or is there a point where it's worth calling it & day & moving on...? You must have been itching to move to another object at Kelling with those dark skies (I know I would of) - Very impressed you stayed on it for another 5hrs.....
John
Mark, I knew it would be good but it's turned out much better than that, absolutely superb. As I said before, the original was ripe for an image of the month but if you don't get it with this then the people at Astronomy Now must be blind. You should also put it forward for that Greenwich Observatory competition...
Thanks for your comments - I'm certainly very pleased with the result. It was an experiment to try out what would happen with a very long total exposure
Daniel - it was a pretty cold that night - temperatures dropped to around 4C so, in a sense, it was a cooled CCD! In the Winter, a Canon is as good as a cooled one shot colour camera.
John - I really wanted to see if noise levels really do continue to reduce with longer total exposure. Well they do! The maths says that once you have chosen the length of your subs, the signal to noise level in your stacked image is proportional to the square root of the total exposure.
i.e.
Double your total exposure and the S/N improves by 1.4
Quadruple the total exposure and the S/N improves by a factor of 2 - and when the S/N improves by a factor of 2, you can see objects twice as faint in your image.
Normally I go for 2 hours total - this time I went for nearly 8 hours and it made a huge difference (as predicted by theory). But to make another wothwhile improvement I would have to go to 16 hours, probably. And that is the law of diminishing returns at work.
Mark
Mark,
An absolutely excellent image, :o and with your Canon 350D. (mine doesn't take images like this)
All I can say is that it was LUCKY that you had your camera with you, and was able to guide it for 7.5 hours and from 2 countries.
I suppose it's that old saying again 'Right place at the right time' ;)
Tony G
I agree with you there Tony. Right place right time. Mark, your next star party will be in Wookie Hole at lunchtime.
No I'm not jealous, not a bit :)
Mind you, knowing Mark, he'd come out with a time lapse film of stalactites growing...
Mark, there is not a lot left to say. Extremely good. Do you think that was an experiment or would you have the patience to do that length again?
Fay,
It has made such a big difference, I will probably do most of my imaging like that in future i.e. spending many hours on a single subject. I really think this is the way to go.
Mark
I'll be very Dissappointed if I don't see this one in at least one of next months magazines, It's begging for a full page spread! By the way, have you thought of getting a Hyperstar conversion for your C11, 1 hour on the Hyperstar would be equal to 30 hours at F10, albeit with a wider field, so probably wouldn't be the way to go for galaxys!
Daniel
:O)
Mark,
I've managed to get a 40cm x 40cm gloss print out of this image, and it looks stunning.
Give me a PM with your address and I'll drop it around.
Tony G
If it prints well at 40 x 40 would it be worth a shot at "Astronomy Photography of the Year"? - The worse that can happen is they say no
Your post Mark -
http://forum.orpington-astronomy.org.uk/index.php?topic=4354.0 (http://forum.orpington-astronomy.org.uk/index.php?topic=4354.0)
Stunning image by the way Mark, I hope to see it in A.N. at least
Fantastic.
there is so much detail.
even ic4278 and ic4277 both at mag 15 are very clear.