How long to image the NGC 891 with the DwarfLab DWARF II
From a Bortle 6 suburban sky, the DwarfLab DWARF II needs about 9 h 24 min (2,257 subs of 15 s) for a solid image of the NGC 891. A quick look takes 2 h 21 min; a showpiece 38 h. Under a Bortle 3 rural sky the solid figure drops to 4 h 39 min. At Bortle 6 the limit is a mix of skyglow and read noise. 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 | 1 h 03 min252 subs | 4 h 11 min1,005 subs | 17 h4,017 subs |
| Bortle 2Typical dark site | 1 h 05 min261 subs | 4 h 21 min1,043 subs | 17 h4,170 subs |
| Bortle 3Rural | 1 h 10 min279 subs | 4 h 39 min1,116 subs | 19 h4,462 subs |
| Bortle 4Rural / suburban transition | 1 h 21 min323 subs | 5 h 23 min1,292 subs | 22 h5,167 subs |
| Bortle 5Suburban | 1 h 38 min393 subs | 6 h 33 min1,572 subs | 26 h6,285 subs |
| Bortle 6Bright suburban | 2 h 21 min565 subs | 9 h 24 min2,257 subs | 38 h9,027 subs |
| Bortle 7Suburban / urban transition | 3 h 43 min891 subs | 15 h3,564 subs | 59 h14,253 subs |
| Bortle 8City | 5 h 49 min1,398 subs | 23 h5,592 subs | 93 h22,367 subs |
| Bortle 9Inner city | 10 h2,480 subs | 41 h9,918 subs | 170+ h39,672 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 12 h of run time. That is more than one night: over 2 nights, about 6 h 07 min each. The DWARF II’s battery is rated at about 3 h, less near freezing, so each night needs an external power bank. (Bortle 6, solid image; we allow 30% over the integration time, and 30% off the battery for a November night.)
- USB-C PD power bank 10000mAh 18W18 W PD input; runs while charging.
- 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.
Affiliate links: the retailer pays us a small commission and you pay the same price. These are search links to the named product, not endorsements of a particular listing; check the listing matches your model.
Everything that fits the DWARF II →
How it frames
The NGC 891 is 13.5′ × 2.5′ across. The DWARF II frames 3.19° × 1.79° at 2.99″ per pixel, so it fills 13% of the frame’s short side.
About the NGC 891
A perfect edge-on spiral split by a dust lane. Faint per pixel; a dark sky or a long stack shows the lane.
Caldwell 23, Silver Sliver · Galaxy in Andromeda · magnitude 10.0 · 13.5′ × 2.5′ · best in Oct, Nov, Dec. 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 II
The original pocket scope. 24 mm aperture and tiny 1.45 µm pixels mean it is slow per pixel, so bin or downsample and be patient.
15 s is the hard maximum in any mode; DwarfLab recommends EQ mode at 15 s. Two built-in filters, VIS and Astro (IR-pass); no dual-band. The optional UHC filter is no longer sold.
The DWARF II uses fixed 15 s subs, so the only levers you have are the sky you shoot from, the filter, and total time.
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 891 from a DWARF II? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- NGC 891 with the ZWO Seestar S50: 2 h 44 min from Bortle 6
- NGC 891 with the ZWO Seestar S50 Pro: 3 h from Bortle 6
- NGC 891 with the ZWO Seestar S30: 2 h 53 min from Bortle 6
- NGC 891 with the ZWO Seestar S30 Pro: 3 h 10 min from Bortle 6
- NGC 891 with the DwarfLab DWARF 3: 3 h 58 min from Bortle 6
- NGC 891 with the DwarfLab DWARF mini: 2 h 43 min from Bortle 6
- NGC 891 with the DwarfLab Draco: 2 h 15 min from Bortle 6
- NGC 891 with the Vaonis Vespera II: 2 h 44 min from Bortle 6
- NGC 891 with the Vaonis Vespera Pro: 6 h 08 min from Bortle 6
- NGC 891 with the Vaonis Vespera 3: 2 h 37 min from Bortle 6
- NGC 891 with the Vaonis Vespera Pro 2: 5 h 51 min from Bortle 6
- NGC 891 with the Unistellar eQuinox 2: 2 h 30 min from Bortle 6
- NGC 891 with the Unistellar Odyssey: 12 h from Bortle 6
- NGC 891 with the Celestron Origin: 43 min from Bortle 6
- NGC 891 with the Celestron Origin Mark II: 59 min from Bortle 6
All telescopes for the NGC 891 · All targets for the DWARF II