Test report : Lumicon OIII filter.

In this day and age it seems that no matter where you go to observe there is some form of light pollution. To combat this there is now a large array of light pollution filters from a variety of manufacturers. Earlier this year I purchased an OIII filter by Lumicon, but does it really make much difference?

The first object to be tested was M27 Dumbbell Nebula, this usually very prominent planetary nebula in Vulpecula, appeared quite faint and washed out due to a hazy sky and a first-quarter moon still high in the sky. Not really a night for deep-sky, so would the OIII make a difference? Screwing the filter into the barrel of the eyepiece revealed a slight problem - the filter was about 0.5mm too small. Although I could screw it in, the filter was quite slack and I was worried it might fall out if the scope was knocked. Carefully wrapping a narrow piece of sticky tape around the thread cured it. So back to the observing, WOW! M27 was extremely bright, the dumbbell shape was very clear, surrounded by a thick glowing mist.

Moving onto another planetary, M57 Ring Nebula in Lyra. Without the OIII it appeared as a small, grey, faint, fuzzy oval. Adding the filter to a higher power eyepiece the nebula exploded into detail. The ring like structure was obvious, with the left and right-hand sides distinctly thicker giving it an oval shape - wow again!

Next was the faint planetary NGC6210 in Hercules. This is one of my favourite little planetary nebulae due it's pronounced green colour. Normally this appears stellar even under fairly high magnification, however with the OIII it immediately became at least a magnitude brighter, revealing a small, but very bright, hazy disc approx. 8" in dia., slightly brighter towards the middle

To round off the evening I tried for the faintest object yet. The Veil Nebula, a supernova remnant in Cygnus. Even on the darkest, clearest nights I still hadn't been able to pin this object down. So with a hazy, moonlit night I wasn't very hopeful. I added the filter to a low power eyepiece and pointed the scope towards the star 52Cyg. In the eyepiece was a thin band of pale light running right across the field of view. Success! Moving across slightly I picked up the other half of the loop, which to my eyes, appeared brighter still with hint of the filamentary structure for which this object is famous. All in all, not bad for night when I wouldn't normally have even attempted a deep-sky session.

Although the filter was quite expensive (£99 + p&p, from BC&F), it has become an invaluable piece of kit, enabling me to find those faint, elusive nebulae that were previously well beyond the range of my scope - an 8" dob.