How long to image the M54 with the ZWO Seestar S30 Pro
From a Bortle 6 suburban sky, the ZWO Seestar S30 Pro needs about 33 min (198 subs of 10 s) for a solid image of the M54. A quick look takes 8 min; a showpiece 2 h 12 min. Under a Bortle 3 rural sky the solid figure drops to 15 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 9% 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 | 3 min20 subs | 13 min79 subs | 52 min314 subs |
| Bortle 2Typical dark site | 3 min21 subs | 14 min82 subs | 55 min328 subs |
| Bortle 3Rural | 4 min23 subs | 15 min89 subs | 59 min356 subs |
| Bortle 4Rural / suburban transition | 4 min27 subs | 18 min106 subs | 1 h 10 min423 subs |
| Bortle 5Suburban | 6 min34 subs | 22 min133 subs | 1 h 28 min530 subs |
| Bortle 6Bright suburban | 8 min50 subs | 33 min198 subs | 2 h 12 min792 subs |
| Bortle 7Suburban / urban transition | 13 min81 subs | 54 min323 subs | 3 h 35 min1,291 subs |
| Bortle 8City | 22 min130 subs | 1 h 26 min517 subs | 5 h 44 min2,065 subs |
| Bortle 9Inner city | 39 min233 subs | 2 h 35 min930 subs | 10 h3,717 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 43 min of run time. The Seestar S30 Pro’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.)
- USB-C power bank 10000mAh 5V 3A5 V 3 A input and it runs while charging.
- Seestar S30 Pro dew shieldActive anti-dew is built in; a shield adds margin. The S30 Pro front differs from the S30, so check the listing.
- 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 S30 Pro →
How it frames
The M54 is 12′ across. The Seestar S30 Pro frames 3.99° × 2.24° at 3.74″ per pixel, so it fills 9% of the frame’s short side.
Longer subs
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, which needs the TH10 head. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 15 min89 subs | 22 min133 subs | 54 min323 subs |
| 20 s | 13 min39 subs | 20 min61 subs | 52 min156 subs |
| 30 s | 15 min30 subs | 19 min39 subs | 51 min103 subs |
| 60 s | 30 min30 subs | 30 min30 subs | 51 min51 subs |
Leave the dual-band filter out for the M54. It is a globular cluster, 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 12 times slower.
About the M54
A globular that actually belongs to the Sagittarius Dwarf galaxy being eaten by the Milky Way. Low from the north.
NGC 6715 · Globular cluster in Sagittarius · magnitude 7.6 · 12′ · best in Jun, Jul, Aug. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Globular clusters are point sources packed tight, so they come quickly: the core resolves into stars within a handful of minutes on any smart scope. More time deepens the halo and pulls in the faint outer members. Use short subs so the core does not saturate into a white blob, and no filter.
About the ZWO Seestar S30 Pro
The S30 optics upgraded to a quadruplet in front of an 8 MP IMX585. Same speed per pixel as the S30, four times the pixels, so you can crop hard.
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, which needs the TH10 head. Built-in UV/IR-cut, dual-band (OIII 30 nm / Hα 20 nm) and dark filters on the telephoto camera.
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 M54 from a Seestar S30 Pro? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M54 with the ZWO Seestar S50: 28 min from Bortle 6
- M54 with the ZWO Seestar S50 Pro: 31 min from Bortle 6
- M54 with the ZWO Seestar S30: 30 min from Bortle 6
- M54 with the DwarfLab DWARF 3: 42 min from Bortle 6
- M54 with the DwarfLab DWARF mini: 28 min from Bortle 6
- M54 with the DwarfLab Draco: 23 min from Bortle 6
- M54 with the DwarfLab DWARF II: 1 h 36 min from Bortle 6
- M54 with the Vaonis Vespera II: 28 min from Bortle 6
- M54 with the Vaonis Vespera Pro: 1 h 03 min from Bortle 6
- M54 with the Vaonis Vespera 3: 27 min from Bortle 6
- M54 with the Vaonis Vespera Pro 2: 1 h 01 min from Bortle 6
- M54 with the Unistellar eQuinox 2: 25 min from Bortle 6
- M54 with the Unistellar Odyssey: 1 h 55 min from Bortle 6
- M54 with the Celestron Origin: 8 min from Bortle 6
- M54 with the Celestron Origin Mark II: 10 min from Bortle 6
All telescopes for the M54 · All targets for the Seestar S30 Pro