Should I get a Oiii or UHC filter?

[StarDuke82]

I will start by saying I live under Bortle 5/6 skies on the best nights I can see hundreds of stars and on the worst I can barely see M81 faintly overhead. I know my view’s won’t improve much unless I truly get out to a Dark Sky site nearest is a Bortle 2 zone several hours away but would getting an Oii or UHC filter help a little. I am mainly doing visual at the moment and beginning to get into imaging and will probably get more into imaging as time goes by, I know not to expect much as these filters work by stopping certain wavelengths of light and only letting the narrow and dim wavelengths of light from DSO through so basically it darkens the sky, just wondering if adding them my list of things to add to my growing kit are they worth it and which ones are best?

Edited May 10, 2023 by StarDuke82
Information asking which were best wasnt in initial post

[DirkSteele]

The filters in question only really work on a specific set of deep sky objects, specifically emission nebula like M42 (stellar nursery), M27 and M57 (planetary nebula) or The Veil nebula (supernova remnant). These objects are known to have strong emissions at specific wavelengths such as the Oxygen III line and Hydrogen Beta lines. By using filters that isolate these wavelengths and reject all others, it improves the contrast of object visually and at the end of the day astronomy is a contrast game. They may actually make the target object slightly darker than without but the background is much darker which enhances visibility.

 

They will not help on any other objects such as M81 that you mention as galaxies for example radiate light across the visible spectrum and all you are doing is rejecting most of that light. Unfortunately, for improved views of galaxies, globulars, open clusters and reflection nebulae, the only real solution is darker skies.

 

So which one if you are interested in enhancing emission nebulae? UHC is generally considered the better starter choice as it tends to have better response to more objects whereas the O III is more aggressive (lets less wavelengths through) but is better for certain specific objects. You may find you end up with both in the end.  There is also a question of aperture used. Some conventional thinking suggests O III needs big aperture because it is more aggressive. I tend to find they are usable with small apertures but finding the optimum exit pupil may dictate a lower power in a smaller scope.

 

Hope that helps.

[StarDuke82]

10 hours ago, DirkSteele said:

The filters in question only really work on a specific set of deep sky objects, specifically emission nebula like M42 (stellar nursery), M27 and M57 (planetary nebula) or The Veil nebula (supernova remnant). These objects are known to have strong emissions at specific wavelengths such as the Oxygen III line and Hydrogen Beta lines. By using filters that isolate these wavelengths and reject all others, it improves the contrast of object visually and at the end of the day astronomy is a contrast game. They may actually make the target object slightly darker than without but the background is much darker which enhances visibility.

 

They will not help on any other objects such as M81 that you mention as galaxies for example radiate light across the visible spectrum and all you are doing is rejecting most of that light. Unfortunately, for improved views of galaxies, globulars, open clusters and reflection nebulae, the only real solution is darker skies.

 

So which one if you are interested in enhancing emission nebulae? UHC is generally considered the better starter choice as it tends to have better response to more objects whereas the O III is more aggressive (lets less wavelengths through) but is better for certain specific objects. You may find you end up with both in the end.  There is also a question of aperture used. Some conventional thinking suggests O III needs big aperture because it is more aggressive. I tend to find they are usable with small apertures but finding the optimum exit pupil may dictate a lower power in a smaller scope.

 

Hope that helps.

Thank you for your response I was considering getting one to view many of the nebulae that are currently visible in the sky right now I realize nothing helps with viewing galaxies perhaps I should have used something other than M81 to help explain my skies, 😅in any event you have helped me make my decision on adding one or both to my kit thank you again.