Hello! I recently got the L-ultimate and I wonder if it is a good idea to make a trip to a bortle 2 zone and use it. Should I buy a uv/ir cut or I can use the L-ultimate? I have to mention I am not interested in capturing dark nebulae.
Cristian Arhip:
Hello! I recently got the L-ultimate and I wonder if it is a good idea to make a trip to a bortle 2 zone and use it. Should I buy a uv/ir cut or I can use the L-ultimate? I have to mention I am not interested in capturing dark nebulae.
Yungshih Lee:
People often consider dual-band filters as light pollution filters, and many manufacturers promote them as such. They are actually two distinctively different things. Dual-band filters such as L-Ultimate only allow the bandwidth of Ha and OIII (or in some other cases, other emission lines such as SII) to go through and are really narrowband filters. The obvious example to explain why narrowband filters are different from light pollution ones is that many Hubble images are shot with narrowband filters and Hubble does not really suffer from much light pollution, at least if compared to the ground telescopes.
The purpose of narrowband filters is to reveal only signals of specific emission lines, not to prevent light pollution, even though they do have that effect. So the Bortle scale of a site is not relevant to whether a dual-band filter should be used, but rather what kind of target is being shot. L-Ultimate or L-eXtreme, etc. is generally only good for emission nebulae, or to add Ha, OIII signals to a broadband image. Using them on galaxies, reflective nebulae, dark nebulae, molecular clouds, etc. would give very poor results and could give inaccurate colors to stars and star clusters.