Tag Archives: calculations

Geometry and The Moon

Please do not run away. We are about to use adult language here. For example we will be using the word trigonometry. Still here? Good.  Here is a very pedestrian looking lunar eclipse photo taken with a 280mm lens*, cropped.

Near and Distant Neighbors

Very Ordinary Photo of the Lunar Eclipse with the planet Uranus in the lower left.

This past lunar eclipse several of us put our heads together to try to come up with a more creative photo than the one above. We had a trigonometry problem, however. On the West Coast the last moment of totality occurred at 4:24 AM PDT. We were brave enough to be out at any time of night – even if it meant extreme sleepiness in our day jobs but our problem was that the lowest the moon would be in the sky at the last bit of totality was 32.6 degrees above the horizon. We determined that angle using Stellarium, by the way. Unfortunately there is pretty much nowhere to go to get a nice large moon near an interesting object when the moon is almost 33 degrees high.

Wait: Why do we want the moon and the object to be similarly sized? Here is why… we want the moon to be noticeable like the Fantasy version below, not merely “present” like the real photo on the right. Even bigger would be better, right!?


Notice above right (Reality) and below how tiny the moon is compared to the building in the foreground?  Indeed, if you see a photo taken from anywhere on the West Coast where the eclipsed moon is significantly lower in the sky or larger than shown against foreground, you know it has been “photoshopped“.

Plan C: San Jose City Hall Eclipse Sequence

In short, it is nigh impossible to get the large moon effect with an altitude (angle) of 32 degrees here is why:

Calculating the Angles

Calculating the Angles

Just how far away do we need to be in order to get the moon the same size as an object of interest:

114.6 x object size

In other words, an object that is one foot tall, requires us to stand 114.6 feet away to make the 1/2 a degree angular size of the moon the same angular size as that 1 foot tall object.  The number “114.6” is from this calculation:

1 / TAN (0.5 degrees)

Yeah, that is trigonometry. Using still more trigonometry it is possible to calculate how high above the horizon a 9 inch tall object has to be so that it is “moon sized”.  We did that for you in the “Calculating the Angles” diagram above. Once you calculate the distance from the camera of 85.9, you can multiply that by the sine of the angle to calculate a height of about 46 feet! Here is the trigonometry:

Height = 85.9′ * SIN (32 deg)

You can go one step farther and calculate the distance from the object with ‘distance = 85.9 * COS(32 deg)’.

Of course after all that calculating you will still need to find a location, have contingency plans for weather and so on. At StarCircleAcademy we have built some tools and put together materials to help in all these endeavors.  We teach these things in our NP111 Catching the Moon Webinar.

The Road To The Temple

Below is where we ended up. This image is from our friend and co-conspirator Andy Morris.

Lunar Eclipse over Temple by Andy Morris of PhotoshopScaresMe

Four of us plotted and schemed to get an interesting shot. Above is Andy Morris’ result.  Click the image and you can read a great article about how he created the shot using Photoshop Skills at his site: PhotoshopScaresMe.com. In fact, it’s a great article which we strongly encourage you to read. You’ll learn how he composited the images together in Photoshop as layers.

The Long Conversation to Pick a Location

Andy has more details including how alcohol played a part in the process. Mostly I, Steven, was the wet blanket explaining why the geometry was all wrong.

  • The Stanford (Hoover) Tower looks like it is shrouded in trees from the needed angle
  • Bank of Italy (formerly BofA) in SJC doesn’t work
  • The main problem with the wind turbines is that the angle to the top of them is something around 12 degrees above the horizon which is 40 moon diameters below the eclipse.
  • Here is why the GG Bridge doesn’t work…
  • This seems to be the best solution I could find: the Coit Tower…
  • Darn. It would appear the coast is out. Forecast calls for Fog from SF to HMB
  • This might make an interesting foreground (see below)… Somebody want to check if they will mind us being on their property in the wee hours?

*Ok, we lied, it was actually a 70-200mm lens with a 1.4 TC on a full frame camera, but the net is the same: 280 effective mm focal length.

Where did you go and what did you get in your planning efforts?  Post a comment and link below… we’d love to see what you came up with!

Plan C: How To Plan a Time Sequence Shot

If you missed the last total lunar eclipse, don’t worry. You’ll have another chance in October, 2014. For that, I’m grateful since as you can see I had some problems with my apparatus (the CamRanger). The battery failed after the 7th shot of the moon you see below, and then it stopped working again after 3 more shots, and needed to be slayed and restarted just as the moon was transitioning to fully eclipsed.

But this column is not about our troubles, it is about how I planned for the lunar eclipse shot you see below.

Plan C: San Jose City Hall Eclipse Sequence


The planning began with a list of possible foreground subjects. The San Jose City Hall Rotunda was “Plan C” and the least well researched of my plans. What were plan A and B? Those were one of my favorite lighthouses and a favorite landmark in San Francisco, California. For each arrangement I had to:

  1. Calculate where to stand to make sure the moon would be in an interesting phase above the object. The plan required solving these problems
    1. Determine how high in the sky the moon would be (to know what viewing angle was best)
    2. Determine which DIRECTION I needed to face to capture the moon.
    3. Determine how “wide” a lens I needed to get the sequence I wanted.
  2. Monitor the weather at each location.

After planning all that was left was to make a last-minute decision where the most likely target would have favorable conditions and make any final on-site adjustments.  I had a Plan D, too… but it was also in San Jose so it would have only been chosen had I found some serious obstacle at the City Hall rotunda.

San Jose City Hall Panorama

Calculating the Angles

Determining the angles needed is pretty simple. I used The Photographer’s Ephemeris including all the nifty tricks we teach in our Catching the Moon Webinar. Below you can see a screen shot from the Photographer’s Ephemeris which shows the moon altitude and direction at the beginning of the eclipse. I also moved the time ahead to show the same for the middle of the eclipse.  The moon’s altitude angle (32 to 41 degrees) gave me an idea how close to be to the rotunda to get the moon overhead.  Lower angles allow me to get farther away which allows me to photograph the moon larger relative to the foreground object. This eclipse, however, and the one in October will have the moon high overhead.

Coming up with a Foreground

There is no good substitute for knowing what interesting foregrounds are possible. And also knowing which direction(s) you should be facing.  I knew that the San Jose City Hall Rotunda was generally easterly because I had watched a sun rise through it. I also knew that the eclipse would be at maximum when the moon was in the southern sky so I knew that the range was SE to S directionally.  You can see a diagram from The Photographer’s Ephemeris below for more complete planning.

Calculating Where to Stand

I had to know approximately how tall the foreground object is. For the San Jose City Hall I flat-out guessed.  I found the overall height of the building through Google, and I guess the Rotunda was 60 to 80 feet tall.   My original calculations had me much closer to the building… it was only when I got on site that I realized that there were adaptations that needed to be made.

Watching the Weather

Remember that the Rotunda was plan C.  I kept a close eye on the weather for each of the planned sites.  My favorite weather app is provided by weather.gov – in particular the hourly graphs. We talked about this tool in detail in a prior column.  Why do I like it so much? Because it gives me numbers instead of “partly cloudy”.  It was pretty obvious that the coastal region for Plan A, and the San Francisco Landmark (plan B) were likely to have bad weather – both fog and clouds. Indeed my friends who headed those directions were frustrated by poor visibility.  We had clouds passing through San Jose, but as the weather predictions had read: it got clearest right near totality, and overall was not a hindrance.

Last Minute Adaptation

When I first got to the site, I realized that the Rotunda was taller than I thought. I set up across the street in order to be able to have the moon over the Rotunda… but there were other problems, too. One of the problems is the floodlight on the top of the building. Another was a street light just to the right of where the red marker is in the graph below. These are problems that would only reveal themselves if you visit at night!

And then there are all of those flag posts.  My original guess at the Rotunda Height would have allowed me to stand between the fountain (brown area) and the building… but that clearly didn’t work as the rotunda was too high.  Setting up across the street (and very low) also had its challenges… namely buses and cars that came regularly.  I also realized that I had miscalculated the eclipse time by an hour (forgot it was now daylight savings time).  The miscalculation turned out to be a good thing as it left plenty of time to move around.  It would seem the ideal spot was in the MIDDLE of Santa Clara Street, but that wouldn’t have worked, of course.  Eventually I picked the spot with the red marker as a compromise between altitude of the moon above the structure, removing the glare from the tower lights, the wash-out of the street light, and the many flag poles in the way.

Planning Moonrise

If only my CamRanger had cooperated, I’d have had a continuous sequence of shots of the moon passing over the Rotunda.  There is always October… and maybe Plan A will work for that!

Of course that’s not ALL that was required to get the shot. I also had to composite each of the moon shots into their proper locations. I did that by first taking a panorama of the area, then making sure that when the exposures began I had a piece of the rotunda in each shot so I could properly align the moon over its actual location.  The creation of the image used the Easy HDR method we have previously described.

Catching the Moon Simplified

Freedom Gazes at the Moon [5_055475-7deB]

Freedom – the statue at the summit of the Nation’s Capitol – Gazes at the rising Moon

One of our popular webinars is Night Photography 111: “Catching the Moon (and the sun)”. The next webinar is April 2, 2014, by the way. Long before the many tools that now exist to help solve for moon+landmark alignments I began working on a tool I call the MoonChase Tool. As snazzy tools came into being like Stephen Trainor’s Photographer’s Ephemeris, SunMoonCalc, MoonSeeker, and many more, I neglected the MoonChase Tool and focused more attention on the Advanced Stacker PLUS. In fact, after Google discontinued the V2 map interface upon which MoonChase was built the tool languished for about a year and a half. I also stopped teaching how to use it in the NP111 Webinars. But, I kept finding that all existing tools just didn’t do what I needed, so I resurrected the MoonChase tool. I ported it to the newest Google Maps API (V3), and I then added some of the features I had on my wish list.  I’m really proud of what the tool can do now. And I have some fiendishly clever plans for the future of the tool, time permitting, of course. Operationally the MoonChase Tool is simple. The hardest part is coming up with the location where you want to stand and the landmark you want to face. If you know that there is a sightline to a landmark in the distance you can fire up MoonChaseTool and in 3 steps know when to go to get the moon or sun behind your landmark!  That’s right. You paste, paste, click and click. Or drag, drag and click. We cover how to cook up good locations in the Webinar. How do you get your hands on this tool? We’ll tell you! If you’ve attended a NP111 webinar with us, or purchased the video and notes you already HAVE access through the “private page” (you did save the password, right?).  You’ll find the link to the MoonChase Tool on the private page.  Or sign up for our webinar which includes the notes and video AND access to the MoonChase Tool – and you don’t have to wait for the webinar, we send you all the links when you sign up (see below). The tool isn’t especially pretty, we admit that.  But it is pretty EASY to use and it works even from your iPad or tablet as long as you have internet access.

3 Steps to Moon (or sun) catching

3 Steps to Moon (or sun) catching. And there is more: you can check the view with Google Street View, and even check the weather with the weather button.

After clicking “Moon” you get the report thanks to Jeff Conrad’s SunMoonCalc tool. Be careful to be sure it selects the time correctly. Below it’s off by an hour due to Daylight savings time.


Moonrise over Lick Observatory from near SJC Airport… all opportunities from this location for the next 4 years!


What Problems Does the MoonChase Tool Solve?

The tool was designed to do the trigonometry for you. Did you know there is trigonometry involved?  Don’t worry, you don’t have to know trigonometry or math.  Nor do you have to know about spherical coordinates, azimuths, altitudes or the three different kinds of twilight.  All you have to know is where you want to stand, and what you want to be in your picture. Drag the markers around on the map and click one of the Solve buttons. OR use the tool in concert with The Photographer’s Ephemeris.

What Do I Need to Know to Do?

It’s very helpful to be able to do the following things: grab GPS coordinates from Google Maps and/or Photographers Ephemeris.  We teach how to grab GPS coordinates in the course. You’ll also want to know how to find heights of your favorite landmarks. Google comes in really handy for finding heights of buildings!  One more thing you’ll want to verify is whether you can See the landmark from the place you want to stand. Again, we describe 4 different ways you can do that in the webinar. The rest is dragging and clicking!

How Long Will it Take?

If you already have the coordinates, it will take perhaps thirty seconds – or not even that long.

I WANT THAT! How Do I Get It?

Easy: Sign up for the webinar and you’ll get immediate access to the private page plus the videos and notes. If you’ve already taken the webinar, go to the private page and you’ll find the link in the Resources section.  Or as a prior purchaser, just sit tight as we’ll be sending the new materials out to all prior purchasers over the next 3 weeks.

Webinar: NP111 Catching the Moon and the Sun
Not Scheduled but usually 7:00 PM PDT (7 MDT / 8 CDT / 9 EDT) for 2 hours
Captured [C_044450-2tc] In this 110 minute Webinar, you will be introduced to several free (and almost free) tools that you can use to plan a moon (or sun) shot - including a tool written by Steven and made available only to attendees. Have you wanted to capture the moon "right where you want it" but weren't sure how? If you know you could resort to photo editing and fake it but you'd rather get the real deal then this class is for you. Steven will demonstrate how to determine when and where to go to capture an image like the Moon over Lick Observatory or the moon at the Transamerica Building or the sun shining through a portal in the Pacific Ocean (below). This is a Webinar so you can conveniently attend from your computer at work or home anywhere in the world. This course includes notes, access to a private page with details - including landmark events Steven has already solved for you, an online viewable recorded webinar with unlimited online viewing that you can watch NOW before the webinar is held. One indispensable tool covered in detail is the Photographer's Ephemeris by Stephen Trainor.

What You'll Learn

Steven will show
  1. How to Plan a moon or solar "contact" shot.
  2. How smartphone based tools may help - or sabotage - your attempts to get an alignment
  3. How to use the moon to illuminate your foreground,
  4. How the presence of the moon affects photos of the night sky,
  5. How to find information about interesting celestial events,
  6. How to find compelling locations for "alignment" images, and
  7. What camera settings you need to get it all exposed just right.
Photon Worshippers **Winner Astronomy Photographer of the Year, 2010 - People and Space **
Remember that this event INCLUDEs online videos, notes, and access to a special tool that Steven uses to solve lunar and solar contact shots.
New Dome [5_009671]

The moon rises behind Lick Observatory on Mount Hamilton, San Jose, California