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The new integral 10-position filterwheel contains 9 filters:

Astrodon L,R,G,B,Hydrogen Alpha, SulphurII, OxygenIII
& then 2 spectroscopic filters (diffraction gratings):
100 lines/mm & 500 lines/mm.

The latter allows much higher resolution spectra to be obtained, at the cost of needing longer exposure times to capture sufficiently bright spectra.

The last position of the filterwheel is blank. This wheel is moved to this position when we want to capture light for photometric data from filters in the existing filterwheel, which is now in front of this 10-position wheel.

The existing wheel contains 5 filters for photometric measurement: Schuler U, V, B, R & I.

Position 6 of the old wheel is empty, allowing unfiltered light to pass through to the new wheel, so that we can use the filters in the new wheel instead.

The whole setup means we can do one of 4 types of imaging:

1)Tri-colour imaging (using the Astrodon L,R,G,B filtes)
2)Narrow band tri-colour imaging (using the Halpha, SII & OIII)
3)Spectroscopy (using the 100 & 500 lines/mm filters)
4)Photometry (using the Schuler filters in the old wheel).

Lastly, the old wheel still has the mirror in position 7, where light is divertable to a 2.5/5X converter with a Philips webcam on the back - allowing us to use the whole setup for planetary imaging. The converter is actually a 5X Powermate, but poor seeing conditions in Bristol mean that this magnification is unfortunately often too high, so at the moment, there is a 2x focal reducer screwed into the end of the webcam to limit the magnification. The webcam also has an infra-red blocking filter attached, to prevent out of focus infra 'ghosting' of planetary images. (See the Saturn images elsewhere on this site).