Coatings & Filters

Bubble-Nebula_Ha2-OIII-Sync_PS2-V1-Sideways-4STM--Scaled

Can an OIII nebula filter be called “oh-three”?

I have an ongoing dispute with everybody. I say an OIII nebula filter cannot be “oh-three,” since OIII stands for doubly ionized oxygen atoms. I call it an “oh-two” filter. Who’s right? Sorry Philip, you lose. Not only is “oh-three” the universal usage; it makes sense. Well, sort of. A neutral, non-ionized oxygen atom,...

Baader filter.

What’s the difference between nebula filters and light-pollution filters?

What’s the difference between nebula filters and light-pollution filters? Nebula filters block out most of the visible spectrum while transmitting the handful of finely tuned colors that emanate from the most luminous constituents of cosmic gas clouds: hydrogen atoms and oxygen ions. Light-pollution filters, by contrast, are designed to block the colors emitted by...