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Tuesday, July 15, 2014

Finding the Milky Way with Sky Guide

Knowing when and where the Milky Way would appear over this alpine lake was easy with the Sky Guide app.
Sky Guide makes it easy for astro-landscape photographers to know in advance when and where the Milky Way will appear over any landscape feature in the world. Sky Guide is a star and constellation guide app designed for both iPhone and iPad (not available for Android).

Compared to Stellarium: For the last two years I have used and recommended the free, open-source, planetarium desktop program, Stellarium. Why? Because Stellarium can look into the future and tell you where the stars and the Milky Way will be positioned on any day, and at any location on the earth. There are dozens of star reference apps out there, but very few can do predictions.

Despite Stellarium's lofty position with many astronomers, It's a love-hate relationship for some. It's a program designed by geeks, for geeks. Although Stellarium is very accurate, it's anything but user friendly. Sky Guide is less exact, but it is elegant and fun to use.

A Stellarium screen capture where the latitude and longitude grids were applied to help better define positions.
Sky Guide only shows the eight major compass headings (i.e. N, NE, E), but images are very elegant and realistic.
Both Sky Guide and Stellarium use preference settings to display or remove mythology or folklore. 
Stellarium is plain vanilla compared to Sky Guide's more realistic displays —which were developed from over 37,000 actual photographs of the night sky! However, when you need super accurate predictions of the Milky Way's alignment with landscape objects, Stellarium will allow you to drop in a grid (placed every 10º); whereas, Sky Guide only displays eight compass headings —requiring you to interpolate within the 45 degrees between each heading.

Sky Guide Features: I was impressed that Sky Guide functioned with or without a Wi-Fi, data, or GPS signal, as I was able to use it in true wilderness conditions, and it worked flawlessly. I loved the visuals in this star app. With the high-resolution photographs in this app you’ll see millions of stars—not just a few thousand simulated points. You can also control the intensity of star light with HDR brightness gestures to dial in your local viewing conditions. Here is a list of features:
  • Rich content: Generous amounts of stunning graphics, original artwork, and detailed articles. 
  • Soundscape: Designed by Mat Jarvis, the most featured composer in the award-winning soundtrack for the game Osmos. Stars have sounds based on their temperature and size.
  • Useful anywhere: Works with or without a GPS or data signal. Built-in access to hundreds of articles no matter where you are.
  • Time controls: Know where objects will appear in the future with cinematic time-lapse effects.
  • New as of vesrion 3.2: Filter: X-ray the sky and explore invisible wonders. More languages! French, Italian, Spanish, Portuguese, Russian, Japanese, Korean, Chinese (Traditional) and Chinese (Simplified).
  • HDR brightness gestures: Dynamically control how bright the sky is to match how many stars you can see under light-polluted skies.
  • Red night mode: Preserve your dark-adapted eyesight.
Most Important Features to the Astro-landscape Photographer: I think Sky Guide's best features are its Time Controls: giving you the ability to see where objects like the Milky Way will appear in the future —and with very cool cinematic time-lapse effects!

Time Controls Demo: The best way for you to appreciate this great feature is for me to demonstrate how Sky Guide helped me plan for the photo at the top of this post. Here is an iPhone panorama I took of the area the day before:

A 180º iPhone panorama of a small alpine lake in Utah's High Uintas.
Cropped version of the above image: My plan was to photograph the Milky Way in a near vertical
position, just slightly to the left of center. I knew from previous experience that the MW would
be in the southern part of the sky in the late evening, but I didn't know exactly when or where.
This is where Sky Guide comes in...
Top middle "Compass" button lets
Sky Guide use your current location
My iPhone compass indicated that the area where I would like to have the Milky Way appear in my photo was at a heading of 210º —only about 15º to the left of a SW heading (225º). The big question was what time of night would the Milky Way be in that position, and how would it appear in the sky? I was hoping for a more vertical MW for the ultra wide angle, vertical composition I had planned (using a 14mm lens, with a 114º angle of coverage).

It was currently about two hours before sunset. Using Sky Guide on my iPhone, I touched the "Compass" button at the top of the screen. This allows SG to use my current position and show me what the sky looks like right now, both above and below the horizon. By swiping up, with my finger, from the bottom edge, I am able to get SG to reveal the Time Center at the bottom of the screen.

It's currently 6:48 PM —about two hours before sunset. With the iPhone (an older 4s model) facing
between the East and SE, I can see that the Central Bulge of the Milky Way is still below the
horizon, and lying in a horizontal position to the horizon. By swiping up from the bottom
edge of the screen I have activated the Time Center and I'm ready to do
some serious time travel. Let the fun begin!
Although Sky Guide's mythology or folklore is helpful in locating the star constellations, I decide to turn this and the "Labels" feature off, in order to see an uncluttered view of the night sky. This is quickly accomplished via the Menu > Preferences.

Now the magic begins. With the Time Center activated at the bottom of the screen, I touch the fast forward button (double arrows on the right). Your first tap give you real time, "1x" forward speed. A second tap gives you "10x" forward speed. A third tap equals "100x". A fourth tap = 1000x, and so on. Now, the sky is really moving in a time-lapse, cinematic fashion! At about 11:15 PM I tap the pause button to review the sky...

(I've rotated my iPhone to the horizontal positions for a wider view of the horizon, and turned off
the mythology and label.) With the Time Center fast forwarding @ 1000x, it only takes about
14 seconds to time-lapse from 6:48 PM to 11:15 PM! The Milky Way has rotated during
this time from a near horizontal position to about a more diagonal position, with the
Central Bulge high in the sky, and in a near South heading.
I again use the Time Center's fast forward button to go forward @ 1000x until the Milky Way is in a near vertical position. To my joy, it is also positioned just before the SW compass heading, or about 210º! The Time Center tells me the time in the future will be about 2:44 AM for this shoot.

Fast forwarding (@ 1000x) until the Milky Way reaches a near vertical position, I tap the pause button
and check the MW's position and date in the future: Just left of the SW (225º) heading and
2:44 AM in the future (early tomorrow morning).
I then rotate my iPhone back to a vertical position and move it around until I get the composition I like. With this snapshot into the future, I have a good idea as to when and where I will take my real NightScape early the next morning.

Compare this Sky Guide "into-the-future" composition with the final NightScape I shot (at the top of the
page) —taken at 2:42 AM. The differences: My atmospheric conditions were somewhat different, with
airglow and a little light pollution on the right side (coming from Salt Lake City, about 60 miles away,
"as the crow flies"). My final shot is with a wider angle lens (a 14mm with 114º angle of view). The
other differences are the reflection in the lake and the tree line above the horizon that obscures
part of the Milky Way and the large star, Antares.
Planning for other Locations: Like Stellarium, Sky Guide can also help you see into the future at locations that are not your "Current Location". Go to Menu > Location and choose the "Manual Location" option. You will be presented with a list of countries in the world. Touch the country you want, and you'll get a list of major cities in that country. Choose the city closest to the location you want to plan around, and the coordinates will appear right under the "Manual Location" heading.

Limitations: I only wish Sky Guide would also allow you to put in your own coordinates, rather than choosing a city closest to your destination. In the example to the right, I had to choose "Salt Lake City, UT", which was about 60 miles from my alpine lake location —other smaller cities and town that were much closer, were not on SG's list. (Keep in mind that being 60 miles off from the actual location will only affect your positioning of the Milky Way by about two or three degrees and less than five or six minutes off in timing.)

Other Time Control Adjustments: If your next NightScape photo shoot is months into the future, you can also use the Menu > Time & Date and choose the "Select Time" feature. This will get you closer to your date, and then you can use the Time Center fast forward controls. I've also used this feature to go back in time to help me identify a star or constellation in one of my photos.

Conclusion: Pros: For only $1.99, Sky Guide is a steal! It is truly elegant, and easy to use. The "Time Controls" place this app's usefulness way beyond other products for the astro-landscape photographer (and for photographers, no other product, with their "simulated" stars will do once you've used SG)! Cons: Although the ability to manually set your location via a country and city list is a great option, having the ability to manually set your own coordinates would have been even better. And, having the ability to drop in a grid of longitude and latitude would increase location accuracy, but I understand the limitations of a small screen, so I'll not complain too loudly on this one.

Sky Guide is available through the iTunes Store for $1.99. It has a 5 out of 5 star rating on both the current (3.2) version (1200+ ratings) and all previous versions (8600+ ratings).


Android Version? Sky Guide is not currently available as an Android app. The closest thing I can suggest is SkySafari ($2.99).

Royce's 2014 Workshop, Lecture & Video Conference Schedule: NightScapeEvents.com


8 comments:

  1. Have you tried "SkySafari"? I'm using it on my Android phone. It is very user friendly och can show you the location of the Milky way, planets, constellations, Sun/Moon etc :)

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  2. Bah. iOS only.Looking into SkySafari mentioned above. Thanks for the suggestion.

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  3. what is the purpose of taking the iphone photo? If you know the direction of your anticipated picture can't you just point the app in that direction and see what happens over time? Or does the app take into account the elevation of formations in the skyline - so you can see exactly when it comes over the foreground feature, and arch, for example?

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  4. You said, "If you know the direction of your anticipated picture can't you just point the app in that direction and see what happens over time?" Yes, that is what I did (speeding it up by 1000x). You said, "what is the purpose of taking the iphone photo?" The top photo is NOT an iPhone photo. The focus of this blog is about "NightScape" style photography, which requires high-ISO's of around 6400 ISO (the iPhone only goes to about 400), and camera's with huge sensors and low noise at those high ISO's. The daylight photos were taken with an iPhone, only to demonstrate the position that I wanted to achieve with the landscape.

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  5. ah, thanks Royce. Sorry for my poorly worded question. Let me give a more precise example of my question. Say I have an arch and I would like the Milky Way to be in a specific position when I take a picture. Does this app allow me to take a picture with my iphone with the approximate composition I want, and then I can walk through the day/time to see exactly when it will be in that position? Most apps do not take into account the specific skyline and foreground so its always a guess of when it will be in position.

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  6. Sorry for the delay. I've been in the bush the past 3 weeks. You can take a photo of the arch with your iPhone, but it will not correlate with the app, it would just be for your reference. You would have to take a compass reading to see the direction you were aiming when you took the photo, then do a time lapse (forward) in Sky Guide to see when the MW moved to that position, and refer to the time it takes place. Once you've had experience with SG in the field, you can judge the height of the MW features to see where they would align with the opening of your arch.

    ReplyDelete
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