Category Archives: Reviews

A selection of Android applications for astronomers

When talking to visitors at the Baker Street Irregular Astronomers events in London, there is often discussion about useful / interesting applications that people might have on their phone. This blog lists the various applications that I currently have on an Android phone that are useful for astronomers. There are many others available beyond this list, some of which may be better; these just happen to be the ones I currently use. Some are available for iOS too, or have equivalent options available.

Google Skymap (Free without ads)

One of the challenges when learning astronomy is identifying stars, constellations, planets in the sky. This is where a planetarium application steps in the help. With the gyroscopes built into all modern smartphones, the device knows which direction it is pointing in as you move around. This allows you to hold up the phone pointing at a nightsky and have the planetarium application display a chart of what you are pointing at. There are several applications available which offer this capability, with Google Skymap being a no frills, but effective, free option. If willing to pay for a planetarium app, then the well known Stellarium desktop app is also available as a paid for option.

Sunrise Sunset (Free with ads)

It can’t escape anyone’s attention that the Sun and Moon rise and set at a different time every day. The same is true for all the planets in the solar system that astronomers might want to view. It is thus useful to have a quick reference for when the rise and set times are for all the main bodies in the solar system. This provides details on the different stages of sunrise/sunset, and the rise and set times of each planet in a quick to access manner. A slight annoyance is that the app sometimes gets stuck and displays a blank page.

Eclipse 2.0 (Free with ads)

Eclipses, whether solar or lunar, are relatively rare events. A total solar eclipse happens a couple of times a year somewhere on the planet, but any given spot may have to wait decades between events. Lunar eclipses are a bit more frequent, but it might be a year or more between total lunar eclipses. This application will display a list of all future events (for a 100 years hence), and can optionally filter them based on the viewing location.

Solar Eclipse Timer (Paid per eclipse event)

When travelling to view of photograph a total solar eclipse, it is critical to know exact timings for the start and end of the eclipse, as well as the start & end of totality. These times vary depending on your precise physical location so an app is needed to provide localized timings. You don’t want to be fiddling with the phone at these times, so this app provides useful spoken audio alerts to each phase of the eclipse, allowing you to focus on more important things.

Clear Outside (Free)

For visual observers and astrophotographers, many an observing session will be ruined by poor weather conditions. This is particularly frustrating when certain events (eclipses, planetary conjunctions, comets) are only visible at very specific days and times. It is thus vital to both understand the current weather conditions and get predictions for forthcoming nights. There are a great many weather applications available, but general purpose forecasts don’t usually provide the level of detailed desired by astronomers. This application is designed specifically for astronomers, showing many fine details otherwise not available. It includes percentage cloud cover at three levels in the atmosphere, rain predictions, general visibility, wind speeds and more. It also details lunar phases since illumination from the moon can be as bad as city light pollution in drowning out fainter targets.

GPS Status (Free)

When calibrating / aligning telescope mounts it is often useful to know about the observing location’s longititude and latitude, as well as which direction is north. Phones all have builtin gyroscopes which can provide direction information, and GPS receivers to provide the location. The GPS status application presents this data in an easily accessible format and also provides the ability to recalibrate the internal compass which is worth doing periodically as some phones quite easily loose calibration.

ISS Detector (Free with ads, or paid without ads)

An event that always gets attention from attendees, particularly from first timers, at BSIA events is a flyover of the International Space Station. The ISS makes an orbit of the Earth approximately every 92 minutes, but it will follow a different track each time affecting where it appears in the sky, when viewed from a fixed point. The time relative to sunrise or sunset also affects how long it is visible for and its brightness magnitude. The “ISS Detector” application crunches the numbers and presents information on when passes are visible from the current observing location for the next 7 days or so. It will illustrate the path it will take across the sky with start/end times and magnitudes. It can be made to trigger a phone alert shortly before the flyover takes place to minimize the chance of accidentally forgetting when it happens. Despite the name it can provide track info for other objects besides the ISS.

ISS Transit (Free)

Some of the more interesting events for astrophotographers focusing on solar system objects are conjunctions and occultations. Flying in low earth orbit, the ISS has quite frequent alignments with other solar system objects, especially the moon and sun. These events are interesting to photograph allowing the ISS to be seen in silhouette against the Sun, or brightly illuminated against the Moon. Whether these events are visible is highly dependant on the exact viewing position on the ground and thus require advance planning and travel to quite specific sites. This application is able to perform calculations to show where forthcoming interesting transits are taking place.

Heavens Above (Free with ads)

The earlier mentioned ISS detector application focuses on fly overs of the ISS. There are many more satellites in orbit around the Earth that while often not visible to the naked eye, can appear in photographs either intentionally or unintentionally. This application provides information on all the satellites that are likely to be overhead for any given night.

Dark Sky Map (Free)

With an ever increasing portion of the population living in towns and cities, light pollution is a big problem to deal with. Even though the switch to LED lighting can have the potential to reduce light pollution by having strictly downwards facing illumination, in practice there’s been light obvious benefit as the lights are often brighter. Whether deciding on where is best to live, or planning day excursions or extended holidays, it is useful to understand the extent of light pollution across the country / world. The dark sky map  provides this information in an easily understandable format overlaying a map with colour coded bands for light pollution.

Aurora Watch (Free, no ads)

Aurora, often known as “Northern Lights” form when energetic particles from the Sun interact with the Earth’s atmosphere and magnetic field. As the name suggests, they occur more frequently the further north you or (or further south in the Southern hemisphere). There is a high correlation between the flux of particles received from the Sun and the visibility of Aurora. The application provides aurora visibility forecasts for the days ahead and active alerts when high thresholds are exceeded.

Polaris View (Free, no ads)

When setting up an equatorial tracking mount care needs to be taken to accurately align the mount with the North Star, Polaris. It is not as simple as just putting Polaris in the dead center, as it is not quite at true north in the sky. Instead it needs to be offset by a small amount. The direction in which it is offset depends on the time of day / night, and the amount of the offset varies from year to year as the Earth wobbles on its axis. Mounts will typically have a polar scope / sight to facilitate this alignment process, but may require knowledge of the direction in which Polaris should be offset. The application provides a simple view of the sky simulating what it should look like through a polar scope. The astronomer simply needs to align their scope so that the position of Polaris matches that shown in the app.

Night Shift (Free, no ads)

This application is a new & promising discovery, aiming to provide a summary of everything that is interesting in the night sky for any given night. It displays visibility of all the solar system planets and the Moon. The viewer can enter information about their telescopes and viewing location and it can then highlight which other constellations, nebula, and deep sky objects are likely to be possible to view. It effectively combines functions of many of the previously discussed applications into one convenient dashboard.

Sun Position Map (Free, no ads)

When planning photographic shots featuring the sun or moon in combination with foreground objects, it can be useful to understand exactly where the sun will be in relation to the foreground. This application provides an overlay for Google maps, showing the path of the sun from rise to set. Just find the object to be photographed on the map, and the app will show where the sun will be in relation to it. It can also overlay a field of view indicator for various camera lens focal lengths.

London Photographic Light Painting Workshop

Through the London Photographic Meetup group I’ve been to many different photographic workshops, learning a great deal. Over the past couple of years, the group has had quite a strong focus on lighting related workshops, covering various aspects of studio lighting & off-camera flash. It was one of the off-camera flash workshops, 3 years or so back, that motivated me to create the Entangle Photo application for Linux desktop users.

The workshop that I’ve long wanted to attend, but never had the chance to, is their “Light Painting” one. Last week I finally got the opportunity and was not disappointed. The location varies from event to event, with this particular workshop taking place in Green Park. We started out in a cafe where the organizers described the various pieces of equipment we’d be using. There were basically two devices, a light string (a long cable with a bundle of 30 leds on its end) and a light stick (a ~1m long piece of wood with an led every ~3cm). Neither are things you can buy pre-built in the shops – the London Photographic organizers home-build them all from electronics purchased on eBay.


The weather was a bit on the iffy side, so we started out with umbrellas being held over our cameras, but we didn’t let that put us off the evening’s activities. In any case, the rain had pretty much stopped after the first 30 minutes of the session. The plus side was that the rain made the ground reflect a little more of the light. As might be expected, the exposures are on the long side, with the iso/aperture dialled in to achieve the desired ambient illumination, while still allowing on the order of a 1 minute shutter opening to give time to produce the light effects. Needless to say, the cameras were on tripods and shutters triggered using cable release. With such long shutter speeds, we’re shooting in “bulb” mode with someone counting time on a stopwatch.

Light orbs

The first effect attempted was to produce basic light orbs. These are achieved using the light strings, by swinging the string in a circular motion in front of your person, while slowly rotating your feet through 180 degrees. Done correctly this results in an attractive orb shape

Light tunnels

Another effect that can be produced using the light strings, are tunnels / tubes of light. The starting premise is much he same as for the light orbs, simply swinging the string in a circular motion in front of your person. Instead of rotating on the spot though, you slowly walk forward / around the scene.

Light trails

Following on from the basic light orbs, the organizers got out the light sticks. The light sticks have fancy controllers for choosing between a range of different colours, or even strobing through the colours in a sequence. The technique is simplicity itself, simply turn on the light stick and walk it around the scene. The key is to keep your motion of the stick fluid, to avoid jagged edges on the light trails.

The Peacock

As mentioned above, smooth movement of the light stick is key to getting continuous light trails. For the next trick, the goal was to produce perfect circles of light. Acceptable results cannot be achieved by hand-holding the light stick, so the trick here was to put a bolt through one end of the light stick, and then fasten this to a tripod head in some manner. The light stick can now be smoothly rotated through 360 degrees, producing perfect circles of light, which I’ve named “The Peacock”

The Brain Orb

The final technique of the night was the most difficult and time consuming. This involved a long pole, with a bundle of leds on its end. Kneeling in one spot, the goal is to trace out a sequence of hoops gradually building up the doom pattern, which our organizers nick-named “The Brain Orb”, though it reminds me of an igloo.

Parting thoughts

The general aim of the workshop was for the organizers to demonstrate the techniques above so that we, as photographers, understood how to achieve the various different light painting effects. The workshop lasted several hours, late into the evening, but even with the small group (~15 photographers) there wasn’t time for us to try out every technique ourselves. The idea is that after completing the workshop we’d have the knowledge required to go off and put the techniques into practice ourselves. I’m certainly intending to do some experimentation in this area myself. The organizers themselves did a great job at running the event & getting through the material. If anyone reading this is interested in light painting, and based in London, it is well worth keeping your eyes open for future repeats of the light painting workshop (won’t be until autumn time though, due to need for dark evenings!).

One idea I had to improve the results from “The Peacock” technique is to bring in an off camera flash. The camera settings are dialled in to expose for the ambient, while giving plenty of time for the light painting technique. What we can’t do with this, is get a nice exposure of the subject’s face. By adding in a low power pop of off-camera flash at the end of the exposure, we could nicely bring out the features in the subject’s face.

A review of the JJC LED ring light

One of my photography related Christmas gifts this year was a JJC LED ring light from a UK Highland Photography via Amazon. As can be seen from the photograph, the LED ring component attaches from the front of the camera lens using one of six possible adapters (thread sizes 49mm/52mm/55mm/58mm/62mm/67mm). Power is either from 4x AA batteries in a pack which attaches to the camera base via a standard tripod screw thread, or from a 240v  mains A/C adapter. The build quality on the unit is very good and there’s not much weight to it (aside from the AA batteries). The photo below shows the ring light attached to the battery pack, in turn attached to my Nikon D90 via the tripod bolt

LED Ring Light

First of all, it is not really right to compare this LED ring light with much more expensive ring flashes like this Metz. The latter cost several £100 while this LED ring light costs a mere £30. A ring flash will provide a significantly more powerful light, making it suitable for a wide variety of scenarios in particular as a fill light for portrait photography. While the LED ring light is very bright to look at, it is only really powerful enough if used fairly close to the subject, for example, in macro photography.

To get an idea of its power, I did a couple of test shots, First of all, just a boring shot of a cutting mat, positioned 10 cm from the camera. The ambient light provided an exposure of 4s @ f/8 + ISO 400 (left hand image); With the ring light on, the exposure was much more satisfactory 1/320 sec @ f/8 + ISO 400 (right hand image). NB the colour difference here is primarily due to different white balance – the ambient was approximately tungsten, while the ring light is approx flash.

Cutting Mat Cutting Mat

The second test was done using a slightly more interesting subject – a dried fruit Christmas decoration

Christmas Decoration - Dried Fruit

To evaluate light falloff, I made a variety of exposures with different camera <-> subject distances. Starting at a distance of 8cm, ambient light provided an exposure of 20 secs @ f/29 + ISO 400; With the ring light on, the exposure was 1/60 sec @ f29 + ISO 400. Moving the camera out to 20cm from the subject, the ring light provided an exposure of 1/30 sec @ f/29 + ISO 400. Moving further out to 30 cm, the ring light provided an exposure of 1/10 sec @ f/29 + ISO 400.

LED Ring Light


From these figures you can see that if you tend to use tiny apertures (eg f/64) and fast shutter speeds (eg 1/200 sec) at the same time, then this light probably isn’t sufficiently powerful on its own, unless you are willing to raise ISO and work very close to the subject. On the plus side, since it provides a continuous light source, this ring light greatly facilitates focusing, arguably making it more useful than a ring flash for macro work. My take away from the test shots is that this product provides a great general purpose light source for macro work. In scenarios where it isn’t powerful enough on its own, it could be paired up with an off camera flash, the ring flash serving as illumination for focusing & the fill light, and the flash serving as the key light. For the price point, IMHO, you can’t go wrong using this LED ring light for macro work.