Mars Filter Comparison

The following is taken from a post I made in the beginners forum based on an observing report for the morning of 09-08-05.

This morning I compared several filters in a DSH-6 on Mars. All were used with a 12.5mm Highlight Plossl with Ultima barlow (2.2x) for ~200x. Observations were made from 5:00 a.m. (total darkness) to 6:00 a.m. (pre-dawn). Seeing was good (3-1/2 out of 5) under clear skies. Mars was directly on the meridian at the start of this session. The line-up included the following:

* Meade #23A Light Red
* Orion #80A Medium Blue
* Orion #15 Deep Yellow
* Orion Variable Polarizing Filter 1%-40% Transmission
* Baader Contrast Booster

23A

Under dark skies this filter increased contrast of dark surface features very noticeably. Not huge, but a definite improvement. The Southern Polar Cap was still visible but not enhanced. As dawn approached and my dark adaption failed this filter become too dark for use in a 6" scope. It would probably do well in larger scopes.

#80A

Reduced glare and slightly highlighted the SPC, but was no help with surface detail.

#15 Yellow

No help. Just thought I'd try it. Edit ? this filter did cut some glare, as any amount of filtering would do. For me, it didn't make any more detail visible.

Orion VP

Big improvement in very dark skies but became too much for a 6" scope as dawn approached, even at the lowest setting. Reduces glare and overall brightness. Best for seeing the SPC, even better than the 80A. Noticeable increased detail in surface features. Adds no false color! Overall this was a very close second to the Baader contrast booster in this 6" scope. I should note that during a similar test last Friday in my DSH-8 I actually preferred this filter over the Baader.

BCB

Best overall filter in this scope. Reduces glare markedly. Reduces overall brightness enough to enhance both surface features and the SPC. Lets more light thru than the VP. It adds a bit of orange to the image or maybe it just allows the planet's true color to show thru. The 23A was close to this good at showing surface detail in very dark skies, but the edge went to this filter. As the sky lightened this was the last filter to remain useful.

No filter

As dawn approached and my dark adaption failed Mars was best viewed unfiltered.

If you're viewing with a barlow, try sliding the EP partway out of the barlow and refocusing for increased power (poor man's zoom EP). When seeing allows, the increased power may dim Mars enough to view unfiltered. Try it!