Pleiades Stretched

[Nighthound]

I went back in to see if I could squeak out a little more nebulosity from my original in Photoshop. Image taken with Takahashi Sky 90 II / Losmandy G-11 Mount / Canon 20D

Original:
http://i3.photobucket.com/albums/y67/Nighthd/PS%20Gallery/m4507bcc.jpg

Stretch using Curves in PS:
http://i3.photobucket.com/albums/y67/Nighthd/PS%20Gallery/m4508strtch-1.jpg

[Jim G]

Awesome! Very subtle work with the curves..

[Johnny9s]

Great shot Steve. You really work some magic with your post processing.

[Adrena1in]

You know what I need...I need someone like you to put a video camera on your shoulder, and record what you do to an image when you're processing it. "Stretching" and "clipping" and all that half-makes sense to me, but I really need to *see* it done so that I know what it's all about.

Great shot though, whenever I pick up my binos and look at the Pleiades I always see your photo of them in my mind, as it was the first I ever saw of the lovely nebulosity around the sisters. :)

[Jeff]

I'll vote for "Nighthound's YouTube Videos" too. :) Nice images as always!

[Nighthound]

Thanks everyone.

I've always said that post processing is half the job. Of course it took years to get my gear to perform decently so now I'm able to focus more on processing and not trouble shooting the mount, etc.

I use curves more than any other adjustment on a stacked deep-sky image(TIF). The first thing to do when processing is to be sure you've got your color profile for the image set to Adobe RGB 1998. This is a much wider color gamut than sRGB. You can save a jpeg - sized image for posting online in sRGB from your master.

I keep my histogram and channels on my desktop and monitor them along the way. Stretching is a finesse thing and it's best done slowly and methodically. Just like everything else in this hobby, no shortcuts. A heavy hand may appear to be moving the image along in the right direction but for me it almost always ended with either excessive noise, clipping of the black point(histogram dark point slammed all the way left), or star bloating. Of course to avoid these pitfalls you need an understanding of how curves work. The diagonal line on screen slashes through the value range of the image. At one end the highlights and at the other the darks. Everything in between value-wise can be adjusted from that line. By placing points for adjustment and anchor points on this line you can adjust the value area you want and use the anchor points to protect the value area you don't want those adjustments to have an effect on. For example to avoid "star bloat"(brightest stars becoming excessively large while stretching) you'll want to anchor the high end(highlights) while stretching the mid tones. Again, anchors protect so this same method is applicable to the black point or low end of the value scale to avoid clipping the black point. I know some of you are getting tired of me saying that but when you clip your black point you're tossing out subtleties(precious photons) that you worked hard to gather. Curves requires practice to grasp and can be a bit frustrating. It also isn't a cure all and will be most effective when you have enough data to work with. If your exposures are very short, say 30 seconds and you stack 100 of them you will technically have 5 minutes of exposure time which is great. Stacking is a terrific process but it can only raise the signal that is in the image and a 30 second exposure doesn't contain all of the detail/data you're attempting to coax out that you've admired in very long exposure shots posted online. In other words, stacking raises the existing signal and lowers noise, but the more signal contained the easier and less frustrating stretching in curves will be. As I like to say, you can't make chicken soup from chicken poop. :D

If you don't have Noel Carboni's Astro Tools (PS actions) I would suggest you take a look. They are extremely effective and a valuable tool in my processing.

Hope this helps in some way. If you have questions while processing I'll do my best to assist, just ask.

[disc_lover]

awesome shots!

[andrikos]

wow, awesome!

[Nighthound]

Thanks disc_lover and andrikos. Greatly appreciated.

[Dusty]

Absolutely gorgeous, well done Steve !
I just love this patch of the sky.

[Nighthound]

Thanks Dusty. I agree, like diamonds on black velvet.

[Celestron]

Good job on stretching Steve ! I can see the difference .

[dpastern]

Steve - wonderful stretching in #2. Super details!

Dave

[Nighthound]

Wow Dave, you had to dig deep for this one. :D

Thanks man, I hope I get out and get some fresh data soon. Clouds, clouds, clouds...

[dpastern]

Clouds, clouds and more clouds...I had some clear skies tonight but I'm having more and more problems with my scope setup which is really just frustrating the hell out of me. If my problems continue I'll just end up selling the gear to be honest. I've spent more time screwing around with the new gear than observing/imaging :( Now I can't even focus with the damn focuser with the camera on, and even with it off, it's not focusing properly, silly thing keeps slipping when focusing in. grrr...

Dave

[MidnightSun]

Great shot and brief tutorial...:cool:Lots of clouds here lately also, lots of time to work on the processing....

[Nighthound]

Thanks Dave and Dave. Hope skies clear for you soon, I've been suffering the same problem for months.

DP(Dave), Sorry to hear your gear is frustrating you. I can completely relate. Check the adjustment(tension) screws near the focus knob shaft on the underside. Sometimes these get loose and cause slippage. With the added weight of the camera the slippage will be even greater, literally making the focuser spin in place. While in there it would be a good idea to check the lubricant and see if it's sufficient or possible loaded with metal fragments from being loose for some time. Let me know what you find. Not knowing your gear there may be a different mechanism for tension, not sure.

[markjpcs]

Excellent work Steve!

[rgfrison]

Steve, all your shots are simply amazing.

[dpastern]

Thanks Dave and Dave. Hope skies clear for you soon, I've been suffering the same problem for months.

DP(Dave), Sorry to hear your gear is frustrating you. I can completely relate. Check the adjustment(tension) screws near the focus knob shaft on the underside. Sometimes these get loose and cause slippage. With the added weight of the camera the slippage will be even greater, literally making the focuser spin in place. While in there it would be a good idea to check the lubricant and see if it's sufficient or possible loaded with metal fragments from being loose for some time. Let me know what you find. Not knowing your gear there may be a different mechanism for tension, not sure.

Thanks Steve, I'm a bit afraid to pull things apart to be honest. I'd be OK if I had a schematic, or someone to who knew the gear showing me the first time, but I *hate* pulling things apart blindly. Especially expensive things that are still covered by warranty.

I'll google a bit on this and see if it's a common problem. I've heard good things about the Equinox focusers though.

Dave

[Nighthound]

Thanks Mark and rgfrison.

Dave, maybe an email to tech support or the like will get you more info and possible a replacement focuser. It's such a critical part of the scope, no much can be done with a scope that won't focus. If it's under warranty, put that into play. You're only asking for your money's worth. Good luck and let me know what you find out.

[MacDogg]

Is processing like this 'adding' data to the picture or is it 'finding' more data in the picture? I hope my question makes sense.

[Nighthound]

Makes perfect sense. Adding data would yield the best results. Doing so would increase signal, reduce noise and ultimately enhance detail, depth, etc.

But in this case I was using Photoshop curves to pull out as much information from the existing file(multiples stacked > saved as tif) as I could. Often when I go back and look at an image with fresh eyes and some spare time I'll attempt to coax out more detail. It's a bit of a balancing act since over doing it can produce quite a bit of noise and you risk degrading one value range to gain in another. But when done carefully some additional details can be had.

I hope my answer makes sense. :D

[toysport_photo]

wow... so mystical. great shots!

[MacDogg]

Makes perfect sense. Adding data would yield the best results. Doing so would increase signal, reduce noise and ultimately enhance detail, depth, etc.

But in this case I was using Photoshop curves to pull out as much information from the existing file(multiples stacked > saved as tif) as I could. Often when I go back and look at an image with fresh eyes and some spare time I'll attempt to coax out more detail. It's a bit of a balancing act since over doing it can produce quite a bit of noise and you risk degrading one value range to gain in another. But when done carefully some additional details can be had.

I hope my answer makes sense. :D

Sure does. Thanks for the info!

[Nighthound]

wow... so mystical. great shots!

Thanks very much.