julian weßel - astrophotography

Stratos at Night

I'm happy to tell you that my Stratos Project is going one better with Stratos at Night.
My latest launch was a full success and over 20 Million people all over the world watched the result.
Since then I wanted to go further and wanted to make a video nobody has seen before.
Launching a weather balloon at night, capturing the stars and the city lights like the astronauts see them from the international space station.


Click here for an introduction in how to launch a weather balloon.



Camera 

To capture images in the pitch black of the night I need to use a high sensitive camera. The best one on the market is the Sony a7sII.
This camera is a beast when it comes to low light imaging and I was overwhelmed when I first tested this camera.

For the flight I'll use a Canon 14mm f/2,8 to get the best out of the camera.

Here you can see some test shots with it. Notice how good the perfomance is even at ISO 510000 or higher.



Space Capsule

I built a new space capsule which is well filled with padding material so the camera is safe in the capsule. Even at a strong impact on earth it won't cause any damage to the equipment.


Due to the bad batterys I needed an external power source. I used a normal power bank for this with a storage of 5200mha. It will keep the batterys running for ober 4 hours.
Because of the big costs of the Equipment I used 2 GPS tracker instead of 1 like on my first launch. Just to be safe I'll find my stuff after the landing.


Data Logger

Another great new feature is the Data Logger which loggs temperature, pressure,GPS,velocity, density and humidity over time.
You can visualize all parameters on stratoflights.com. They've produced an online tool to show your Coordinates over google Earth or just simple diagrams.


Heat production inside the capsule:

In this diagram you can see the temperature over time at a -20 Degrees celsius test in a refridgerator. At first I wanted to put heaters into the capsule but tests show that the
heat production of the camera is enough to keep the capsule at a temperature above zero. With heaters inside the camera started overheating and shut down.


Flight Area

This is Europe as seen from space at night

The idea is to start at the Ruhr area to capture as much city lights as possible and then at a high altitude capture the stars, milkyway and shooting stars. The ideal landing point would be north of the start location, because there is not much population and the topography is flat.






Here you can see how I prepare my capsule in a video: 


Flight

I'm glad to tell you that the Stratos at Night Project was a full success. In windy conditions we managed it to capture the light of the earth and stars from a maximum altitude of 27000m.


Full video on YouTube:


German TV Report


Here you can see the flight path:


3D Animation



Interpretation of Data

In these charts you can see the evaluation of the Datalogger which was inside the capsule.

Temperature over Altitude

These lines show the internal and external temperature over altitude. The smooth lines are from the ascent and the fuzzy lines from the descent. The most characterizing feature of the Stratosphere is the temperature isn't constantly going lower like you would assume. At a height of about 20000m the temperature starts rising again. This is because the Ozone Molecules which are located at this height interacting much more with the sun rays than other molecules. This heats up the Stratosphere up to 0 degrees celsius. Therefore no convection can happen in this part of the atmosphere. 


Pressure over Altitude

The blue line shows the pressure over altitude. You can see the  pressure is going lower by altitude this is because the atmosphere is way more thinner at this height. Gravitational forces pull down the atoms with more mass. Only light atoms stay at this altitude.