[ausastronomer (John Bambury)]

I have for Sale a brand new 2" (48mm) HOYA 85B Colour Filter. I have had this filter for about 15 or 16 years but somehow I ended up with 2 x 85B so this one has never been out of the case before tonight's photographs.

This will screw straight onto any 2" threaded eyepiece or accessory like a barlow, paracorr or a threaded diagonal etc. I actually fit mine to the bottom of the Feathertouch Focuser drawtube via a 52mm to 48mm stepdown ring.

This is one of the older Japanese made Hoya colour filters and is of far superior quality to the cheaper Chinese/Taiwanese colour filters.

It is one of the most useful of all the colour filters for visual planetary observing. It is an Orange filter similar to the Wratten #21 but a little bit darker. It is used to enhance the following planetary features:-

Mars - Lightens reddish areas and accentuates dark surface markings; helps to penetrate the Martian atmosphere.

Jupiter - Helpful for accentuating the cloud bands.

Saturn - Helpful for accentuating the cloud bands.

Mercury - Helps to highlight the planets phases.

Because it is a bit darker than the #21, I would recommend using it in Telescopes over 4" aperture only. Smaller telescopes would be better with the #21.

I am asking $20 for this plus $5 postage.

Cheers
John B