Taking Spectrum Of A Neon Lamp

[l3gendluk3 (Luke)]

Hi,

I am having some trouble taking a spectra of a neon emission lamp at around 1.5m in front of the telescope. I can take a spectrum with the sbig SGS on my bench but I have yet to take a spectrum with it on my telescope. I placed the neon lamp on the floor and manually moved the telescope so that the lamp is around the middle (I didn't have an eyepiece so I tried to place it near the secondary mirror) and marked the center of the finder on the floor. The slit holder isn't reflecting much light and images from the tracking ccd can barley show the slit.

Is 1.5m too close or am I doing something wrong?

Thanks,

Luke

[Merlin66 (Ken)]

Hmmm,
probably too short an exposure...
I have a neon bulb illuminating the slit - a distance of about 60mm and still need 8sec exposure to get good neon reference lines.
What exposures were you using?

[clive milne]

Luke,
if you put the lamp at the focal position of a finderscope or camera lens, the light exiting the lens will be parallel (like starlight) If you then point the finderscope with the neon bulb at your main telescope and align them correctly, the main telescope will concentrate the light from your artificial neon star on to the spectrograph's slit. You could conceivably focus sufficient light on to the slit from the neon as to warrant attenuation.
best
c