How long to image the NGC 2903 with the DwarfLab DWARF 3
From a Bortle 6 suburban sky, the DwarfLab DWARF 3 needs about 3 h 25 min (820 subs of 15 s) for a solid image of the NGC 2903. A quick look takes 51 min; a showpiece 14 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 13% 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 | 14 min57 subs | 56 min226 subs | 3 h 46 min903 subs |
| Bortle 2Typical dark site | 15 min61 subs | 1 h 01 min244 subs | 4 h 04 min976 subs |
| Bortle 3Rural | 17 min70 subs | 1 h 10 min279 subs | 4 h 38 min1,114 subs |
| Bortle 4Rural / suburban transition | 23 min91 subs | 1 h 30 min362 subs | 6 h 02 min1,448 subs |
| Bortle 5Suburban | 31 min124 subs | 2 h 04 min495 subs | 8 h 14 min1,978 subs |
| Bortle 6Bright suburban | 51 min205 subs | 3 h 25 min820 subs | 14 h3,277 subs |
| Bortle 7Suburban / urban transition | 1 h 30 min360 subs | 6 h1,439 subs | 24 h5,754 subs |
| Bortle 8City | 2 h 30 min600 subs | 10 h2,400 subs | 40 h9,598 subs |
| Bortle 9Inner city | 4 h 38 min1,113 subs | 19 h4,450 subs | 74 h17,797 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 4 h 26 min of run time. The DWARF 3’s battery is rated at about 5 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 February night.)
- 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.
- 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 3 →
How it frames
The NGC 2903 is 12.6′ × 6′ across. The DWARF 3 frames 2.93° × 1.65° at 2.75″ per pixel, so it fills 13% 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 | 1 h 10 min279 subs | 2 h 04 min495 subs | 6 h1,439 subs |
| 30 s | 1 h 05 min130 subs | 1 h 59 min238 subs | 5 h 55 min710 subs |
| 60 s | 1 h 03 min63 subs | 1 h 57 min117 subs | 5 h 53 min353 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 10 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 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 NGC 2903 from a DWARF 3? 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 mini: 2 h 20 min from Bortle 6
- NGC 2903 with the DwarfLab Draco: 1 h 56 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
All telescopes for the NGC 2903 · All targets for the DWARF 3