Shooting M51 - Needing advice!

[CKemu]

Finally got to the point where I feel capable of photographing galaxies and recently produced my first shot of M51.

I've not attempted "flats" yet, but dis-regarding that, I need advice and opinions.

I have seen spectacular shots recently and despite grabbing a large number of shots so far, I feel that I am far from the level of detail people are able to capture - of course given my location it would be easy to blame light pollution - but I am hopefully going to be out with the scope tonight and other nights attempting to capture M51.

Below are three shots of M51, no tweaking, single light sub frames. I am curious to know if you (the forums) feel that it's worth perusing the settings I am currently using, or if I should be aiming for longer exposure subs, lower ISO etc? - Indeed will capturing more of what I have yield any improvement.

ISO 3200 - 5 minutes:

ISO 1600 - 6 minutes:

ISO 1600 - 12 minutes:

[ollypenrice]

Galaxies have lots of faint outer parts not far above the background level so, number one, you need flats. Get used to the idea because it isn't going to go away!!!

Then you need to colour balance. These days I use Pixinsight for that. All the images above are far too green but just in Photoshop you could make sure that, in Levels, the top left of the histogram peaks in each colour line up. That would help.

And then here's Levels and Curves. Check out RobH's tutorials by Googling Rob Hodgkinson Middle Hill Observatory.

You'll get there!

Olly

[CKemu]

Thankyou for the advice, shot some flats against the dusk sky. Hope they help! Just as a quick question - when I stack these subs, I still get a grainy image! How are yours coming out so smooth?!

Oh and magnificent work on your amazing M51!

[Shibby]

How many subs are you stacking CKemu? For single subs, I'd say there's plenty of detail showing there!

The way to reduce noise is to stack more and more images. I recently took 23x5mins for M51, but would have preferred more. Once you've reduced the noise significantly, you can start playing with the levels and curves to bring out the detail!

[CKemu]

Well I managed to get out last night to shoot off a few more frames, alas the cold got the better of me and I ended up wussing out around 2am (I had frost all over my laptop and couldn't feel my feet!)

Just stacked these images combined with the last series of images and thrown in a few 12m subs for good measure.

All ISO 1600:

40 x lights

- 34 x 6m

- 6 x 12m

30 x Darks

- 27 x 6m

- 3 x 12m

20 x Flats

DSS used 34/40 lights it seems - not a bad return as I lost 36m of light.

Now I am starting to tentatively process the image - going to share the TIF I've generated, so if anyone is bored, has spare time or just curious to see if I have made a mess of this - feel free to tweak, process and otherwise examine.

I hope to see if I can process it to whatever you guys get, also curious for feedback, do I need more subs etc

As I say, this is my first serious attempt at getting detail out of a galaxy, heck this is actually the first galaxy I've successfully (?) photographed.

http://vividphoton.com/uploads/m51/02.TIF

File is 70.8MB

I have also added two screenshots of my DSS output, and the singular adjustment I made.

[CKemu]

Well here's my first attempt at a process:

[ollypenrice]

That's getting there nicely now! You asked how I got my M51 to be relatively free from grain or noise. Very simple; I shot about 16 hours of data... and with a cooled CCD I can do subs of 15 minutes for LRGB so that further reduces noise. Sigma stacking is very powerful for removing noise (and satellites and hot pixels...) but it needs at least a dozen images to do its thing.

Olly

[CKemu]

Alas stomach ache and a headache persuaded me to stay in doors tonight, despite it being wonderfully clear - hopefully whatever is wrong with me tonight goes away! Plan on capturing more data!

Thank you for the excellent advice, I aim to one day be as good as yourself! 16 hours of data, that's remarkable!

Would be extremely interesting to have teams of people photographing a singular target, dropping that data on to a server and stacking those images.

16 hours of data between two people reduces that to 8, 16 between four becomes four hours etc etc...

[JimStan]

Nothing can take the place of a LOT of subs taken at a lower ISO setting , but you can achieve a "smoother" background without losing a lot of important detail, by using the "surface blur" tool in PhotoShop. I took the freedom to do just that with your submitted cropped image, and this is the result. Note that the very distant NGC galaxy is still present in the photo, and the foreground stars are not significantly smeared by the process. You have to be very careful in doing this, so as not to wipe out detail that you have gained with your careful focusing and other concerns . Don't forget, this is only a rework of your jpeg image. I am sure you can do better than this with your original data. Nice job ! ( don't forget to click on the thumbnail to see the full-sized image )

Jim

[Slim]

I'll start by saying I'm no expert and your raw data is better than I have managed so far but I took your raw data and played with levels and curves in GIMP and this was the result. Some nice detail in the galaxy and I'm sure someone who knows what they are doing could get this looking really nice.