How long to image the M71 with the ZWO Seestar S30 Pro
From a Bortle 6 suburban sky, the ZWO Seestar S30 Pro needs about 22 min (132 subs of 10 s) for a solid image of the M71. A quick look takes 5 min; a showpiece 1 h 28 min. Under a Bortle 3 rural sky the solid figure drops to 11 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 5% 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 min16 subs | 10 min61 subs | 40 min242 subs |
| Bortle 2Typical dark site | 3 min16 subs | 10 min63 subs | 42 min251 subs |
| Bortle 3Rural | 3 min17 subs | 11 min67 subs | 44 min267 subs |
| Bortle 4Rural / suburban transition | 3 min20 subs | 13 min77 subs | 51 min308 subs |
| Bortle 5Suburban | 4 min24 subs | 15 min93 subs | 1 h 02 min372 subs |
| Bortle 6Bright suburban | 5 min33 subs | 22 min132 subs | 1 h 28 min528 subs |
| Bortle 7Suburban / urban transition | 9 min52 subs | 34 min207 subs | 2 h 18 min827 subs |
| Bortle 8City | 13 min81 subs | 54 min323 subs | 3 h 35 min1,292 subs |
| Bortle 9Inner city | 24 min143 subs | 1 h 35 min571 subs | 6 h 20 min2,282 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 29 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 M71 is 7′ across. The Seestar S30 Pro frames 3.99° × 2.24° at 3.74″ per pixel, so it fills 5% 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 | 11 min67 subs | 15 min93 subs | 34 min207 subs |
| 20 s | 10 min30 subs | 14 min43 subs | 33 min100 subs |
| 30 s | 15 min30 subs | 15 min30 subs | 33 min66 subs |
| 60 s | 30 min30 subs | 30 min30 subs | 33 min33 subs |
Leave the dual-band filter out for the M71. 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 11 times slower.
About the M71
A loose globular in Sagitta that was long mistaken for an open cluster. Rich Milky Way background.
NGC 6838 · Globular cluster in Sagitta · magnitude 8.2 · 7′ · 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 M71 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
- M71 with the ZWO Seestar S50: 19 min from Bortle 6
- M71 with the ZWO Seestar S50 Pro: 21 min from Bortle 6
- M71 with the ZWO Seestar S30: 20 min from Bortle 6
- M71 with the DwarfLab DWARF 3: 28 min from Bortle 6
- M71 with the DwarfLab DWARF mini: 19 min from Bortle 6
- M71 with the DwarfLab Draco: 16 min from Bortle 6
- M71 with the DwarfLab DWARF II: 1 h 03 min from Bortle 6
- M71 with the Vaonis Vespera II: 19 min from Bortle 6
- M71 with the Vaonis Vespera Pro: 42 min from Bortle 6
- M71 with the Vaonis Vespera 3: 18 min from Bortle 6
- M71 with the Vaonis Vespera Pro 2: 40 min from Bortle 6
- M71 with the Unistellar eQuinox 2: 16 min from Bortle 6
- M71 with the Unistellar Odyssey: 1 h 13 min from Bortle 6
- M71 with the Celestron Origin: 5 min from Bortle 6
- M71 with the Celestron Origin Mark II: 7 min from Bortle 6
All telescopes for the M71 · All targets for the Seestar S30 Pro