focal reducers and filters

[zcdawson]

My Atik, Hyperstar and wedge will be here next week. Currently I have a 2" narrow band LP filter and a 1.25 OIII narrow band filter. For focusing I have the feather touch (nice functioning focuser). The auto focuser for the feather touch will also be here next week. I have gone a little crazy on the AP stuff and need to get the scope setup to last a little while. I have a few bucks to spend so I was considering a couple more 2" filters and a focal reducer for the other end of the scope, also there is a filter adapter for the Hyperstar that I was looking at. A good GEM will be added in a few months. Any ideas on filters or focal reducers? Is there anything that makes "The big difference"?

[Ikonnikov]

For narrowband (Ha, OIII, SII) you'll need to use a minimum of ~12 nm bandwidth (e.g. Astronomik) or alternatively dedicated high-speed filters (e.g Baader) to get decent light transmission at F2 since the centre wavelength shifts considerably from the original value. Regarding filter size, the C8 and above Hyperstar adapters come with a 2" filter screw fitting but you can get away with using smaller filters (with an appropriate screw-thread adapter) depending on the chip size and image circle.

I have heard some people have had issues with getting the filter drawer to keep filters exactly orthogonal to the chip which is important for image quality at fast f ratios but haven't tried it myself (I just unscrew the camera to change filters in the default adapter but I only tend to use one or two filters per evening so not much of a hassle). 

Regarding focal reducers at the back end it depends on what scope model you have (HD or XLT).

Paul