Hello,

This is my second version of this PNe. Version 1 was the first DSO image I ever took and there were some significant issues with the data (not least a dim halo in the O2 caused by light from near infrared leaking though the Baader O3 filter), so 6 years on here it is again. I have more experience of image capture and processing and better filters this time round, so hopefully it is an improvement! I also now have an N2 filter so I can collect extra information this time.

The nebula was captured using the narrow band filters.  The stars were captured using the red, green and blue broadband filters. In the nebula only image, the narrowband filters were allocated to colours as follows: N2 is in the red, Ha is a mixture of red and green, O2 is a mixture of green and blue. Where N2 is stronger in the red, it has been boosted compared to the Ha and where the Ha is stronger in the green it has been boosted compared to the O3. Various tweaks with Histogram and Curve transformations were made to the nebula only image to get it's final appearance. Stars were removed from the narrowband image using StarXTerminator. 

Star broadband images were combined and stretched with Histogram transformation. Interestingly I used BlurXTerminator on the stars (prior to HT) to get them a bit sharper, but good old fashion deconvolution on the nebula image to sharpen it up a bit. The nebula was removed from the broadband images to give me a stars only broadband image 

In this image north is (approximately) to the bottom, east is (approximately) to the left of the image. Somewhat annoyingly I still haven’t been able to get the central star. Despite its high luminosity, distance and size conspire to make it quite faint, at least to my equipment. My star subs were only 60s long and only for a total of 30 minutes per filter, so I should probably go for longer to capture the central star. Maybe next year!

Professional studies suggest the central star weighs in at 0.615 solar mass, is 2668 times brighter than the Sun and a has surface temperature of 113,190K. However, other estimates put the luminosity at 5800 times solar and a temperature of 96,800K. It all depends on the distance you pick: ~4800 light years or 2600 lightyears!

NGC 78662 is thought to be around 5100 years old (distance dependant!) and has three components. The bright inner shell (17.9” x 12.4”) is shaped like a rugby ball with the northeast end pointing towards us. The second shell is a larger version of the first, although not as elliptical (30.8” x 27.2”) and expanding at a faster rate than the inner shell (~78km/s vs ~63km/s). The whole is surrounded by a halo 134” wide.

The numerous bright spots around the rim of the second shell are known as FLIERS: Fast Low Ionisation Emission Regions, a little understood aspect of PNe. Being low ionisation features they show up well in N2 images. The small “jets” that can be seen just above the northern and southern rims of the outer shell are also FLIERS and can be seen in detailed HST images (with much better resolution than I have here 😊 ) See  [url=http://HST_WFPC2 imaging analysis and cloudy modeling of multiple shelled PNe NGC 3342, 7626 and 7662.pdf]HST_WFPC2 imaging analysis and cloudy modeling of multiple shelled PNe NGC 3342, 7626 and 7662.pdf[/url]  figure 3.

The outer halo material is thought to be the remains of material blown off the progenitor star during its AGB stage. It should be noted that the halo is the faint ring of material that encircles the inner shells (and overlaps the 3 bright stars in the NE quadrant). The bright blue that immediately surrounds the 2nd shell is scattered light from the inner shells (see [url=file:///D:/Users/IanSmith/Downloads/Planetary_nebula_haloes_II_-_NGC_7662_and_shock_he.pdf]Planetary_nebula_haloes_II_-_NGC_7662_and_shock_he.pdf[/url] plate 1). The halo material is hotter than the material in the shells but has a lower density. The heating effect is attributed to a fast wind leaving the central regions and crashing into the previously eject material.

I hope you enjoy my second attempt.

Cheers,
Ian