IC4592 Blue Horsehead Nebula

: IC4592 Blue Horsehead Nebula; captured from Atacama Lodge, San Pedro de Atacama, Chile on 11 March 2024

Fun facts

IC 4592 (also known as the Blue Horsehead Nebula) is a reflection nebula in the Scorpius constellation that is lit by Nu Scorpii.

Distance: 400 light years
Apparent magnitude: 12
Dimensions: 40 light years
Constellation: Scorpius
Designations: IC4592, Blue Horsehead Nebula

{From: https://en.wikipedia.org/wiki/IC_4592}

Capture & Processing Notes

On night #6, the final imaging night of the Atacama Desert trip, I ran out of targets! I never would have imagined or dared to hope for 6 completely clear nights in a row!  So, I went into the Imaging the Southern Sky book and found another segment of the Vela SNR – in the vicinity of the Spiral Flame Nebula and built a sequence to image it to start the night.  I’d planned to image Vela SNR until it set at about 0400, then switch to Gum 22-23 for the rest of the night.  While the Vela SNR was beginning (PHD2 calibration), it dawned on me that I had intended to image the IC4592 Blue Horsehead Nebula, since it is always so low on the horizon from the Northern Hemisphere.  While the PHD calibration was on-going, I pulled up Stellarium to see what the visibility was from the Atacama Lodge.  I was delighted to find that it rose at about 0130 crossed the meridian at 0630 (just about the time I’ve been terminating my sequences at the end of astronomical twilight) and was very high in the sky!  So, that became my night’s second target. 

IC4592 is visible from the Northern Hemisphere and I have tried in the past to image it from the front patio. But it never rises above 20° and its predominant blue colors make it impossible to image from anything but dark skies – which I have never had the right opportunity to try.  So, when I found that it was visible, essentially overhead, and I WAS in dark skies – it became the target of choice!  Besides the fact that Danita is a horse-woman, it seemed especially appropriate to capture this as a momento of the trip for her!

All the imaging went extremely well, with no glitches whatsoever.  Like Danita mentioned – “you’ve had 6 days in a row of practice, rather than sporadic imaging sessions with time in-between to forget what you learned from one to the next.” 

Sequence Plan:

  • Sequence plan: Gain 158, Temp: 0°C, 52x5min, Total time = 260 minutes, 4:20 hours.
  • Captured: Night of 11 March 2024 (12Mar2024, 0211CDT – 12Mar2024, 0641CDT)
  • Shooting location: Atacama Lodge, San Pedro de Atacama, Chile

Processing summary: Captured with SGP. Stacked in APP. Star removal with Starnet++. Processed in LR/PS


All equipment controlled by HP Probook (DSO CTRL 1) Windows 10 laptop running Sequence Generator Pro v4.3.0.1305.  

  • Polar alignment: QHYCCD camera (controlled by Polemaster for polar alignment)
  • Imaging: (Southern Cross) Askar FRA600 on Rainbow Astro RC-135E, ZWO ASI2400MC#1 camera
  • Autofocuser: ZWO EAF ( Electronic Automatic Focuser)
  • Mount: Rainbow Astro RST-135E (controlled by iHubo ASCOM driver)
  • Autoguiding:  Orion 60mm Multi-Use Guide Scope with Orion StarShoot AutoGuider Pro Mono Astrophotography Camera (controlled by PHD2)