Quote:
Originally Posted by p1taylor
Thanks for your info will set it up to 50mm as suggest, is there a way I can test it during the day as weather is so bad ether ran or freezing, if I put a neon bulb in fount of scope will that do.
peter
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A handy way to test the set-up indoors is to get a chromed ball-bearing and set it up far enough away that you can focus on it (e.g. down the other end of a long hallway).
Turn off the general room lights, and set up a light source some distance away, pointing at the ball bearing so that the light source doesn't shine into the telescope (e.g. a torch or spotlight set up next to the telescope works well) - you should see a brilliant point reflection on the ball bearing. Focus on this image, and you will get the spectrum through your SA grating.
A 10 mm ball bearing works well - the smaller the sphere, the smaller the reflected image of the light source, and the easier it is to get a nice sharp spectrum. Preferably, mount the ball bearing on some matte black card or similar, to give a dark background for the spectrum.
Try changing the light source, and you will immediately see the different spectra - a halogen bulb gives a full broad spectrum, extending well into both the IR and UV (unless it is a UV-filtered bulb). Fluorescent lights (e.g. a CFL globe) give an emission line spectrum for mercury and various other elements. An RGB LED shows three spikes for each of the Red, Green and Blue LED elements, while a bright-white LED gives a prominent Blue spike and a broad spectrum across the Red to Yellow. A laser pointer will just show a single narrow spike.
Using a broad spectrum source (such as an incandescent or halogen globe), you can try putting various filters in front of your camera - for example, you can measure the transmission of your astronomical filters by comparing the filtered spectrum with the unfiltered spectrum.
And all of this can be done indoors, before you even get your set-up out under the stars!
If you take the ball bearing out into your backyard under the Sun, you can get a really nice spectrum of a typical Class G2V star - good ol' Sol!
