What is the primary function of the Shelyak Spacer for Star Analyser?
Its primary function is to increase the physical distance between the Star Analyser's diffraction grating and your camera sensor. This action spreads the star's spectrum out over a larger area of the sensor, a property known as increasing the dispersion.
Does adding the Shelyak Spacer improve the resolution of my spectra?
No, it is very important to note that it does not. The spacer increases dispersion (the physical length of the spectrum on the sensor) but does not change the resolution (the ability to distinguish fine details). Resolution is an intrinsic characteristic of the Star Analyser grating itself.
How does the Shelyak Spacer help when imaging the spectrum of a star like Vega (Alpha Lyrae) with a large-format camera?
When the grating sits close to a large camera sensor, a star's spectrum can appear short and compressed. By using the Shelyak Spacer, you can increase the dispersion to spread the spectrum of Vega across more pixels, making its characteristic absorption lines easier to sample, see, and measure.
Is the Shelyak Spacer useful for a planetary camera with small pixels?
Not because of the pixel size itself. At the same distance, smaller pixels already sample the spectrum more finely, since dispersion per pixel is proportional to pixel size divided by the grating-to-sensor distance. Add spacers when your grating-to-sensor distance is below the recommended minimum for your sensor size.
Can I use more than one Shelyak Spacer for my Star Analyser?
Yes, the spacers are designed to be stackable. You can thread multiple spacers together to achieve a greater distance between the grating and sensor, which will further increase the dispersion of the resulting spectrum.
Is there any downside to using the Shelyak Spacer?
The main trade-off is surface brightness. As you increase the dispersion, the light from the star is spread over more pixels. This reduces the brightness of the spectrum at any given point, which may require longer exposure times to achieve the same signal-to-noise ratio, especially for fainter targets.
