Colour adjustment/enhancing

[PlasticSpanner]

Can anyone give me some pointers to get me started? I got some good star photos a couple of weeks ago but a couple were spoiled by car headlight pollution. This particular one I want to keep as it has 2 shooting stars in it and a rather nice star cluster near the bottom left of center.

Is it possible & how, to level out the "background colour to just get a very dark blue/black but keeping the detail of the stars and how can I enhance the star cluster to make it more noticeable?

Many TIA

[Meysha]

This is tough!!
I've played with it a bit in PS and got a few options for you to try. To get rid of the pollution change it into a black and white picture wither either the channel mixer (click the monochrome box at the bottom) or I tried it with Image->Adjustments->Match Colour and increased a bit of the luminosity and reduced the colour intensity.
What you'll want to end up with is the stuff you want to keep white and the stuff you want to dissapear blackish.

Then create a layer beneath that with the sky colour you want. Then change your now B&W stars' layer blending mode. Try a bunch of different ones like Pin Light, Linear Light and Hard Light.
I found that Pin Light worked the best for me - but you lost the star trails, but it did bring the stars out a little more.

Also, you've got a glitch in this scan on the left hand side the scanner stuffed up and blurred a big long line.

[Meysha]

Forgot to post a pic of what I got. It's not very good but at least it's got rid of that yukky orange glow.
Photo1

Oh , if you then make a duplicate of your star layer and change it's blending mode to Colour Dodge you'll bring out more of the background stars (or that could just be pollution I can't tell.
Photo2

Edit: Took photos down, due to pure shame and a much better version done by pursuer.

[Cuervo79]

I personally would not do the color dodge, but play with the color burn option so the light part in the center starts to have the same tone as the edge, then just flatten image and play with the curves.....

[Nikon Fan]

I would suggest trying to duplicate the layer and then choosing a blend mode of multiply or overlay. You could probably also add a solid color either dark blue or black and choose different blend modes until you come up with something you like. You could also adjusts curves and levels as well...that should give you a start, but not really sure how well it will work

[pursuer]

This is a common problem in astrophotography and is easily solved.

Duplicate the image in PS, apply a dust and scratches filter to the the copy just strong enougth to remove all the stars. You will be left with just the background color, subtract this from the origional.



Adjust levels and apply Usharp mask to taste


Whoops, I almost forgot, its been awhile since I have done this. Another method which often gives better results is to invert the copy then appy it to the origional using color burn, after applying the dust and scratches filter of course.



This method preserves more of the stars color, red to blue depending on the tempature of the star.

[Meysha]

Ok say bye bye to my attempts.
That's the difference between the astrophotography god that is pursuer and me - someone who can't even see the stars in my current city.

[pursuer]

Oh and I would be interested in hearing the exposure details for this, film, digital, apature, ISO, Exposure time, equipment used?

Edit: don't feel bad Meysha, there are a lot of funky tricks used in astro photograpy.

[PlasticSpanner]

Thanks Pursuer Thats amazing! I was trying Meysha's suggestion & was going to ask how I can preserve the star colours too!

Many thanks to everyone with their suggestions! I've copied them to a text file for future rescues! Meysha, why did you take your attempts down? You should see some of mine!

I don't really like using PS to alter a photo but prefer to get it right on film the 1st time if possible!

The Photo was taken with a Praktica BMS, ASA200 colour film, 18 second exposure. 28mm lens on F1.8. A better one was with the same settings but for 12 seconds but it didn't capture the 2 shooting stars (and another at 15 seconds had a plane through it!) ! The extra 6 seconds caught more stars in the Milky Way but over exposed the constellation stars and Achird just below!

The Constellation is Cassiopeia (The 5 brightest stars just below centre looking a bit like a stretched out W) and the bottom of the frame is just above the Andromeda Galaxy. Next time I'll put Cassiopeia at the top of the frame & get Andromeda too!

Any suggestions on un-trailing star trails? I have a couple of good ones that have gone on for just a bit too long & stretched the stars!

[pursuer]

Quote: Originally Posted by PlasticSpanner

Thanks Pursuer Thats amazing! I was trying Meysha's suggestion & was going to ask how I can preserve the star colours too!

No problem, im glad I could help.

Quote: Originally Posted by PlasticSpanner

The Photo was taken with a Praktica BMS, ASA200 colour film, 18 second exposure. 28mm lens on F1.8.

A better one was with the same settings but for 12 seconds but it didn't capture the 2 shooting stars

(and another at 15 seconds had a plane through it!) !

The extra 6 seconds caught more stars in the Milky Way but over exposed the constellation stars and Achird just below!

You can't over expose stars, they are just points of light With the aid of tracking mounts exposures often run ten minutes or more, the deeper the better Are the overexposed stars in this image or did you crop them out?

Quote: Originally Posted by PlasticSpanner

Any suggestions on un-trailing star trails? I have a couple of good ones that have gone on for just a bit too long & stretched the stars!

It is possible to some degree with specialized astrophoto software that includes a deconvolution function, but if you want my advice I wouldn't bother. Just keep the exposures short enougth that the stars are still pin point.

Quote: Originally Posted by PlasticSpanner

I don't really like using PS to alter a photo but prefer to get it right on film the 1st time if possible!

Normally I would agree with you 100%, but astrophotography is an exception to the rule. Post processing, often heavy post processing is the required norm.

For example because you are just using a tripod that doesn't account for the earths rotation you can only take short 10 sec exposures.

What I would do I your case is take 15-20 10 sec exposures of the same area. Then I would use software such as registar to make sure all the images were perfectly aligned. Once the images were aligned I would stack or combine them in photoshop and do the standard level adjustments. Lots of processing involved but the end result would overcome the short exposure times and produce a killer image.

[PlasticSpanner]

By Over exposed I mean they have lost their colour and just turned white!

I have a reflecting telescope but a friend has a bigger scope with a motor drive that I can piggyback on! He also has AstroArt software but I've never used it & it takes him ages to finally sit down & use it!

This exposure isn't too bad for trailing as it's quite close to the pole star polaris (North). With a 50mm lens at F 2.4 I can get 20 seconds without trailing but further away I am down to about 10-12 seconds.

I have a film in for processing today with moon shots on so I'll have to see how they come out! My last attempts were too bright & blurry!
My attempts at Jupiter and moons with a 200mm F4 lens turned out blurry too (a bit like the image when star testing a scope) This might be in the lens so I'm going to try a prime focus off my friends telescope.

[PlasticSpanner]

Is Registar any easier to use than AstroArt?

[pursuer]

Registar is very easy to use and does an extremly good job, but all it does is register images using the star fields as a reference. I have never used Astroart, I do all my processing with MaximDL, Pleiades pixInsight, and photoshop CS. pixInsight is a very good program and it was free last time I checked.

What kind of newt do you have, dob, EQ? I have a 10" skywatchwer on an EQ-6 mount, but the weather around here hasn't been cooperating at all lately

You can get some great results piggybacking, just remember not to use the maxiumum apature of the lens. Always stop down a bit as image quality of most lenses suffer a bit at extreme apatures and astrophotography is the ultimate test of any lens.

Be sure to post your astro pics! It is good to have someone else interested in astronomy around here

[PlasticSpanner]

I have a little 114mm on an Azumith mount (handy coz it's portable!) & my friend has an 8" 1000mm reflector on an EQ5. He has the scope to use & I have the cameras & lenses!

Being an electrician he is also into CCD imaging which is why he has the AstroArt software (perfect for prime focus imaging!)

Do you have ant tips to clean up and enhance a photo of Orion & the Orion Nebula? It's not avalable to photograph yet but should be in a month or so.

Where I live we can drive for about 30 mins down country lanes to get dark skies but I cant stop cars on main beam at 3am!

[pursuer]

Every image is different, but if light pollution is a big problem keep exposures short and stack multiple images. There are a lot of tutorials online for the specific processes but in general what you want to do is:

Align or register the images, level adjust so all are similar, If light pollution gradients are present flatten the background in a program like MaximDL, stack or combine the images, do a level adjustment, apply noise reduction, wavelet processing, color correction. Many books have been written on the post processing of astrophotos, there is no one solution.

here is a modest attempt I made at the orion nebula last winter, this is the result of stacking 10 or so short 30-45 sec exposures. Light pollution is a big problem where I am as well. Im showing you this just to give you an idea of what can be done by stacking short exposures. Take as long of exsposures as the tracking of the mount and light pollution allow and then stack, good luck.

[PlasticSpanner]

Thats an awsome photo! Quite magnified too! What lens was that with?

[pursuer]

That was taken with a canon 300D at prime focus with my 10" (1200mm)

Here is M42 taken with a 200mm zoom lens piggy backed on my EQ-6. Not the greatest photo, bad chromatic abberation, didn't know enougth to stop down back then. This was actually one of my first images. But it gives you an idea of the magnification a simple zoom can give you.

[PlasticSpanner]

Thats the kind of photo I want to get of it!

This is one of Polaris using the colour burn method which really does seem to be the best way!