IC 5070 — Pelican Nebula
Cygnus · Askar FRA400 · ToupTek ATR585M · Sky-Watcher AZ-EQ6 PRO · 2026-03-01
Acquisition
| Filter | Exposures | Sessions |
|---|---|---|
| H-alpha 6.5nm | 37 × 300s | 2 |
| OIII 6.5nm | 61 × 300s | 2 |
| SII 6.5nm | 48 × 300s | 2 |
Total integration: 12h 10m
Astrometric Data
Field Center
20h 51m 04.6s
+44° 13′ 41″
Pixel Scale
1.449 ″/px
Orientation
271.86°
Field Radius
0.889°
Objects in Field
Main Challenges
OIII signal in the Pelican is notoriously faint relative to Hα — biasing the integration heavily toward OIII was necessary to bring out the fine ionisation front detail without drowning it in hydrogen.
From the Field
Five nights over eight days, all working the same arc — waiting for the Pelican to clear 20 degrees and riding it up to transit near 54–56 degrees before the window closed. The first night (March 26) ran the full SHO sequence plus RGB stars, testing how far the filter wheel automation could go in one session. After that, the RGB was dropped: the SHO palette doesn't need star color, and the time was better spent on OIII. The narrowband rejection rate came out higher than expected — 31% of raw frames didn't make the final stack, mostly from the earlier sessions when airmass was still high and the Pelican hadn't climbed far enough above the horizon. The March 31 session ended with three consecutive autofocus failures as the target started to set: 'no stars detected' each time, the focuser unable to grip anything through the thickening atmosphere. April 3 was the cleanest night of the run — guide RMS dropped to 0.13 arcsec, the target entered the frame already at 23 degrees, and the session ran without a single AF issue.
Opening night. Full SHO + RGB stars to test the sequence. After this session, RGB was dropped in favour of more narrowband time.
Heavy OIII emphasis — 31 frames to push the ionisation front detail. Extra R frames captured alongside. Two AF runs, both succeeded.
Pure SHO from this night on. Balanced acquisition across all three channels.
Best airmass of the run (minimum 1.20). Session ended with 3 AF failures as the target set back below 30°.
Best-guided session of the run (0.13" total RMS). Single AF success at open, no further focuser intervention. 9 HA frames — sequence ended before the full allocation ran.
Process Notes
The Pelican Nebula (IC 5070) sits just east of the North America Nebula in Cygnus, separated from it only by a dark molecular cloud. At roughly 1,800 light-years away, it's one of the most active star-forming regions visible from the northern hemisphere — a turbulent frontier where newborn stars are sculpting the surrounding gas with their ultraviolet radiation.
My framing prioritises the ionisation front — the sharp, luminous ridge where the Pelican's "beak" meets the dark lane. That edge is where the physics gets interesting: dense pillars of cold gas being slowly eroded by the radiation pressure from nearby OB stars, some of them barely a few million years old.
The SHO Palette
Pure narrowband, no RGB stars. The sulphur (SII) maps the shock-excited outer shell, the hydrogen (Hα) dominates the broad emission across the body of the nebula, and the oxygen (OIII) traces the hottest, most ionised zones along the ionisation front — giving the beak region its distinct teal edge against the warm hydrogen glow.
The heavy OIII integration (5h 05m vs 3h 05m Hα) was a deliberate choice: the Pelican's OIII signal is faint, and under-integrating it would collapse the colour contrast that makes the SHO palette worthwhile here.
Software
Stacked and processed in PixInsight. Acquisition managed with N.I.N.A., autofocus via ZWO EAF.
Behind the Scenes
Out of 212 raw narrowband frames, 66 were rejected before the stack was finalized. That's a 31% discard rate — and I consider it quality control, not waste. The Pelican's data was collected as the target was climbing out of low altitude at the start of each session, which meant the first frames of every night were carrying more atmospheric distortion than the later ones. The ones that didn't pass the quality threshold were protecting the final stack from softness that would have undermined everything above them.
Sessions
| Date | Frames | Filters | Window | Alt range | Guide RMS | Focus drift |
|---|---|---|---|---|---|---|
| 2026-03-26 | 52 | 9×Hα + 16×OIII + 12×SII + 5×R + 5×G + 5×B | 02:01–05:33 | 21.1°–51.3° | 0.18″ | 13 steps |
| 2026-03-27 | 67 | 9×Hα + 31×OIII + 15×R + 12×SII | 01:49–05:24 | 19.6°–53.3° | 0.18″ | 10 steps |
| 2026-03-29 | 44 | 16×Hα + 16×OIII + 12×SII | 02:41–06:21 | 20.1°–54.3° | 0.23″ | 10 steps |
| 2026-03-31 | 43 | 15×Hα + 16×OIII + 12×SII | 02:46–06:24 | 21.9°–56.1° | 0.15″ | 10 steps |
| 2026-04-03 | 36 | 9×Hα + 15×OIII + 12×SII | 02:47–05:52 | 23.4°–52.9° | 0.13″ | 10 steps |
The March 26 and 27 sessions also captured RGB frames for star color reference — 15×R, 5×G, 5×B — which were not used in the SHO stack but archived for potential future composites.
Autofocus
Two nights gave the autofocus trouble, and the reason was identical both times: the Pelican was still too low. On March 31 at 02:39, the focuser tried to run its routine with the target at just over 20 degrees altitude and failed three consecutive times. Two minutes later it tried again and failed again. On April 4, the same pattern — four consecutive failures between 02:53 and 02:54, a final attempt three minutes later that finally locked in. In both cases the culprit was seeing: at low altitude, atmospheric turbulence smears star profiles enough that the focuser's curve fitting can't find the minimum. The sequence continued with the last-known focus position, and the subsequent frames were usable once the target had climbed.
The April 3 session was the cleanest of the run: single autofocus run at the start, no failures, and a guide RMS of 0.13″ — a number that reflects what this scope and mount can produce when conditions cooperate. The March 31 session matched that quality in the data even though it started with three AF failures, because by the time good frames were being acquired the Pelican was already at 30+ degrees and the seeing had settled.
March 27 saw two successful AF runs — one at 01:58 and a re-run at 02:18. The second was likely triggered by a filter change or a temperature nudge; both succeeded without incident.
What Got Rejected
Raw narrowband: 58×Hα, 94×OIII, 60×SII. Published: 37×Hα, 61×OIII, 48×SII. The largest absolute losses were in Hα (21 frames) and OIII (33 frames), which were the channels most represented in the early low-altitude acquisition windows. SII lost 12 frames. All three channels lost proportionally similar amounts, which suggests the rejection was driven by altitude/seeing conditions common to all filters rather than any filter-specific problem.
Post-mortem
Five sessions over eight nights produced a clean SHO stack, but the 31% rejection rate is a honest accounting of what it costs to image a target that only enters the usable window late in the session. The guide RMS improved across the run — 0.18″ on the first nights, 0.13″ by April 3 — which likely reflects both better conditions and PHD2 tuning settling in as the mount accumulated more runs on similar targets. The OIII-heavy integration strategy (61 frames vs 37 Hα) was the right call: the Pelican's oxygen emission along the ionisation front is genuinely faint, and anything less would have collapsed the colour contrast that makes the SHO palette meaningful here.