The Helix Nebula (also known as NGC 7293 or Caldwell 63) is a planetary nebula located in the constellation Aquarius. Discovered by Karl Ludwig Harding, most likely before 1824, this object is one of the closest of all the bright planetary nebulae to Earth (Wikipedia). The distance, measured by the Gaia[i] [/i]mission, is around 655 light-years. It is similar in appearance to the Cat's Eye Nebula and the Ring Nebula, whose size, age, and physical characteristics are similar to the Dumbbell Nebula, varying only in its relative proximity and the appearance from the equatorial viewing angle. The Helix Nebula has sometimes been referred to as the "Eye of God", as well as the "Eye of Sauron" (my preferred choice :-)   ).

I selected this nebula because is among my preferred deep sky objects. However, the nebula is located at -20 degrees, meaning that from Spain, this object never exceeds 31°. As every astrophotographer know, this has two main constraints: the higher turbulence leading to a loss of resolution and the significant shorter time that can be exploited to immortalize the nebula. To achieve this result I only selected the best Ha images with HFR values below 5.0 (Bin1). I thus discarded approximately 30% of the images I took this summer. In total I spent 15 nights to achieve the result illustrated here.

From the processing angle, I did apply a moderate level of BXT (070) on the Ha layer and a low level of Denoising (010) to avoid degrading the image. Showing the weakly emitting regions of the nebula was particularly challenging because as soon as the signal became detectable, the noise became very disturbing. So, I selected a compromise between showing more signal with a blurred image and a clean background without signal.

With respect to the end result, by considering the current setting and location of the scope I am very happy with the result obtained, although I really wish one day to have the possibility to shoot from the southern hemisphere.

As usual don't hesitate to provide your input and critics on the proposed image.

CS!

Nicola