How long to image the M22 with the ZWO Seestar S30 Pro
From a Bortle 6 suburban sky, the ZWO Seestar S30 Pro needs about 14 min (86 subs of 10 s) for a solid image of the M22. A quick look takes 4 min; a showpiece 57 min. Under a Bortle 3 rural sky the solid figure drops to 7 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 24% 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 | 2 min10 subs | 6 min37 subs | 25 min148 subs |
| Bortle 2Typical dark site | 2 min10 subs | 6 min39 subs | 26 min154 subs |
| Bortle 3Rural | 2 min11 subs | 7 min42 subs | 28 min166 subs |
| Bortle 4Rural / suburban transition | 2 min13 subs | 8 min49 subs | 32 min193 subs |
| Bortle 5Suburban | 2 min15 subs | 10 min59 subs | 39 min236 subs |
| Bortle 6Bright suburban | 4 min22 subs | 14 min86 subs | 57 min342 subs |
| Bortle 7Suburban / urban transition | 6 min34 subs | 23 min136 subs | 1 h 31 min544 subs |
| Bortle 8City | 9 min54 subs | 36 min215 subs | 2 h 23 min857 subs |
| Bortle 9Inner city | 16 min96 subs | 1 h 04 min382 subs | 4 h 14 min1,525 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 18 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 M22 is 32′ across. The Seestar S30 Pro frames 3.99° × 2.24° at 3.74″ per pixel, so it fills 24% 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 | 7 min42 subs | 10 min59 subs | 23 min136 subs |
| 20 s | 10 min30 subs | 10 min30 subs | 22 min66 subs |
| 30 s | 15 min30 subs | 15 min30 subs | 22 min44 subs |
| 60 s | 30 min30 subs | 30 min30 subs | 30 min30 subs |
Leave the dual-band filter out for the M22. 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 M22
One of the brightest globulars in the sky, outshining M13, but low from northern Europe. Superb from the south.
NGC 6656 · Globular cluster in Sagittarius · magnitude 5.1 · 32′ · 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 M22 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
- M22 with the ZWO Seestar S50: 12 min from Bortle 6
- M22 with the ZWO Seestar S50 Pro: 13 min from Bortle 6
- M22 with the ZWO Seestar S30: 13 min from Bortle 6
- M22 with the DwarfLab DWARF 3: 18 min from Bortle 6
- M22 with the DwarfLab DWARF mini: 12 min from Bortle 6
- M22 with the DwarfLab Draco: 15 min from Bortle 6
- M22 with the DwarfLab DWARF II: 41 min from Bortle 6
- M22 with the Vaonis Vespera II: 12 min from Bortle 6
- M22 with the Vaonis Vespera Pro: 27 min from Bortle 6
- M22 with the Vaonis Vespera 3: 12 min from Bortle 6
- M22 with the Vaonis Vespera Pro 2: 26 min from Bortle 6
- M22 with the Unistellar eQuinox 2: 11 min from Bortle 6
- M22 with the Unistellar Odyssey: 48 min from Bortle 6
- M22 with the Celestron Origin: 5 min from Bortle 6
- M22 with the Celestron Origin Mark II: 5 min from Bortle 6
All telescopes for the M22 · All targets for the Seestar S30 Pro