Handbook for the SX remote control Spectrograph Issue 1, 17/8/20
3) Centring the spectrum:
The SX spectrograph is supplied with the middle part of the visible spectrum centred on the CCD position, but you might
want to change this. If so, try pressing the ‘Wave’ buttons until the appropriate region is seen. A small change of the focus
setting may be needed to optimise the definition.
Using the spectrograph
Your spectrograph is now ready for general use. The basic sequence of operations might be as follows:
1) Locate the field of your subject star or nebula and centre the subject in the slit cursor of PHD2.
2) Find a suitable guide star in the field and click the mouse cursor on it. Click the PHD2 target button to start guiding.
3) Start an exposure with your imaging camera software. The exposure time required will depend on the subject brightness,
but 5 or 10 minutes will suffice for many fairly bright objects. Stacking multiple exposures may be necessary for faint ob-
jects. For example, T Coronae Borealis (usually around mag. 10) needs about 10 x 300 second exposures to get a good sig-
nal to noise ratio. Adjust as necessary.
4) Save your spectrum image as a FITS file. You might also like to ‘stretch’ the image contrast and save the result as a jpeg
or Tiff for easy import into other software (such as RSpec - see below).
These simple instructions are sufficient for capturing a spectrum, but you will probably want to identify spectral lines and,
perhaps, perform further analysis of the data. To this end, we recommend using the third party program ‘RSpec’. RSpec is
an easy to use spectral analysis software that can show a graphical plot of your spectrum and will allow you to calibrate the
wavelengths of the visible spectral lines. The current full price is a very reasonable $99, but we have included in your pur-
chase price of the Starlight Xpress spectrograph, a license for this software. You can begin using the software immediately
by downloading a 30-day trial version from their website:
www.rspec-astro.com/download.
To remove the 30-day re-
striction on the downloaded version, contact them at
, providing the serial number of your
spectrograph, the date of purchase and the dealer from whom you purchased the spectrograph."
Once RSpec is installed on your computer, start the program and click on ‘Open’ at the lower left side of the screen. Find
your jpeg or Tiff image and open it. RSpec will show your spectrum in the small image box at the left hand side of the
screen. Now drag the upper and lower cursors so that the spectrum is neatly boxed between the cursors - the large window
will display a plot of the line profiles in the spectrum. The following image shows a spectrum of the Orion nebula (M42)
and you can see the strong oxygen lines etc. very clearly.
