How long to image the Ghost of Cassiopeia with the DwarfLab DWARF mini
From a Bortle 6 suburban sky, the DwarfLab DWARF mini needs about 1 h 46 min (426 subs of 15 s with the built-in dual-band filter) for a solid image of the Ghost of Cassiopeia. A quick look takes 27 min; a showpiece 7 h 06 min. Under a Bortle 3 rural sky the solid figure drops to 1 h 14 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 14% 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 | 18 min72 subs | 1 h 11 min285 subs | 4 h 44 min1,138 subs |
| Bortle 2Typical dark site | 18 min73 subs | 1 h 12 min289 subs | 4 h 49 min1,155 subs |
| Bortle 3Rural | 19 min75 subs | 1 h 14 min297 subs | 4 h 57 min1,188 subs |
| Bortle 4Rural / suburban transition | 20 min80 subs | 1 h 19 min317 subs | 5 h 17 min1,268 subs |
| Bortle 5Suburban | 22 min88 subs | 1 h 27 min349 subs | 5 h 48 min1,394 subs |
| Bortle 6Bright suburban | 27 min107 subs | 1 h 46 min426 subs | 7 h 06 min1,704 subs |
| Bortle 7Suburban / urban transition | 36 min144 subs | 2 h 23 min574 subs | 9 h 34 min2,295 subs |
| Bortle 8City | 50 min201 subs | 3 h 21 min803 subs | 13 h3,212 subs |
| Bortle 9Inner city | 1 h 21 min323 subs | 5 h 23 min1,292 subs | 22 h5,168 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 2 h 18 min of run time. The DWARF mini’s battery (rated about 3 h 30 min) 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.)
- 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 Ghost of Cassiopeia is 10′ × 3′ across. The DWARF mini frames 2.13° × 1.20° at 3.99″ per pixel, so it fills 14% 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 14 min297 subs | 1 h 27 min349 subs | 2 h 23 min574 subs |
| 30 s | 55 min110 subs | 1 h 08 min136 subs | 2 h 04 min249 subs |
| 60 s | 45 min46 subs | 58 min59 subs | 1 h 54 min115 subs |
| 90 s | 45 min30 subs | 55 min37 subs | 1 h 51 min75 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| Astro (no light-pollution filter) | 1 h 04 min257 subs | 1 h 46 min425 subs | 4 h 50 min1,160 subs |
| dual-band | 1 h 14 min297 subs | 1 h 27 min349 subs | 2 h 23 min574 subs |
About the Ghost of Cassiopeia
A small emission and reflection wisp being eroded by the star Gamma Cassiopeiae. Keep the bright star's glare under control.
IC 63 · Emission nebula in Cassiopeia · magnitude 10.0 · 10′ × 3′ · best in Sep, Oct, Nov. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Emission nebulae glow in a few narrow lines, mostly hydrogen-alpha (deep red) and doubly ionised oxygen (teal). A dual-band filter passes those lines and blocks most skyglow, which is why it cuts the time needed from a suburban sky so dramatically. Use it. From a genuinely dark site the gain is smaller because there is less skyglow to block, and read noise becomes the limit, which is where longer subs (EQ mode, or Expert Mode on a Vespera) earn their keep.
Stars lose colour through a dual-band filter; a short broadband stack blended in fixes that if you care.
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 Ghost of Cassiopeia from a DWARF mini? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- Ghost of Cassiopeia with the ZWO Seestar S50: 1 h 48 min from Bortle 6
- Ghost of Cassiopeia with the ZWO Seestar S50 Pro: 2 h 01 min from Bortle 6
- Ghost of Cassiopeia with the ZWO Seestar S30: 2 h 06 min from Bortle 6
- Ghost of Cassiopeia with the ZWO Seestar S30 Pro: 2 h 11 min from Bortle 6
- Ghost of Cassiopeia with the DwarfLab DWARF 3: 2 h 15 min from Bortle 6
- Ghost of Cassiopeia with the DwarfLab Draco: 1 h 26 min from Bortle 6
- Ghost of Cassiopeia with the DwarfLab DWARF II: 9 h 43 min from Bortle 6
- Ghost of Cassiopeia with the Vaonis Vespera II: 2 h 50 min from Bortle 6
- Ghost of Cassiopeia with the Vaonis Vespera Pro: 6 h 21 min from Bortle 6
- Ghost of Cassiopeia with the Vaonis Vespera 3: 2 h 43 min from Bortle 6
- Ghost of Cassiopeia with the Vaonis Vespera Pro 2: 6 h 03 min from Bortle 6
- Ghost of Cassiopeia with the Unistellar eQuinox 2: 2 h 35 min from Bortle 6
- Ghost of Cassiopeia with the Unistellar Odyssey: 12 h from Bortle 6
- Ghost of Cassiopeia with the Celestron Origin: 45 min from Bortle 6
- Ghost of Cassiopeia with the Celestron Origin Mark II: 1 h 02 min from Bortle 6
All telescopes for the Ghost of Cassiopeia · All targets for the DWARF mini