M74 .. last night .. seeing not that good :-(

[SlimPaling]

I managed to get my first images of M74 last night.

The seeing was not that good here in Nottinghamshire ... but I am happy to get something. I have read that this is not an easy object to image much of the time.

I took 3 x 300 sec LRGB subs .... approx. an hours worth of exposure.

Hopefully I can try again when the sky conditions are better to see if I can improve the clarity.

Any comments appreciated :-)

Mike

[Davey-T]

Nice image Mike, one of my favourite " small " galaxies , I've got a WIP on it from last year in need of more data.

Dave

[wimvb]

A very nice image. More data will help a lot to lift the weak structures above the noisy background. Total integration time is usually measured in hours. Usually you would gather luminance data under the best conditions, to get as much detail as possible, and rgb under less favourable conditions. But if you have light pollution, you can try just shooting rgb, and create a synthetic luminance image from the rgb data.

[SlimPaling]

18 minutes ago, wimvb said:

A very nice image. More data will help a lot to lift the weak structures above the noisy background. Total integration time is usually measured in hours. Usually you would gather luminance data under the best conditions, to get as much detail as possible, and rgb under less favourable conditions. But if you have light pollution, you can try just shooting rgb, and create a synthetic luminance image from the rgb data.

Hi again Wim ...

Thanks for these helpful comments. I will take all of this on board .... the skies here are more often "less favourable" :-(((

Can you please explain/expand your comment ... "create a synthetic luminance image from the rgb data" for me? This is something new for me.

Mike

[wimvb]

56 minutes ago, SlimPaling said:

Hi again Wim ...

Thanks for these helpful comments. I will take all of this on board .... the skies here are more often "less favourable" :-(((

Can you please explain/expand your comment ... "create a synthetic luminance image from the rgb data" for me? This is something new for me.

Mike

Use the rgb data to create a colour image, and extract the luminance data from this. In essence, you desaturate the image completely, so that only the lightness information is kept. The result is a gray scale image from the rgb image. In PixInsight, there is a button for this. In PS, there's probably something similar (convert to grayscale image, or convert to b/w image).

When you have the luminance image, you treat it as luminance data: noise reduction, sharpening, etc etc. The rgb image is processed to reveal as much colour as possible. Then recombine the luminance image with the rgb image again, as you would with normal lrgb. You can even do this twice, to create an llrgb image.

If you have the luminance and rgb data at the same resolution, you can do a hybrid: combine the luminance image with the grayscale image that is extracted from the rgb image.

Some astrophotographers shoot just rgb data, and don't bother with the luminance anymore. All lightness information is already available in the rgb data. It's just a matter of experimenting while the skies are "less favourable".

Have fun

[SlimPaling]

I managed to get some clear skies last night and took some extra LUM subs (an extra 50 minutes worth)... which I have now added to my first effort.

I can see some improvement by adding more luminance subs to my original set.

I am slowly getting there :-)

[Davey-T]

Useful LLRGB tutorial here.

Dave

http://www.astronomersdoitinthedark.com/dslr_llrgb_tutorial.php

[SlimPaling]

1 hour ago, Davey-T said:

Useful LLRGB tutorial here.

Dave

http://www.astronomersdoitinthedark.com/dslr_llrgb_tutorial.php

Thanks for this Dave .... I will be looking at this avidly !!!

Mike

[SlimPaling]

Well I have now reprocessed my original subs using a new LLRGB method that was suggested by others ..... I think the final results shows a big improvement :-)))