Tag Archives: selection

Adding Special Touches to Your Astro Landscape

1000 ISO, f/2, 3 minute exposure with some augmented stars

Because stars are pinpoints of light, the camera does not capture them as our eyes see them. To our eyes, brighter stars stand out more noticeably than dimmer ones. At a workshop in Alabama Hills, one of the participants, Julian Köpke, was using a diffusion filter so the stars captured would look more like you see with the naked eye. Sometimes nature provides its own diffusion filter in the form of high, thin cirrus clouds as shown below. The large bright orb is the star Sirius in the constellation Canus Major (Big Dog). The orange star near the top of the frame is Betelgeuse in the constellation Orion. One nice thing about the blur that the clouds added is the star color is more noticeable. But the diffusion here is not uniform because the belt stars (Alnitak, Alnilam and Mintaka) and “corner” stars (Bellatrix, Rigel, Saiph) in Orion are all noticeably brighter than the surrounding stars while in this photo only Betelgeuse and Rigel stand out.

Dog Star [C_065586]

You can create a make-shift diffusion filter by shooting through a nylon stocking – or buy a diffusion filter. The disadvantages of using a filter are that everything is blurred – including the foreground and you reduce the amount of light collected. Most night sky photographers try to avoid clouds and you will get an image like this:

The moon and Teapot Asterism in Sagittarius – over Lone Pine Peak – as shot.

When what you had in mind is something like this:

Same Photo as above, but with the Teapot Asterism in Sagittarius enhanced.

How to Bring Out Star Color And Enhance The Apparent Star Size

Our Advanced Stacker Plus has two built-in ways to increase star brightness. We call those Bump Up and Pump Up the stars. Bump Up creates a small blur by literally duplicating the shot , nudging the duplicate(s) and recombining .  Pump Up is more sophisticated and tries to find the stars so it can then apply enhancements to just the stars. But there is a new tool in the arsenal that I have begun using: Star Spikes Pro from ProDigital Software.  Version 4 is the latest as of this writing.

NOTE: Star Spikes Pro and HLVG described later are currently only available on Windows machines.

You can use the Star Spikes Pro plugin to add diffraction spikes and diffusion. The most common diffraction spikes you see with stars are due to obstructions in the telescope used to photograph them and many people come to think of the spikes as evidence of astrophotography.  You can create diffraction spikes easily on your own.- just stop down your aperture;  however stopping down to make stars create those spikes will not work well.

The first time I tried to use Star Spikes Pro it did not quite work as I expected.

Look hard. Star Spikes Pro decided the moon was a huge star outclassing all others.

Indeed it took me a bit to realize what was going on. The good news is it was easy to work around. The huge moon looks like a huge star to Star Spikes Pro – and that makes perfect sense since the plugin is usually used with Astrophotography that does not involve landscapes.

Here is how I made it work as I wanted and limited the effect to just the desired stars.

Layer Palette and Steps to Enhance The Teapot Asterism

Above left is the layer palette. Look carefully and you may spot the fix. After loading the image (1) I first duplicated the original and called the new layer Heal (2). I then did minor contrast adjustments, used the healing brush to remove hot pixels and other offenses (short satellite trail). Next I duplicated the Heal to another layer (3) and fed it into Hasta La Vista Green – a free plugin written by Rogelio Bernal Andreo of DeepSkyColors. HLVG removes green which is an unnatural sky color usually caused by RGB artifacts. HLVG operates on the entire layer and does not know the difference between land and sky. To leave the natural green in my landscape I used the quick selection tool, dragged it across the sky followed by Select -> Modify -> Expand 4 pixels. Then I created a Layer Mask using “Reveal Selection” (4). That made the foreground come back to its normal state. If you look carefully you will notice I also used a white brush to add some of that green removal back onto the mountain by painting on the HLVG layer mask (4).

The next operation was a finger twisting sequence that has no menu equivalent: Ctrl-Alt-Shift-E (on Mac that’s Command-Option-Shift-E). What that sequence does is “flatten” all the visible layers and create a NEW layer in the process (5). That layer I called Input to SSP.  Since I had discovered that Star Spikes Pro was confused by the moon (and could be confused by the foreground), I used the quick selection tool again and brushed it across the foreground. By default using the quick select tool again ADDs to the current selection so I brushed it around inside the moon and its halo. At this point I did not need to create another layer (Ctrl-J/Command-J or Duplicate Layer) but I did so that it was easy to see what happens next. After creating the new layer I selected it and used the delete key. Delete removes the selection making it transparent – that is the foreground and moon were now gone (6).

Next up: let Star Spikes Pro loose on the image. First deselect (Ctrl-D Command-D) or Select -> Deselect), and feed the sky layer to Star Spikes Pro via Filter -> ProDigital Software -> Star Spikes Pro.  The defaults for SSP produced the image below (I’ve zoomed in on the teapot asterism)

I felt the color was a bit too strong, and I did not want the diffraction spikes. The next step was to select “Advanced” – just below Settings, set the Primary quantity to zero. Next was the Secondary tab where I reduced the quantity to 44, the intensity I bumped up to 23. Soft flare I set quantity to 12, bumped up the intensity, dialed down the size a little and dialed down the Hue to -21. These adjustments were all based on eyeballing the image and were made for aesthetic appeal.  After all the adjustments looked about right, I saved the settings as a new adjustment I called “DiffusionOnly”. Finally I clicked OK and my layer was all nicely done by the SSP filter.

The filter processed a few more stars than I intended to augment. The simple solution was to create a “Reveal All Layer Mask”, select a brush, the color black and paint out all the effects I did not want on the layer mask (7).

The final operation was to use an Adjustment Layer (8) to increase the contrast and restrict that adjustment to the sky (where you see white) and tone the adjustment down a little with a low-flow back brush on one area that looked a little too dark.

The topmost layer in the layer palette is my watermark.

There Is An Easier Way!

With some experimentation, and some coaching from the plugin author I discovered that Star Spikes Pro has several features that make the process easier than I imagined. Instead of creating the transparency (deleting the moon and landscape) I only needed to select the area I wanted Star Spikes Pro to operate on.

Also, instead of masking off the stars I did not want affected after the fact, Star Spikes Pro has two tools to greatly simplify things the: “Hide” tool to turn off any effect that I did not want, and the “Show” tool to turn the effect on.


Star Spikes Pro limited to specific section of the sky via a selection and using the Hide tool to turn off an effect.


The net is that you can get that nice diffusion effect for your stars without having to compromise by shooting through a diffusion filter. However if you DO want to try a diffusion filter, I recommend you take two shots quickly. One with the filter off, one with the filter on. You can then place the diffused shot over the normal shot. Set the diffused shot to Lighten and mask in (or out) the areas where you want the diffusion to show through.

If you’re wondering whether there is a way to get the diffusion effect on a Mac or without purchasing Star Spikes Pro, there is, but it requires a lot of Photoshop twiddling and it is not anywhere near as pleasant as using ProDigital Software’s Star Spikes Pro.

Disclaimer and Book

I am not affiliated with ProDigital Sofware. I am a happy customer of Star Spikes Pro (and another product called Astronomy Tools). I was not paid, or encouraged to write about the product. I chose to because it is that good. Rogelio Bernal Andreo  author of Hasta La Vista Green and purveyor of DeepSkyColors is a friend and a multi-multi award-winning astrophotographer. He has a Kickstarter Project that I recommend you look into called Notes From the Stars

Notes from The Stars: 10 Award Winning Authors

Foreground – o – Matic

One of the lovely things about stacking star trails (or stacking in general, for that matter), is you are presented with many opportunities for a choice of foreground. Did someone walk through your shot wearing a flashing nametag? No problem. Did a passing car blow out that wonderful rock in your foreground… no worries.  Did you play around with different lighting and find none of them quite met your desires. No cares.

Invariably at workshops and shooting events something will go wrong with hours long shots. But with a plethora of shots to select a foreground from the odds are greatly improved that you can get what you wanted even if it means working around problems created by uncontrollable elements.

Consider my effort atop Mauna Kea.  All the shots are here in this video.

But as you may have noticed, the radio dish was moving nearly constantly and is thus blurred in many shots.  When I stacked all the images together in the normal fashion, this is the result:

Unless you’re into that Dali-esque melting radio telescope vibe you may not want that result.  Or perhaps some dunderhead walked through the scene with a flashlight making a wicked blow out – or any number of possible complications. What to do?

Answer: Find the image or images with a more desirable foreground and fix it!  Fortunately I have LOTS of frames from my 7 hour-long star trail. When I created the image originally I chose this foreground:

Resulting in this image which was selected for the shortlist of the Astronomy Photographer of the Year, 2011.

Listening to the Sky [B_025555-714]

But, in putting together this article I noticed a foreground I think will work even better. This one:

The result will be the radio dish “staring” into the center of the star circle. So lets replace the Dali-Esque portion of the original stack with the foreground above.


Here are the steps we’re going to take – you can download the images using the links below and try for yourself if you wish – of course you may not post your derivative work or claim it as your own.

  1. Start Photoshop
  2. Load the foreground and background (stacked) image.
  3. Plop the foreground image onto the stacked image.
  4. Set the foreground opacity to 40% to see what you are working with
  5. Use the quick select tool to capture the foreground elements you wish to remain.
  6. Use “Layer -> Layer Mask -> Reveal Selection”
  7. Adjust the foreground opacity to 100%
  8. Flatten and save!

Step By Step

Easiest for me is to drag and drop my images into Photoshop. Choose your own method if you’d rather but beware that depending on your approach, Photoshop may decide to do your layers as “smart objects” which creates more constraints and steps.

Note that you might decide to load more than one foreground so you can mix and match to choose what result you like best!

Once you’ve got your two (or more) images loaded select the foreground image, then Ctl-A (Select All), Ctl-C (Copy) then select the background image and do Ctl-V (Paste). If you have more than one foreground, repeat the process of overlaying the foregrounds onto the background stack.

When done this way with equally sized images, the layers will be exactly over one another. You can accomplish the same layering goal by using the “move tool” and the process described by Harold Davis as “Plopping”. Or if you were really on the ball, you could  load the images into Photoshop as Layers. For me that method “Files -> Scripts -> Load Files into Stack -> File / Folder Selection tool” is unnecessarily complicated and forces me to use the more impoverished Photoshop file selection tool. Plus I can almost never remember to look under “File -> Scripts” (I always expect it under “File -> Open” or File -> Automate. Even File -> Import would make more sense!)


Though it is not necessary here, it is usually a good practice to convert your background to a layer, and name your layers to keep them straight.

We will also adjust the opacity of the foreground to around 45% by selecting it in the Layer tool (Window -> Layer)





After adjusting the opacity, we can see clearly how the layers align and make a determination about which parts of which photos we want in the final image.

A quick look indicates that we can replace everything below the mountains with our foreground making the task trivially simple.  We will use the quick selection tool (look under “Magic Wand” if you don’t see it). Select the foreground, then click the selection tool somewhere at the edge and below the sky. Drag across the frame to the other edge and if you’re lucky, the selection will be like this:

The next step is to turn the selection into a mask so that the sky remains intact and the foreground is replaced by our selection.  Layer -> Layer Mask -> Reveal Selection does the trick.

After completing the Reveal Selection we adjust the foreground to 100%

For fun and excitement we can clean up the final concoction using various adjustments. Here I’ve used Curves and Hue/Saturation adjustments to reduce the green cast and crisp the image up just a bit.

Final image with replaced foreground

Now we flatten and save and post and brag!

What if Quick Select Doesn’t Work?

If your selection area is more complicated there are other alternatives.

One alternative is to use a gradient mask. But that may not work either such as when a tree reaches up into the sky with lots of tiny branches. Another approach is to do hand masking/layering. The following provides a rough idea of both how to approach the hand masking problem and how much more difficult the process can become.

Here I used a “Hide All” mask on the foreground. Next I painted in white on the foreground mask (notice that the mask is selected in the layer window). Wherever I paint white in the mask allows the foreground to “replace” the background. In this case it’s messy because the foreground is clearly darker than the background.  However this technique can work very well for small improvements. For example did you notice that there is a red streak of car tail lights in the middle mountain above?  It would be simple to replace that small area with one (or more) frames from the rest of the stack using this hand masking technique.

If you want to get the full scale, nitty gritty detailed write up of this hand blending technique, I heartily suggest you purchase Harold Davis‘s “The Photoshop Darkroom” book. It will be money well spent!

Or, join us on our next workshop or webinar.