Automatic Image Calibration with Vespera Pro

The new automatic calibration feature allows Vespera Pro users to capture sharper, more detailed images effortlessly. By effectively reducing digital noise and optimizing observation quality, while keeping the capture process simple.

What is the Role of Image Calibration?

Capturing images of galaxies and nebulae requires highly sensitive sensors and long exposure times. This process not only records the light from celestial objects (the "signal") but also introduces unwanted "noise" partly  caused by the sensor’s electronics. It includes artifacts like hot pixels—points that remain illuminated regardless of the actual signal.

Vaonis smart telescopes automatically use a stacking technique to reduce noise and produce high-quality images. However, even greater image clarity can be achieved by calibrating individual frames before stacking.

By taking an image in complete darkness (with the lens covered), a calibration image, or dark frame, is created. This dark frame maps the sensor’s imperfections, allowing these flaws to be subtracted from the captured images.

A 20-minute capture without (left) and with (right) automatic calibration. With automatic calibration, noise level is reduced, and details are more defined.

How Does Automatic Calibration Work?

The noise generated by the sensor depends on exposure time, gain, and ambient temperature. Traditionally, specific calibration images must be captured under conditions similar to those of the observation, which can be inconvenient.  

Vaonis has streamlined this process by developing an innovative technique: the Universal Master Dark. This single calibration model is applicable to all observation conditions and also incorporates offset or bias data. Once created, the Universal Master Dark can be used for all observations, eliminating the need to frequently capture new calibration images for each session. 

How to Generate a Universal Master Dark.

Steps to Create the Universal Master Dark:

• Turn on your Vespera Pro and connect it to your smartphone or tablet via Wi-Fi. 
• Open the Singularity app and confirm that the instrument is detected.  
  
• Place the supplied lens cap over the telescope’s aperture and ensure the arm is folded down (the telescope does not need to be initialized).  
  
• Access the instrument settings through the corresponding widget.  
  
• Select "Calibration Frames" and follow the on-screen instructions.  

If you interrupt the operation during the capture, you'll need to start over from the beginning.

Duration and Frequency:

• Generating the Universal Master Dark takes approximately 30 minutes.  
• This file only needs to be created once, but it is recommended to renew it every 12 months.  

Optimal Conditions:

Perform this operation in a warm ambient temperature (20–25°C) and ensure complete darkness by using the lens cap. This task can easily be done indoors during the day.  

How to Enable Automatic Image Calibration.

Once the Universal Master Dark is generated:  

• Go to the instrument’s Settings screen.  
• Select "Settings."  
• Enable the option "Use the Master Dark."  
• Begin your observation as usual.  

Note:Automatic calibration is only applied to observations involving stacking (e.g., galaxies, nebulae). It is not used for live observations, such as those of the Moon or the Sun.  

Q&A : Automatic Calibration and Master Dark.

Does automatic calibration work in all observation conditions?
The Universal Master Dark applies to any observation involving stacking with exposure times between 1 and 25 seconds, gain levels between 1 and 27 dB, and regardless of temperature.  

How can I verify that automatic calibration is active during an observation? 
When automatic calibration is active, a specific icon will appear at the top of the observation screen.  

What is the difference between using the Universal Master Dark through automatic calibration and capturing darks in expert mode?  
Darks captured in expert mode are intended for manual stacking after the observation. These darks do not affect the ongoing observation.  

Does automatic calibration affect the individual FITS images recorded by the telescope?  
No. FITS images should remain unchanged as they are intended for manual stacking, possibly with the manual capture of darks.  

Does automatic calibration affect the 16-bit TIF images intended for manual processing?  
Yes. TIF files for manual image processing are generated from the automatically calibrated images (if the feature was enabled before the observation).  

Can I use the Universal Master Dark with traditional astrophotography software for manual stacking?  
No. The Universal Master Dark uses specific algorithms developed by Vaonis that are not implemented in traditional astrophotography software. For manual stacking, use expert mode to capture traditional darks.  

Does automatic calibration apply when capturing mosaics?  
Yes. Ensure that the feature is enabled before starting the capture.  

Does automatic calibration apply for observations using Plan My Night?  
Yes, as long as the feature is activated at the time the plan is launched.  

What happens if I enable or disable automatic calibration during an observation?  
The observation settings applied are those defined at the start of the observation. If you forget to enable automatic calibration, you will need to restart the observation and enable it to benefit from it.  

How does automatic calibration affect multi-night observations?  

• If you start a multi-night observation with automatic calibration enabled, it will remain active when resumed, regardless of the setting in the Singularity interface.  
• Conversely, if automatic calibration is disabled at the start, it will remain disabled for the resumed observation.  

Does automatic calibration impact the acquisition speed during observation? 
No.  

Does automatic calibration affect the file size of the images?  
No.

Cover Image: The Heart Nebula captured with Vespera Pro using automatic image calibration. 2 hours of data acquisition. Post-processed image.