O-III or not there

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  • Member since
    March, 2008
O-III or not there
Posted by Antitax on Thursday, February 06, 2014 4:05 PM

   I had only very faintly glimpsed M97 a few times over several years in my 5" catadioptric, during passages or large dry air masses, and only when very high above the horizon. It was kind of an unresolved issue; this shell nebula is not dim, I should have seen it better than that.

   Then I tried again with the serious 12" after seeing the M82 supernova in the same constellation, under good urban conditions, dry air, pretty high in the sky, but no hint of the nebula. So I didn't bother with the broadband filter and went immediately for the narrowband O-III in a 24mm Hyperion (62x). Star-hopped to where Sky Atlas 2000 shows it and bingo, immediate sighting!

   Finally seeing it was less surprising than how easily I saw it: no need to search the field with averted vision and such, it was, bold, round, large, as a Messier showpiece should be. The 13mm (115x) made some darker feature visible, with no clear hint of its size, shape and location within the nebula, but better conditions (no Moon in the countryside) would surely put the two large dark eyes of the Owl at their rightful place in its face.

   Bottom line, get an O-III filter; chasing emission nebulae from the city without one is asking for disappointment.

+666.

   My neighbor's angora cat just walked on the keyboard while I was typing this, and wrote this ominous +666 sign. Funny coincidence as cats are said to be linked to the supernatural, I hope it's not a curse.

   But seriously, after locating M97 with the Baader O-III filter, I tried again with an Astronomik UHC broadband filter; the nebula was much less detached from the glow. However when chasing galaxies in Virgo and Coma, the larger bandwidth helped.

   Galaxies were a bit fainter but the glow was even more so; the overall view was better, as testified by more stars showing up. After about a half-hour of galaxy viewing with the UHC filter, I tried again with no filter and Ugh! The dirt! Not only the unnatural orange tint, but a sick dirty feel to the field, I realized it's really pollution, as disgusting as chemicals and soot.

   O-III and broadband filters are standard arsenal for a good reason. They not only improve contrast, but also remove the ugly from the city.

TS 8x40 Wildlife, 10x50 Marine/Fujinon 16x70/TS 80mm triplet, 6x30 finder, EQ-3 mount, TS 2" 99% diagonal/Celestron C5+ and 6x30 finder, DIY tripod/5" Bahtinov/12" GSO dob, 8x50 finder/Meade 2" 24mm 82°/Hyperion 24,13,10mm 68°/TS Expanse 17mm 70°/SW 7mm Panorama 82°/Ultima 2x barlow/Astronomik UHC-E filter/Baader O-III/Astro Solar 5" & 80mm filters/Sky Atlas 2000/Rükl's Moon Atlas/Canon 400D/5mW green laser

  • Member since
    March, 2009
Posted by pastorg on Thursday, February 06, 2014 4:46 PM

Glad you were able to bag the Owl Nebula Antitax!  I have viewed it a few times with my Z12 dob with and without an OIII filter, and the filter does improve the contrast.  I still have to depend on averted vision to make out the darker areas of the nebula.

Clear skies to ya!

pastorg

Zhumell Z12 Dob, Celestron Omni XLT 102mm refractor on CG-4 Mount,  Meade AZ70 refractor, Celestron Ultima 2X Barlow 1.25, Telrad with 4 3/8 Riser, Zhumell Skyglow Filter, Zhumell OIII Filter, Baader UHC-S Filter, Meade ND96 Moon Filter, Baader Planetarium Hyperion 21mm, 13mm, 8mm and 5mm eyepieces, Meade 9mm and 25mm Plossls, Zhumell 9mm Plossl and 2 inch 30mm SWA,  6mm Orion Expanse and Pentax 10 x 50 PCF WP ll Binos

  • Member since
    March, 2008
Posted by Antitax on Friday, February 07, 2014 3:50 PM

   Another shell nebula had bothered me for a while: NGC 2371-72. Yes, it has a dual NGC number because it has two lobes. On paper it shouldn't be tough to see but it was always extremely difficult or impossible with the C5, and even the 400mm in the countryside didn't show it that well. It was very easy to photograph on short exposures with that giant newtonian (f/6), though.

   Now that I own that O-III glass and Gemini is well-placed in the evening, I try again, this time with a 300mm dob from the same old city. And finally, I spot the treacherous NGC 2371-72 without having to search much.

   At 62x I could detect it at first sight, no need to search the field with averted vision at length this time. Then 115x and maybe also 150x - memory is vague - and its amorphous glow is present, no problem spotting it.

   The O-III filter is essential. No less than essential.

TS 8x40 Wildlife, 10x50 Marine/Fujinon 16x70/TS 80mm triplet, 6x30 finder, EQ-3 mount, TS 2" 99% diagonal/Celestron C5+ and 6x30 finder, DIY tripod/5" Bahtinov/12" GSO dob, 8x50 finder/Meade 2" 24mm 82°/Hyperion 24,13,10mm 68°/TS Expanse 17mm 70°/SW 7mm Panorama 82°/Ultima 2x barlow/Astronomik UHC-E filter/Baader O-III/Astro Solar 5" & 80mm filters/Sky Atlas 2000/Rükl's Moon Atlas/Canon 400D/5mW green laser

  • Member since
    April, 2012
  • From: North Carolina east coast USA
Posted by stepping beyond on Saturday, February 08, 2014 1:17 PM
I agree Antitax, there are many that disagree but, they must have GPS or goto mounts. I rather enjoy my cruise thru the cosmos than let a computer find its location for me. Although those mounts are beneficial in AP. I just enjoy what I have and leave it at that.

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