How long to image the NGC 6781 with the DwarfLab DWARF mini
From a Bortle 6 suburban sky, the DwarfLab DWARF mini needs about 2 h 40 min (639 subs of 15 s with the built-in dual-band filter) for a solid image of the NGC 6781. A quick look takes 40 min; a showpiece 11 h. Under a Bortle 3 rural sky the solid figure drops to 1 h 51 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 27 pixels across.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 27 min107 subs | 1 h 47 min427 subs | 7 h 06 min1,706 subs |
| Bortle 2Typical dark site | 27 min109 subs | 1 h 48 min433 subs | 7 h 13 min1,732 subs |
| Bortle 3Rural | 28 min112 subs | 1 h 51 min446 subs | 7 h 25 min1,782 subs |
| Bortle 4Rural / suburban transition | 30 min119 subs | 1 h 59 min476 subs | 7 h 55 min1,901 subs |
| Bortle 5Suburban | 33 min131 subs | 2 h 11 min523 subs | 8 h 43 min2,091 subs |
| Bortle 6Bright suburban | 40 min160 subs | 2 h 40 min639 subs | 11 h2,556 subs |
| Bortle 7Suburban / urban transition | 54 min216 subs | 3 h 35 min861 subs | 14 h3,442 subs |
| Bortle 8City | 1 h 15 min302 subs | 5 h 01 min1,205 subs | 20 h4,817 subs |
| Bortle 9Inner city | 2 h 01 min485 subs | 8 h 04 min1,938 subs | 32 h7,751 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 3 h 28 min of run time. The DWARF mini’s battery is rated at about 3 h 30 min, which is cutting it fine; take a power bank. (Bortle 6, solid image; we allow 30% over the integration time.)
- USB-C PD power bank 10000mAh 20W7,000 mAh inside, about four hours; a PD bank extends the night.
- 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 mini →
How it frames
The NGC 6781 is 1.8′ across. The DWARF mini frames 2.13° × 1.20° at 3.99″ per pixel, so it is small in the frame, about 27 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 caps subs at 15 s; 30 s and longer need EQ mode, and 90 s is the ceiling. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 15 s | 1 h 51 min446 subs | 2 h 11 min523 subs | 3 h 35 min861 subs |
| 30 s | 1 h 22 min165 subs | 1 h 42 min204 subs | 3 h 06 min373 subs |
| 60 s | 1 h 08 min68 subs | 1 h 27 min88 subs | 2 h 52 min172 subs |
| 90 s | 1 h 03 min43 subs | 1 h 22 min55 subs | 2 h 47 min112 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| Astro (no light-pollution filter) | 1 h 36 min385 subs | 2 h 39 min637 subs | 7 h 15 min1,740 subs |
| dual-band | 1 h 51 min446 subs | 2 h 11 min523 subs | 3 h 35 min861 subs |
About the NGC 6781
A ghostly ring planetary in Aquila, larger and fainter than the Ring Nebula. Dual-band recommended.
Aquila planetary · Planetary nebula in Aquila · magnitude 11.4 · 1.8′ · best in Jun, Jul, Aug. 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 DWARF mini
DwarfLab’s answer to the Seestar S30: same sensor and focal length, big pixels, dual-band filter built in, and 90 s subs in EQ mode. Sensitivity over megapixels.
Auto mode caps subs at 15 s; 30 s and longer need EQ mode, and 90 s is the ceiling. Built-in Astro (430 to 690 nm), dark-frame and dual-band Hα / OIII filters; no plain VIS filter on the tele camera.
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 90 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 NGC 6781 from a DWARF mini? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- NGC 6781 with the ZWO Seestar S50: 2 h 42 min from Bortle 6
- NGC 6781 with the ZWO Seestar S50 Pro: 3 h 02 min from Bortle 6
- NGC 6781 with the ZWO Seestar S30: 3 h 09 min from Bortle 6
- NGC 6781 with the ZWO Seestar S30 Pro: 3 h 16 min from Bortle 6
- NGC 6781 with the DwarfLab DWARF 3: 3 h 22 min from Bortle 6
- NGC 6781 with the DwarfLab Draco: 2 h 08 min from Bortle 6
- NGC 6781 with the DwarfLab DWARF II: 15 h from Bortle 6
- NGC 6781 with the Vaonis Vespera II: 4 h 15 min from Bortle 6
- NGC 6781 with the Vaonis Vespera Pro: 9 h 32 min from Bortle 6
- NGC 6781 with the Vaonis Vespera 3: 4 h 04 min from Bortle 6
- NGC 6781 with the Vaonis Vespera Pro 2: 9 h 05 min from Bortle 6
- NGC 6781 with the Unistellar eQuinox 2: 3 h 52 min from Bortle 6
- NGC 6781 with the Unistellar Odyssey: 18 h from Bortle 6
- NGC 6781 with the Celestron Origin: 1 h 07 min from Bortle 6
- NGC 6781 with the Celestron Origin Mark II: 1 h 33 min from Bortle 6
All telescopes for the NGC 6781 · All targets for the DWARF mini