5 minute read

If you love to look out at the stars (with or without a telescope) on a clear, crisp evening, you'll know just how important it is to have one eye on the weather conditions. Fortunately, there are several products you can use at home to help you find the best conditions to view your favourite celestial objects, with options to suit all budgets. Let's take a look at favourable weather conditions for astronomy and how you can track them.

Good Weather Conditions for Astronomy

Cloudless Skies

Cloudless skies remove the most common barrier to viewing the stars and planets: clouds! It's important to identify clear stretches of cloudless time before setting up for an observation session. Don't waste your time setting up the perfect angle and configuring your telescope without knowing whether you'll have to pack it away due to clouds blocking your view, or worse, those clouds raining on you and your equipment. Online cloud trackers such as the MetOffice Cloud Cover Forecast can come in handy here.

With complete weather stations such as the Davis Vantage Pro2 or the ClimeMET CM2000, you can measure wind speed and rainfall to help you determine if the conditions are getting too risky. You can even set wind or rain alarms to be triggered at specific speed or volume thresholds - ideal for protecting sensitive astrophotography equipment. These tools are easy to set up and use from home, and are a great investment for those wanting a full picture of the weather conditions in their location.

Transparency

Transparency, meaning the opacity of the atmosphere, isn't a parameter that most weather watchers usually concern themselves with, but it's highly important when it comes to stargazing. For transparency, we really need to look at moisture and dust levels in the air.

Measuring humidity with a weather station or hygrometer is key, as high humidity lowers the transparency. This is where your rain gauge might come in handy, too, as transparency is often best right after a rainstorm.

Typically, transparency reaches peak conditions in the winter, while summertime often presents murky night skies due to dust and humidity. Transparency can also improve with altitude, but it's not always practical to move location, so if you're struggling with transparency where you are, focus on stargazing brighter objects during these conditions.

Seeing

Seeing has a slightly different meaning. Seeing conditions refer to how stable the atmosphere will remain through your viewing session; a measure of atmospheric turbulence if you will. When you look through your telescope and stars seem to dance and blur in the viewer, you're experiencing poor seeing conditions. For best results, schedule your viewing session late at night to avoid the changing atmosphere of early evening.

Those living in flat areas will be pleased to know that these locations typically have the best seeing conditions, as it is partly the air moving over structures such as mountains and hills that can create this atmospheric turbulence. Weather conditions such as rainstorms and strong winds can also reduce seeing.

You may have noticed that it appears there is often a trade-off between transparency and seeing, with transparency improving at altitude and after a rainstorm, but seeing deteriorating in mountainous areas, and after heavy rain. It's something that many stargazers have to contend with, but most of us are unable to change the topography of our location, which is why keeping an eye on the changing weather is so important.

High Pressure

High pressure systems usually result in more favourable viewing conditions, whereas low or falling pressure can result in clouds and strong winds for unsettled viewing conditions. When it comes to measuring pressure, you can opt for a manual dial barometer such as the ClimeMET CM4202, or you can get a digital read-out from one of our complete weather stations.

With these two options very much at opposite ends of the spectrum when it comes to budget, desktop weather stations can be a great compromise, taking the guesswork out of viewing conditions for entry-level astronomers who don’t want to commit to a installing complete weather station. We recommend the ClimeMET CM9088 or the Technoline WS6750, which are easy to operate. These units measure pressure, but also track sunrise and sunset, moonphase, humidity and temperature. The Technoline model even displays moonrise and moonset times, so you can determine the brightest and darkest times of the night.

Cold Fronts

While a cold front might make stargazing a bit chillier, it can also present unique opportunities to view the objects you're searching for. When a cold front first moves in, it creates an area of high pressure which is great for viewing conditions.

Wind Speed

Low wind speed makes it easier to stargaze for a number of reasons. First, wind speed affects the stability and accuracy of any equipment you're using as well as the comfort level of viewing. Second, wind speed affects whether cloud cover can migrate from other areas to obscure your viewing session. Remember also how high wind speeds can reduce seeing?

Most of our complete weather stations measure both wind speed and wind direction, or you can choose to measure wind speed with a handheld anemometer, which has the advantage of being transportable to the exact location you’re stargazing from. The JDC Skywatch BL Anemometers even connect via Bluetooth to deliver weather data right to your mobile phone.

Moongazing

Beginner astronomers often turn their eyes on our nearest neighbour. For best moon viewing, we recommend instruments that display moonrise and moonset as well as the phases of the moon, such as the Technoline WS6750. If you want to see as much of the moon's surface as possible, for example, you will choose a clear night with a waxing moon or full moon.

For those just wanting a bit more info about what they're seeing when glancing up at the sky of an evening, moon phase clocks provide all the information you need.  For the more minimalist astronomer, the ClimeMet Moon Phase Clock has a simple face and comes in four colours to suit any home décor.