Hi all,
A few days back I posted my first ever Nebula picture which happened to be the Tarantula.
18 x 20 second exposures @ ISO 1600
10 x Dark frames
10 x Flat
10 x Bias
Put through DSS
The first time I tried to add the colour as I wasn't too sure how to bring it out of the greyscale looking DSS output.
I have since had another couple of goes at it. I used controls like brightness, contrast, saturation, shadows, highlights, and vibrancy to bring out colours that seem to be already there if you look hard enough.
Just asking if you look at images 1, 2, and 3, if you think I'm on the right track or going backwards? I suppose one thing is that I don't know how well my pictures actually represent the nebula in the first place - I see some online that look a bit similar and some that look nothing like mine. Also, in the final picture, I'm not sure if the coloured region on the left and below should actually be there?
Any advice or criticism welcome as I want to learn.
BTW - I wasn't sure if I should have tacked this on to the end of my other thread or start a new one - once again, happy to be advised if I have done the wrong thing.
Pic 1 is the best by far. You've killed the star colours in the other shots.
Assuming this is a DSLR capture, i havent done tarantula yet myself but from memory shots i've seen were a bluer nebulosity and i assume those were due to filtered shots and processing (Ha O Si etc).
That coloured region on the left I think is glow, and shouldnt be there. Its like an internal reflection from a cheap lens element. It should be removeable with a gradient removal tool. Alternatively if you can reshoot, try to see if you can rotate your camera/sensor around 180 degrees and see if the region moves and you can combine the two sets of captures to help reduce its prominence if you have no gradient tools.
Pic 1 is the best by far. You've killed the star colours in the other shots.
Assuming this is a DSLR capture, i havent done tarantula yet myself but from memory shots i've seen were a bluer nebulosity and i assume those were due to filtered shots and processing (Ha O Si etc).
That coloured region on the left I think is glow, and shouldnt be there. Its like an internal reflection from a cheap lens element. It should be removeable with a gradient removal tool. Alternatively if you can reshoot, try to see if you can rotate your camera/sensor around 180 degrees and see if the region moves and you can combine the two sets of captures to help reduce its prominence if you have no gradient tools.
Thanks Sil. Yep, it's a modded Canon 60D at prime focus on the telescope. I should probably mention these things.
Next time I will turn the camera around and see if the glow moves or stays put. It is hard to see though until DSS gets through with it. I've attached an untouched image for you to see - maybe you will see it with the extra experience in looking at astro images.
The Tarantula's a weird one - loads of Oxygen III in there so it doesn't come out looking the regular shade of pink you might expect. Yellowish is much more realistic.
Ive always found it comes out a bit green
Your first pic is the best.
Thanks Jennifer, Cam, and Sil,
Shows what I know. A couple of times I have had blue/green/yellowish colours showing but thought they were wrong so tried to get rid of them.
Don't worry too much what it looks like - all our first images looked like that (and some years later). A lot of the result is also in the processing. I used a free program called fitswork4 to remove the gradient in your image, then photoshop to increase star colour, reduce background noise and reduce coma.
With practice you can get a better colour balance. A lot of nebulae look very different in a standard DSLR. A lot of them will look blue/teal instead of red.
Your image is quite good - just need more practice with processing. here's a lot of people here who will be happy to help!
Ive always found it comes out a bit green
Your first pic is the best.
Quote:
Originally Posted by Tony_
Nice start Mick,
Don't worry too much what it looks like - all our first images looked like that (and some years later). A lot of the result is also in the processing. I used a free program called fitswork4 to remove the gradient in your image, then photoshop to increase star colour, reduce background noise and reduce coma.
With practice you can get a better colour balance. A lot of nebulae look very different in a standard DSLR. A lot of them will look blue/teal instead of red.
Your image is quite good - just need more practice with processing. here's a lot of people here who will be happy to help!
Tony.
Thanks Tony, I'll definitely get fitsqork4 and have a go. I'm not after a full tutorial, just wondering if you could point me in right direction for main processes you used in Photoshop.
Hi Mick, I agree with others number 1 is best, the spider was my first target back in March, when I finally got a CCD, here is the first process I did, using, from memory, Max DL and PS CS6. The second image is the same data reprocessed in the last week or two with PixInsight and a lot of practice.
Hi Mick, the easiest way to see what colours you should see in 2070, is
to take a single sub at ISO 3200 of 60 to 75 secs duration. This will show
colour clearly in 2070 when you view it on the camera's LCD screen.
Obviously, the quality of the image is irrelevant, so a JPEG is fine.
I have attached a JPEG of ISO 1600 of 70 secs duration as an example.
ISO 3200 or higher would show a little more colour.
raymo
Hi Mick, I agree with others number 1 is best, the spider was my first target back in March, when I finally got a CCD, here is the first process I did, using, from memory, Max DL and PS CS6. The second image is the same data reprocessed in the last week or two with PixInsight and a lot of practice.
Hi Mick, the easiest way to see what colours you should see in 2070, is
to take a single sub at ISO 3200 of 60 to 75 secs duration. This will show
colour clearly in 2070 when you view it on the camera's LCD screen.
Obviously, the quality of the image is irrelevant, so a JPEG is fine.
I have attached a JPEG of ISO 1600 of 70 secs duration as an example.
ISO 3200 or higher would show a little more colour.
raymo
Thanks Raymo. Never thought of doing what you suggested. It makes a lot of sense and I'll be doing it from now on to give me the target colours.
I used fitswork4 to fix the gradient as Tony suggested and then used Paintshop Pro to decrease saturation in the stars and increase it in the Nebula. I didn't try to change any of the colours this time just bring out what seemed to be already there.
I understand I only have 6 minutes of data so it's never going to be a masterpiece, but I hope this is a bit better.
BTW - anyone else think this nebula looks creepy? I know it's called Tarantula but I don't see a spider both rather something demonic
Next time I will turn the camera around and see if the glow moves or stays put. It is hard to see though until DSS gets through with it. I've attached an untouched image for you to see - maybe you will see it with the extra experience in looking at astro images.
Mick
Yes, GradientXTerminator is the sort of thing I was talking about. It's a common feature in many astrophotography processing programs and has many names. For example in PixInsight its called DynamicBackgroundExtraction, it removes the glow gradient and colour tint of the sky leaving star on a black background.
No, I can't see any hint of that glow patch in your image, sometimes you can on a camera preview. I remember an old technique with photoshop where you duplicate the image to a new layer, use clone tool to "erase" bright features like a planet or nebulosity, use a huge gaussian blur which should make the stars vanish and you should be left with a subtly mottled blurry picture of the overall colour cast. Then you could subtract that layer and you essentially remove a large chunk of the skyglow without effecting the stars or nebulosity.
But these days gradient removal feature are common and easier (and really photoshop I find is useless for astrophotography).
Just a comment on your last image. Desaturating the stars i think is a poor choice. Its a cliche beginners technique in photography to have your subject in colour and the surround in black & white. It gets over used and rarely very well, a bad photo processed this way is still a bad photo. Here its not relevant to astrophptpgraphy, the sky it typically black with white dots and so it just looks like a hand painted colour smudge instead of a wonder of night sky.
Also the blacks look heavily clipped so theres a harshness to the shot. Its better to keep some of the "almost black" values there as the noise adds a realism and texture to the shot.
Yes, GradientXTerminator is the sort of thing I was talking about. It's a common feature in many astrophotography processing programs and has many names. For example in PixInsight its called DynamicBackgroundExtraction, it removes the glow gradient and colour tint of the sky leaving star on a black background.
No, I can't see any hint of that glow patch in your image, sometimes you can on a camera preview. I remember an old technique with photoshop where you duplicate the image to a new layer, use clone tool to "erase" bright features like a planet or nebulosity, use a huge gaussian blur which should make the stars vanish and you should be left with a subtly mottled blurry picture of the overall colour cast. Then you could subtract that layer and you essentially remove a large chunk of the skyglow without effecting the stars or nebulosity.
But these days gradient removal feature are common and easier (and really photoshop I find is useless for astrophotography).
Just a comment on your last image. Desaturating the stars i think is a poor choice. Its a cliche beginners technique in photography to have your subject in colour and the surround in black & white. It gets over used and rarely very well, a bad photo processed this way is still a bad photo. Here its not relevant to astrophptpgraphy, the sky it typically black with white dots and so it just looks like a hand painted colour smudge instead of a wonder of night sky.
Also the blacks look heavily clipped so theres a harshness to the shot. Its better to keep some of the "almost black" values there as the noise adds a realism and texture to the shot.
Thinks Sil, I very much appreciate the feedback. I've had another stab at it without mucking around with the stars this time - so there are a few discoloured stars. All I did was remove the unnaturally glowing region with fitswork4 and then use Paintshop Pro to increase the saturation and brightness of the nebula a bit.
In all my attempts the colour looks a bit tacked on to me.
Play around with fitswork a bit - you will get better with practice. There is a balance between selecting too much and not enough for the gradient calculation. If you don't select enough nebulosity it tends to get deleted.
Try not to blacken the background too much. It is called "clipping" and it tends to ruin the stars and looks less natural. Don't worry - I used to do this to all my images when I started and it took a long time before I even knew there was an issue.
The noise reduction I use in photoshop is:
Open image
Layer, duplicate layer, background copy
Filter, noise, reduce noise. (for more extrme reduction you van use Median).
Then play with the sliders to get what you sort of like (you can do the procedure more than once).
Typical: Strength 10, Preserve details 15%,reduce colour noise 100%,
sharpen details 15%. This depends on the image and what you prefer.
"Ok"
Add layer mask (icon - square with a circle in it).
Click on background image.
Ctrl A, Ctrl C (select all, copy)
Alt + left click on Background copy. (should be white)
Ctrl V (Paste), Ctrl I (inverse), Ctrl L (Levels).
Slide the left pointer to right(about 80%) and the right pointer to the left.
Black objects will be protected, white will have the noise reduction applied.
When you are happy with the levels of black and white press OK.
Then click on the eye for the backgound copy. Clicking this on and off will show the before and after.
If you like it - "Layer" flatten image, deselect - save new image.
Play around with fitswork a bit - you will get better with practice. There is a balance between selecting too much and not enough for the gradient calculation. If you don't select enough nebulosity it tends to get deleted.
Try not to blacken the background too much. It is called "clipping" and it tends to ruin the stars and looks less natural. Don't worry - I used to do this to all my images when I started and it took a long time before I even knew there was an issue.
The noise reduction I use in photoshop is:
Open image
Layer, duplicate layer, background copy
Filter, noise, reduce noise. (for more extrme reduction you van use Median).
Then play with the sliders to get what you sort of like (you can do the procedure more than once).
Typical: Strength 10, Preserve details 15%,reduce colour noise 100%,
sharpen details 15%. This depends on the image and what you prefer.
"Ok"
Add layer mask (icon - square with a circle in it).
Click on background image.
Ctrl A, Ctrl C (select all, copy)
Alt + left click on Background copy. (should be white)
Ctrl V (Paste), Ctrl I (inverse), Ctrl L (Levels).
Slide the left pointer to right(about 80%) and the right pointer to the left.
Black objects will be protected, white will have the noise reduction applied.
When you are happy with the levels of black and white press OK.
Then click on the eye for the backgound copy. Clicking this on and off will show the before and after.
If you like it - "Layer" flatten image, deselect - save new image.
Regards,
Tony.
Thank you very much Tony, the encouragement and advice is much appreciated. I'll fine give a go on the weekend as Photoshop isn't installed on my work computer
Last edited by mikeyjames; 12-11-2016 at 07:34 AM.
