Messier 5 - Globular cluster in Serpens...

Object: M5 (NGC 5904)

Type: Globular cluster
Constellation: Serpens
Distance: 2450 light years

Date: 4th & 5th May 2018
Equipment: SXV-H9, Vixen 114mm f5.3 ED refractor, NEQ6 mount, guiding with Lodestar X2/PHD

Subframes: 50 x 30s, 30 x 100s and 20 x 300s luminance, 25 x 100s each for RGB (2 x 2 binned), 20 flats for each channel.

At a magnitude of 6.4, M5 can readily be glimpsed through binoculars as a "fuzzy star", midway between fourth magnitude stars Epsilon Serpentis and 109 Virginis.

M5 often seems to be overlooked in favour of its flashier cousin, the "Great Globular Cluster" M13 in nearby Hercules, yet it is only half a magnitude fainter and in many ways is a more rewarding object to view through a telescope.  In my 8-inch Vixen VC200L , M5 shows up as a cluster of pin sharp stars, gradually brightening, yet still resolvable, right the way to its bright core.  M13, although bigger and brighter, doesn't offer as "granular" an appearance, at least not to me.

For imaging, the challenge is to capture M5's outlying stars, without having a "burning out" look to its bright core.  Luminance stacks of three different exposure lengths were layered and blended in PaintShop, to give a final luminance frame showing an apparent resolved core of stars.  This was combined with an RGB stack in AstroArt to give the final image.

Skies were very clear for the two nights needed to acquire the frames I wanted, but the seeing seemed a little variable, giving rise to a PHD guiding graph that often resembled an ECG trace.  Still, PHD worked its magic and the stars still came out OK-ish, with only a trace of distortion towards the outermost corners of the final image.  Clear skies also helped keep the background noise down, without having to resort to clipping or smoothing.

And it was so nice be able to sit out at night in the observatory at a balmy 10 degrees...

More info on this galactic shepherd can be found here...