Mars filter

Please help me - I'm trying my best to get a good view of Mars, but I think I need a good filter. The standard Meade filters I bought aren't cutting it. Thank you!

Orion XT 8
Burgess Planetary 6 mm
Tak LE 7.5
Meade UWA 4000 8.8mm/14mm
Televue 2x Barlow

Filters for astronomical use also share a similar condition with photographic filters. This has to do with 'factors' and how much light they block. The higher the factor, the darker the shade of color the filter has.

As you increase magnification to high levels, the image starts to become 'dimmer' and thus starts to become less tolerant of increased factors. This becomes more important as you try to tease out the very subtle albedo shadings.

What this means is that one filter with a factor of 'X' will be great at 'n' magnification and not so great at 'n X 2". Thus, with my 5" refractor, I was cycling through my Baader Contrast Booster, FL-D, #85 and #82A for the best views of the albedo. For the seeing and mag (195X - 260X) I was using, these worked the best out of a collection of 21 filters and 1 mm stepped orthoscopic eyepieces with a 1.8 barlow (7mm, 6mm, 5mm, 4mm, 3mm).

Since you are using a 8" scope with a different range of eyepieces and eyepieces with different lens configuration, your milage will vary.

To get a nice range of filters, go to a specialty art supply store and pick up samples of color transparancies if they have them. Then you can experiment with them by holding a sample in front of the eyepiece when viewing Mars or any other planetary object.

Hope this helps.

Clear and steady skies,

Darlene

I use a #21 Orange filter (Celestron) with my 10" Dob and it works really well to bring out the dark areas on the surface. You have to be patient and wait for times of good seeing. Mars is so bright right now, I actually feel like I need a filter to cut some of the brightness back. I have been happy enough with the results from this filter to not worry about getting any other ones.

Clear skies,
Steve Murphy
Raleigh, NC