First time spectroscopy user

[moriniboy]

Afternoon,

Our astronomy club has just been gifted this  and I'm looking for some advice about using it.

Looks like its for visual use only in a 2" drawtube, is it as simple as that?

Thanks Nigel

 

[Merlin66]

Nigel,

That's a 600 l/mm replica transmission grating.

It's normally used in a "school spectroscope" and it's of limited use in astronomy.

You really would need to mount it in a basic slit spectrograph like the Watkin's design.

[moriniboy]

Thanks for the info, will see how I get on.

[robin_astro]

Some school lab diffraction gratings are not too bad. The Star Analyser started out as one of those.  (All gratings you can buy are replicas from a master, that has nothing to do with the quality)

The simplest thing you can try is put it in front of a DSLR camera and image some stars with it. It will turn the stars into smeared out spectra. Like this on my website using a Star Analyser but use a shorter focal length lens with your grating perhaps around 20-30mm otherwise the spectrum will be too long and faint. (test it by pointing at a bright street light first before trying on stars)

http://www.threehillsobservatory.co.uk/astro/spectroscopy_11.htm

http://www.threehillsobservatory.co.uk/astro/spectroscopy_17.htm

It will work on the brightest stars but how well it works on fainter stars though will depend on the efficiency of the grating. If you look through it by eye at a point light source, you will see some light which goes straight through and several spectra either side of that. If it is a good grating  one spectrum will be brighter than the others. Something like this  on Christian Buil's website.

http://www.astrosurf.com/buil/us/stage/session0/img2.jpg

All the other light except in that spectrum is wasted light so the more light is in one of the spectra the better

If you want to try something more sophisticated to mount on a telescope here is a simple design also from Christian Buil which would work with your 600 l/mm transmission grating. Use it without the slit so it is simple to use as you don't have the problem of putting the star on the slit and guiding it there.

http://www.astrosurf.com/buil/us/loris/loris.htm

Here it uses a 300 l/mm grating. For 600l/mm you would need to double the angle. 

Cheers

Robin

Edited September 22, 2021 by robin_astro
added link corrected to omit slit in loris