How long to image the M108 with the Celestron Origin
From a Bortle 6 suburban sky, the Celestron Origin needs about 23 min (138 subs of 10 s) for a solid image of the M108. A quick look takes 6 min; a showpiece 1 h 32 min. Under a Bortle 3 rural sky the solid figure drops to 8 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 17% 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 min11 subs | 7 min42 subs | 28 min166 subs |
| Bortle 2Typical dark site | 2 min12 subs | 7 min45 subs | 30 min178 subs |
| Bortle 3Rural | 2 min13 subs | 8 min51 subs | 33 min201 subs |
| Bortle 4Rural / suburban transition | 3 min16 subs | 11 min64 subs | 42 min254 subs |
| Bortle 5Suburban | 4 min22 subs | 14 min85 subs | 57 min340 subs |
| Bortle 6Bright suburban | 6 min35 subs | 23 min138 subs | 1 h 32 min550 subs |
| Bortle 7Suburban / urban transition | 10 min60 subs | 40 min238 subs | 2 h 38 min949 subs |
| Bortle 8City | 16 min99 subs | 1 h 05 min393 subs | 4 h 21 min1,569 subs |
| Bortle 9Inner city | 30 min181 subs | 2 h723 subs | 8 h 02 min2,892 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 30 min of run time. The Origin’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.)
- portable power station 300W AC outletRuns the supplied 12 V adapter in the field; the dew shield and heater are already built in.
- red LED head torchRed light keeps your night vision; white light costs you twenty minutes of dark adaptation every time.
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How it frames
The M108 is 8.7′ × 2.2′ across. The Origin frames 1.27° × 0.85° at 1.48″ per pixel, so it fills 17% of the frame’s short side.
Longer subs
10 s auto subs (15 s with the Nebula Filter); manual 1 to 30 s on the alt-az mount, longer only with the EQ wedge, and 60 s and up needs the StarSense Autoguider too. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 8 min51 subs | 14 min85 subs | 40 min238 subs |
| 15 s | 8 min32 subs | 14 min55 subs | 39 min157 subs |
| 30 s | 15 min30 subs | 15 min30 subs | 39 min78 subs |
About the M108
An edge-on spiral with a mottled, dusty disc, a degree from the Owl Nebula. Frame both together.
NGC 3556 · Galaxy in Ursa Major · magnitude 10.0 · 8.7′ × 2.2′ · best in Feb, Mar, Apr. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Galaxies are broadband targets: their light is mostly starlight spread across the spectrum, so a dual-band filter throws most of it away and makes things slower, not faster. Shoot without a filter (or with a plain UV/IR cut) and rely on total time and a dark sky. The core of a galaxy is usually many times brighter than its outer disc, so a short stack shows the nucleus long before the arms; the figures here are for the arms and disc, not the core.
Field rotation in Alt-Az mode crops the edges of the stack over a long session, so on a big galaxy re-centre now and then or use EQ mode where your scope supports it.
About the Celestron Origin
The first-generation Origin: a 6-inch f/2.2 RASA in a smart package and the fastest system here by a wide margin. Superseded by the Mark II in late 2025 and no longer sold new; Celestron offers a camera upgrade to the Mark II sensor.
10 s auto subs (15 s with the Nebula Filter); manual 1 to 30 s on the alt-az mount, longer only with the EQ wedge, and 60 s and up needs the StarSense Autoguider too. Filter drawer takes 1.25-inch or 2-inch filters, including dual-band; Celestron sells an optional Nebula Filter.
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 30 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 M108 from a Origin? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M108 with the ZWO Seestar S50: 1 h 26 min from Bortle 6
- M108 with the ZWO Seestar S50 Pro: 1 h 34 min from Bortle 6
- M108 with the ZWO Seestar S30: 1 h 30 min from Bortle 6
- M108 with the ZWO Seestar S30 Pro: 1 h 40 min from Bortle 6
- M108 with the DwarfLab DWARF 3: 2 h 06 min from Bortle 6
- M108 with the DwarfLab DWARF mini: 1 h 26 min from Bortle 6
- M108 with the DwarfLab Draco: 1 h 11 min from Bortle 6
- M108 with the DwarfLab DWARF II: 4 h 54 min from Bortle 6
- M108 with the Vaonis Vespera II: 1 h 26 min from Bortle 6
- M108 with the Vaonis Vespera Pro: 3 h 13 min from Bortle 6
- M108 with the Vaonis Vespera 3: 1 h 22 min from Bortle 6
- M108 with the Vaonis Vespera Pro 2: 3 h 04 min from Bortle 6
- M108 with the Unistellar eQuinox 2: 1 h 18 min from Bortle 6
- M108 with the Unistellar Odyssey: 5 h 57 min from Bortle 6
- M108 with the Celestron Origin Mark II: 31 min from Bortle 6