How does a smart telescope's image sensor work?
13 Aug. 2025
Vespera Pro is equipped with the largest image sensor ever integrated into a smart telescope. Combined with Vaonis patented automatic mosaic capture mode, it’s capable of producing images up to 50 megapixels in resolution. This means it can capture even the largest nebulae in their entirety, and thanks to the sensor’s high-density pixels, you can zoom into the image to reveal fine details of celestial objects, all while maintaining impressive image quality.
Beyond technical specifications, have you ever wondered how smart telescopes actually transform the faint light from distant stars into vivid color images? This article breaks it down so you can understand the magic behind the lens.
An astrophotograph of the Eagle Nebula,
captured with Vespera Pro in wide field,
then zoomed in to reveal the intricate details of its core.
Turning Light into Electricity
At the heart of the smart telescope is the image sensor, composed of millions of tiny light-sensitive cells called photosites. Each photosite corresponds to one pixel in the final image.
When photons (the particles of light) pass through the telescope’s optics, they’re directed toward the sensor. Each photon carries a small amount of energy, and the sensor’s job is to convert that energy into an electrical signal.
When a photon hits a photosite, it releases an electric charge proportional to the amount of light received. The more photons a photosite collects, the stronger the signal it generates. This analog signal is then converted into a digital value, which corresponds to the brightness of that pixel in the image.
However, no sensor can convert 100% of incoming photons into electrical signal. The quantum efficiency of a sensor describes the percentage of photons it successfully converts. For example, the Sony IMX585 sensor used in Vespera II has an excellent quantum efficiency of 91%, allowing it to collect light very efficiently. This makes the telescope extremely sensitive and “fast,” capable of capturing deep-sky objects in less time.
Color-Blind Sensors and the Bayer Matrix
While image sensors can detect the intensity of light, they are fundamentally color-blind, they can’t distinguish between different wavelengths of light on their own.
In traditional astrophotography, this limitation is overcome by taking three separate black-and-white images through red, green, and blue filters. These filtered images are then combined to create a full-color photo. While this method can produce great results, it is complex, time-consuming, and not well-suited for smart telescopes designed to offer a seamless, autonomous experience.
Instead, smart telescopes like Vespera use OSC (One Shot Color) sensors, which can capture full-color images in a single exposure. This is made possible by the Bayer filter array, a microscopic matrix of color filters — red, green, and blue — placed over the sensor’s photosites (image below). Each photosite only receives light of one color based on the filter placed above it.
To recreate a complete color image, an algorithm performs demosaicing, interpolating the missing color values for each pixel based on its neighbors. The result is a balanced, full-color image created from a single exposure, no manual filtering required.
Choosing the Right Sensor: A Matter of Trade-Offs
Astrophotography has two main goals:
- Capture as much light as possible to reveal faint celestial objects
- Resolve the finest possible details in those objects.
Because light from space is so faint, long exposure times are required to collect enough photons. The size of each photosite determines how much light it can capture in a given time. Larger photosites collect more light, meaning the telescope can produce a clean image faster.
However, larger photosites also mean lower resolution. There’s a trade-off between light sensitivity (speed) and detail (resolution). A sensor optimized for one will inevitably sacrifice some performance in the other.
Vespera Pro, for instance, uses a sensor with 2 micron photosites, compared to 2.9 microns on Vespera II. This allows Vespera Pro to deliver much higher-resolution images, ideal for deep zooms and large-scale prints. The trade-off is that it requires longer exposures to gather the same amount of light than Vespera II.
As a result, Vespera II is better suited for live or assisted visual observing, where shorter acquisition times are preferred. Vespera Pro, on the other hand, is suitable for astrophotography, where integration times of several hours are common and even expected.
To make this easier, Vespera includes an exclusive automatic multi-night capture mode, allowing users to accumulate many hours of exposure across several sessions in a very easy way.
