How long to image the NGC 2903 with the DwarfLab Draco
From a Bortle 6 suburban sky, the DwarfLab Draco needs about 1 h 56 min (232 subs of 30 s) for a solid image of the NGC 2903. A quick look takes 29 min; a showpiece 7 h 43 min. Under a Bortle 3 rural sky the solid figure drops to 43 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 17% 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 | 9 min18 subs | 36 min72 subs | 2 h 23 min286 subs |
| Bortle 2Typical dark site | 10 min20 subs | 38 min77 subs | 2 h 33 min306 subs |
| Bortle 3Rural | 11 min22 subs | 43 min86 subs | 2 h 51 min343 subs |
| Bortle 4Rural / suburban transition | 14 min28 subs | 54 min109 subs | 3 h 36 min433 subs |
| Bortle 5Suburban | 18 min36 subs | 1 h 12 min144 subs | 4 h 48 min576 subs |
| Bortle 6Bright suburban | 29 min58 subs | 1 h 56 min232 subs | 7 h 43 min927 subs |
| Bortle 7Suburban / urban transition | 50 min100 subs | 3 h 19 min399 subs | 13 h1,595 subs |
| Bortle 8City | 1 h 22 min165 subs | 5 h 29 min658 subs | 22 h2,632 subs |
| Bortle 9Inner city | 2 h 31 min303 subs | 10 h1,211 subs | 40 h4,844 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 2 h 31 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, and 30% off the battery for a February night.)
- 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.
- 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 Draco →
How it frames
The NGC 2903 is 12.6′ × 6′ across. The Draco frames 1.66° × 1.24° at 1.46″ per pixel, so it fills 17% of the frame’s short side.
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 | 43 min86 subs | 1 h 12 min144 subs | 3 h 19 min399 subs |
| 60 s | 37 min37 subs | 1 h 06 min66 subs | 3 h 13 min194 subs |
| 120 s | 1 h30 subs | 1 h 03 min32 subs | 3 h 10 min96 subs |
| 300 s | 2 h 30 min30 subs | 2 h 30 min30 subs | 3 h 08 min38 subs |
Leave the dual-band filter out for the NGC 2903. 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 11 times slower.
About the NGC 2903
A bright barred spiral below the Sickle of Leo that Messier somehow missed. Bright core, well-defined arms.
UGC 5079 · Galaxy in Leo · magnitude 9.0 · 12.6′ × 6′ · best in Jan, Feb, Mar. 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 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 NGC 2903 from a Draco? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- NGC 2903 with the ZWO Seestar S50: 2 h 21 min from Bortle 6
- NGC 2903 with the ZWO Seestar S50 Pro: 2 h 34 min from Bortle 6
- NGC 2903 with the ZWO Seestar S30: 2 h 28 min from Bortle 6
- NGC 2903 with the ZWO Seestar S30 Pro: 2 h 44 min from Bortle 6
- NGC 2903 with the DwarfLab DWARF 3: 3 h 25 min from Bortle 6
- NGC 2903 with the DwarfLab DWARF mini: 2 h 20 min from Bortle 6
- NGC 2903 with the DwarfLab DWARF II: 8 h 04 min from Bortle 6
- NGC 2903 with the Vaonis Vespera II: 2 h 21 min from Bortle 6
- NGC 2903 with the Vaonis Vespera Pro: 5 h 16 min from Bortle 6
- NGC 2903 with the Vaonis Vespera 3: 2 h 15 min from Bortle 6
- NGC 2903 with the Vaonis Vespera Pro 2: 5 h 01 min from Bortle 6
- NGC 2903 with the Unistellar eQuinox 2: 2 h 08 min from Bortle 6
- NGC 2903 with the Unistellar Odyssey: 9 h 55 min from Bortle 6
- NGC 2903 with the Celestron Origin: 37 min from Bortle 6
- NGC 2903 with the Celestron Origin Mark II: 51 min from Bortle 6