Orion, Canis Major, and the Winter Milky Way soar over Sunset Crater

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FEB 13, 2010 - 01:00 AM MST
Canon EOS 300D + Kit Lens @ 21 mm • ISO 800 • f/4.5
Composite: 11 x 30 sec. aligned, stacked, and composited separately for sky and foreground

I said I was going to try this again. Things worked a little better this time (including remembering to check my ISO setting). I arrived early (12:30 AM :) at Cinder Hills Overlook to work on an observation and sketch of Messier 101. Orion and Sirius would be in good position over Sunset Crater between 12:30 and 1:30 AM. After getting the series of shots I wanted, I couldn't resist shooting another set to the northwest showing Orion, the Hyades, and the Pleiades all setting behind the hills and trees.

Mars, Procyon, and Sirius line up over Sunset Crater

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FEB 13, 2010 - 01:00 AM MST
Canon EOS 300D + Kit Lens @ 21 mm • ISO 800 • f/4.5
Composite: 6 x 30 sec. aligned, stacked, and composited separately for sky and foreground

I got three shots into that series before Rigel winked out behind the mountain. At that point, I noticed that Sirius, Procyon and Mars were making a brilliant alignment over the peak of the volcano. So I worked on a vertical series to capture them.

Mars, Procyon, and Sirius line up over Sunset Crater

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FEB 13, 2010 - 01:00 AM MST
Canon EOS 300D + Kit Lens @ 21 mm • ISO 800 • f/4.5
Composite: 6 x 30 sec. aligned, stacked, and composited separately for sky and foreground

Shooting 30 second tripod exposures makes random course-corrections pretty simple...perhaps too simple.

Processing one set of images is hard enough. Adding a second and third gave me a workout. It was a much needed workout too, since it forced me to refine my process. I made some improvements on the second image, and then again on the third image. By that time, I felt I had to go back and re-do the first and second again.

I've felt pretty confident handling stacking and compositing for sky and foreground. The processes I find challenging are:

1. Removing green/red blotchiness from the dark sky background
2. Removing just the right amount of noise without making the sky look plastic or crystalized
3. Reducing the appearance of vertical and horizontal bands in these short exposures.
4. Tamping down light pollution gradients with some level of finesse

Briefly, some of the solutions I arrived at:

1. To color balance the background, I create a temporary layer, blur it extremely, and read RGB values in different parts of the sky that aren't hit hard by light pollution or air glow on the horizon. I then apply a curves adjustment layer to balance the background to an average of neutral. Unfortunately, that doesn't remove the color blotches. So I add a Hue/Saturation adjustment layer to substantially reduce saturation, and then use Astronomy Tools "Select Bright Stars" to create a mask for this layer that blocks out the stars, and leaves their color intact. Unfortunately, this removes the ability to feature any photographic color in the Milky Way, but for the type of color noise I have to deal with in these 30 second exposures, I think it's a good sacrifice. I also like the way it better conveys the more neutral visual experience of the sky.
2. I use Neat Image to tackle noise. Wide field images like this tend not to have decent sized empty areas that the software can sample for average noise. As a result I have to play with the settings over and over again to get what I like. I still don't have a good system here. Just experimentation. I've saved my latest setting in hopes that I can use it again, but I have a feeling I'll still have to fiddle with it quite a bit every time.
3. The Astronomy Tools "Horizontal/Vertical Banding Noise Removal" action really does a great job removing much of the banding. However I've got some pretty huge bands in these frames, and it doesn't remove those. Wherever these hit a soft hint of Milky Way, they become impossible to remove. A new camera may eventually help this situation :)
4. A couple of the shots contained a pretty ripe light pollution tongue that tore right into the Milky Way. It doesn't seem that obnoxious visually, so I did want to tame it a bit. I found that examining the individual color channels tended to give me some options. The green channel is the cleanest representation of the sky, but the blue channel hides the light pollution the best...the blue channel also seems to do a nice job of giving star groupings and the brightest blue stars a nice glow. I can do some channel blending operations to merge the best of these two channels to create a "Luminosity" layer. By setting this layer to Luminosity mode, I can trim the light pollution, bring out the Milky Way a little more, and in an added bonus, it blunts the horizontal/vertical banding a bit more if I'm careful how I blend blue and green (the blue usually has much worse banding than green). Adding a Hue/Saturation adjustment layer that subtly reduces the intensity of the yellow in shadow and midtones (to exclude stars) helps too.

I've still got a lot of improvement to do, but with the system I've scripted out, I have high hopes it will go smoother on my next attempts.

Orion, Canis Major and the Winter Milky Way soar over Sunset Crater as seen from Cinder Hills Overlook

Cinder Hills Overlook is a cul-de-sac at the top of a small hill on the eastern edge of Sunset Crater National Monument. The site is situated amid a stunning volcanic landscape with gorgeous, dark skies after evening twilight. The entrance to the park is a mere 12 miles north of Flagstaff on Highway 89.

Because this is within the boundary of a national monument, be sure to obey any posted signs. One standing rule is that there is no camping allowed inside the monument. So, if you need some sleep after packing things up for the night, you will need to move down the road a bit. There is a forest service road just across the main road from the Cinder Hills Overlook entrance. This forest service road heads outside the monument, and there are a number of places to pull off to get some rest.

This is common sense, but it bears stating--please treat this site with respect so that others will be able to enjoy it in the future:

• Park and set up equipment in a way that does not block vehicle traffic that may need to pass
• Pack out all trash
• Do not hike off road or off trail inside the monument
• Obey posted signs
• Cooperate with park personnel

The site can accommodate several vehicles. However, if you wish to plan an observing event, please contact a ranger at the visitor center beforehand to discuss your plans.

Updated February 11, 2010.

Orion and Canis Major setting over Sunset Crater

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JAN 15, 2010 - 03:00 AM MST
Canon EOS 300D + Kit Lens @ 21 mm • ISO 200 • f/4.5
Composite: 5 x 30 sec. aligned and stacked for sky + 5 min. foreground

While observing at Sunset Crater a couple weeks ago, I was struck by the beauty of Orion and Canis Major setting over the snow-covered volcano. So I took a break at about 3 AM to take some photos. It was a spur of the moment decision, so I didn't get everything right. The photo above is a combination of 5 30-second shots aligned and stacked for the sky, and a 5 minute exposure of the foreground. I adjusted exposure on both sky and foreground to try and convey the relative brightness of both as naturally as possible. The moon wasn't out, so the snow is lit by starlight.

A couple of the things that went wrong--
I was in a hurry to get the shot before the bright stars in Canis Major's legs dipped behind the peak, so I rushed through focus, and think I could have done better there. I also goofed up and didn't check my ISO setting...which was set to 200. D'oh! If I had set to ISO 800, I think I could have pulled the Milky Way out nicely. As it is, the Milky Way barely breaks through some severe horizontal banding noise, so I had to leave it alone. It's all about signal to noise, and I didn't grab enough signal. I did have the foresight to shoot in RAW, so I had otherwise decent data to play with. I could probably do better with the processing, but astro photos are really hard to process--especially when sensor noise wants to demolish the sky with every tiny curve move. So I called it good where it's at.

I do have plans to shoot this again when I head back out there in a couple weeks to work on a sketch for the May column. There should still be plenty of snow up there to catch the starlight. Also: ISO 800...ISO 800...ISO 800...