Visual comparison in M97, Owl Nebula
There had not been much activity under the stars, in part because of other stuff that keep me busy (AKA Motorcycles), but also because I got bored of seeing the same star patterns in my little window in between the redwoods. However, some time ago I decided it was time to get a nebula filter and following the recommendations of the prairie astronomy club 1, I bought my very first filter: a Lumicon UHC Filter. I think it is a first generation, as I bought it pre-owned from a seller in Cloudy Nights.
Some days later, I got the filter in the mail. A1.25” ring with a shiny silver finish. The box has a sticker that tells the following information about its transmission nebula lines: Oxygen-III 496nm 95%, Oxygen-III 501nm 93% and H-Beta 486 nm 96% (this last and the percentages were hand written so I had to confirm with the technical specs). When I look through it in the daylight, everything looks greenish and I think I could see some flaws in the glass. I don’t think these will affect the performance at least with visual only.
I tried it out a few nights later on every single object I could target in my tight window. It was mostly galaxies so I got disapointed really quick because it did not show any visual improvement, but a darker background and dimmer stars and the DSOs themselves.
More time passed by. Clouds, rain, the moon or my back pain were in my way so not so much stargazing lately. Clear night, moonless and not so cold so I decided to give it a try. Near the zenith I could see stars up to 5th magnitude with my eyes alone. I think I got a good transparency, but a poor seeing (Polaris was flickering at low magnification). Seeing did not really matter because I was not going to try for a planet. In fact, I can’t see planets from my location. They all hide behind the trees.
I waited until the polar bear (AKA Ursa Major) was mostly out of the trees and went straight to Merak (βUMa). From there, it was just one step to M97. I have to mention that I also saw M108, The Surfboard Galaxy and the view was very pleasant. Finally, I focused on M97. With my 40mm eyepiece I could see it like a ghostly circle. It was bright enough to be perceived with direct vision. This time, like the last ones, I could not see the eyes of the owl. I added more magnification, first with my 15mm Luminos grenade, but the light coming from the PN was too dim to fulfill the raise in magnification so I could only perceived it with averted vision. Then, I tried again 40mm, but this time with the filter screwed to the back of the eyepiece: background was definitely darker, less stars visible in the FOV but the PN remained intact. In fact I think it looked brighter, but I know that was just a trick of the mind. Immediately, I tried the filter in communion of the 15mm but no luck. It was actually harder to see than when I used no filter so I abandoned the idea if using that much magnification with this specific object.
When I had spent enough time contemplating the nebula with both filter and no filter, I decided it was time for a sketch. First, I did an unfiltered sketch and then I used it as a template to put key stars on my filtered sketch. I tried to be as accurate as I could, but since it was not a side by side comparison, it’s more like an approximation of the view. The mind and the eyes are deceived, specially in low light conditions, but what is important to know here is that the filter works with PNs. In the future, I will try to add more PNs to the records of this filter. My goal is to be able to check the southern skies where the most beautiful nebulaes are laid.
During this quarantine I wish you the most dark and clear skies!
Edited by: Jennifer Carvajal (editor in chief).