UHC Filter
I bought a UHC filter (Astronomik UHC) with the hope of seeing faint planetary nebulae in spite of the light pollution in the sky. The filter arrived yesterday but I couldn't use it due to the cloud cover. Tonight was clear but the RH was 81% so it was slightly misty.
I started off with the M42 which did show a greater extent and more structure. Then I went for the real test with the planetary nebulae. I went for the bright Eskimo Nebula (NGC2392). The centre was bright but I still could not see the surrounding halo. I then viewed M46 to see if I could observe NGC2438 (mag 11; surface brightness 11.7). I was never certain I had seen this nebula but with the filter it was quite evident. I then tried the Owl Nebula (NGC3587) in Ursa Major. I had seen this only once on an exceptionally clear night. This nebula has a magnitude of 11 and a surface brightness of 12.1. Without the filter it couldn't be seen but with the filter I could see its ghostly shape quite well.
The filter also improved the view of the M1 Crab Nebula (mag 8.4; surface brightness 11) but not as much as for the planetaries.
Saturn is one day from opposition and worth a look. The moon Tethys was to the East of the rings, Dione to the West of the rings and Rhea close to its North East. Titan was further West with Iapetus near to its North.
I started off with the M42 which did show a greater extent and more structure. Then I went for the real test with the planetary nebulae. I went for the bright Eskimo Nebula (NGC2392). The centre was bright but I still could not see the surrounding halo. I then viewed M46 to see if I could observe NGC2438 (mag 11; surface brightness 11.7). I was never certain I had seen this nebula but with the filter it was quite evident. I then tried the Owl Nebula (NGC3587) in Ursa Major. I had seen this only once on an exceptionally clear night. This nebula has a magnitude of 11 and a surface brightness of 12.1. Without the filter it couldn't be seen but with the filter I could see its ghostly shape quite well.
The filter also improved the view of the M1 Crab Nebula (mag 8.4; surface brightness 11) but not as much as for the planetaries.
Saturn is one day from opposition and worth a look. The moon Tethys was to the East of the rings, Dione to the West of the rings and Rhea close to its North East. Titan was further West with Iapetus near to its North.
posted by Albireo at 10:06 PM
3 Comments:
Nice report as usual,. I enjoy them.
I am curious about your observations as you report not seeing the halo around n2392. Could you make it out without the filter?
n2392 is an easy target in optics as small as 4" and observed regularly with the 10", both with no filter. However, I have yet to see n3587 from Central Park. More curiosity: could you see M108 nearby without the filter?
I haven't used a filter here yet in the city but it is something I should consider next time at the astro store.
peter
With my 8" I can easily see ngc2392 but even with the filter I could not see the eskimo's "bonnet". ngc3587 is much fainter, like a ghost. I only saw it once without the filter but last night with the filter it stood out against the darker sky. I have seen M108 on clearer nights but last night it was not visible with or without the filter, but then the UHC filter allows the OIII and H-alpha through so its main use is for nebulae which emit in these wavelengths and not for galaxies which emit at all wavelenghts
thank you for allowing for me to comment
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