How long to image the M79 with the ZWO Seestar S30
From a Bortle 6 suburban sky, the ZWO Seestar S30 needs about 17 min (100 subs of 10 s) for a solid image of the M79. A quick look takes 4 min; a showpiece 1 h 06 min. Under a Bortle 3 rural sky the solid figure drops to 9 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 13% 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 min12 subs | 8 min47 subs | 31 min186 subs |
| Bortle 2Typical dark site | 2 min12 subs | 8 min48 subs | 32 min192 subs |
| Bortle 3Rural | 2 min13 subs | 9 min52 subs | 34 min205 subs |
| Bortle 4Rural / suburban transition | 2 min15 subs | 10 min59 subs | 39 min235 subs |
| Bortle 5Suburban | 3 min18 subs | 12 min71 subs | 47 min282 subs |
| Bortle 6Bright suburban | 4 min25 subs | 17 min100 subs | 1 h 06 min399 subs |
| Bortle 7Suburban / urban transition | 6 min39 subs | 26 min156 subs | 1 h 43 min621 subs |
| Bortle 8City | 10 min61 subs | 40 min242 subs | 2 h 41 min967 subs |
| Bortle 9Inner city | 18 min107 subs | 1 h 11 min426 subs | 4 h 44 min1,703 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 22 min of run time. The Seestar S30’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, and 30% off the battery for a December night.)
- USB-C power bank 10000mAh 5V 3A6,000 mAh inside; a 10,000 mAh 5 V 3 A bank roughly doubles a session.
- Seestar S30 dew shieldHeater is built in; a cheap shield reduces dew and stray light.
- red LED head torchRed light keeps your night vision; white light costs you twenty minutes of dark adaptation every time.
- hand warmers long lastingAir-activated packs give hours of heat for the person; winter nights are long and you spend most of them standing still.
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Everything that fits the Seestar S30 →
How it frames
The M79 is 9′ across. The Seestar S30 frames 2.13° × 1.20° at 3.99″ per pixel, so it fills 13% 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 | 9 min52 subs | 12 min71 subs | 26 min156 subs |
| 20 s | 10 min30 subs | 11 min32 subs | 25 min75 subs |
| 30 s | 15 min30 subs | 15 min30 subs | 24 min49 subs |
| 60 s | 30 min30 subs | 30 min30 subs | 30 min30 subs |
Leave the dual-band filter out for the M79. 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 M79
A winter globular below Orion, unusual for the season. Low but compact.
NGC 1904 · Globular cluster in Lepus · magnitude 7.7 · 9′ · best in Nov, Dec, Jan. 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
Wider and lighter than the S50 with the same 2.9 µm pixels, so its per-pixel speed on extended targets is close despite the smaller aperture. Ideal for big nebulae.
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.
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 M79 from a Seestar S30? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M79 with the ZWO Seestar S50: 16 min from Bortle 6
- M79 with the ZWO Seestar S50 Pro: 17 min from Bortle 6
- M79 with the ZWO Seestar S30 Pro: 18 min from Bortle 6
- M79 with the DwarfLab DWARF 3: 23 min from Bortle 6
- M79 with the DwarfLab DWARF mini: 16 min from Bortle 6
- M79 with the DwarfLab Draco: 15 min from Bortle 6
- M79 with the DwarfLab DWARF II: 53 min from Bortle 6
- M79 with the Vaonis Vespera II: 16 min from Bortle 6
- M79 with the Vaonis Vespera Pro: 35 min from Bortle 6
- M79 with the Vaonis Vespera 3: 15 min from Bortle 6
- M79 with the Vaonis Vespera Pro 2: 34 min from Bortle 6
- M79 with the Unistellar eQuinox 2: 14 min from Bortle 6
- M79 with the Unistellar Odyssey: 1 h 02 min from Bortle 6
- M79 with the Celestron Origin: 5 min from Bortle 6
- M79 with the Celestron Origin Mark II: 6 min from Bortle 6
All telescopes for the M79 · All targets for the Seestar S30