Why is this Shelyak 50µm fiber called an "Object" fiber?
In a fiber-fed spectroscope system like the Shelyak eShel, two fibers are used. The 50µm "Object" fiber carries the starlight from the telescope to the spectroscope. A second, larger fiber is often used for calibration, carrying light from a calibration lamp. This fiber is specifically designed for the primary starlight signal path.
What is the advantage of a "High-OH" fiber for my spectroscopy?
A High-OH (high hydroxyl) fiber has excellent transmission characteristics in the ultraviolet and blue parts of the spectrum, down to 380nm. This is critical for astrophysical studies, such as analyzing the Balmer series lines in A-type stars or the prominent Calcium H and K lines, which are found in the violet end of the spectrum.
Will I lose significant signal with this 10m Shelyak fiber compared to a shorter one?
No. The fiber material itself has a transmission close to 100%, regardless of length up to several dozen meters. The signal attenuation of <0.5dB is almost entirely from coupling losses at the connectors. A 5m, 10m, or 20m Shelyak fiber will deliver virtually identical signal strength to your spectroscope.
Is this 50µm fiber suitable for capturing the full spectrum of Vega (Alpha Lyrae)?
Yes, absolutely. Vega is an A-type star with very prominent hydrogen absorption lines (the Balmer series) across the visible spectrum. The 380-800nm range of this High-OH fiber is ideal for capturing everything from the H-beta line (486nm) in the blue-green to H-alpha (656nm) in the red, making it perfect for studying such stars with an eShel system.
Can I use this Shelyak fiber to analyze emission nebulae like the Orion Nebula (M42)?
Yes. The excellent transmission of this fiber makes it well-suited for analyzing the distinct emission lines of nebulae. Key lines for objects like the Orion Nebula (M42) are well within its range, including Hydrogen-alpha (656nm), Hydrogen-beta (486nm), and the two Oxygen-III lines (496nm and 501nm).
What does the NA=0.22 numerical aperture mean for my eShel setup?
The Numerical Aperture (NA) of 0.22 defines the acceptance cone of light the fiber can efficiently capture. It's designed to match the focal ratio of the telescope beam as it enters the Fiber Injection and Guiding Unit (FIGU). This ensures that the starlight is coupled into the 50µm fiber core with minimal loss, maximizing the signal sent to the spectroscope.
