"Nebular filters don't help with galaxies". "Nebular filters don't help with star clusters". Or so it is said, but how much of this is hearsay and how much is experienced fact? Maybe it depends on the accuracy of the filter's transmission curve. Maybe the local recipe of light pollution changes the result; in my case it's almost entirely sodium orange, with very little mixing of other tints.
Well, anyway the german-made Astronomik UHC-E helps with everything in the deep sky: galaxies, nebulae, open clusters, globular M15, from my 62,000 freaks town bordering a 200,000 freaks city.
Before going to bed I set my alarm clock to ring before dawn so I could view Jupiter; Sat24's infrared map had shown a neat pack of dry air sliding down the large british isle's eastern border. When I woke up lingering clouds bothered me for a while but they went away without me really noticing, while I was star-hopping left and right (from my eastern window with the tabletop scope resting on the window's marble).
This night and a another one in early September the UHC-E had proven its worth again: Orion's M42 looked like a woven basket, but most striking was the soot-dark cloud bordering the fluorescent green: it said through the glass "I'm sinister and I loom ominously in the night! Oooww! Oooowwww!". Pretty much the closest thing to seeing a black ghost; when a view becomes a scene and seeing becomes feeling, you know you have the right instruments. In this case it was the Celestron 5 and Astronomik's sharply-tailored filter.
M1, on the same night, was there with the filter and not there without it at its low altitude. But back to this night, or this predawn, more accurately. While switching gear and targets, I tried the interference filter on Jupiter and it acted pretty much the same as a tinted-glass green filter, everything dark on Jupiter was much enhanced. But where it allows many more targets is with open clusters: the three showpieces in Auriga, M36-37-38 were better seen.
Fainter stars, obviously, but much blacker foreground (light-polluted air is not the "background" as is often said, the "background" would have to be farther away than the stars). At first it seems to be a tie but with some insistence more stars show up than without the filter, and a black sky looks more natural than orange photon soup, for sure.
Gemini's gigantic M35 also showed up, no surprise, but at 5:18 local, with dawn lightly blueing the sky and the cluster about 45° high, its faint sidekick NGC 2158 also showed up in the filtered viewfield. After some insistence it revealed itself as nebulous, then I averted my gaze at 12 o'clock, 3 o'clock, 6, 9, averted the sight a little more, 12 o'clock, 3 o'clock, 6, 9, etc, than a little more until it became grainy and then resolved into discrete stars. Thanks to the unusually dry air, no doubt, because in normal conditions it's just a blur.
To end the session I aimed at M81/M82 with a 13mm Hyperion (96x) and said filter, they both showed up real easily (how would they look in an arid mag 7 sky?). M82 was a disheveled stretched blob of cotton while M81 was its more clear-cut sharp nucleus in a squarish glow, with a couple faintish stars close to the nucleus, this filter really knows what to stop and what to let through.
Well, this is the spur-of-the moment review of this neat german optical gem. Keep in mind it is the least expensive filter in Astronomik's range, yet it works splendidly. Later in the day I will receive Baader's O-III filter I ordered yesterday. Been following it with its tracking number while observing. Incoming dawn, computer screen light, street lights, all the little diodes always lighting up an apartment, far from total dark adaptation but none of that prevented the UHC-E from performing.
By the way I experimented with an oversize 105mm x 85mm eyecup on one of the eyepieces I used in this session. It's made of black grainy superthick paper, cut and curved to fit my nose-face-orbit shapes closely, right against the skin. It does improve contrast but most of all it cuts all the distracting blurs in the peripheric vision - you notice how annoying they are when they finally disappear, then you never want to see them again - so you can focus effortlessly on the round image in the lens, with only neat blackness surrounding it.
Having nothing to see but what is in the lens relaxes you in a way you have to feel to realize how eyecups are all defective. They're all too small, however leaving no gap between them and the face would cause dew in the cold, this has to be solved. One way is to make the eyecup even larger and to not press it against the face. Or use an old-fashioned black hood but I would prefer to keep the other eye on the surroundings, and not look like a medieval executioner.
Anyway, try making an oversize eyecup and see how your attention suddenly straightens when all the vague edge-of-sight ghosts stop pulling it in all directions. I suggest cutting the eyecup from mousepad rubber, it's black, nonreflective, pliable, easy to cut and washable. And cheap to experiment with. Remember, black is good because contrast is everything.
Gee, this improvised review turned real long, got to stop now.