WeBo1 and Mel15

Do you remember december molecular trophies? There were hydrogen alpha only band of Melotte 15 open cluster in the middle of the Heart nebula IC1805. I collected some more – oxygen III band and RGB star color and here comes the color result below. It is all pictured with QHY163M camera, 130mm Photoline refractor and EQ6 mount. All from my backyard, and that is total about 15 hours of exposures. Pretty lot, huh?

Melotte 15 in the IC1805 Heart nebula. HaOiiiRGB composite
Melotte 15 in the IC1805 Heart nebula. HaOiiiRGB composite

IC1805 Heart nebula in Cassiopeia is well known hydrogen cloud, very appreciated by astroimagers. This object is placed 6000 light years away. In its apparent center there is very young open star cluster – Melotte 15. Actually the cluster is about 50 light years closer to us than nebula. Average star age in this cluster is only 1.5 million years. Melotte 15 in IC1805 contains few bright stars OB about 50 times more massive than Sun, and pretty many small stars that are much less massive, than Sun. 

Three bright stars in the arc at right of Melotte 15 cluster are spectral type O, which are the brightest and most massive stars known. They also live very short, typically 3 to 6 million years. Our Sun for comparison burns already 4.5 billion years, and it is in the middle of its way. 

Clear skies!

4 thoughts on “WeBo1 and Mel15”

  1. Lucas,

    What gain setting do you use for N.B. work? I’m using now 20 gain, but I’m not sure if I should drop to near unity, like 13 or so?


    1. Luis,
      I use gain 0 and offset 40 for narrowband pictures. And 600s exposures with f/5.5 refractor. I also thought about unity gain, but then full well capacity is pretty low, and stars become oversaturated much quicker.
      Basically I do all long exposure work with gain set to 0. I did some lucky imaging with times 2-10 seconds and then I’ve been using unity gain settings.


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