M31 (work in progress) 17.9.2010

[Carole]

This is still a work in progress both from the point of view of processing and also I took some shorter subs so part of the work in progress is to try to reduce the core and add more subs.  However as I haven't done much for a while I thought I'd post this for now. 

I took 2 hours worth last night, but DSS has only stacked 1hour 35mins, my first DSO from the Observatory.
Therefore:
1hr 35 mins of 5 min subs @ ISO 800, + darks, flats, dark flats and Bias
Modded Canon EOS 450D
WO Megrez 72 doublet APO F6

[Mac]

looking good.

The core's a tad burnt out, but you can recover that by taking the shorter subs and then use them for the core detail.

Mac

So is the first light from the observatory?

[Carole]

So is the first light from the observatory?

Not quite, I did a Moon Mosaic, but this is the first DSO from the Observatory. 

As you know I was held up with the Pier adapter problems and then I have just spent almost a month away on holiday.

Carole

[PhilB]

Very nice image, Carole. Great amount of dust and other detail in the spiral arms.

[Carole]

Thanks Phil.  I've noticed the guiding was a bit off.  I think I know why that happened though, so hopefully next time I can rectify that.

Carole

[MarkS]

It's more or less impossible to get a decent image of M31 from the suburbs but you've got all the main features there.  Your capturing and processing looks good though it takes some effort to get the core looking right.

If you were to tackle this at Rother Valley with no filters you would be stunned at the difference.

Mark

[Carole]

Thanks Mark,

Despite it's shortcomings I am quite pleased with this as it's a big step up from my last effort (before guiding) and I know there is lots more I can do to improve it.  Had a crack at the core with shorter subs but not quite managed it yet, maybe I didn't do enough shorter subs.

What length shorter subs should I do, how many and at what stage do I merge them?  I did some 30 sec and 1 min subs but only about 5 of each.  

i.e.
a) when stacking
b) When both long and short subs have been stacked but not processed
c) after both have been processed.

I am inclined to think it might be b)

If you were to tackle this at Rother Valley with no filters you would be stunned at the difference

Good thought, I keep forgetting about darker skies being the key to good images.  

Carole

[MarkS]

Carole,

Do full processing on the long subs and the short subs and then merge them carefully using layers in Photoshop.

Alternative is to first create a HDR (High Dynamic Range) image but I think this makes things more difficult.

Mark 

[Carole]

Thanks Mark, so you think merge AFTER you've stretched them in photoshop.

Just need to work out now whether I need 1/2 min, 1 minute, 2 minute shorter subs and how many of them I need to do.

Many thanks as ever

Carole

[Mike]

Experiment.

Trail and error is a damned good way to learn astrophotography.

[MarkS]

Just need to work out now whether I need 1/2 min, 1 minute, 2 minute shorter subs and how many of them I need to do.

You can't work out what length subs to use - try it out instead and check the core doesn't burn out.  Just like Mike said: trial and error!

Same with processing - there are few hard and fast rules - just do what works best for you.

Mark

[Mac]

Experiment.

in a nut shell .

Try all of them.

10 images at 30 secs is only 5 mins!!

and 10 at 2 mins is only ....... you get the idea.

take 10 @ 30 secs and the work your way up.

all of them can be used, although you will probably find that something like 90 secs will probably be the better starting place.
as it will probably capture more of the core detail without being burnt out. if the central part is burnt out then use 60 secs.

also capture as many as you can. The more you get the lower the noise will be in the final image.

Mac

[Fay]

Carole, your M31 looked very good at the meeting, your best so far!

[Carole]

Thanks Fay, I think it looked a bit washed out on the projector screen. 

OK Guys, I get the picture (Pun.... yuk), about shorter subs, I was really only wondering whether there was a recognised rule about shorter subs, obviously there isn't.

I need to take some more shorter subs as I didn't do very many which is obviously why it didn't work.

Just waiting now for another suitable evening. 

90 secs will probably be the better starting place.
as it will probably capture more of the core detail without being burnt out. if the central part is burnt out then use 60 secs

Sounds sensible, will give this a try. 

Carole

[Rocket Pooch]

Lets not talk abut dynamic range and layering then, it might get more complex about the exposures...

[mickw]

I think it looked a bit washed out on the projector screen.

Carole, everything looks washed out on the projector screen to some degree.
Don't forget that the projector is also magnifying a 15" image to about 5 feet 

[Carole]

Carole, everything looks washed out on the projector screen to some degree.

Yes Mick, I could see it did the same to the other images, it's just that mine wasn't so good as others so it showed it up more. 

Lets not talk abut dynamic range and layering then

It's OK Chris I know how to do layering, just wasn't sure at what stage to do it.

Carole