Category Archives: Weather

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!?

N_281-608714+C_281-8150

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.

Where to Go for Dark Skies?

No matter where you live on earth you have a chance to witness the incredible experience of watching bits of space debris streak through our atmosphere and create cosmic fireworks. In an older column I described How to Photograph Meteors – it is a daunting and luck laden process. Here I want to give some useful hints about WHERE to go to get the best view. These same hints may also help you find a location to view the Milky Way.

What I am not planning to tell you is where *I* would go because many of you are reading from all over the world and it would be little help to you for me to mention Yosemite, or Windy Hill Open Space Preserve.  Instead, what I want to do is to give you the insight to figure out where the best place is for YOU.  Here are the parameters to weigh:

  1. Goals
  2. Weather
  3. Accessibility
  4. Distance
  5. Darkness

Goals

It might seem strange, but I pick different locations depending on what it is I want. If I just want to watch meteors then I will pick a place that may compromise the other factors.  Assuming my goal is to photograph meteors, I have a second important decision: Do I want meteors, or do I want meteors in the context of a landscape?  For me the answer is almost always in the context of a landscape for the reasons I illuminated in this article.  In my opinion a shot of a meteor might be interesting, but a shot of a meteor over a lovely mountain, lake or landmark is WAY more interesting. For example compare the two photos below. The first shot is an Iridium flare (not a meteor, though it looks like one). The second is definitely a meteor. Which one is the most interesting? Yeah, the second one!

Meteor or Iridium Flare? [5_028205-dk] Star Man and Perseus [C_059960-1]

The next part of the goal is to figure out WHICH direction the landmark needs to be.  For example the Geminid Meteor shower is one of the few showers where the “radiant point” is visible all night long. But that also means that it may be best to shoot East after sunset, or West before sunrise and around midnight you’ll want to point south when the constellation will be high in the sky.  Of course meteors appear anywhere in the sky, but I like to keep a part of the radiant in my shots.

Once I’ve figured out which direction I’d like to face, only then can I start including and excluding locations. Of course an ideal place would allow me to face ANY direction, but the truth is not many ideal places are left in the world.

Weather

Now that I know which direction I’d like to face, I have to decide how much I am worried about bad weather.  Out here on the US West Coast a drive of 4 hours will get me to a mountain – the Sierras, 5 to 7 hours can take me to a desert area where it will generally be clear – but often windy, and a shorter drive will get me to a coastal area that may be fog plagued in some seasons.  In short, I would like to be as certain as I can about the weather conditions and thus will always have a plan B.  I have previously discussed the tools I use to track and plan for the weather.

Accessibility

While I would love to pass the time at a High Sierra location watching a meteor shower (awesome!), it might be really impractical or impossible for me to get there with my equipment in the dead of winter – even if the weather itself is not the problem. Road closures, park closures, etc. may interfere.  If I want to take friends or clients I need to restrict the amount of schlepping and walking required.  Some areas, like state, county and local parks which might be ideal are usually CLOSED, locked and gated at night.  National Parks and BLM designated land are generally open at night so rank high on my favorite places list.

Not only should my desired location be easy to get to by car but I would prefer a short walk to a safe location, and preferably in an area that has little or no car travel at night to ruin my night vision or my night shots.  Sometimes little intangibles like the direction and slope of any nearby roads makes a big difference. If a location is the top of the hill but a road points directly at it means I probably want to be on the other side of that hill to prevent the intrusion of headlights.  The arch shot above is an example of that hazard – a bend in the road causes cars to sweep their headlights across the landscape at that location.

It’s also unwise to attempt to use private land without permission. Being an unwelcome guest could result in embarrassment, hassle or hazard!

Distance

I have already touched upon this, but by distance I really mean time, effort and cost to reach the location. Since meteor showers occur annually, I am less inclined to make a huge effort if the circumstances do not look like they will be ideal.  On the other hand, I had no problem driving 1,000 miles roundtrip to put myself in the path of the Transit of Venus – an event that will not happen again in my lifetime (or yours).

Darkness

The one commodity that we are perhaps in the least supply of is darkness. So many cities, so much light pollution. But I do not need TOTAL darkness. If I have decided the best view is to the south, I just need to make sure no major cities lie south of my location. If my intended view is east, then I want mountains or distance to insulate me from the glow of light pollution to my east.  Unfortunately darkness is also a function of weather.  Humidity, clouds, water vapor and air particulates can turn a generally dark location into an awful mess through the effect of human-made light sources. A place that is clear and dark during most of the winter might be horrible in the balmy summer.

Prior experience is often the best indicator of where deepest darkness is found. Sometimes the easiest way to find a dark place is to simply look at a map – making note of the terrain and where the cities are in relation to your desired direction of view.  There is a dark sky locator that may help as well.  And you can do your part by joining the International Dark Sky Association and being an advocate for responsible lighting ordinances. I am a member.

Putting it All Together

You’ve probably already figured out that finding a combination of an interesting foreground that is easily accessible but a not too distant place with reliable weather is no small feat.  Some people think that if you go where astronomers like to go you’ll get all the right stuff. But that’s not true. Astronomers do care about almost all of these things, but the one thing that matters little to an astronomer is the landscape.  Astronomers are looking at the sky so a featureless high plateau is just fine. Oh, and if you want to light paint your foreground, you will really tick off astronomers!

So now you may have also surmised why I do not freely share my hard found locations. BUT if you join me on a workshop or webinar you will find out!

 

Oh the Weather Outside is Frightful – or Not

Published: May 18, 2012
Updated: May 3, 2016

One of the necessary tools a night (or landscape) photographer must have in their tool bag is a decent weather forecasting tool.  Though I’ve been known to ignore the forecast for some events, like an Annular Solar Eclipse, I definitely am more inclined to go where the weather is clearer (Nevada) than where it will be cloudy (Crescent City, CA).

A forecast like this despite how detailed it seems to be is all but useless to me:

Weather.com forecast

Weather.com forecast

This is the hourly forecast. The “daily forecast” is less helpful. How partly is partly cloudy? And how mostly is mostly cloudly? Other sites sometimes just say “sunny” during the day and give no idea what night will be like.  Compare the above with the Weather.gov forecast from NOAA.

NOAA to the Rescue (no Ark)

Fortunately the US National Weather Service provides a nicely detailed “click point” forecast with charts of the hour-by-hour conditions.

Weather.gov oh yeah.

Weather.gov oh yeah.

There is quite a lot to take in here but it’s all good stuff.  The “partly cloudy” at 7PM  shows as 72% cloudy (Sky Cover) on weather.gov. Not only are the forecasts different, but I get more useful numbers.  It looks like the wind will be very gusty during parts of the day. But the humidity won’t be so severe that dew will form.  If it weren’t for the mostly cloudy skies, night photography might work out ok.

Where do you find this great tool. Start here:  http://weather.gov

Once you get to the forecast, look for a small graphic on the right under “Additional Resources”.  But that, my friend, is where the good stuff is. Before you rush off on the hourly thing, though, take a look at the little map window.

Weather.gov forecast area highlighed in green.

Weather.gov forecast area highlighed in green.

You can get a forecast for any specific area by clicking on the map!  So, for example clicking on the summit of Mission Peak (just off the screen to the north) may give you a significantly different forecast – one that is adjusted for the difference caused by altitude.

Do remember that these are “forecasts” not actualities, so be prepared for whatever may happen.

Wunderground Classic

I used to use Weather Underground. Then they changed it so that the good stuff was only in “Classic”. But really, no need to use it at all any more.

May the wind not be at your back or in your face, may the road not be muddied by rain and may the clouds gather only when you really want them i.e. at sunrise and sunset.