I currently use an L-Enhance filter from a sky on the darker end of a Bortle 6 (~19.4 SQM); Bortle 5 is just a mile or so away. My most used local sites are in the 20.7 - 21.3 range.
If I recall correctly, requisite imaging time is proportional to 2.512^(delta SQM). So if I image from, say, Warren Rupp Observatory (~20.7 SQM on the 2020 Light Pollution Map), the 1.3-mag difference in SQM means 1 hr at WRO ~ 3.3 hrs at home.
This recent image of the Leo Triplet required 3.3 hours under a dark sky. :
https://www.astrobin.com/opmn2j/
It's depressing knowing I could've gotten this in just an hour at WRO. But WRO is 1hr 15min away--not a great worknight option unless it's winter and the skies are totally dark by 7 p.m.
So OSC duo-band filters is something akin to an "equalizer". I use an L-Enhance filter that has a 24nm O-III + H-Beta and 10nm H-alpha bandpass. I need MUCH longer imaging times to get the same degree of background exposure. I never kept track of the amount, but suffice to say it's easily several times more. From memory, I want to say 4-5X longer (If anyone actually has this exact data for the L-Enhance, please let me know...)
Anyhow, if it's ~4X longer, it would stand to reason it's the equivalent of imaging from a sky of ~21 SQM, which is really good.
So a few questions come to mind.
1. I'm thinking of upgrading my dual-band filter. Part of me is thinking the IDAS NBZ because of the lack of haloes, another is thinking the Askar Color Magic 6nm or the Antlia ALP-T 5nm. How much of an improvement / darkening of the background sky would these filters accomplish vs. my L-Enhance? And is it really worthwhile for, say, an L-Ultimate (3nm)?
2. I've thought up til now that galaxy imaging boils down to a hard choice between a trip to a dark sky or a long integration. But I've heard good things about the Antlia Triband Ultra RGB filter. How much of an sky darkening will this filter accomplish, and for those who've done a comparison, how does it compare to, say, an L-Pro?
Clear Skies,
Phil
If I recall correctly, requisite imaging time is proportional to 2.512^(delta SQM). So if I image from, say, Warren Rupp Observatory (~20.7 SQM on the 2020 Light Pollution Map), the 1.3-mag difference in SQM means 1 hr at WRO ~ 3.3 hrs at home.
This recent image of the Leo Triplet required 3.3 hours under a dark sky. :
https://www.astrobin.com/opmn2j/
It's depressing knowing I could've gotten this in just an hour at WRO. But WRO is 1hr 15min away--not a great worknight option unless it's winter and the skies are totally dark by 7 p.m.
So OSC duo-band filters is something akin to an "equalizer". I use an L-Enhance filter that has a 24nm O-III + H-Beta and 10nm H-alpha bandpass. I need MUCH longer imaging times to get the same degree of background exposure. I never kept track of the amount, but suffice to say it's easily several times more. From memory, I want to say 4-5X longer (If anyone actually has this exact data for the L-Enhance, please let me know...)
Anyhow, if it's ~4X longer, it would stand to reason it's the equivalent of imaging from a sky of ~21 SQM, which is really good.
So a few questions come to mind.
1. I'm thinking of upgrading my dual-band filter. Part of me is thinking the IDAS NBZ because of the lack of haloes, another is thinking the Askar Color Magic 6nm or the Antlia ALP-T 5nm. How much of an improvement / darkening of the background sky would these filters accomplish vs. my L-Enhance? And is it really worthwhile for, say, an L-Ultimate (3nm)?
2. I've thought up til now that galaxy imaging boils down to a hard choice between a trip to a dark sky or a long integration. But I've heard good things about the Antlia Triband Ultra RGB filter. How much of an sky darkening will this filter accomplish, and for those who've done a comparison, how does it compare to, say, an L-Pro?
Clear Skies,
Phil
