The Blue Horsehead Nebula, designated as IC 4592, is a beautiful reflection nebula in the constellation Scorpius, which is low in the southern skies, near the rising Milky Way core.
Distance:
The Blue Horsehead is about 420 light-years (2.5 trillion miles) away from Earth.
Equipment:
• Telescope: SVBony SV503 80ED 560mm, an f/7 Doublet Refractor telescope with a 0.8 Reducer/Flattener to reduce the focal length to 448mm and aperture to f/5.6
• Mount: SkyWatcher HEQ5 Pro
• Camera: ZWO ASI2600 MC Pro
• Filter: None needed – Bortle 3 dark sky area
• Guiding: ZWO ASI120mm Mini Monochrome Guide Camera with the ZWO 30mm f/4 Guide Scope
• Automation: ZWO ASIAir Mini
Imaging:
Since this target is a reflection nebula, lit by the multiple star system called Nu Scorpii, no filters are needed for narrowband emission wavelengths, for example. However, it is a very faint nebula that really requires dark skies to and longer sub-images to get sufficient details.
We went to the dark sky site of Florissant, CO, a Bortle 3 area, so I could target these darker and fainter targets. However, due to cloudy skies, I was only able to capture 21 sub-images of 5 minutes each (105 minutes total), calibrating a stack using 60 darks, 60 flats, and 60 dark flats. processed in Siril, stretching and color processing in GIMP, and adding final touches in PhotoShop. In another evening, I tried shorter sub images, due to the clouds, and got 40-3 minutes images, but the single-to-noise was not sufficient to pull out the details.
After seeing the resulting image from a limited amount of 5-minute subs, I’m definitely looking forward to re-imaging this target at our next dark sky site, hoping for clear skies!
