Another M51

[MarkS]

M51, the Whirlpool Galaxy is one of my all time favourites.

This one was taken last week Thursday 19 April as part of an experiment with a new setup:  Sony A7S on Celestron C11 with Starizona 0.72x large format corrector.

This is 240x30sec at ISO 10000 i.e. 2 hours total exposure:



Large version, a crop at 100% scale is here:
http://www.markshelley.co.uk/Astronomy/2018/M51_C11_20180419.jpg

Mark

[Carole]

It's a beautiful image Mark, but why go back to the C11 with it's much slower focal ratio?  Is it because you wanted to get in "closer" to the Galaxy? 

Carole

[JohnP]

Very nice Mark - loads of detail in the full size - I'd be well haps with that experiment...

[MarkS]

It's a beautiful image Mark, but why go back to the C11 with it's much slower focal ratio?  Is it because you wanted to get in "closer" to the Galaxy? 

Yes, it's all about focal length.  This will get me close into those small objects.  The read noise is so low on the Sony A7S that the slow F-ratio isn't a serious issue. 

Mark

[Carole]

Gotcha, makes sense now.

Carole

[MarkS]

I've done a complete re-process, this time using the Bayer Drizzled version, for increased sharpness.  The previous version was also a bit too green.

So here's version 2:



Larger version:
http://www.markshelley.co.uk/Astronomy/2018/M51_C11_20180419_v3.jpg

Mark

[JohnP]

definitely less noise visible & colours do look better - nice one - John

[Carole]

Much prefer the new version, both the colour and smoothness.

Carole

[The Thing]

Very nice Mark love the knotty clumps.  I prefer the second version as well.

As 'tis the season of galaxies. I've got my ASI294 on my LX90 for doing galaxies and Jupiter at the moment Hopefully a go at a planetary or two as well.

[Fay]

Lovely M51 Mark. you seem happy with the Sony now. is it still difficult to process the subs, is it something you have to get to know how to do it?

[MarkS]

Lovely M51 Mark. you seem happy with the Sony now. is it still difficult to process the subs, is it something you have to get to know how to do it?

Thanks.  Processing the subs is not difficult.  It's just time consuming and occupies too much disk space - hundreds of subs for every image.

Mark

[NoelC]

An amazing image thanks Mark
The difference in texture between the two galaxies really comes out in your image.
Noel

[Mac]

Very nice,

all these images are screaming at me to get back outside an image........

Mac.