Trimming a filter to view moons of Mars

Part of an article on Page 107 of the August issue of Sky & Telescope talks about trimming a gelatin filter (Violet or Deep Blue) to aid in viewing the moons of Mars. Basically, this means cutting the filter in half. When using the filter position Mars in the filtered half of the field, and look for the moons in the unfiltered half.

I am not exactly sure what a gelatin filter is. I think all of my color filters are glass.

Has anybody tried this?

Gerry
State College, Pa.

Hi Gerry

Can't help you with the filter question but I can tell you that the bar works. From the same article (but off the web site), I made a bar from tin foil an put it on an Ortho 18 mm. It worked.

Pat G.

Gerry,

Photographers use Wratten Gel Filters. However, they are not cheap. I googled gel filters and found a site that sells a 4" X 4" 23A for $15.95 and a 4" X 4" 25 for $23.95. If you are interested, here's the site:

http://osnews.pricegrabber.com/search_attrib.php?page_id=587&sortby=popular-&vendors%5B%5D=0&lo_p=0&hi_p=0&form_keyword=23a&Update+Results=Update+Results&ut=9efcd6aa9147d730

Frankly, I think you would be better off trying Pat's bar recommendation

Darlene