Astrodon

Mounting

Guidelines for Mounting Filters

SBIG CFW-8a and Tru-Technology for 1.25" Astrodon Filters

Most customers will order 1.25" Astrodon filters mounted in screw-in holders compatible with SBIG CFW8a filter wheels.  Simply screw them into these filters wheels.  This includes the Tru-Tech CFWs, as well.

Astrodon 1.25" filters come mounted unless otherwise indicated. Astrodon 50 mm filters always come unmounted. This document has links to show how to install unmounted Astrodon filters into several filter wheels from various suppliers.

FINGER LAKES CFW-2 for 1.25" and CFW-7 for 50 mm Astrodon Filters

Finger Lakes Instruments (FLI) makes several color filter wheels (CFW) that require unmounted filters, including the CFW-2 with 8 1.25" positions and the newer CFW-7 with 7 50 mm filter positions. For these FLI CFWs, Astrodon supplies viton o-rings (022  1" x 1 1/8"; McMaster-Carr #9464K76 for CFW-2 and  133   1 13/16: x 2"  McMaster-Carr #9464K133 for CFW-7) that are placed into each position as a spacer that brings the surface of the Astrodon filter to the surface of the filter carousel. The filter is then secured into place with the FLI-provided washers and metric, metal cap screws.  PLEASE NOTE THAT THE O-RINGS PROVIDED BY FLI MAY NOT WORK WITH ASTRODON FILTERS. The link provided here shows the procedure for the 1.25" FLI CFW-2, but the procedure is identical for the larger CFW-7 using larger o-rings supplied by Astrodon.

Remove the two cap screws and washers.

Place the o-ring into the filter position and tap down with a tool such as an allen wrench.

Place the Astrodon 1.25" filter on top of the o-ring with the ^ on the side of the filter pointing toward the telescope.

Secure the filter with the washers and cap screws, blow off with a puffer or compressed air and replace the cover to the CFW.

 

 

SANTA BARBARA INSTRUMENT GROUP (SBIG) STL for 50 mm Astrodon Filters

SBIG's STL CCDs have internal filter wheels with 5 positions for 50 mm or 2" filters.  The unmounted  3 mm thick Astrodon filters, being 49.7 mm in diameter, do not fit as snuggly as the slightly larger SBIG filters. Both SBIG and Astrodon sell filters that are 3 mm thick. Astrodon supplies hard rubber washers with all 50 mm filter orders that fit under the SBIG-supplied thumbscrews that provide a secure fit for the filters.

The washers supplied are now typically red or grey in color, 0.031&quot thick and 3/8 O.D. The provide sufficient overlap with the filter to make a secure hold.  Just remove the cap screw, put the supplied wide washer down first, the narrower SBIG-supplied washer over it and then tighten them down. 

Please place the arrow ^ on the side of the filter toward the telescope (facing down in the above view.

Make sure you handle the filter only by the edges.  If you get a fingerprint on the filter, use a lintless cloth, like a Kimwipe, and isopropyl alcohol or methanol with just a drop or two (not saturated) and lightly wipe the filter in one direction. You'll want to blow off the surface first to remove any loose dirt or particles before wiping.

The other issue is what sequence of filters to use and where to put them.  This took some time to figure out. Adjacent to each filter hole is a stamped label, e.g. 1/R.  Position 1 is the "home" position, which is assumed to be red, because Maxim and CCDOPS have this default built in.  The Optec wheel is different. This label is centered between the two holes and refers to the position on the opposite side of the wheel.  So, whatever filter you put into the hole immediately adjacent to 1/R becomes the top slot when you define it in your software.  Let's say you put Red, Green Blue, Luminance and H-a into 1/R, 2/G, 3/B, 4/C and 5/L, respectively.  If you use Maxim, your Filter Wheel Setup Screen should look like:

 

 

 OPTEC IFW

The Optec IFW has removable "carousels" as shown above.  The filter slots are numbered across from the filter. In this picture, red is #1, green is #2, blue is #3, and so on.