Vega comparison with various cameras

[jnp]

Thought I'd try something different 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.

Conclusions?

• The resolution of the 300 l/mm slit spectrometer resolves elements not visible on a slitless sa100 setup, (Ok that was obvious!).
  
• QHY5 has the best UV response
  
• The multiple lens elements, (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

John

[Merlin66]

Interesting results, well presented.....

[Gasman]

Interesting comparison John, shows you don`t need a super duper camera to get started in spectro!. It also shows what a difference a slit can make.

regards

Steve

[robin_astro]

Hi Steve

Interesting comparison John, shows you don`t need a super duper camera to get started in spectro!. It also shows what a difference a slit can make.

Its not so much the addition of the slit but the collimating optics which allow the dispersion to be cranked up without the aberrations that you get if you try to do the same with the simple converging beam Star Analyser type setup.

Cheers

Robin