How long to image the Bow-Tie Nebula with the DwarfLab Draco
From a Bortle 6 suburban sky, the DwarfLab Draco needs about 17 min (34 subs of 30 s with the built-in dual-narrowband (Hα + OIII) filter) for a solid image of the Bow-Tie Nebula. A quick look takes 5 min; a showpiece 1 h 07 min. Under a Bortle 3 rural sky the solid figure drops to 15 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it is small in the frame, about 33 pixels across.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 5 min10 subs | 15 min30 subs | 51 min102 subs |
| Bortle 2Typical dark site | 5 min10 subs | 15 min30 subs | 51 min103 subs |
| Bortle 3Rural | 5 min10 subs | 15 min30 subs | 52 min105 subs |
| Bortle 4Rural / suburban transition | 5 min10 subs | 15 min30 subs | 54 min109 subs |
| Bortle 5Suburban | 5 min10 subs | 15 min30 subs | 58 min117 subs |
| Bortle 6Bright suburban | 5 min10 subs | 17 min34 subs | 1 h 07 min134 subs |
| Bortle 7Suburban / urban transition | 5 min11 subs | 21 min42 subs | 1 h 24 min168 subs |
| Bortle 8City | 7 min14 subs | 27 min55 subs | 1 h 50 min220 subs |
| Bortle 9Inner city | 10 min21 subs | 41 min83 subs | 2 h 46 min332 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 22 min of run time. The Draco’s battery (rated about 5 h) 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 20000mAhRated 5 h on its 10,000 mAh battery. DwarfLab has not published the charging input, so check PD support before relying on it mid-session.
- red LED head torchRed light keeps your night vision; white light costs you twenty minutes of dark adaptation every time.
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How it frames
The Bow-Tie Nebula is 0.8′ × 0.6′ across. The Draco frames 1.66° × 1.24° at 1.46″ per pixel, so it is small in the frame, about 33 pixels across. It is worth doing, but the result is a crop rather than a full frame; a longer focal length would resolve more of it.
Longer subs
Auto Mode picks the exposure; Pro Mode allows up to 300 s, held by built-in guiding and field derotation. The 30 s default here is our assumption. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 30 s | 15 min30 subs | 15 min30 subs | 21 min42 subs |
| 60 s | 30 min30 subs | 30 min30 subs | 30 min30 subs |
| 120 s | 1 h30 subs | 1 h30 subs | 1 h30 subs |
| 300 s | 2 h 30 min30 subs | 2 h 30 min30 subs | 2 h 30 min30 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| No filter | 15 min30 subs | 15 min31 subs | 36 min73 subs |
| dual-narrowband (Hα + OIII) | 15 min30 subs | 15 min30 subs | 21 min42 subs |
About the Bow-Tie Nebula
A red-tinged planetary near the pole with a bright central star. Small; dual-band brings out the bow.
NGC 40, Caldwell 2 · Planetary nebula in Cepheus · magnitude 11.6 · 0.8′ × 0.6′ · best in Sep, Oct, Nov. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Planetary nebulae are small but intensely bright per pixel in OIII and H-alpha, so they respond very well to a dual-band filter and do not need much time for the main shell. The faint outer halos most of them have are a different proposition and need hours. Keep subs short if the central region saturates.
About the DwarfLab Draco
DwarfLab’s big scope: 90 mm of folded f/3.8 optics, the most aperture of any Seestar or DWARF, a narrow 13 nm dual-band filter and 300 s subs with built-in guiding. A small-target scope; big nebulae need its mosaic mode.
Auto Mode picks the exposure; Pro Mode allows up to 300 s, held by built-in guiding and field derotation. The 30 s default here is our assumption. Built-in Hα + OIII dual-narrowband filter, 13 nm per line; the SHO Edition adds an SII option.
Longer subs matter most under dark skies, where read noise rather than skyglow sets the floor. From a city the difference between 30 s and 300 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 Bow-Tie Nebula from a Draco? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- Bow-Tie Nebula with the ZWO Seestar S50: 21 min from Bortle 6
- Bow-Tie Nebula with the ZWO Seestar S50 Pro: 23 min from Bortle 6
- Bow-Tie Nebula with the ZWO Seestar S30: 23 min from Bortle 6
- Bow-Tie Nebula with the ZWO Seestar S30 Pro: 25 min from Bortle 6
- Bow-Tie Nebula with the DwarfLab DWARF 3: 28 min from Bortle 6
- Bow-Tie Nebula with the DwarfLab DWARF mini: 21 min from Bortle 6
- Bow-Tie Nebula with the DwarfLab DWARF II: 1 h 32 min from Bortle 6
- Bow-Tie Nebula with the Vaonis Vespera II: 27 min from Bortle 6
- Bow-Tie Nebula with the Vaonis Vespera Pro: 1 h 01 min from Bortle 6
- Bow-Tie Nebula with the Vaonis Vespera 3: 26 min from Bortle 6
- Bow-Tie Nebula with the Vaonis Vespera Pro 2: 58 min from Bortle 6
- Bow-Tie Nebula with the Unistellar eQuinox 2: 24 min from Bortle 6
- Bow-Tie Nebula with the Unistellar Odyssey: 1 h 48 min from Bortle 6
- Bow-Tie Nebula with the Celestron Origin: 7 min from Bortle 6
- Bow-Tie Nebula with the Celestron Origin Mark II: 10 min from Bortle 6
All telescopes for the Bow-Tie Nebula · All targets for the Draco