How long to image the Iris Nebula with the DwarfLab DWARF 3
From a Bortle 6 suburban sky, the DwarfLab DWARF 3 needs about 2 h 45 min (659 subs of 15 s) for a solid image of the Iris Nebula. A quick look takes 41 min; a showpiece 11 h. Under a Bortle 3 rural sky the solid figure drops to 56 min. At Bortle 6 the limit is skyglow, so a darker site or a filter helps more than longer subs. In this scope's field it fills 18% of the frame’s short side.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 11 min46 subs | 46 min183 subs | 3 h 02 min730 subs |
| Bortle 2Typical dark site | 12 min50 subs | 49 min198 subs | 3 h 17 min789 subs |
| Bortle 3Rural | 14 min57 subs | 56 min225 subs | 3 h 45 min899 subs |
| Bortle 4Rural / suburban transition | 18 min73 subs | 1 h 13 min292 subs | 4 h 52 min1,167 subs |
| Bortle 5Suburban | 25 min100 subs | 1 h 39 min398 subs | 6 h 38 min1,592 subs |
| Bortle 6Bright suburban | 41 min165 subs | 2 h 45 min659 subs | 11 h2,635 subs |
| Bortle 7Suburban / urban transition | 1 h 12 min289 subs | 4 h 49 min1,156 subs | 19 h4,622 subs |
| Bortle 8City | 2 h482 subs | 8 h 02 min1,927 subs | 32 h7,708 subs |
| Bortle 9Inner city | 3 h 43 min893 subs | 15 h3,572 subs | 60 h14,287 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 3 h 34 min of run time. The DWARF 3’s battery (rated about 5 h 30 min) should cover it; a power bank still keeps the phone running the app alive. (Bortle 6, solid image; we allow 30% over the integration time.)
- USB-C PD power bank 20000mAh 18W18 W PD input and it runs while charging; needs a C-to-C cable for PD.
- red LED head torchRed light keeps your night vision; white light costs you twenty minutes of dark adaptation every time.
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Everything that fits the DWARF 3 →
How it frames
The Iris Nebula is 18′ across. The DWARF 3 frames 2.93° × 1.65° at 2.75″ per pixel, so it fills 18% of the frame’s short side.
Longer subs
Auto mode caps subs at 15 s; 30 s and longer need EQ mode, and 60 s is the ceiling on the tele camera. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 15 s | 56 min225 subs | 1 h 39 min398 subs | 4 h 49 min1,156 subs |
| 30 s | 52 min105 subs | 1 h 36 min192 subs | 4 h 45 min571 subs |
| 60 s | 51 min51 subs | 1 h 34 min94 subs | 4 h 43 min284 subs |
Leave the dual-band filter out for the Iris Nebula. It is a reflection nebula, and it shines right across the spectrum. A dual-band filter keeps two emission lines and throws the rest away, so most of the light you came for is being stopped along with the sky. From a Bortle 6 sky it would be roughly 10 times slower.
About the Iris Nebula
A blue reflection nebula wrapped in dark dust. No filter helps, and the surrounding dust needs a dark sky and hours.
NGC 7023, Caldwell 4 · Reflection nebula in Cepheus · magnitude 6.8 · 18′ · best in Jul, Aug, Sep. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
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.
About the DwarfLab DWARF 3
Small pixels on a 35 mm f/4.3 lens give a sharper image than its aperture suggests, and EQ mode with 60 s subs makes it the read-noise winner in dark skies.
Auto mode caps subs at 15 s; 30 s and longer need EQ mode, and 60 s is the ceiling on the tele camera. Three built-in filters: VIS, Astro (430 to 690 nm) and dual-band Hα 656 nm / OIII 501 nm.
Longer subs matter most under dark skies, where read noise rather than skyglow sets the floor. From a city the difference between 15 s and 60 s subs is small; from a rural site it can halve the total time, especially with a dual-band filter in place.
Stack across nights. Every smart scope app can continue a stack or you can combine the saved frames on a computer; the figures here are totals, not single-session limits.
Have an image of the Iris Nebula from a DWARF 3? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- Iris Nebula with the ZWO Seestar S50: 1 h 53 min from Bortle 6
- Iris Nebula with the ZWO Seestar S50 Pro: 2 h 04 min from Bortle 6
- Iris Nebula with the ZWO Seestar S30: 1 h 59 min from Bortle 6
- Iris Nebula with the ZWO Seestar S30 Pro: 2 h 12 min from Bortle 6
- Iris Nebula with the DwarfLab DWARF mini: 1 h 53 min from Bortle 6
- Iris Nebula with the DwarfLab Draco: 1 h 33 min from Bortle 6
- Iris Nebula with the DwarfLab DWARF II: 6 h 29 min from Bortle 6
- Iris Nebula with the Vaonis Vespera II: 1 h 53 min from Bortle 6
- Iris Nebula with the Vaonis Vespera Pro: 4 h 14 min from Bortle 6
- Iris Nebula with the Vaonis Vespera 3: 1 h 48 min from Bortle 6
- Iris Nebula with the Vaonis Vespera Pro 2: 4 h 02 min from Bortle 6
- Iris Nebula with the Unistellar eQuinox 2: 1 h 43 min from Bortle 6
- Iris Nebula with the Unistellar Odyssey: 7 h 58 min from Bortle 6
- Iris Nebula with the Celestron Origin: 30 min from Bortle 6
- Iris Nebula with the Celestron Origin Mark II: 41 min from Bortle 6
All telescopes for the Iris Nebula · All targets for the DWARF 3