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OD4 with 10nm band pass or OD5 with 20nm band pass

Equipment Filters Planetary Nebula
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Which is a better filter?
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AstroÅmazer avatar
AstroÅmazer avatar
Which is a better filter, OD4 with 10nm band pass or OD5 with 20nm band pass?

I am thinking of getting some industrial grade filters from Edmund Optics for planetary nebulae, specifically He-II with CWL at 468nm, He-I at 587nm and O-I at 630 nm. These are some examples:

https://www.edmundoptics.com/p/630nm-cwl-od5-20nm-fwhm-bandpass-filter-25mm-dia/55923/

https://www.edmundoptics.com/p/467nm-cwl-25mm-dia-hard-coated-od-4-10nm-bandpass-filter/40064/

Here is the T-mount I plan to use:
https://www.edmundoptics.com/p/25254mm-diameter-t-mount-thin-lens-mount/10576/

Which would be the better option?
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andrea tasselli avatar
andrea tasselli avatar
OD4 is good enough in my book and the narrower the pass-band the better in isolating it, although it beats me why would you want to get those filters as these emission lines are in general weak when non-existent for most PNs. Unless you have a really BIG scope.
AstroÅmazer avatar
AstroÅmazer avatar
On a C9.25 SCT.

A lot of PN have more HE-II at 468nm than S-II. Some have good O-I at 630nm. My SCT is a hand me down and visual only right now. Was thinking about trying it for small PN.

Going of this old survey: https://web.williams.edu/Astronomy/research/PN/nebulae/search/index.php#galactic_milky_way
andrea tasselli avatar
andrea tasselli avatar
My expectation is that you'll be disappointed, especially about collecting data @ F/10 but a bravo for trying!