Tag: B33


Horsehead nebula is IMHO the most beautiful deep space object. It is located in the constellation Orion. Everybody knows this constellation because it can be easily identified by three aligned stars (Alnitak, Alnilam, and Mintaka), which forms the belt of the Orion.

The nebula is very dim. Therefore, visual observation is nearly impossible, unless you have a telescope, having at least 1 meter in diameter. To photograph it, one needs a very long exposure time. I used 5 minutes per image and I took 36 of them. The nebula complex is visually very large, so the optimal focal length should be shorter than 750 mm. I used a Newtonian telescope with a focal length of 1000 mm but reduced to 750 mm by the Nexus coma corrector. It turns the Newtonian into a light-collecting bucket, but the quality suffers from that. The stars in the corners are everything, but round. Moreover, I used dual-band filter Optolong L-eXtreme, which increased the contrast of the nebula, but also made the asymmetric halo around the bright stars. I played a bit with the white balance and pushed the colors into the orange tint, to reach the warmer feeling in cold February.

TelescopeNewton 254/1000 mm
Aperture254 mm
Focal length750 mm
MountGemini G53f
AutoguidingZWO 174MM, TS 60/240 mm
CameraZWO 071 Pro @-10°C
CorrectorNexus coma corrector
FiltersOptolong l-eXtreme
Exposure36x300s, Gain 95, bin 1x1,

B33 Horsehead Nebula

Horesehead nebula is a dark nebula located in constellation Orion, approximately 1550 light years from Earth. The bright star is on the picture is called Alnitak (eastern star of Orion’s belt). Horsehead shape is a cloud of cold gas, blocking the light coming from ionized hydrogen in the background.

This nebula is my favorite, but it’s not so simple to photograph, due to its dimness. Even with very fast telescope (f-stop 2.8) I had to use quite long exposure times – 6 minutes. The picture was postprocessed by bi-color technique, which means putting 27 H alpha pictures into red channel and 17 OIII pictures into green and blue channel. This was done in Pixinsight software.