Tag: Horsehead nebula


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,

iOptron SkyGuider Pro, Askar FMA180 f4.5 review

I made a big step towards ultra-portable astrophotography. On Kythira I first time placed my workhorse Canon EOS 6Da on mini mount Baader Nanotracker and made quite stunning pictures of the Milky Way. I was so excited and started to think about more serious “pocket-size” astrophotography. The requirements were the following: no external batteries, telescope, and camera should have max. 1.5 kg weight, focal length around 200 mm. The camera it’s simple, I simply keep using my modified Canon 6D.

The telescope is quite trickier, but I found Askar FMA, which has a 220 mm focal length, which is shortened by included a full-frame reducer to 180 mm. Aperture 40 mm yields for this focal length to speed F 4.5. The scope weighs only 400 g (700 g with the rings and EOS adapter). There is an M48 thread at the front of the telescope, which is very useful to attach the 2” mounted filters, particularly if you live in a light-polluted area.

There are several travel mounts on the market. Probably the most famous is Skywatcher Star Adventurer. I was about to pull the trigger on this mount, but I found another one, which will fulfill my requirements even better – iOptron SkyGuider Pro. iOptron has the same payload (5 kg with counterweight, 1.5 kg without) and has many interesting features:

  • Integrated illuminated polar scope
  • The torque from the motor to the worm gear is transmitted by a belt (this should minimize the backlash),
  • Integrated battery, which can be changed by USB cable
  • ST-4 socket for autoguiding

iOptron is slightly lighter than Skywatcher, so the decision was made. And how does it perform? I must say: VERY WELL! I got a chance to use it at home, so I screwed the IDAS NB1 filter in front of the Askar and captured the center region of the Orion and California nebula. The mount is tracking very accurately even without any counterweight and the number of bad photos caused by poor tracking was zero.

The telescope surprised me very positively as well. The connection to the camera is done by T-thread (M42), so I expected significant vignetting on the full-frame sensor, because the diameter of the thread is 42 mm, whereas the diagonal of the sensor is 43 mm. Surprisingly, it vignettes very little, and even flat frames are not necessary. The darker corners can be corrected by dynamic background extraction in PixInsight. The stars are a little bit oval at the bottom corners, but we are here looking at a full-frame sensor. In the end, I am very happy with the price/weight/performance ratio of Askar.

Let’s have a look at how heavy is the whole rig:

Tripod2.3 kg
iOptron SkyGuider1.5 kg
Canon EOS 6D0.8 kg
Askar0.7 kg
Total5.3 kg

This can fit into any backpack.

Here are the pictures:

Technical details:

LensAskar FMA180 F4.5
CameraCanon EOS 6Da
MountiOptron Skyguider Pro
Exposure60x60s, ISO 1600

Technical details:

LensAskar FMA180 F4.5
CameraCanon EOS 6Da
MountiOptron Skyguider Pro
Exposure44x120s, ISO 1600

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.