Thread: Which Filters
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Old 08-10-2011, 08:01 AM
avandonk's Avatar

avandonk is offline
Join Date: Aug 2005
Location: Melbourne
Posts: 4,786
After reading as much as is available on line and the advice offered here, thanks all, I have decided to go with the following.

I think I will get the ten position filter wheel that takes 50mm square filters. This gives me more filter options without constant swapping that I do not even know about yet.

Initially I will buy the Astrodon LRGB filter set as I like the idea of the Sodium street light pollution suppression with the limited red filter or the hole Jason mentioned.

The Astrodon fiters have far better specifications as far as filter thickness variation (More parfocal - thickness 3+/-0.025 mm) and so not affect focus. This of course assumes that the rest of the optical system is perfect as far as CA etc is concerned. But why add more variables?

They also have a nifty red 5nm continuum filter that can be used for subtracting stars from NB data. Has anyone tried this or seen it done.

Finally I have decided to go for broke literally and get the full set HA,OIII and SII with 3nm spectral width. I am more interested in 'real' nebula colours than artificial pallettes. This may change with time.

They also make a 3nm NII filter although how many objects have this emission line I can only guess at. This NII line is passed by a 5nm HA but not the 3nm HA.

See here

As Mike said we just do not know what will work but the Astrodon filters seem to have a better lot of specs all round at least on paper.

Any further advice is gratefully accepted.

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