First Light with New Camera Lens - Heart of the Milky Way

Discussion in 'Nature & Wildlife' started by astrostu, Jul 1, 2008.

  1. astrostu

    astrostu Guest

    My 70-200mm f/2.8L IS lens arrived yesterday. These photos aren't quite first light, but they're the first real attempt to photograph something of consequence with the lens. These were really just to test the lens, and I'd say it was quite a success. Now I need another clear night and a few hours to actually do it well and right.

    These two photos are 25% size. The first one is centered around M8 (the Lagoon Nebula), while the second is centered a little higher up, around M17 (the Omega or Swan Nebula). They were taken at f/3.2 instead of f/2.8 to make 'em slightly sharper.

    The apparent fog or clouds throughout both frames (though much more in the second) are hundreds of thousands of stars towards the center of our galaxy. I can attach a version with labels if folks want.

    [​IMG]

    [​IMG]
     
  2. Bifurcator

    Bifurcator TPF Noob!

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    You did a pretty good job processing. With a little more you can get the clouds looking very 3D-ish and bring out more colors in the nebula. Anyway, I really like astrophotography! Thanks for posting these!
     
  3. flygning

    flygning TPF Noob!

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    I think they're gorgeous. This is what I'd like to do...someday :)

    I don't think they need any more processing at all-- there comes a point where you're misrepresenting what you see out there.
     
  4. osirus

    osirus TPF Noob!

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    nice :)

    how long were the exposures?
     
  5. icassell

    icassell TPF Noob!

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    These are gorgeous. Would you mind sharing technique a bit? Was this lens-only or through a telescope? Exposure information? Filters? Was your camera mounted on a clock drive?

    I've only tried the moon and this looks like fun.
     
    Last edited: Jul 2, 2008
  6. Tyjax

    Tyjax TPF Noob!

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    "...and somewhere you are, and insignificant dot, on an insignificant dot somewhere in the forgotten backwaters of a small spiral galaxy." -THGTTG

    Anymore the word 'awesome' is misused, misaligned and maltreated. In this particular instance awe inspiring and the trickle of fear and trepidation it brings, adequately describes the emotions evoked by this view of the heavens.



    Awesome.
     
  7. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    Really nice work there and great early work with the new lens!

    Hope to see much more in the future!
     
  8. astrostu

    astrostu Guest

    I've been wanting to take these kinds of photos for a few years. Now I can. :)

    Agreed. I go for realism.


    A total of 6 minutes for the first one and 13.5 minutes for the second.


    The equipment was just the lens, a remote, the camera, and a mount that tracked the sky. This is actually why I really like this kind of astrophotography - it shows what's really visible without the use of giant lenses or mirrors.

    To focus, I used the f/2.8 aperture and took photos of Jupiter and its 4 main moons. Focusing was done manually, just rotating the focus ring slightly until I got what was the best focus. I did this for both the 200mm shot (the top one) and the 120mm shot (the bottom one) because the focus point does move slightly on zoom lenses depending upon your focal length.

    I took 3 photos at each location, the top one being 120 sec each, the bottom 270 sec each (I also did 120, but didn't process those). When I do this again, I'll probably do both 120 sec and 300 sec and do an effective HDR because the brightest stars saturate and lose their color at the longer exposures. I used f/3.2 instead of 2.8 to help make 'em a little bit sharper, but I didn't want to stop it down any more because then I'd loose the point of having such a large aperture.

    The steps and processing were as follows, though keep in mind they are not technically the correct way to process astrophotos, but I did this more as a proof of concept with my new lens:

    Opened them in Photoshop and adjusted the temperature and tint to bring the sky to a neutral gray color. This is technically not necessary due to later steps, but I did it anyway. Same with the step here where I brought up the Black slider until there was a part of the histogram that was at the far left. They were then opened as 16-bit images.

    I copied two of the images into separate layers in the third image, and then I made them into a Smart Object (new in CS3) and set the stack mode to Median.

    I then selected each color channel of the stack (R, G, and B) and copied them into separate layers. I set the layer blending mode of the G and B to Screen. I attached, to each layer, a Gradient adjustment layer that went from black to red, green, or blue depending upon which layer it was attached to. This effectively re-colorized the image.

    Then I attached Levels adjustment layers to each layer and set the % clips at 0.05% and 0.01%. This helped to equalize the intensity of each color, hence why adjusting the temperature and tint in RAW wasn't really necessary.

    I then put on a Curves layer that was not attached to any of the ones below it. I brought up the low end of the curves to bring out the Galaxy. This is usually one of the worst things you can do with astrophotos because it brings out the noise, but in these particular images, the galaxy dominated the lower intensities so it was reasonably okay, though it did increase the noise somewhat.

    I then effectively added a color glow. I hid the Curves and flattened the other layers. I copied them and then undid the flattening. I pasted the image into a top layer. I then added a Gaussian Blur of around 15 px to it. I then adjusted the Levels and Curves of it to just bring out a faint colored glow around the brightest objects (the nebulae, bright stars and brightest parts of the Galaxy). Finally I made that layer's blending mode Screen.

    And that's about it for these. Now, if I'd done it "right," I should have also flat-fielded it and dark-subtracted (removing camera sensor noise and optical artifacts). But I didn't because I was just interested in getting a proof of concept at the moment. I hope to do better and get more in on Friday when it's supposed to be nice 'n' clear.

    I also would've (but forgot to bring) taken some shots with a 4-pt cross-screen filter, processed those the same way, and then added them onto the images to get the diffraction spikes, which help to bring out the colors of the stars more.
     
    Last edited by a moderator: Jul 2, 2008
  9. icassell

    icassell TPF Noob!

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    That is sooooo cool. I'm definitely going to have to try this with my 100-300. How hard is it to rig up a tracking mount?
     
  10. astrostu

    astrostu Guest

    Do you have one or have you ever used one? I ask that for the reason that I think if you have, you probably wouldn't be asking that question. As such, I'll address it as if you don't have one.

    It all depends on the mount. I have one available to me that has to be mounted on a pole that is at a right angle to the celestial north pole. It's simple to set up, assuming you have the pole, as there's a hole in the bottom that a lens or camera can screw into with a standard screw. This was actually an old telescope mount where the telescope broke and so was retrofitted for this purpose. A problem is that it's not very good nor designed for a heavy lens. It'll work for a few minutes with a light lens at a "normal" focal length, but not more than 20 seconds with a 1000mm focal length.

    I have another one that the head of the observatory and I worked on last Spring that is physically attached to the 18" telescope. That one works where I have a "saddle" I screw onto my camera or lens and then the saddle slides onto the plate on the 18" and I secure it on that.

    Standard ones that someone may buy would probably be a simple telescope mount. A problem there is actually just rigging a camera up instead of the telescope, since they're simply made for telescopes.

    More expensive ones (like this) have special saddle plates designed to work like a regular tripod mount.


    So yes, it's fairly easy to rig up a tracking mount with a camera. Hence why I kinda assume that you don't have one nor have you used one. The problem is actually obtaining a good one.
     
  11. The Empress

    The Empress TPF Noob!

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    Beautiful!!!! I love the stars! lol
     
  12. icassell

    icassell TPF Noob!

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    I guess my question was poorly worded ... sorry. No I don't have a mount. I was just wondering if a mount was something one could build or if you had to go and shell out alot of $$ for one. Maybe I should just cruise by the local telescope store and look at them.
     

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