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Old 12-01-2018, 10:46 AM
Tropo-Bob (Bob)
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NGC 2440- Planetary Nebula

This was very much in the class of the Blinking Nebula. When I looked directly at it, it would completely disappear.

The Nebula appeared much smaller than I was expecting. The Bright Star Atlas (BSA) gives its size at 74"x42". Burnham's Celestial Handbook states it as 50"x20". I thought it was more like the size of I418, which was only 14"x11". Perhaps I was only seeing the inner core of the Nebula.

The Nebula also appeared fainter that I418, even though BSA lists them as Mag 9.3 and 9.4 respectively. Nevertheless, it was much brighter than Burnham's figure of 11.5.

I may have being using my imagination to see blue light from the nebula. It certainly was not like many planetaries where this is a notable feature.

Internet articles list the central star as a white dwarf with an extreme surface temperature of 200,000 Kelvin. Its distance is approximately 4000 light years.

I used my Tak 100D to make these observations.

An Astronomy photo of the day for NGC 2440:

https://apod.nasa.gov/apod/ap070215.html
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Old 12-01-2018, 01:54 PM
bigjoe (JOSEPH)
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Quote:
Originally Posted by Tropo-Bob View Post
This was very much in the class of the Blinking Nebula. When I looked directly at it, it would completely disappear.

The Nebula appeared much smaller than I was expecting. The Bright Star Atlas (BSA) gives its size at 74"x42". Burnham's Celestial Handbook states it as 50"x20". I thought it was more like the size of I418, which was only 14"x11". Perhaps I was only seeing the inner core of the Nebula.

The Nebula also appeared fainter that I418, even though BSA lists them as Mag 9.3 and 9.4 respectively. Nevertheless, it was much brighter than Burnham's figure of 11.5.

I may have being using my imagination to see blue light from the nebula. It certainly was not like many planetaries where this is a notable feature.

Internet articles list the central star as a white dwarf with an extreme surface temperature of 200,000 Kelvin. Its distance is approximately 4000 light years.

I used my Tak 100D to make these observations.

An Astronomy photo of the day for NGC 2440:

https://apod.nasa.gov/apod/ap070215.html
Bob... Skysafari lists it at Mag 9.3 of size 1.2 x 0.7 arc minutes...So it is bright.
Most observers see a bipolar form to it; gray blue perhaps and no central star...I will look myself tonight ..if its not CLOUDY.

PS: Its in Puppis very close to M46 .
bigjoe
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Old 19-01-2018, 05:26 PM
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Tinderboxsky (Steve)
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Bob, I visited this planetary last night after IC418 to follow up your observations.
At 62X I could see a bluish spot that on close examination, was obviously non-stellar. In a cursory view of the star field it would be easy to overlook this as a just another pale blue star.
At 229X it appeared as an irregular elongated shape with no clearly defined outer edge. It was a smokey blue and reasonably bright even at this magnification. I judged the size to be about 50% greater than the apparent size of IC418 and brightness to be similar to IC418. Averted vision revealed slightly sharper edge detail. I could not see any central star.

Telescope Vixen NA140SS on TRex mount and LVW 13 & 3.5 eyepieces.
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Old 19-01-2018, 06:53 PM
bigjoe (JOSEPH)
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Re N2440

Quote:
Originally Posted by Tinderboxsky View Post
Bob, I visited this planetary last night after IC418 to follow up your observations.
At 62X I could see a bluish spot that on close examination, was obviously non-stellar. In a cursory view of the star field it would be easy to overlook this as a just another pale blue star.
At 229X it appeared as an irregular elongated shape with no clearly defined outer edge. It was a smokey blue and reasonably bright even at this magnification. I judged the size to be about 50% greater than the apparent size of IC418 and brightness to be similar to IC418. Averted vision revealed slightly sharper edge detail. I could not see any central star.

Telescope Vixen NA140SS on TRex mount and LVW 13 & 3.5 eyepieces.
I have not yet had an opportunity to revist this one near M46.

That mag 14.3 central star looks a tough one Steve , maybe I'll try when it culminates, with a bigger SCT...than the 6 inch refractor .

Ive added some screenshots of where its located for others interested...and its distance from M46 for those without goto etc....about 2 24'.33 ".

Skysafari plus is great for giving the distance between objects of interest.. and double star separations!....were getting spoilt now.
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Last edited by bigjoe; 19-01-2018 at 08:42 PM. Reason: Adding info on SS
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