M44 Praesepe open cluster: Headfirst into the Beehive

Nice, bright star cluster in constellation Cancer. This cluster have fallen into the sweet spot of my optics, so the halos around bright stars are at least center-symmetrical and not comet-shaped. Yes! This one turns out at steady 3 out of possible 5.

 

This shot and this share the same effective resolution so the apparent sizes can be compared. This only applies to "original" size of the images. M67 is tiny compared to Praesepe/Beehive. And has only 7,5m against 4m of the Beehive.

 

Aquisition time: 13.04.2013 ‏‎around 23:45:00 MSK (GMT+4).

Equipment:

Canon EF 70-200 f/2.8L lens + Canon EF 2x III extender on EOS 60D mounted on Celestron CG-4 GEM (German equatorial mount) with RA drive.

Aperture 71 mm

Focal length 400 mm

Tv = 30 seconds

Av = f/5,6

ISO 800

Exposures: 85 + 12 dark frames

Processing: contrast was set to "linear" and vingetting was corrected with Canon DPP, 16 bit TIFFs were stacked in DeepSkyStacker, contrast'n'colors adjusted in Photoshop. Image scaled down 50% (cheat!).

Notes: this time I have recorded the steps of contrast adjustment. I'll better have bluish sky than reddish.

Done