Tag Archives: angles

The Ideal Handheld App For Catching the Sun, Moon and Stars

Here at StarCircleAcademy we’ve been consuming and testing quite a number of photography related apps. So far none have risen to the promise that a handheld app could bring to the table.  Rather than illuminate what is missing from each app, here I describe what I want to DO with my handheld App.

In the Evening [5_057775+92]

  1. First, I need an app with accuracy to within 0.2 degrees! Why? Because the moon and sun are only 0.5 degrees in angular diameter. If I want to catch the moon exactly behind the Pigeon Point Lighthouse less accuracy will result in a “miss”.
    Monumental [C_038216]
  2. I want the app to accurately measure and save all the relevant data so I can reuse it and share it.  At minimum it needs to keep track of: From location, to location, altitude at the to location (degrees above horizontal), and any additional constraints like the fractional number of degrees that each measurement can vary. In some locations like the shore of a lake there is more leeway to move. In other spots, like the balcony of a building there is little leeway to move.  An ideal app would allow me to stand in two or more different spots to define that leeway.Rise and Shine [C_037951+77]If I’m solving for the moon, I’d like it to also remember the moon phase I’m interested in (usually full or slender crescent). The ability to take notes including things like height of the landmark is a big plus.
  3. Ideally I can save an image representing what I want with ALL data on the image so that if all I have is a photo, I can reconstruct the parameters in other tools or other ways.
    For example, SpyGlass shows me my GPS coordinates, the elevation, altitude and azimuth (compass direction) – though as you can see it’s calculation on where to find the moon is off by about 15 degrees (30 moon diameters) due to iPhone 4 compass inaccuracy.

    SpyGlass copy

    SpyGlass snap. Note that the plotted location of the moon is off due to iPhone compass hardware.

  4. I’d like to be able to pull up my saved locations and re-execute a search to find the next occurrence. For example, a Pigeon Point Lighthouse vista that I really like only occurs a few times a year. It’s not enough to keep track of the one event I photographed or plan to photograph.
    Project Impact [5_057573-615br]
  5. Bonus points if the data is stored in a server somewhere to make it easy to share. Extra bonus points if there is a way to have the server periodically check possible alignments and send me alerts or emails when such alignments are soon to become possible.
  6. For planning shots with the Milky Way or other prominent sky features (like the Andromeda Galaxy and the Great Orion Nebula), the app needs to accurately plot the course of those objects on an Augmented Reality frame. Images of the Milky Way presented must be realistic.  A poorly illustrated Milky Way won’t help me find the galactic center (which is what I most often want) or compare the alignment I want with the foreground I am trying to capture.
    Inflow [C_072091]
  7. For night related photography, the app must also factor in twilight and moonlight. That is, I want to be able point my device at say the Transamerica building and ask the app when (or if) the Andromeda Galaxy will appear above it when there is little or no moonlight.
  8. Make it easy to use, of course.  Most of the apps that embed maps in them are difficult to use on the tiny real estate of an iPhone – and require data connections as well.

Is it unrealistic to think a handheld app could meet these requirements?  I don’t think so. The biggest problem is overcoming the accuracy limitations in the current devices. The iPhone and iPad, for example have quite inaccurate compass readings except in perfect scenarios… but there are some clever ways (I think) to correct for that inaccuracy.  The tilt angle calculations from the on-board accelerometers and gyroscopes seem to be pretty accurate.

What We’ve Tried

  • Inclinometer. Great for measuring angles above the horizon. Even has a voice mode where it says aloud the measurement. Doesn’t do Now includes augmented reality mode so you don’t have to sight along an edge of the device. On an iPad, it seemed to be accurate to about 0.2 degrees!
  • GoSkyMap. Fun interactive sky map. You can change the date / and time and point it “at space” and it will show you great details about what is there. BUT you have to make sure you set the location correctly. Doesn’t have an Augmented Reality mode so you can’t tell how the mountain in the foreground interacts with the Milky Way, for example, but you can ask it where to find constellations and it will indicate which direction you should look.
  • Sky Map. Like GoSkyMap it’s an interactive planetarium.  I prefer to use it without the “point features”. It’s my Planosphere (Sky chart) in hand. Also includes things like Meteor Showers and radiants, a list of “what’s up tonight” showing rise and set times, moon phase, etc.  No Augmented Reality.
  • PhotoPills. Lots of things rolled into one app. Biggest complaints about this app are saving and reusing Plans, usability quirks, a grossly oversized moon or sun icon in the Augmented Reality modes and an inaccurate Milky Way representation. Oh, and I’d really like it if it would measure for me!  The planner would be great if I could have the Augmented Reality compute the Azimuth and Altitude (aka Elevation) for me, especially since it doesn’t seem to have a way to measure like the Inclinometer tool does. I see, for example where someone saved the “Manhattanhenge” event. It would be great if I could load it and click “find next occurrence”. That feature alone might be worth booking a flight to New York!
  • SpyGlass. Clever app with lots of onscreen information in Augmented Reality mode. We especially like the onscreen measurements which are saved when you grab an image.

Do you know of an app that’s highly accurate and will meet our requirements? Let’s hear about it. If it exists on an Android I’ll buy an android!

Hunting Comets and other faint objects in not-dark skies

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.


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?


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.


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.


Painting with Light

Originally Published: Sep 18, 2012
Last Updated: May 11, 2016

Cascade of Stars [C_049409+12]

A Flickrite asked me a question:

 I’d like to know how long do you shine the light or use flash when you are shooting

I was really tempted to give the answer “as long as I need” but I’d just seem cruel to answer the question that way.

The truth, however is “as long as it takes”. Eric Harness, one of my partners in the Star Circle Academy endeavor uses a quite different technique than I do. He prefers to reduce the ISO and paint with light for the entire length of the exposure.  I like to keep painting short and purposeful. Each strategy has its strengths and weaknesses.

How Long?

Voyage into Pointy Land [C_061012]Painting for best effect is a knack, not a science.  You just have to try it and refine your technique based on your results.  Remember to check not just the LCD, but also your histogram when deciding how well you’ve done.  Here are some important points that will influence both the method and how long you will paint with light:

  1. Check your ISO and f/stop.  The lower the ISO or higher the f/stop the longer you will have to paint and the brighter the light has to be.
  2. The distance to the things being painted (due to the inverse-square law). You may spend a fractional second on a granite boulder nearby and long slow seconds on dark, light-eating evergreens in the distance.
  3. Brighter lights require less painting but a more deft hand.
  4. Ocean foam or white water in a waterfall will reflect a lot more light than lava rock – you have to paint the rock much longer.  A still pond or lake require a LOT more light than you would expect. The reflectivity (texture) of the surface matters quite a lot.
  5. It is harder to be precise with wide beams, but easier to uniformly illuminate.
  6. Spotlight or narrow beams make it easier to highlight specific things – but also makes blow outs and hot spots harder to control.
  7. When trying to highlight a certain thing or reveal some shadow detail you will need more light.
  8. House in the Wood [C_049613-17]Often there is too much to paint in a single shot. Using stacking techniques you can paint the scene in sections – and even in different light knowing that they are easily combined later. Or you could expose longer and try to get it “all in” but it is hard to get it just right like that.

Power and Direction

I think most people overpaint – they make the subject stand out too much or blow out the details.  Neither of these are blown out, but they have obvious hot spots.
Beholders of the Galaxy [C_061001] vs Anticipation [C_050158]

  • Don’t paint “head on”. Paint at a 30-45 degree angle to the camera view – and even from behind the subject for rimlight.
  • Consider painting from both sides to fill in shadows – but paint less from one side than the other to keep the scene from looking flat.
  • Be mindful of the color you are painting with and the thing being painted.  Bluish LED lights produce a very different feel from warmer incandescent light
  • Be cognizant of the color “bias” due to existing light.
  • If you use a flash, set it on manual and don’t try to expose all at once. Tilting the flash upward helps to even out the exposure.
  • When painting with a bright light, quick movement is essential. Continuous circular motion helps prevent hot spots.
  • Sometimes you can get more even and pleasing light on what is in front of the camera by painting the ground or rocks BEHIND you – much like bouncing a flash off an interior wall.
  • For dimmer light slow methodical movement is better.
  • Moonbow with Character(s) [C_039385]Try throwing in some color!

Star Man and Perseus [C_059960-1]


About now you may be wondering what flashlight(s) to get.  We can’t really answer that, however we do suggest you snag the following:

  1. A BRIGHT light (120 lumens or better)
  2. A SPOT light (one with a very narrow beam)
  3. An incandescent light
  4. A broad, dim light (like a keychain light)
  5. Colored lights (red, amber, blue, purple) or some cellophane or gel.

Sooner or later you’ll be like us and carry EACH of the above. Oh, and don’t spend a lot!  Get some cheap stuff – like you find at the checkout counter in a hardware store.

Nonetheless here is a list of our favorite illumination toys. Some or all of them may no longer be available.

Alignment (Part 2 of 2)

If you are finding these articles useful, please spread the word. Share us, Tweet Us, Digg us. Like us on Facebook. And if you would like one on one instruction please consider a Star Circle Academy Workshop. Now back to your regularly scheduled program.

In a previous column: Alignment Part 1 of 2, I touched upon the many elements that complicate capturing the moon near an object on the horizon. Here they are again for consideration:

  • The amount of moon illumination changes daily.
  • The moon’s rising and setting location must be accurately calculated – and it changes daily.
  • Exposures to capture moon detail require the right amount of foreground illumination.
  • The site chosen must have an unobstructed view of the sky in the desired direction.
  • To get a “big moon” it is necessary to get far enough away from the foreground.  If too close, depth of field problems may arise.
  • A well supported telephoto lens is required.
  • Capturing a shot of the moon near the horizon means the atmosphere must be relatively clear of clouds, dust and haze and when very low in the horizon there is more atmospheric distortion.

Figuring out how to tackle the moon location is computationally challenging. Fortunately with the internet there are many free resources to aid in this endeavor. And more fortunately, there is one tool which is almost ideal for the task: The Photographer’s Ephemeris.

We will address the problems step by step.

  1. Obtain the appropriate camera gear.
  2. Identify a suitable target.
  3. Calculate how far away we want to be from the target.
  4. Identify possible vantage points to shoot that target.
  5. Verify (visually, if possible), that the target is viewable from the vantage point and that there is sky behind our target.
  6. Verify that the moon will pass near our target and at an opportune time of day.
  7. Determine how high in the sky the moon should be.
  8. Fine tune the location to be sure the geometry is correct.
  9. Pray for good weather!

The camera gear element of the puzzle is easy: get the longest telephoto lens available. 2,400 mm will work great with a 35 mm (full frame) camera. I do not have anything that big (or expensive), so I use a 70-200 mm lens with a 1.4x extender on a 1.6 crop factor camera.  That effectively gets me 200 \times 1.4 \times 1.6 = 448 mm focal length. The “short” focal length of 448 millimeters means I can not fill my frame with the moon – it would take 32 moons laid out in a grid. Getting more foreground in the shot creates more opportunity for an arresting image however. Besides, those really big lenses are not only expensive, but unwieldy. In fact, they call them telescopes! Working with a crop camera in this scenario is a benefit.

No telephoto? Well then I probably would not bother – at least I would not bother trying to capture moon DETAIL.

Picking a Target

The moon is obviously one of our targets, but we want something interesting in the foreground to pair the moon with. Ideally we want a target that clearly stands above the surroundings and preferably one that allows us to get the proper distance away to maximize the “big moon phenomenon”. How far away?  Here is an easy formula: multiply the height of the object by 114.6.  If the object is 100 feet tall, the proper distance is 1,114.6 feet away.  If the object is 20 meters tall, the distance is 2,292 meters.  If 6 inches, then a distance of 687.6 inches is about right.

For the curious, the number 114.6 corresponds to 1 \div {\tan{(0.5)}}, where 0.5 is the number of degrees of the angular size of the moon from anywhere on earth. If shooting from somewhere else in space more advanced trigonometry may be needed.

It might be tempting to start with something short and nearby, like a golf ball. But getting a good depth of field is going to be difficult.

Let’s get started on the target, shall we? Fire up The Photographer’s Ephemeris (TPE) and follow along with me.  Switch to Ephemeris Mode (it is the first selection in the upper left). In the search bar (lower left), enter “Pioneer Park, San Francisco, CA“.

Now would be a good time to make the TPE window as large as possible, and select the “Satellite” mode in the map.

Figure 1: Pioneer Park Coordinates and Elevation according to TPE

Right above the upper right corner of the map you should notice two things: an elevation (here shown as +190 ft), and the GPS coordinates (37.8…blahblahblah).  If you prefer metric (or it shows metric and your prefer feet, you can change that using “Configure”).

Looking at the zoomed in map, put the cursor over the map near the bottom and click and drag upward. The map should move and soon you should see a conical shape casting a long shadow. Hooray. You found the Coit Tower. Double click in the center of the structure and it should look about like this.

Figure 2: Coit Tower in Pioneer Square, San Francisco, CA

Here I cheated and moved the elevation (+266 ft) and the GPS coordinates on to the image from above the map from the bar above.  I also zoomed out a bit so you can see the parking lot that you first landed on.

Did you notice that the elevation moved up from 190 to 266 feet?  You gained 76 feet in just a few parking spaces! It is steep there, but that number is NOT a measurement of the height of the tower, my friend. That is the elevation of the BASE of the tower. Don’t believe me… click a few spots near, but not on the tower or the building.  Click things farther away if you like, I’ll wait.  As you can see from the image at left taken from the parking lot, there is clearly not a gain of 76 feet between the two places.  The elevation information comes from a variety of sources, mostly the United States Geological Services (USGS) data.

What you hopefully learned is not to COMPLETELY trust the elevation shown. The elevation does not include buildings or trees and is not that precise, but it will probably be good enough.

In a while you will need to know the height of the tower above the base. Guess where you can find that? Yep, Google. Did you find it yet? It’s 210 feet (65.4 meters) tall.

So doing the math: ideally we’d like to be 210 x 114.6 feet away (24,066 feet or 4.5 miles) to have the moon’s apparent size be as big as the tower. Unfortunately going to the east, our choices are mostly in the San Francisco Bay, farther away on the Oakland Shore (near the Bay Bridge), or closer. Treasure Island looks like a good spot. It’s 2.11 miles and there is a lot of flat, publicly accessible shoreline to move along to align the moon behind the Coit Tower.  And besides even though the Coit Tower sits up on a high hill, only about the top half of the tower is above the sky line. So 2.11 miles might work out very nicely.

Since we have chosen a site to the east of the Coit Tower when can the moon appear behind it?  Near moon SET of course.

If you want your diagram to look exactly like mine, change the calendar to June 15, 2011. And change the Ephemeris mode to “Detail” (use the D key, or click the box down near the calendar).

When you switch to Detail mode, a hollow little gray marker will appear. Usually to the right of the red marker near the right edge of the map. Don’t lose it – you’ll need it in a minute.

Calculate the Moon Location Near Moon Set

You may have noticed all those colored lines extending from the Coit Tower in Figure 2. Here is what they mean: the light yellow line is the direction of sunrise, the orange line is the direction of sunset. The light blue line is the direction of moon rise and the dark blue is the direction of moon set.  All by itself that won’t help much. To see the moon setting in the west behind the Coit Tower, you obviously must stand to the EAST. But where?

Zoom out your map until you can see the Coit Tower on the left, and Treasure Island on the right. Make sure you are in Detail Ephemeris mode (you’ll know when you see a graph like this:

Figure 3: Sun/Moon graph and time slider.

Your map will look something like this:

Figure 4: SF Bay Map with Coit (lower left) and Treasure Island (upper right)

I have stripped off all the stuff around it to focus your attention. You’re focused, right?

Now would be a good time to play with the time slider. Click and drag it. Whoa! Did you see the lines moving? The skinny ones, that is.  There is a lot going on here, but the one thing you’re not yet seeing is where you need to stand to see the moon behind the Coit.

Stephen Trainor, the author of TPE put a cool feature in this tool. He did so because I asked politely and I support him with donations – I urge you to do so too. Buy his iPhone/iPad version of the tool (or Android if that’s available) or make a donation if you’re using the desktop (free) version of the Ephemeris. It’s the right thing to do!

Move your time slider to 5:13 as in Figure 3.  Now hold down the shift key. Did you see the thin blue line jump out? That blue line traces roughly where the shadow of the moon would appear. It can’t be completely accurate, however since the exact location would have to take into account topography, trees and man-made structures. We helped ourselves around that worry by choosing a flat shoreline where not much can get in our way.

Now would be a good time to find that hollow gray marker. Lost it? Click “D” then “D” again. It will appear near the right side of your map connected by a dim gray line to the red marker.

Hold down the shift key again, and drag and drop the gray marker on the Treasure Island shore DIRECTLY over the dark thin blue line.  Zoom in if you have to and get the marker EXACTLY on the line. And try not to stand behind a building or a palm tree.

You probably didn’t notice, but three things appeared at the bottom of your Ephemeris Graph in the box labeled Geodetics.  Those are: Apparent Altitude (which here will be negative), Change in Elevation (also negative), and Distance and Bearing.  Each time you move the gray or red marker it will recalculate the distance, altitudes and angle between gray and red.

One last little coup for now… notice next to the word Geodetics it has a little red and gray dot with an arrow over the top? Yeah, click that. The gray and red locations magically flip. Now all of your altitude and elevations will be positive. The calculations are FROM red TO gray. Since red is at sea level now, and gray up 266 feet on the top of Pioneer Hill the angle above the horizon toward the hill is  positive: specifically the base of the Coit tower is 1.1 degrees above the horizon. So can we conclude that the moon must be 1.1 degrees high in the sky?

NOPE. Sorry, we can’t. So close and yet SO far!

Q: What is wrong? Did you figure it out?
A: TPE has no idea how tall the Coit Tower is! (Stephen tells me one day he’s going to add the ability to specify the height at the red or the gray marker), but for now, YOU have to make that adjustment yourself. I’m afraid it’s going to involve some math. Trigonometry, actually.

What is the CORRECT Angle?

If you can answer this question, you’ll get the solution. “If an object at 2.12 miles away is 210 feet taller than the current 1.1 degree elevation, how many more degrees will that be?”

\tan^{-1}(Height / Distance) = altitude\ in\ degrees

Or in this case  InverseTangent( 210ft / 11311ft ) = 1.06 degrees.

So the CORRECT altitude is 1.06 + 1.1 or 2.16 degrees.

Hint Use the built in calculator in MS Windows in Scientific mode (Alt+2). Set the units to degrees. To get to the inverse tangent function (also called tan-1) use the “i” (inverse) key.

NOTE: If you do not want to do the trigonometry, there is another way to find the angle: use your camera.  Go to the desired site, take a picture with your telephoto lens aimed level with the horizon and with the top of the object visible. Determine the angular field of view of your lens/camera combination. Then measure the height of the target on the image and use the ratio of the height of the target to the field of view.  That sounds complicated, but it’s actually pretty easy. Using a 200mm lens, my angular field of view is 4.3 degrees. My photo shows that the tower spans 1000 of 1800 possible pixels. So the tower is 4.3^{\circ} \times (1000 / 1800) = 2.388^{\circ}

Now that we know the moon altitude must be 2.16 degrees we do not have to start over. Let us make sure the red maker is back on the tower and adjust our slider until the moon height is 2.16 degrees, then follow the line of the direction of the moon set to get our new location.

Of course if we move significantly higher, lower, nearer or farther away we must recheck the angle calculations.  In a hilly or mountainous location it is extremely non-trivial to get all the heights and angles just right. Using the “Terrain” mode of the map may help, but changes of a few dozen feet may make a big difference in the alignment.

Just remember the following things:

  1. The satellite maps may be out of date. A tree, building, crater, fence or obstacle might be in the location you want – or directly in front of it.
  2. There is no substitute for prechecking the line-of-sight BEFORE the event (see 1 above)
  3. Terrain maps are not visible when zoomed in.
  4. Elevations of the terrain are ROUGH.
  5. Moving 10 feet to the left or right may make or break the shot.
  6. I am NOT available to solve your trigonometry problems! Ok, I am but there will be a fee!

But wait, there’s more!

Getting the Ideal Exposure

To get the ideal scenario for moon details AND foreground light, it helps that the sun is on the opposite side of the sky and sometime during Civil twilight. In Figure 3, above, notice how the time we arrived at (5:13 AM) has the moon 2 minutes before Civil twilight.

Wondering what Civil twilight is? It is the legal equivalent to either dusk or dawn. Dusk when the sun has set, dawn when the sun has not yet risen. Signs that say park hours are “Dawn to Dusk” mean something quite precise. But those times change daily. For more click on the word “Civil” in the Ephemeris and it will tell you! Or take a look here.

The ideal exposure for detail in a full moon is about 1/100 of a second at ISO 100 and f/9. But atmospheric conditions, and the moon’s altitude may significantly affect the settings to use.  The best choice of aperture is to stop down enough for a sharp shot that keeps the foreground through to infinity (the moon’s focal distance) in focus.  If your foreground is at or beyond your hyperfocal distance (as it most probably will be), you’re good to go.

The problem, of course, is that your foreground is probably not going to fare well unless it is also well lit – so bracketing your exposures is always a great idea. The darker the twilight, the wider the bracketing needs to be.

Verifying The Sight Lines

After all the calculations and planning, a group of Bay Area Night Photographers ran out at the crack of before dawn to capture the “Full Moon Set behind Coit Tower“. One of the bleary-eyed ambitious photographers was Phil McGrew. Phil get’s extra kudos for going the morning before the planned event (that’s two thermoses worth of coffee) and here is what he got:

Photo 5: Coit Tower? And the Moon by Phil McGrew

The moon is in the right spot, but, whoops, there is something else in the shot, too! A big square building blocking the view behind the tower.  A more thorough scouring of the map in Figure 4 might have revealed the problem (see Figure 5).  Behind the Coit, and set up on a hill are a series of apartment buildings.  From almost anywhere else on Treasure Island, or Fort Baker in Marin, the Coit tower sits all by itself on the skyline.

Figure 5: Oops! (Click to see it larger)

What are the takeaways here:

  • There is no substitute for direct observation from the planned location. Any number of things can be a problem from light posts, billboards, trees and shrubs to, well hulking square buildings in the line of sight.
  • Extra scrutiny of the sight lines in TPE *might* save one from a needless trip to get a direct observation.
  • Knowing the local topography helps as does picking a structure or formation that clearly stands above the surrounding area.

Phil also discovered that the lack of brightness on his foreground meant he had to choose between exposing for moon detail, or exposing for the foreground. In Photo 5 he nailed a great foreground exposure and might be able to tease some moon detail out of the RAW file.  Or he could resort to…

One Last Trick – HDR

First I am a hater of images that have been composed by dropping a well exposed (oversized) moon into a separately taken landscape. There are technical challenges to embrace here so why not embrace them! Besides my desire as a scientist and engineer is to maintain reality through honest acquisition.

I am not, opposed, however, to using technology to overcome the limits of technology. Namely a camera can not readily capture the range of exposure – brightest to darkest – that the human eye can so a trick called “High Dynamic Range” photography (also called tone compression, tone mapping or image fusion) is sometime a necessity.

In the morning of June 15th, moonset behind Coit Tower was the target as describe earlier. That evening, moon rise behind the Transamerica Building was the goal.

You can click the diagram to the left to see where we were. As kismet would have it, the very parking space that I had calculated at the correct spot was open and I pulled in!

The haze was heavy, contrast was low. But in the end, the moon peeked (and peaked) right on schedule and right where it was supposed to go. It is always satisfying when things work out like that. More satisfying if the weather is great.

Rising Moon Collage

Photo 6: Moon rising over San Francisco (through the haze)

The fifth shot in the panel above is like all of the others in that it is a three-shot bracketed exposure combined using Photomatix Pro. The three shots were:

Figure 7: Bracketed Exposures

A wider bracketing range may have helped, the haze was quite thick. Using Photomatix Pro, playing with the knobs a bit I got this result:

Yellow Moon [5_032356-8tm]

Photo 7: High Dynamic Range Composite of 3 Images

I can only imagine what having a clear day to shoot in might have accomplished.

Best of luck on your alignments!

Comments, questions, praise, quibbles over the math – we’ll listen. Find us on Facebook.  Or attend one of our workshops. Want to keep it cheap, hook up with me, Steven in the Bay Area Night Photography group.