M83 galaxy: My first galaxy image

[DavidNg (David)]

Hi,

Sydney has been raining last few days, so I am learning to work on image processing instead. This LRGB consists of several hours of older data of various exposures, ccd temperatures as I didn't know what I were doing and messy record keeping. I am not even sure if the calibration masters were accurate or not. Processed with PI, following example on Youtube.

I dont know how or why there is the red band on the right hand side.

Thanks for looking
David

[Tony_ (Tony)]

Hello David,

Nice galaxy image.
I'm not sure what caused the red band - light interference? Overall there is some good data there.

You can process this out a bit - I hope you don't mind but I had a go at it for fun (attached). The colour still isn't balanced but I git rid of most of the gradient - 5 minutes in photoshop. With more time it can be improved further. I'm not that good at processing - still a lot to learn.

Regards,
Tony.

[RickS (Rick)]

DBE is your friend! The perfect tool for removing gradients like that.

[DavidNg (David)]

Originally Posted by Tony_

Hello David,

Nice galaxy image.
I'm not sure what caused the red band - light interference? Overall there is some good data there.

You can process this out a bit - I hope you don't mind but I had a go at it for fun (attached). The colour still isn't balanced but I git rid of most of the gradient - 5 minutes in photoshop. With more time it can be improved further. I'm not that good at processing - still a lot to learn.

Regards,
Tony.

Wow, much improved image Tony , the red band is disappeared and there is now some colour in the stars too. Can you please show us what you did in PS?

Thanks RickS, I've already done DBE with this image, not sure if DBE can used over and over again?

Regards

[Jon (Jonathan)]

Wow. Lovely data, David, and PS magic again.

For the processign novices among us can you show us what you did? And Rick, what is DBE?

I would have just thrown away the data with the red band, not knowing that it could be rescued ...

[Tony_ (Tony)]

Hello David,

Overall your images are far better than anything I do - mine often have gradients. Some of your monochrome images look excellent.
there are plenty of tutorials on the internet.
The processing I used is:

Open the image in PS. Flatten the image ("Image""flatten")
To remove any dust spots etc. is fairly easy. Open the paint brush tool and choose a brush size of around 15 (depends on image). "Alt Click" on a clear background near the spot. Then click on the spot. This will fill in the spot with the background colour.

To remove the gradient:
Flatten the image.
Then "layer" "duplicate layer" "ok".
You want to create a blank image of the gradient.
Now the hardest bit is to remove as much of the image and brighter stars as possible (from the duplicate). I usually do this with the paint brush tool also.
Open paint brush tool.
"alt click" on clear background near area to be erased.
click and move brush over area to be erased. The better you match the background colour the better this will work. You will need to "alt click" often to match the background gradient as best as possible at all points.
You do not have to remove all the stars - but the more patient you are with this is best.
Once you have finished do "filter" "noise" "median" and choose a value somewhere around 20 - 40 which ever looks best. Now you have a background gradient.

Next step is to create an offset.
Open original image (bottom right)
then "layer" "new" "layer" "ok"
Then click on set foreground colour (left icons near bottom).
On the colour picker window move the selector to near the bottom left to give RGB values of around 10 - 20.
click ok.
View the new layer (close the viewer for the other 2 layers).
This layer will be blank - or black and white squares.
Open the paint bucket tool - left icons half way down (you may need to right click on the gradient tool to see it).
Then click on the layer image- this will create an offset. On the bottom right menu above the layers - click on the box that says "normal" and change it to linear dodge.
Open the view (eye in the box) in all 3 layers.
Then "fx" "blending option" and change blend options to either difference or subtract.
This should delete the gradient from the original image.
flatten the image.

You can then adjust saturation etc.

Let me know if you need more help.

Regards,
Tony.

[RockHound]

Hi David

Nice image.

I have just started using PI my self and have found the following tutorials very helpful. In them he does process M106 so some of the techniques might be very helpful for you

http://www.harrysastroshed.com/pixinsighthome.html

Paul.

[ChiefDreamer (Hun)]

Awesome pic

[Tony_ (Tony)]

Hello David,

Regarding the red band - look at your subs.If the red band is in the subs then its something optical (light etc.).
If the red band is not in the subs then it is probably processing based.

Regards,
Tony.

[DavidNg (David)]

Originally Posted by Jon

Wow. Lovely data, David, and PS magic again.

For the processign novices among us can you show us what you did? And Rick, what is DBE?

I would have just thrown away the data with the red band, not knowing that it could be rescued ...

Thank you Jon, yes there are so much to learn in image processing, an art in it self. Hope we will learn along the way in this wonderful IIS forum.

DBE is DynamicBackgroundExtraction, it is a process in PixInsight software, DBE I believe is to get rid of gradient such as the red band in my original image.

Regards
David

[DavidNg (David)]

Originally Posted by RockHound

Hi David

Nice image.

I have just started using PI my self and have found the following tutorials very helpful. In them he does process M106 so some of the techniques might be very helpful for you

http://www.harrysastroshed.com/pixinsighthome.html

Paul.

Thanks Paul for your link. I am learning this tutorial

[DavidNg (David)]

Originally Posted by ChiefDreamer

Awesome pic

Thanks ChiefDreamer. Couldn't done it without the help of members here

[DavidNg (David)]

Originally Posted by Tony_

Hello David,

Overall your images are far better than anything I do - mine often have gradients. Some of your monochrome images look excellent.
there are plenty of tutorials on the internet.
The processing I used is:

Open the image in PS. Flatten the image ("Image""flatten")
To remove any dust spots etc. is fairly easy. Open the paint brush tool and choose a brush size of around 15 (depends on image). "Alt Click" on a clear background near the spot. Then click on the spot. This will fill in the spot with the background colour.

To remove the gradient:
Flatten the image.
Then "layer" "duplicate layer" "ok".
You want to create a blank image of the gradient.
Now the hardest bit is to remove as much of the image and brighter stars as possible (from the duplicate). I usually do this with the paint brush tool also.
Open paint brush tool.
"alt click" on clear background near area to be erased.
click and move brush over area to be erased. The better you match the background colour the better this will work. You will need to "alt click" often to match the background gradient as best as possible at all points.
You do not have to remove all the stars - but the more patient you are with this is best.
Once you have finished do "filter" "noise" "median" and choose a value somewhere around 20 - 40 which ever looks best. Now you have a background gradient.

Next step is to create an offset.
Open original image (bottom right)
then "layer" "new" "layer" "ok"
Then click on set foreground colour (left icons near bottom).
On the colour picker window move the selector to near the bottom left to give RGB values of around 10 - 20.
click ok.
View the new layer (close the viewer for the other 2 layers).
This layer will be blank - or black and white squares.
Open the paint bucket tool - left icons half way down (you may need to right click on the gradient tool to see it).
Then click on the layer image- this will create an offset. On the bottom right menu above the layers - click on the box that says "normal" and change it to linear dodge.
Open the view (eye in the box) in all 3 layers.
Then "fx" "blending option" and change blend options to either difference or subtract.
This should delete the gradient from the original image.
flatten the image.

You can then adjust saturation etc.

Let me know if you need more help.

Regards,
Tony.

Thank you so much Tony, I am still playing around with it over the weekend. Will post my version of fixing soon