What is the main purpose of the Shelyak FIGU F/6 – 50µm?
Its primary role is to act as an interface at the telescope's focus, precisely injecting the light from a star into the optical fiber of an eShel or Whoppshel spectrograph while also allowing for guiding.
What else do I need to use the Shelyak FIGU?
You will need a compatible telescope with the correct focal ratio, a Shelyak eShel or Whoppshel spectrograph, a guiding camera, and a calibration module with its own optical fiber. These items are not included.
How does the Shelyak FIGU help with guiding on a target star like Deneb (Alpha Cygni)?
The FIGU has a port for a guide camera that sees the area around the fiber entrance. You can place Deneb directly on the fiber, and then use the guide camera to keep it perfectly centered during long exposures, preventing signal loss from atmospheric turbulence or tracking errors.
How does the remote-controlled mirror on the FIGU work?
The internal mirror can be electronically flipped between two positions. One position directs the light from the telescope to the spectrograph's fiber. The other position blocks the starlight and instead directs light from a separate calibration fiber into the spectrograph, allowing you to take calibration frames.
Can I use the Shelyak FIGU with any telescope?
No, this FIGU model is specifically designed for telescopes operating at a particular focal ratio to ensure the light cone correctly matches the acceptance angle of the optical fiber. Using it with significantly faster or slower telescopes will result in inefficient light injection.
Why is switching to a calibration source important for spectroscopy with the FIGU and an eShel?
High-resolution spectroscopy requires calibration frames (like Thorium-Argon lamps) to accurately wavelength-calibrate the science data. The FIGU's remote switching lets you capture these calibration frames immediately before or after your science exposure without touching the setup, ensuring the highest possible accuracy.