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Hello Fellow ABers, I bought a brand new (mistake, I know) Duo filter from ASKAR in the summer to complement my Optolong L-Extreme (of which I am very pleased with) so that I can use both on my 2 main rigs. And I have used it for the past 5 months but on subjects which, in the main, are reasonably bright intrinsically at the two transmission bands of the filter (Ha and OIII). However, on very faint subjects, I found the results more than somewhat lacking in terms of overall brightness. Originally I though it was due to the vagaries of air transparency, which can be very poor where I live. But as results are stacking up I cannot discount the possibility that in fact I have been landed a dud. Sadly it is too late to return and not sure I can demonstrate that the results or lack thereof are due to the filter and not something else (despite the something else never have changed, at least for the image train). To make it blunt, comparisons between the same subject shot with the L-eXtreme and the Duo D1 are depressing at the thought of the hours spent for so little return (from the D1, that is). Am I the only one with disappointing results or are there more out there in AB? Thanks, Andrea |
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| I’m sorry you’re having issues! I have both the D1 and D2 versions of the Askar color magic filters and I’ve found the performance of both to be very good on faint targets. I guess the only way to tell if you have a bad filter would be to test with a spectrograph. |
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| I mostly concur with what @Rob says. I have found the brightness of D1 filter images to be quite reasonable. However, I have found that the D2 filter images are dimmer but that is expected because its S2 component is usually quite weaker than the D1's Ha. As a result, I generally increase the D2's exposure time to compensate. |
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Jim Thompson mande a in depth analysis of this filter just like he dows with lots of OSC filters You may find the discussion here https://www.cloudynights.com/topic/848478-optolong-l-ultimate-askar-colour-magic-3nm-duo-narrowband-testing/ The thing is: yes, this filter is not even close to a decent spectral precision nor bandpass efficiency You might get your hands on Antlia filters. They are a bit more expensive but best quality on the market if you are after OSC filters |
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Rafael Amarins: Thanks for the link but my dual-band filter is the 6nm version of those. I thought it would have been no issues unfortunately with transmission (therefore efficiency) being apparently lacklustre on those filters I'm afraid I got the wrong one. To be 100% sure I'll do a back-to-back test and compare with the L-eXtreme (once the clouds part, that is). I'm sticking with the Optolongs for the moment being. |
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I've posted this before on various CN discussions on this topic. I have an L-eXtreme and the D2 filter (Sii and Oiii), and the Oiii is much better through the L-eXtreme, even though I think they are supposed to be the same bandpass. Could just be my sample, but hard to argue with this example:  |
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Richard Carande: Thank you so much for your posting, that is exactly what I was looking for! I think my main issue isn't as much in the OIII band (although I think there is less signal there compared to the L-eXtreme) but in the Ha band where the difference *appears* to be more noticeable. |
