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Dual band <4nm halo free OSC filters

Equipment Filters Narrowband Duo-Narrowband
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RobertM avatar
RobertM avatar
Hi all,
 I’m looking around for a pair of ultra narrow band filters to use with my 2600mc camera.  I already have an NBZ to use with my fast scopes but need something a bit more tailored to the light polluted UK skies (Bortle 6-7).  I have had good success with the NBZ even with the Squid nebula but the contrast has been poor in my local skies.Presently I’ve been looking at the Altair Astro 4nm certified DualBand Ultra filters.  I’ve had good feedback from someone but I really need to look at  more images before deciding - they are pretty expensive and my loathing of haloes is extreme!  I’ve seen no images of known problem stars (for example Sadr, 52Cyg) so it’s a bit of a difficult investment decision.On the plus side these filters do specify out of band blocking (OD 4-5) ‘over the majority of unwanted visual wavelengths’ although cameras do have sensitivity outside the visual wavelengths.Has anyone experience if these particular filters or any others that are 4nm and have some guarantee of halo free design?  I’m not interested in wider bandwidth since I have that covered with the NBZ or those that are known to produce haloes (l-ultimate and the like).  Some images with problem stars would be great.

Any help gratefully received.
Robert
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Minh Lết avatar
Minh Lết avatar
Just a note, the filter is one of the major sources that causes halo but it's far from the only one. So be advised that the filter that does not cause a halo on other optics systems might cause one on yours.
RobertM avatar
RobertM avatar
Thank you and yes I am aware, however, those filters that have shown a noticable lack of halo on a number of different optical systems are likely to show the same on others also - it is this confidence that I’m after.  Some filters are now starting to quote optical density as a measure of how much out of band blocking there is as well as incorporating more effective AR coatings hence me mentioning the AA Ultra filters.

Robert
Tareq Abdulla avatar
Tareq Abdulla avatar
I am planning to go with L-Ultimate as many mentioned it ha no halo or very very minimal at best, for me that is not a big deal, my main factor is contrast and narrower band for my LP sky of Bortle 8-9, i do have individual 5nm and 3nm filters which are super amazing, but i also want tor me OSC camera as i will use it mostly for RGB but sometimes for dual band if i have to, and i prefer narrower minimum halo over wider band no halo, after all the stars will be used from RGB and not NB.
RobertM avatar
RobertM avatar
I’ve ruled out the L-Ultimate as a lot of the examples I’ve seen have some sort of halo; some more severe than others.  I also have severe light pollution to deal with but I also loath halos.  I hope the L-Ultimate works out for you as it undoubtedly produces fine contrasty images.
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