Frequently asked questions

How does one start with this hobby?

Very few people start with Astrophotography, but rather with visual astronomy. Binoculars are the most recommended way to get to know the sky. Enjoying observing the sky may or may not lead to wanting to capture its hidden details and beauty. Nowadays there are many affordable and portable small smart telescopes which will allow you to get decent pictures of bright targets like Andromeda or Star clusters, but its a giant leap in cost and time when migrating to dedicated astrophotography setups which cost more than a car and weight more than one can carry.

My recommendation is to get a cheap used DSLR camera and attach it to a telescope which can be used for terrestrial observing and also short exposures of the night sky. After learning the basics of processing astrophotography images and still enjoying it, the hobby evolves in its own rythm.

How small are the objects in your images?

They are actually gigantic. A common misconception is that astrophotography telescopes must have a high zoom. This is only the case for planetary imaging, where the targets (planets) are extremely small. My pictures of nebulae and galaxies actually require a telescope which is only magnifying objects 20x in binocular terms. Most images contain targets which are larger than the full moon in apparent measurement.

Why can’t I see these nebulae with my eyes?

Despite the gigantic size of these nebulae and galaxies, they are extremely far away (sometimes millions of light years) and therefore the amount of light that reaches earth and makes it through our dense atmosphere is very limited. Furthermore a large majority of the light is Hydrogen Alpha (short HA) which is at the deep red spectrum and our eyes are not very sensitive to it, making only extremely bright nebulae like the Orion nebula visible to our naked eye.

What is special about Astrophotography cameras?

The big difference is that they can be cooled. The colder the camera sensor the better, because heat equals light and therefore to a certain extent, astrophotography cameras take pictures of their own sensor heat. Most cameras cool down to 20-30 degrees below ambient, and therefore far below freezing. An ideal sensor temperature is -15 degrees. Another big difference is read noise. Every time a camera reads the values of each pixel, the electrical current creates false signal which is added to the resulting value. Astrophotography cameras are designed with this aspect in mind where one electron more or less of read noise can make all the difference. This aspect is nearly irrelevant for cameras which are used in bright or even dim lighting.

Are those colours in the images real, or artificial?

It depends. Some pictures are declared as ‘RGB’ which stands for Red / Green / Blue and therefore represent the true colours of the picture, even if maybe the balance will be slightly off sometimes due to sky quality or processing techniques. Some nebulae however have been pictured only in the light spectrum of Hydrogen Alpha, Oxygen III and/or Sulfur II, and as Hydrogen and Sulfur both are in very similar red spectrum, astrophotography assigns certain gases to certain colours to give the human eye a possibility to distinguish them. Furthermore as Hydrogen Alpha is nearly always very dominant, a true representation of most nebulae would be an uninterestingly deep red cloud sprinkled with stars. There is a large range of artistic freedom. As long as no data has been artificially added, the colour balance and assignment is very flexible, as long as declared.

Do you need very expensive equipment?

Yes and no. Certain elements can be cheaper and certain need to be the best you can afford. Ironically the telescope its self is the cheapest component in my setup and a fraction of the cost of all the equipment. On the other hand the mount (the device that rotates and counters the earths movement, keeping the target at the same place on the imaging sensor) needs to be highly accurate and reliable. You can always fix poor telescope imaging quality with software, but inaccurate tracking of the target will result in bad pictures, no matter how expensive the telescope and camera is. Assuming you are willing to spend your nights in an open field in the cold, setting up the telescope every time and sourcing the devices from used market places, you can start with 1000 CHF or equivalent.

Why do you need so many pictures / frames to complete one image?

As we’re making pictures of very dim objects, and random universe noise, solar flares and many other issues can cause individual pixels (mostly hundreds per picture) to become ‘bad’. Larger disturbances like airplanes or satellites can cause ‘trails’ which ruin a single frame, but in the larger context of an image are no problem at all. With specialised software these pictures are perfectly aligned and then stacked. Mathematical rejection algorithms sort every pixel by their value ranges, reject outliers, calculate averages and medians and therefore only consider the best pixels of each frame before averaging them. Having between 20 and 30 frames is ideal and reduces noise significantly.