Orbiting hundreds of kilometers from Earth, the International Space Station is inhabited by astronauts from different states, who each time live aboard for months. The space station is often visible to the human eye when it is above its own area, so follow these steps to understand when you can spot it.
Steps
Part 1 of 2: Choosing a Good Time to Watch
Step 1. Consult the International Space Station transit document in your area
You can use one of the links below, or search online for "international space station map." These maps contain a lot of useful information that will help you understand when a sighting is possible. Choose a site that allows you to enter your address, city or postcode; if you enter inaccurate information, the results may not be correct.
- Try these Heavens Above, NASA, or SpaceWeather cards.
- Some sites may try to automatically understand your location based on the internet server closest to you. This method is not always very accurate, so check where the identified area is, and enter a different place if not it is quite accurate.
- Some sites may abbreviate the name International Space Station to "ISS".
Step 2. Identify several periods when the space station is visible for about two minutes
In some cases, from your area, the Station will only take a few seconds to cross the portion of the sky visible to you. Other times, it will take 2 minutes or more. Look for passages where it stays visible longer to have a better chance of spotting it. Mark several of the passages you found.
- Passing by night, within a few hours of sunset or sunrise, it will be easier to spot it. Additional brightness information is provided in the next steps to help you understand if the station will be visible during the day.
- Some cards will have a specific column that indicates the period of time in which the station will remain visible, in other cases you will have to calculate it yourself by subtracting the end time and the start time. These times are usually written with three numbers, in hours: minutes: seconds format. Also check if the site uses the time in 24 hour format or the am / pm system.
Step 3. Use these cards to find the moments when it is brightest
Many cards include "brightness" or "magnitude;" look for another one if the card you found does not include this information. The brightness scale is a bit articulate: a negative number, such as -4, indicates a greater brightness than a positive number, such as +3! Here are some guidelines on brightness levels to understand when the station is actually visible:
- A magnitude of -4 to -2 is the highest possible brightness that is usually recorded, at which the station might even be visible during the day.
- -2 to +4 is usually visible at night, but you may have a hard time spotting it if the city lights are very bright.
- From +4 to +6 it is at the limits of visibility to the human eye. If the sky is clear and there are few lights in your area, you may be able to see it. The use of binoculars is recommended.
- To get an idea of how bright the station will be, make a comparison with these magnitudes: the sun during the day has a magnitude of about -26.7; the moon of -12.5; and Venus, one of the brightest stars, of -4.4.
Step 4. Check the weather forecast
Once you have recorded the times when the station will be visible for the longest time, check the weather forecast for that day. Look for hour-by-hour predictions if you can, to see if there might be clouds at these times. Forecasts are often inaccurate if you check more than a day in advance, so check again 24 hours before the station needs to appear.
Part 2 of 2: Finding the Station in the Sky
Step 1. Find the location of the station on the satellite map
Refer to the space station apparition card at the bottom. It should have a column labeled: "where to look," "appears," "azimuth," or "Az." Check the content to get an idea of where the station will appear in space:
- Check N (north), E (east), S (south), or W (west) depending on the letters or words you find in that column. The card may indicate more specific directions than the 4 above. For example, NW (north west) means halfway from north to west. NNW (North-Northwest) means halfway between North and Northwest.
- Read something about using a compass if you are not practical.
Step 2. Find out what height you need to look at
The chart itself should have a column labeled "altitude," containing numbers indicated as degrees "degrees" (or the degree symbol, º). Astronomers divide the sky into several layers called degrees, so that they can refer to a specific location in the sky. A position of 0º is the horizon, 90º is exactly above your head, and 45º is exactly halfway between 0º and 90º. To roughly find the directions between these gradations, stretch your arm out in front of you and close your hand into a fist. The distance from the horizon to the top of your fist is about 10º. If you are looking for 20º, for example, place your fist just above the horizon, then place the other fist above it. The point above your second punch is about 20º. Keep alternating your punches for more gradations
It might seem strange that the space station suddenly "appears" in the center of the sky, instead of emerging from the horizon. This can happen because the space station is only visible if sunlight reflects on it. When the space station is not covered by the shadow of the Earth, it suddenly becomes visible. It may also happen that it is not visible towards sunrise or sunset because it is hidden by the halo of light caused by the sun
Step 3. Look for the space station at this location
At the time specified on the map, check for the presence of the space station in the position obtained in the previous steps. The space station usually has the appearance of a moving bright spot, white or yellowish. It doesn't blink, but if you're lucky, it may appear brighter the instant the sun hits a more reflective surface.
- It will not have multicolored lights.
- There will be no contrail.
Step 4. Use binoculars only if necessary
Binoculars are useful for distinguishing less bright objects. 50mm binoculars usually allow you to see objects with brightness up to +10 on the magnitude scale described above. However, it may be difficult to locate the space station with binoculars alone, as they only allow you to see a small portion of the sky. It is best to find the space station with the naked eye, and then switch to binoculars without losing direction of the station.
A telescope allows you to see even dimmer objects, but it can be nearly impossible to spot unless you know very precisely where it will appear. Use a strategy similar to binoculars, but choose a time when the station will be visible for several minutes
Advice
- To take a photo of the space station in motion, use a high-quality camera resting on a tripod, point it where the space station will appear. When he arrives, he takes pictures, setting the lens aperture to 10-60 seconds. The longer the lens remains open, the more the space station trail will be visible on your photo. (Given the low amount of light, most cameras are unable to take a photo of the space station while stationary.)
- If you're lucky, you may see another point of light approaching or moving away from the space station. This could be another spacecraft carrying resources or transporting astronauts to the space station.
