Star’Ex, to go further
So with Sol’Ex we have a small but powerful spectroscope… it is then quickly tempting to point the instrument towards other stars to discover the Universe… welcome to Star’Ex (for Star Explorer, obviously).
There are three main differences between observing the Sun and a star:
- With the Sun, the energy available is enormous, and the exposure times are very short. Starlight is much weaker and requires longer exposure times: from several seconds to several minutes.
- It’s easy to point at the Sun (using the telescope’s shadow, for example)… it’s much more difficult to point at a star.
- The Sun shows a large area, while the stars are just a dot, whatever telescope is used. There is no longer any need to “scan” the stars as we do with the Sun. All you need is a long exposure on the star.
So what needs to be added to Sol’Ex to observe star spectra? Mainly a guiding module, which allows the entrance to the spectroscope (a narrow slit) to be observed with a second camera. This allows the star to be precisely selected and held at the Star’Ex input for the duration of the acquisition, which can take several minutes.
To make the instrument brighter, it is also proposed to replace the objective lens with one of shorter focal length. And it is relevant to use a cooled camera, to allow longer
poses. With few additional elements, Sol’Ex can be used on stars and turned into a Star’Ex. And open a new window on fabulous observations.
By keeping the basic Sol’Ex equipment (small telescope, small CMOS camera), it will be possible to make very high resolution spectra, i.e. to see minute details in the profile of an absorption or emission line. These details are the signature of fine movements of the star, or even within the star.
Picture 5. Examples of spectra obtained with a High Resolution Star’Ex
Star’Ex Low Resolution, for objects with low light intensity
But there is still time to explore! Using a small telescope and a high-resolution spectroscope has one important effect: it limits us to very bright objects; let’s say we have to settle for the brightest stars in the sky.
To observe fainter objects – potentially tens of thousands of stars, nebulae, galaxies, etc. – a few things can be changed:
- Use an instrument with a larger diameter; the entrance slit of the spectroscope must also be changed, to collect all the photons coming from the star.
- Change the diffraction grating, to offer a lower resolution; we will see less detail in the spectra (the “magnifying glass” effect of the high resolution), but we will observe a much wider spectral range (potentially the entire visible range).
Star’Ex Low Resolution is therefore a more ambitious instrument, but one that will offer virtually limitless possibilities.
Picture 6. Example of a spectrum obtained with a low resolution Star’Ex
From Sol’Ex to Star’Ex, one approach, several instruments, different
infinite observations, and still much to invent!
Some obvious types of observations have been mentioned: the Sun, stars, galaxies, nebulae: Sol’Ex & Star’Ex will allow you to quickly discover these objects. But Sol’Ex & Star’Ex is really an EXploration project.
For example, in recent months we have seen new observations using polarimetry (to study the magnetism of stars, among other things), a campaign to observe the Sun is starting up with a professional team – amateur astronomers have a large place in it – we can work on interstellar matter, on the movements of galaxies, on light pollution; there is still a lot, a lot to invent! So Sol’Ex & Star’Ex is also a community that grows every day – because together we are much stronger.
To accompany you in these different variants of the Sol’Ex / Star’Ex project, Shelyak offers you several optical kits, which correspond to the different configurations of Sol’Ex and Star’Ex, and to different uses. We are at your disposal to help you in the choice of your configuration, and we work to obtain the best prices with our network of suppliers. Our motivation is simple: through our daily action, we want as many observers as possible, all over the world, to embark on this incredible adventure. In a few words, here is the range of Sol’Ex & Star’Ex kits:
- The basic kit: pure Sol’Ex, the most economical way to enter the Sol’Ex universe
- The add-on kit for upgrading to Star Ex (high resolution)
- The complete Sol’Ex & Star’Ex kit (high resolution). This is a combination of the two previous kits, but at a particularly attractive price (because we want to encourage you to explore the stars too!)
- The Star’Ex Low Resolution Kit
- … and also a complementary kit for using Star Ex Low Resolution in the near infrared (IR)