How long to image the NGC 2403 with the DwarfLab DWARF mini
From a Bortle 6 suburban sky, the DwarfLab DWARF mini needs about 3 h 13 min (771 subs of 15 s) for a solid image of the NGC 2403. A quick look takes 48 min; a showpiece 13 h. Under a Bortle 3 rural sky the solid figure drops to 1 h 10 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 29% 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 | 15 min59 subs | 59 min235 subs | 3 h 54 min937 subs |
| Bortle 2Typical dark site | 16 min63 subs | 1 h 03 min251 subs | 4 h 11 min1,003 subs |
| Bortle 3Rural | 18 min71 subs | 1 h 10 min282 subs | 4 h 42 min1,127 subs |
| Bortle 4Rural / suburban transition | 22 min90 subs | 1 h 29 min358 subs | 5 h 57 min1,429 subs |
| Bortle 5Suburban | 30 min120 subs | 1 h 59 min477 subs | 7 h 57 min1,907 subs |
| Bortle 6Bright suburban | 48 min193 subs | 3 h 13 min771 subs | 13 h3,081 subs |
| Bortle 7Suburban / urban transition | 1 h 23 min333 subs | 5 h 32 min1,329 subs | 22 h5,316 subs |
| Bortle 8City | 2 h 17 min550 subs | 9 h 09 min2,197 subs | 37 h8,787 subs |
| Bortle 9Inner city | 4 h 13 min1,012 subs | 17 h4,048 subs | 67 h16,189 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 4 h 10 min of run time. The DWARF mini’s battery is rated at about 3 h 30 min, less near freezing, so the session needs an external power bank. (Bortle 6, solid image; we allow 30% over the integration time, and 30% off the battery for a January night.)
- 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.
- hand warmers long lastingAir-activated packs give hours of heat for the person; winter nights are long and you spend most of them standing still.
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Everything that fits the DWARF mini →
How it frames
The NGC 2403 is 21′ × 12′ across. The DWARF mini frames 2.13° × 1.20° at 3.99″ per pixel, so it fills 29% of the frame’s short side.
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 10 min282 subs | 1 h 59 min477 subs | 5 h 32 min1,329 subs |
| 30 s | 59 min119 subs | 1 h 48 min217 subs | 5 h 21 min643 subs |
| 60 s | 54 min54 subs | 1 h 43 min103 subs | 5 h 16 min316 subs |
| 90 s | 52 min35 subs | 1 h 41 min68 subs | 5 h 14 min210 subs |
Leave the dual-band filter out for the NGC 2403. It is a galaxy, 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 12 times slower.
About the NGC 2403
A big, loose spiral in Camelopardalis that looks like a small M33, with bright H II regions dual-band can pick out.
Caldwell 7 · Galaxy in Camelopardalis · magnitude 8.9 · 21′ × 12′ · best in Dec, Jan, Feb. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Galaxies are broadband targets: their light is mostly starlight spread across the spectrum, so a dual-band filter throws most of it away and makes things slower, not faster. Shoot without a filter (or with a plain UV/IR cut) and rely on total time and a dark sky. The core of a galaxy is usually many times brighter than its outer disc, so a short stack shows the nucleus long before the arms; the figures here are for the arms and disc, not the core.
Field rotation in Alt-Az mode crops the edges of the stack over a long session, so on a big galaxy re-centre now and then or use EQ mode where your scope supports it.
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 2403 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 2403 with the ZWO Seestar S50: 3 h 13 min from Bortle 6
- NGC 2403 with the ZWO Seestar S50 Pro: 3 h 32 min from Bortle 6
- NGC 2403 with the ZWO Seestar S30: 3 h 23 min from Bortle 6
- NGC 2403 with the ZWO Seestar S30 Pro: 3 h 44 min from Bortle 6
- NGC 2403 with the DwarfLab DWARF 3: 4 h 40 min from Bortle 6
- NGC 2403 with the DwarfLab Draco: 2 h 39 min from Bortle 6
- NGC 2403 with the DwarfLab DWARF II: 11 h from Bortle 6
- NGC 2403 with the Vaonis Vespera II: 3 h 13 min from Bortle 6
- NGC 2403 with the Vaonis Vespera Pro: 7 h 14 min from Bortle 6
- NGC 2403 with the Vaonis Vespera 3: 3 h 05 min from Bortle 6
- NGC 2403 with the Vaonis Vespera Pro 2: 6 h 53 min from Bortle 6
- NGC 2403 with the Unistellar eQuinox 2: 2 h 57 min from Bortle 6
- NGC 2403 with the Unistellar Odyssey: 14 h from Bortle 6
- NGC 2403 with the Celestron Origin: 51 min from Bortle 6
- NGC 2403 with the Celestron Origin Mark II: 1 h 10 min from Bortle 6
All telescopes for the NGC 2403 · All targets for the DWARF mini