Next brightest object: Sirius. Took another 30-sec exposure at f4. For this exercise it was convenient to shoot at f4, because, basically, that's the maximum aperture that the 1.25" grating allows for the 100mm focal length lens, 30 seconds because that's the longest the camera shoots without using "Bulb", and I varied the ISO to yield a bright image on the back-of-camera LCD. ISO 100 suffices for Venus and Sirius. Dimmer stars, higher ISO.

As the kids would say, "Cool!" Look at all that Balmer Series nicely displayed. Seems like the deepest this set-up can go reliably into the UV is about 3800 Angstroms. The next 3 lines in the Balmer Series, H-Eta @ 3835, H-Theta @ 3798 and H-Iota @ 3770, require an extra boost in brightness to show up. See the brightened insert. But I feel there is too much noise at wavelengths shorter than 3800 for satisfactory reliability. Click "original" below right to see the largest version at 1:1, pixel by pixel. Prettiest spectrum I have captured to date...