Category Archives: Animation

Hunting Comets and other faint objects in not-dark skies

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AirGlow Comet [5_070386]

It turns out the much hyped PanSTARRS C/2011L4 Comet is not living up to the hype. Unfortunately failure to meet the over exhuberant expectations  is common since predicting brightness and visibility of an object like a comet is a difficult science. In fact, it’s part science, part black art and part good guessing – mostly the latter.

The photo above was taken on March 12 when the moon and PanSTARRS nestled closely together. The close quarters made finding the comet much easier despite the bands of clouds passing by.  The strategy for finding the comet in that case was simple: use a telephoto lens, put the moon at the right edge of the photo and take different exposures periodically and at different settings (e.g. +2, 0, and -2 stops). Then hunt for smudges.

The IDEAL telephoto lens would be one that was a few angular degrees wider than the difference between the moon’s position and the comet’s position. How to determine the position of each is discussed in the last section below. Figuring out the angular view of your lens is easy using online tools like this one from Tawbaware, makers of Image Stacker (like that program!). If you know the field of view at your minimum and maximum zoom, you can use that information to your advantage.

Finding the Comet with a Nearby Moon

The point at the moon strategy made finding the comet easy because:

  1. There is no way you’d be able to see the comet if you were not able to find the much brighter moon nearby.
  2. On that one night, the comet and the moon were within 4 degrees of one another.  That’s quite close.

I know some people tried to find the comet using wide angle lenses. That strategy might work, but the comet is such a tiny thing and it’s visibility is so tenuous based on the atmosphere, light pollution, and sky brightness that you may only realize – as many did – that you captured the comet after carefully inspecting your photos at home.

Contrails and Comet Tails [B_050938]

The truth is you are unlikely to see PanSTARRS by eye or in your camera’s view finder unless your conditions are nearly ideal.  Hopefully ISON which is coming in December will be brighter and better.

Finding the Comet when the Moon is Farther Away

The following night, both the comet and the moon had moved relative to the sky. On March 13, the moon was 12.5 degrees above the comet and about 4 degrees farther west (again, how I knew this is coming in just a minute).  So one simple strategy for finding the comet would be to zoom your telephoto lens so that it has a field of view of about 14 to 15 degrees in the long direction which for me, is 80 millimeters focal length on a 1.6 crop factor camera.

On a tripod with the camera in portrait orientation adjust the view so that the the moon is in the upper left of the frame. Shoot bracketed shots. Check the lower right corner of each one for the tell-tale comet smudge.  Keep readjusting the view so the moon remains in the upper left for each shot. Zoom out a little bit too, in case your geometry is a little off. Eventually as it gets dark enough or the sky clear enough you should find it.

In fact the way I found the comet last night without using my camera but by using my telescope. The program Clinometer (on my iPhone) measures angles. I sighted the moon with my 8″ Dobsonian telescope and measured the angle along the telescope barrel using the inclinometer program. I then lowered the altitude (elevation angle) of the telescope by 12 degrees to match the altitude of the comet. Then I slowly rotated the telescope northward until I found the comet.  It wasn’t easy from my urban location, but it wasn’t impossible either.  By the time I was able to find the comet it was only about 6 degrees high in the sky – that’s way too low if you have trees, hills, and houses nearby to deal with.  In theory, this strategy would work with a telephoto lens or with binoculars, however, binoculars need to be steady and where I spied from last night had streetlights in the distance and the flare and glare from those streetlights made finding the faint comet nigh impossible.

What if there is no Moon to Find the Comet With?

Unfortunately starting on March 14th, the moon will be quite far from the comet, so the opposite strategy is required:  Use a landmark in a known direction as the starting point and look “upward” from the horizon.  In other words, zoom your telephoto lens so that the field of view covers the angle from the horizon to the comets altitude (angle) above the horizon.  Don’t forget that as the earth spins this angle changes every minute! Orient you camera in landscape mode and point it as close as you can to the correct direction (azimuth). Look along the top of the frame to see if you’ve captured the comet.

IMG_1622.PNG

SpyGlass’s view shows the direction the camera is facing (Azimuth) and the elevation angle (Altitude)

But what direction should you point your lens or telescope? Use a compass application or actual compass. BEWARE however as the compass applications have lots of gotchas and are only accurate to about 5-10 degrees.  And if you aren’t sure how to use a real compass your local magnetic declination might bite you. Better would be a GPS with a built-in calibrate-able compass.  And perhaps even better still would be to use an application like TPE (which I discuss in my Catching the Moon Webinars) to calculate the correct azimuth from the location you plan to stand.  An application that might help a lot is “SpyGlass”
however don’t forget that I found the directional accuracy of my iPhone and iPad to be pretty poor.  Being off by 5 degrees may mean looking in the wrong place.

How Do I Know the Altitude and Azimuth for the Comet?

Stellarium_MoonMarch14

Unfortunately, that’s a tough one.  I use the free program Stellarium. I then added the comet to the “Solar System Data Base” (search around on the web and you’ll find instructions). I selected my viewing location, dialed in the time, did a search for good ‘ol C/2011 L4 and let it tell me the azimuth and altitude.

PanStarrs_March14

Above I’ve dialed up the time and clicked the moon. The highlighted line shows me the azimuth (direction) and altitude (angle above the horizon) for the moon which at that time are 264 degrees or just a little south of west, and 30.5 degrees high.  Clicking on the comet shows 272 degrees – a tiny bit north of west and 9.5 degrees.  So now we know that the comet will be 8 degrees north and 21 degrees south of the moon – and that won’t change significantly for the rest of the night.

Since we also know the direction for the comet is about due west at this time, we can apply the telephoto-lens horizon trick I described earlier.

Another way you can find the azimuth and altitude is by checking my animation HERE – note that the animation is correct for San Francisco  (and most places nearby).  There is also a table of the azimuth and elevation in the text of the Flickr post.

 

By the way, one way to find the right spot on the horizon is to use the sunset location as a guide.

CometIllustration

Foreground – o – Matic

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Published: 2011-Dec-24
Last Updated: 2018-Jun-04

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.

Last Night at Mauna Kea

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.

Overview

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.

Creating a Timelapse Animation Part 2 of 2

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Foundations

Hopefully you’ve already read Part 1 of this column where we showed how to get started with a timelapse animation: choosing exposures, frame rates, etc. Now we’ll get to the good stuff and show several techniques for animating the resulting star shots.

Simple Timelapse – Picasa Movie Maker Option

To do a simple animation using Picasa (free tool from Google) here is how you go about it. Organize all of your identically sized and processed frames into either a single folder or a Picasa Album.

Illustration 1: Picasa with a set of images captured in an Album. Would work the same if a directory were used.

Select the Album (or directory) and click the Movie option.  You’ll get a default title screen.

Illustration 2: The Movie Creation Option of Picasa

Click the “Movie” tab, and change the transition style to “Time Lapse”. Set the slider to 1/10th Sec (or shorter if you wish) and click “Create Movie”.  After a short while you might have something like this:

Now that was simple!

Getting More Advanced – Titling, Credits, and Sound

The Titling and “Slide” options of Picasa are rather limited, so I prefer to add my own titling.  Here’s how:

  1. If still in “Movie” mode select “Clips” then “Get More” which returns you to the “Library” mode.
  2. Select the slide to use for your Title – e.g. the first, last, a composite, or something altogether different. Make sure it’s the same size as your time lapse.  I usually use the first or last slide and use “File -> Save a Copy”.
  3. Load the desired slide.
  4. Use the Text Tool in Picasa to add the text you like sized, angled and colored as you please.
  5. You can animate the title by changing colors, and other effects, but don’t go overboard just yet – as this is not a very efficient way to create titles!
  6. Duplicate the title slide “File -> Save a Copy”.  For each second you want the text to appear you’ll need to have enough frames. So, for example for a 1 second appearance at 1/10th of  a second duration, you need 10 frames.
  7. NOTE: If you want to make the text appear for 5 seconds, you don’t need to make 50 frames, you can make 10 or fewer and reuse them (see step 9 below).
  8. In this example I used the first frame, added my text and saved it 6 times (File -> Save a Copy).
  9. I selected the 6 identical title frames, and clicked “Back to Movie Maker” at the bottom.
  10. I made sure the movie was at the beginning by dragging the slider beneath the window all the way to the left.
  11. Next I drag my “clips” onto the beginning of the movie.
  12. If I need more title frames, I select “Get More”, reselect the same slides and repeat step 11 until happy.
  13. Credits/closing titling can be done the same way as the titles.

After adding credits, and a “The End” (animated in color!) final slide set my movie now looks like this:

Oh, and I added music too. Any MP3 file should work. Just use the “Audio Track” option to load it.  If you want to start the music at a particular point and do fade in, fade out, or cross fade different audio tracks Picasa is not the tool for you.

NOTE: When you add an audio track, be careful that you also have the “Truncate Audio” selected or Picasa will want to extend your movie for the length of the song. You might also need to change the slide duration to your desired speed. Picasa Movie Maker has a bug where it sometimes resets the speed to 24 frames a second (as it did above – did you notice how much faster the newer version was?!)

Getting Even Fancier

What if you want to do something really cool like have the star trails “grow” (or shrink)? Well we’ve got you covered there, too!  Hopefully you’re already familiar with the StarCircleAcademy Stacking Action – if not, give this a read.  We don’t tell you in that blog article, but there is an option available in the Stacking Action (Version 5) to “Stack in LIGHTEN mode creating intermediates“. What that does is super cool. Each time it adds a new frame to the stack, it saves the current results with a unique file name. The final frame is the same as the “Load and Stack in LIGHTEN mode” but every frame along the way is squirreled away where you specify. You can then animate those just as described above. Here is a simple example:

A more interesting example shows what happens when I start the animation near the middle. I then stack ten frames at a time (using Image Stacker) and animate them. I then stack the stacks of 10 into stacks of 50 (which makes it look like it’s moving faster) and finally I then repeat all the frames from beginning to end. It LOOKS like the movie is getting brighter but what is really happening is you are seeing the moon rise!

For another similar example, take a look at this. Be patient though as the good part is toward the end.

If you have only a few frames, you can use other modes to create your timelapse, for example this one uses “cut” mode with photos every 1 second.

If you want to go even farther, there are still more free tools that you can use, like Windows Live Movie.  With Windows Live Movie you can do more advanced titling, have music that fades in and out (only one track at a time, however), and more.

Here is an example using Window Live Movie together with YouTube’s annotation options:

Action! Creating a Timelapse Animation (Part 1 of 2)

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One of the nice little benefits of using the stacking technique to create star trails is  that you can take those many frames and animate them.  My first foray into animation looked like this:

“Star Races” was created using the stacking features of StarTrails.exe (Windows program) and composed into a movie using the “Animation Feature” of that same tool. The vertical format works well with the portrait mode images. This video contains no music or titling as those are not supported by StarTrails.exe.  I will cover the technique to create this in Part 2.

A more elaborate effort with music, stacking and credits is this one created from 8 hours worth of images using the tool Picasa which is free and available for windows and mac:

Not all time-lapses need be created from night images, however. An early example of a daylight animation chronicles my son scaling a rock in Zion. I later did a similar animation using a tripod. The method used to create the animation will depend on the number of frames available and the intent. Let me start at the beginning however.

Shooting Time Lapses

A time lapse requires “frames” – individual pictures used to create the end result.  Usually pictures used to create a time-lapse will be at relatively low resolution (1920 x 1080 or smaller) so shooting them in large format, RAW means extra work will be required to assemble them.  On the other hand, my time-lapse are byproducts of my star trail shots and I always shoot those in maximum sized RAW mode.  An important consideration is the frame rate – that is the number of images shown per second. A movie typically consists of 30 frames per second, so to shoot 5 minutes of video one needs 30 frames per second for 60 seconds x 5 minutes. 30 x 60 x 5 = 9,000 images. Yes, that is a LOT!  However often a frame rate of 10-per-second is acceptable, so only 3,000 images are needed – still quite a lot.  Perhaps we shall start a little less ambitiously and collect 300 frames – enough for a 30 second animation at 10 frames per second. Assuming we are shooting these at night with 2 minutes each exposure it will take 600 minutes (a mere ten hours!). If that still seems like too much work, we can settle on shooting 1 minute exposures and have the shooting done in a 5 hours.  Clearly patience is required. Unfortunately when shooting the night sky it is unrealistic to expect exposures to take less than about 10 seconds even at high ISO.

The software used to assemble the video may also impose limitations. For example in Picasa’s time-lapse mode the minimum frame rate is 6 per second and the maximum is 24. In “Dissolve” or “Cut” mode, the minimum is 1 per second.  The Zion climbing shot is done in Dissolve mode.

Animation Software

Lots of tools exist for this. I’ve already mentioned Startrails.exe and Picasa (Mac or PC), but there is also Windows Live Movie Maker. Each of these tools is free!  Windows Live Movie Maker is the most versatile free tool I have tried with titling and transition options.

Non-free tools for the PC include Adobe Photoshop, Adobe Lightroom, Adobe Premiere. For the Mac there are iLife (iMovie), Final Cut Pro, and many others.

Music, Copyrights and Credits

While a simple time-lapse may be interesting adding music makes it more so. The free tools support music in some (small) fashion but sometimes just barely. Picasa for example will let you select an MP3 song. Unfortunately when creating a time-lapse it will not let you select where to start in the song and does not fade in or fade out – and only one track is allowed.  If you really feel ambitious you can use iTunes to create a segment of a song to include.   Search Google for “creating ringtones in iTunes” (which will help you figure out how to create a snippet), and “export iTunes as mp3”. Creating a snippet using iTunes is not particularly easy, fast or convenient, but it is free – and as a bonus you will discover that you have been wasting money paying for ringtones!

Copyrights and credits can be done in several ways. Live Movie Maker is actually pretty easy to use and allows different text effects. In Picasa you can use captioning (which is only modestly useful for a time-lapse) or text overlays using the Text Tool. The Text Tool is the most versatile but unfortunately in Picasa you can not say “repeat this frame for 5 seconds”, you have to make 5 seconds worth of frames from one image, or keep adding the one image into the movie. If your frame rate is 20 frames per second, you will have to make, gulp, 100 frames for that 5 seconds of copyright or credit!

Creating the Animation

In the next installments, we will show how to use Picasa from beginning to create a time-lapse with music, titles, and credits.

The first 180 images used in the time-lapse are these:

180 of the 675 frames used for the animation

While the title and credit frames looked like this

Title and Credit Frames