Thought I'd try something back to basics while my Mammut CCD gets repaired/replaced or refunded. I dug out an old cheapo black + white security camera (ALDI I think) to see if it would be any good for spectra with a Star Analyser 100 (sa100)? I also had a cheap usb capture stick allowing me to record spectra as videos to my laptop.
The security camera chip is a tiny 1/4" so it took a while to align. Luckily the camera has a Toucam type thread so I had no issues mounting it to the telescope. The video capture control was just limited to brightness + contrast, but I managed to turn it down a bit to avoid saturation. The 30s of video was stacked in Registax6.
Below are Vega spectra taken (on different nights) using different setups, (including a DIY slit spectrometer), but all on the same 8" F5 newtonian telescope.
- The 300 l/mm slit spectrometer resolves lots of elements not visible on a slitless sa100 setup, (Ok that was obvious!).
- QHY5 has the best UV response
- The multiple lens elements, (of the 50mm + 135mm DSLR lenses) or the grating, in the 300 l/mm slit spectrometer seem to degrade the UV/blue sensitivity compared with slitless sa100 Mammut. (I might try just using a simple doublet as the colimator when I rebuild it).
- When you consider the price (£10?), the security camera hasn't done that badly. The hydrogen balmer lines are clearly visible.
I am not suggesting you ditch your CCDs and go for a security camera (as there are other factors that come into play). What this does show is that that you can start spectroscopy with whatever you have to hand.
I want to try Vega with a Phillips 880 webcam next to see if the security cam beats the Phillips web cam because it doesn't have a bayer matrix? Place your bets now!
Thanks for looking