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- This topic has 6 replies, 3 voices, and was last updated 5 years, 5 months ago by Peter Taylor.
3 October 2017 at 10:23 pm #573859
Hi All, At last I got my DIY spectroscope going, this is a neon light bulb I got, is there a way to get it to luck the same as the ones you see in various books with the peaks up from a line
Attachments:3 October 2017 at 10:30 pm #5786025 October 2017 at 8:55 am #578607Andy WilsonKeymaster
At a guess I would say that you have a light leak as a neon bulb should only generate discrete emission lines, no continuum. It is possible that there is a problem with the neon bulb, but I think a light leak is more likely.
You could try taking 2 exposures of the same length, one with the neon bulb turned on, and the other with it turned off.
The other effects that can cause an offset are dark current and bias offset, but they should be roughly uniform, not showing the hump you seen in your spectrum.
Andy5 October 2017 at 9:45 am #578608Paul LuckasParticipant
I’m with Andy. Try imaging the bulb in a completely dark room (ie, with just the Neon lamp turned on) to eliminate other sources of light. If the ‘hump’ is still present, then it may well be the lamp itself.
What are the specifics of the neon “light bulb” you’re using?
Paul5 October 2017 at 2:20 pm #578610
Andy I am not using a neon in the spectroscope have not fitted it yet, is it beter to put it fount or behind the slit, I have tried for light leak there are non.
Paul the neon is a candle lamp out of a standard table lamp.
peter5 October 2017 at 7:15 pm #578616Andy WilsonKeymaster
The neon bulb would have to be placed in front of the slit.
Typically you either have the neon lamp inside the spectrograph in front of the slit, or outside of the telescope so the light goes through the telescope optics and then the spectrograph. The advantage of having it shine down the telescope is you do not have to worry about the lamp position too much. If it is inside the spectrograph, then as I understand it the neon lamp must be carefully positioned so that the light follows the same path as the light coming from the telescope. Otherwise a shift in position of the lamp would cause an apparent but unreal shift in wavelength.
Though there were no light leaks, was the room completely dark or was there an opportunity for other light to pass into the spectrograph optics? Alternatively someone may have a spectrum of a similar lamp, in which case they may know if it also has a broad spectrum component.
Andy6 October 2017 at 8:50 am #578619
Hi Andy, No the room was not at all dark, will have another go Bothe ways and see what happens.
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