How long to image the Sagittarius Star Cloud with the ZWO Seestar S50
From a Bortle 6 suburban sky, the ZWO Seestar S50 needs about 9 min (53 subs of 10 s) for a solid image of the Sagittarius Star Cloud. A quick look takes 2 min; a showpiece 35 min. Under a Bortle 3 rural sky the solid figure drops to 5 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 is 2.1× wider than the frame.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 2 min10 subs | 5 min30 subs | 16 min96 subs |
| Bortle 2Typical dark site | 2 min10 subs | 5 min30 subs | 16 min99 subs |
| Bortle 3Rural | 2 min10 subs | 5 min30 subs | 18 min106 subs |
| Bortle 4Rural / suburban transition | 2 min10 subs | 5 min31 subs | 20 min122 subs |
| Bortle 5Suburban | 2 min10 subs | 6 min37 subs | 25 min148 subs |
| Bortle 6Bright suburban | 2 min14 subs | 9 min53 subs | 35 min212 subs |
| Bortle 7Suburban / urban transition | 3 min21 subs | 14 min84 subs | 56 min334 subs |
| Bortle 8City | 5 min33 subs | 22 min131 subs | 1 h 27 min523 subs |
| Bortle 9Inner city | 10 min58 subs | 39 min232 subs | 2 h 34 min926 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 11 min of run time. The Seestar S50’s battery (rated about 6 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.)
- USB-C power bank 20000mAh 5V 3AThe S50 draws 5 V 3 A over USB-C and runs while charging; no PD needed.
- Seestar S50 dew shieldThe built-in heater copes with most nights; a shield helps in heavy dew and blocks stray light.
- 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 Seestar S50 →
How it frames
The Sagittarius Star Cloud is 90′ across. The Seestar S50 frames 1.28° × 0.72° at 2.39″ per pixel, so it is 2.1× wider than the frame. A mosaic, or choosing the part you want and letting the rest go, is how it gets shot on this scope.
Longer subs
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode (app 2.5 and later). Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 5 min30 subs | 6 min37 subs | 14 min84 subs |
| 20 s | 10 min30 subs | 10 min30 subs | 13 min41 subs |
| 30 s | 15 min30 subs | 15 min30 subs | 15 min30 subs |
| 60 s | 30 min30 subs | 30 min30 subs | 30 min30 subs |
Leave the dual-band filter out for the Sagittarius Star Cloud. It is a star cloud, 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 Sagittarius Star Cloud
A window through the dust into the inner Milky Way, densely packed with stars. Short stacks are enough; it is stars, not nebulosity.
M24, IC 4715 · Star cloud in Sagittarius · magnitude 4.6 · 90′ · best in Jun, Jul, Aug. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Star clouds are dense fields of ordinary stars rather than nebulosity. Short subs, no filter, and a modest total keep the field from saturating while still showing the depth of the Milky Way.
About the ZWO Seestar S50
The scope that made smart astrophotography mainstream. 50 mm triplet, 2 MP sensor, dual-band filter on a wheel. Alt-Az stacking at 10 s, EQ mode unlocks 60 s. Out of production since 2026 and replaced by the S50 Pro, but there are a great many in use.
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode (app 2.5 and later). Built-in dual-band light-pollution filter, switchable in the app.
Longer subs matter most under dark skies, where read noise rather than skyglow sets the floor. From a city the difference between 10 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 Sagittarius Star Cloud from a Seestar S50? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- Sagittarius Star Cloud with the ZWO Seestar S50 Pro: 10 min from Bortle 6
- Sagittarius Star Cloud with the ZWO Seestar S30: 9 min from Bortle 6
- Sagittarius Star Cloud with the ZWO Seestar S30 Pro: 10 min from Bortle 6
- Sagittarius Star Cloud with the DwarfLab DWARF 3: 13 min from Bortle 6
- Sagittarius Star Cloud with the DwarfLab DWARF mini: 9 min from Bortle 6
- Sagittarius Star Cloud with the DwarfLab Draco: 15 min from Bortle 6
- Sagittarius Star Cloud with the DwarfLab DWARF II: 29 min from Bortle 6
- Sagittarius Star Cloud with the Vaonis Vespera II: 9 min from Bortle 6
- Sagittarius Star Cloud with the Vaonis Vespera Pro: 20 min from Bortle 6
- Sagittarius Star Cloud with the Vaonis Vespera 3: 8 min from Bortle 6
- Sagittarius Star Cloud with the Vaonis Vespera Pro 2: 19 min from Bortle 6
- Sagittarius Star Cloud with the Unistellar eQuinox 2: 8 min from Bortle 6
- Sagittarius Star Cloud with the Unistellar Odyssey: 34 min from Bortle 6
- Sagittarius Star Cloud with the Celestron Origin: 5 min from Bortle 6
- Sagittarius Star Cloud with the Celestron Origin Mark II: 5 min from Bortle 6
All telescopes for the Sagittarius Star Cloud · All targets for the Seestar S50