Iris Nebula

NGC 7023, Caldwell 4 · Reflection nebula in Cepheus

Magnitude: 6.8
Size: 18′
Effective surface brightness: 22.3 mag/arcsec²
Best months: Jul, Aug, Sep
Declination: +68°
Filter: None (broadband target)

A blue reflection nebula wrapped in dark dust. No filter helps, and the surrounding dust needs a dark sky and hours.

Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.

How long with each smart telescope

Total integration for a solid image of the Iris Nebula, default sub length, recommended filter, and how much of each frame it fills. Click a cell for the full Bortle 1 to 9 table.
Telescope	In frame	Bortle 3 (rural)	Bortle 5 (suburban)	Bortle 7 (urban edge)
ZWO Seestar S5010 s subs	42%	43 min260 subs	1 h 11 min428 subs	3 h 14 min1,164 subs
ZWO Seestar S50 Pro10 s subs	22%	48 min289 subs	1 h 18 min471 subs	3 h 31 min1,267 subs
ZWO Seestar S3010 s subs	25%	49 min294 subs	1 h 17 min463 subs	3 h 20 min1,198 subs
ZWO Seestar S30 Pro10 s subs	13%	52 min310 subs	1 h 24 min502 subs	3 h 43 min1,339 subs
DwarfLab DWARF 315 s subs	18%	56 min225 subs	1 h 39 min398 subs	4 h 49 min1,156 subs
DwarfLab DWARF mini15 s subs	25%	43 min171 subs	1 h 11 min283 subs	3 h 13 min774 subs
DwarfLab Draco30 s subs	24%	35 min70 subs	58 min116 subs	2 h 40 min321 subs
DwarfLab DWARF II15 s subs	17%	3 h 14 min776 subs	4 h 32 min1,087 subs	10 h2,450 subs
Vaonis Vespera II10 s subs	21%	43 min260 subs	1 h 11 min428 subs	3 h 14 min1,164 subs
Vaonis Vespera Pro10 s subs	19%	1 h 46 min639 subs	2 h 45 min993 subs	7 h 03 min2,540 subs
Vaonis Vespera 310 s subs	20%	41 min246 subs	1 h 08 min407 subs	3 h 06 min1,114 subs
Vaonis Vespera Pro 210 s subs	18%	1 h 40 min603 subs	2 h 37 min943 subs	6 h 45 min2,428 subs
Unistellar eQuinox 24 s subs	53%	59 min892 subs	1 h 17 min1,155 subs	2 h 33 min2,301 subs
Unistellar Odyssey4 s subs	53%	5 h 19 min4,785 subs	6 h 23 min5,739 subs	11 h9,909 subs
Celestron Origin10 s subs	35%	10 min61 subs	18 min109 subs	53 min317 subs
Celestron Origin Mark II10 s subs	40%	12 min75 subs	24 min144 subs	1 h 14 min444 subs

Open in the calculator

Imaging the reflection nebula

Reflection nebulae are starlight scattered by dust, so they are broadband and blue. A dual-band filter removes almost all of it; do not use one. These are among the faintest structures a smart scope can attempt and the figures run long. A dark sky matters more here than for any other type, and the Moon must be down.

Iris Nebula

How long with each smart telescope

Imaging the reflection nebula

Per-telescope pages