Casitas de Gila, Gila, New Mexico, October 26-28, 2022

During my trip to New Mexico, I imaged the Pleiades as the second of two targets each night.  M45 is a very popular target for widefield imaging.  Since I purchased my SVX102T refractor, I have image some of the most photographed deep sky objects.  In M45, the hot, blue stars are so bright that I took 30, 60 and 120 second exposures with the Luminance filter in order to construct an HDR composite image for the details while minimizing star bloat.  Red, Green and Blue broadband filters were used for color.

I processed the data using a similar workflow in PixInsight as with other nebulae.  NoiseXTerminator was used to remove some of the background noise in all integrated and cropped images.  A master luminance was created with the HDRComposition tool using the 120, 60 and 30 second Lum integrated images.  StarXTerminator was used to create starless and stars luminance images.  With a starless image, more faint details emerge during stretching without worrying about star bloat and halos.  The same steps were done with the RGB color image combined using the Red, Green and Blue filter integrated masters.  The stretched starless luminance image was denoised further with NoiseXTerminator, sharpened and then the contrast was enhanced with the HistogramEqualization tool at three kernel sizes.  The RGB starless image was color corrected with the PhotmetricColorCalibration tool.  It was denoised with NoiseXTerminator using an aggressive setting, and then it was stretched.  Both starless and stars RGB images were combined with luminance images.  The colors were adjusted and saturated.  The final starless LRGB nebula was combined with the LRGB stars using the PixelMath combine function with the opscreen() parameter.

M45, the Pleiades or Seven Sisters, is an open star cluster that is very close to us.  You can see it above the horns of the constellation Taurus in the fall.  Galileo was the first to observe the Pleiades through a telescope.   M45 contains over a thousand stars that are loosely bound by gravity, but it is visually dominated by a handful of its brightest members.  But there is more to M45 than just the bright stars.  This image shows extensive clouds of dust lit by the stars and more dark clouds the background.  The stars are moving through the dust and are heading in the direction of Earth.  The gravity and motions of the stars are causing shock waves in the clouds giving them the striations.  M45 is about 444 light years from Earth and has a size of around 17.5 ly (SkySafari Pro, NASA).

Imaging details:

Stellarvue SVX102T with SFR0.74 focal reducer (FL = 528mm, f/5.2)
ZWO off-axis guider (OAG-L) with a ZWO ASI 174MM mini guide camera
Losmandy G11 mount with Gemini 2
ZWO ASI 2600MM Pro cooled monochrome camera (-10C)
Chroma 36mm filters:  Luminance, Red, Green, and Blue
Equatorial camera rotation: 270 deg

Software:    Sequence Generator Pro, ASTAP plate solving, PHD2 guiding, 
    Losmandy Gemini ASCOM mount control and web client interface,
    SharpCap Pro for polar alignment with the Polemaster camera,
    PixInsight 1.8.9 with StarXTerminator (AI version 10) and NoiseXTerminator,
    Photoshop CC 2022

Luminance    30 sec x 59 subframes (29.5 min), Gain 100, Offset 68, 1x1 binning
Luminance    1 min x 90 subframes (90 min), Gain 100, Offset 68, 1x1 binning
Luminance    2 min x 86 subframes (172 min), Gain 100, Offset 68, 1x1 binning
Red        2 min x 40 subframes (80 min), Gain 100, Offset 68, 1x1 binning
Green    2 min x 34 subframes (68 min), Gain 100, Offset 68, 1x1 binning
Blue       2 min x 34 subframes (68 min), Gain 100, Offset 68, 1x1 binning