I've had two very successful nights these past two weeks. I been challenging myself with two difficult planetary nebulae in my 12" Lightbridge. The first, NGC 6210 or otherwise known as the Turtle Nebula in southern Hercules, and second, NGC 6891, located near the constellation Delphinus.
The Turtle Nebula has been described within the pages of the current issue of Sky & Telescope (July, 2010). It was everything the author Ken Hewitt-White described in his monthly column "Going Deep", with one exception. He used a 17.5" dob and I used a 12 inch. The difference in aperture made it rather difficult to see the central star. Something I've been trying to do with every Planetary nebula I observe. A magnification of more than 300X brought into view the shape of the object which has given its name, but poor seeing rendered the image unsteady and fuzzy. Backing off the power to 200X with an 8mm Celestron Ultima LX allowed me to finally catch a momentary glimpse of the central star when the seeing momentarily settled down. It is interesting to note how many of these objects appear small, bright and often colored green or blue. However, as difficult this object was it paled in comparison to the next planetary, NGC 6891.
NGC 6891, located near epsilon Delphinus, is my hardest to locate planetary as of yet. Even harder to find than IC 3568 near the Little Dipper. At close to 10 seconds in diameter it is very small and I passed over it more than once using a 32mm finder eyepiece. It wasn't until I consulted some detail maps and star hopped very carefully (under moderate light polluted southeastern skies), than switching to a 17mm ocular, I finally located this object. I wanted to see this one in particular because some deep sky guide indicated the central star was fairly easy to see in a 150mm aperture telescope. I have to admit it was quite prominent. The nebula appeared as a classic blinker. Round, greenish blue in coloration. Not much more detail than that.
Oh yes, I observed one more planetary that night, the Saturn nebula. Very bright (brighter than the other two previously mentioned), football shaped, brilliant green in color. No central star to observe. I couldn't even pull any more detail out of this object. Sometimes it seems I'm just on the threshold of seeing many of these objects in the detail I want to see in them.
Twelve inches of aperture does not seem enough unless the skies are very dark. Perhaps it was that view I had last summer in the local astronomy clubs 17.5" dobsonian while observing the Cat's Eye nebula. In that telescope I could see the central star easily bluish white surrounded by an indescribably beautiful greenish ring crossed by zigzagging filaments! I tried on many occasions to duplicate this view on my 12" scope. I finally succeeded in my backyard two weeks ago on a dark, clear night. I could hold the central star of the Cat's Eye directly in view for the first time! I could even see some detail within the nebula. However, it still comes up short compared to the bigger scope. Perhaps even darker skies will help somewhat.
As interesting and challenging as the above planetary nebula were, I tried for a second time to see the Veil nebula in my backyard. Using a Baader UHC-S filter attached to my 32mm wide field eyepiece, I caught a faint outline of the eastern arc of this object! This is only the second time I have see this object since I viewed it many years ago in a 22 inch telescope belonging to a astronomy club member at a local star party. When I move to darker skies I expect to see a lot more detail.
Well that is the report for now, Clear Skies everyone! 8)
-Stephen
The Turtle Nebula has been described within the pages of the current issue of Sky & Telescope (July, 2010). It was everything the author Ken Hewitt-White described in his monthly column "Going Deep", with one exception. He used a 17.5" dob and I used a 12 inch. The difference in aperture made it rather difficult to see the central star. Something I've been trying to do with every Planetary nebula I observe. A magnification of more than 300X brought into view the shape of the object which has given its name, but poor seeing rendered the image unsteady and fuzzy. Backing off the power to 200X with an 8mm Celestron Ultima LX allowed me to finally catch a momentary glimpse of the central star when the seeing momentarily settled down. It is interesting to note how many of these objects appear small, bright and often colored green or blue. However, as difficult this object was it paled in comparison to the next planetary, NGC 6891.
NGC 6891, located near epsilon Delphinus, is my hardest to locate planetary as of yet. Even harder to find than IC 3568 near the Little Dipper. At close to 10 seconds in diameter it is very small and I passed over it more than once using a 32mm finder eyepiece. It wasn't until I consulted some detail maps and star hopped very carefully (under moderate light polluted southeastern skies), than switching to a 17mm ocular, I finally located this object. I wanted to see this one in particular because some deep sky guide indicated the central star was fairly easy to see in a 150mm aperture telescope. I have to admit it was quite prominent. The nebula appeared as a classic blinker. Round, greenish blue in coloration. Not much more detail than that.
Oh yes, I observed one more planetary that night, the Saturn nebula. Very bright (brighter than the other two previously mentioned), football shaped, brilliant green in color. No central star to observe. I couldn't even pull any more detail out of this object. Sometimes it seems I'm just on the threshold of seeing many of these objects in the detail I want to see in them.
Twelve inches of aperture does not seem enough unless the skies are very dark. Perhaps it was that view I had last summer in the local astronomy clubs 17.5" dobsonian while observing the Cat's Eye nebula. In that telescope I could see the central star easily bluish white surrounded by an indescribably beautiful greenish ring crossed by zigzagging filaments! I tried on many occasions to duplicate this view on my 12" scope. I finally succeeded in my backyard two weeks ago on a dark, clear night. I could hold the central star of the Cat's Eye directly in view for the first time! I could even see some detail within the nebula. However, it still comes up short compared to the bigger scope. Perhaps even darker skies will help somewhat.
As interesting and challenging as the above planetary nebula were, I tried for a second time to see the Veil nebula in my backyard. Using a Baader UHC-S filter attached to my 32mm wide field eyepiece, I caught a faint outline of the eastern arc of this object! This is only the second time I have see this object since I viewed it many years ago in a 22 inch telescope belonging to a astronomy club member at a local star party. When I move to darker skies I expect to see a lot more detail.
Well that is the report for now, Clear Skies everyone! 8)
-Stephen
