Does Broadband, Narrowband, OIII, H-alpha filters works?

shadowless · Post by **shadowless** » Fri Sep 19, 2008 9:59 am

Hi,
someone told me that these filters does not really work for for Singapore sky

some say broadband is good for scope with smaller aperture, narrowband for larger scope.

some say they only work or astrophotography and was of money for visual observation.

Can some experienced user advice if these filters are of any use for
1. 3.5"refractor
2. 8"sct
3. 10"newtonian
in terms of visual observation in Singapore sky condition.

Post by **weixing** » Fri Sep 19, 2008 11:17 am

Hi,
Broadband (LPR, LPS and etc) Filter: will work on any aperture scope and almost all objects, but the improvement is not that obvious.

Narrowband (UHC) Filter: will work on any aperture scope, but basically only work on emission nebulae.

Line (OIII, H-beta & etc) Filter: work only on larger (>= 6" for OIII and >= 8" for H-beta) aperture scope and only certain emission nebulae (especially for H-beta filters which is a highly specialized filter).

Anyway, they does work in Singapore, but your observation site must have minimum local light pollution (especially don't have those lighting that directly shine at you) for them to work effectively. This is because the filters only allow certain wavelength to pass through, so they are highly reflective. If your observation site is quite bright, the filter won't work properly and you might see the reflection of your eye instead. :p

Basically, the darker your observation site, the better those filter will work and you'll see the improvement more easily in a darker environment.

By the way, if you want to get a filter to use in Singapore, a good Narrowband (UHC) filter is most useful.

Hope the above helps.

Have a nice day.

Meng Lee · Post by **Meng Lee** » Fri Sep 19, 2008 3:39 pm

Just to add on to what Weixing has said. The first thing to note is whether a filter is for imaging or visual.

Example, OIII filters has visual version and imaging version. Imaging filters are not for visual usage.

shadowless · Post by **shadowless** » Fri Sep 19, 2008 5:51 pm

what's the difference between imaging and visual filter? why can't imaging filter be used for visual? Don't believe all brands made imaging filters, so are those for imaging or visual?

Meng Lee · Post by **Meng Lee** » Sat Sep 20, 2008 12:33 am

I think the essential difference between imaging filters and visual filters is the bandwidth of the filters. Imaging filters are much narrower. So looking through an imaging filter, basically see blackness.

The above are for narrowband and line filters.

For broadband imaging filters, such as IDAS LPS, compared to visual LPR/UHC filters, its the issue of colour balance.

Hehe, thats as far as I know.

Post by **acc** » Sat Sep 20, 2008 10:39 pm

In Singapore, due to our light pollution, I find the improvement marginal at best. (your milegae may vary, some like it more than I do). Ironic as it sounds, they work best under dark (e.g. Mersing) skies where the contrast improvement can be astounding on certain objects. E.g. dust lanes in M42 are more extensive and visible. In 8" - 12" scopes, the Veil Nebula is very faint without a filter but awesome with one.