How long to image the M99 with the DwarfLab Draco
From a Bortle 6 suburban sky, the DwarfLab Draco needs about 2 h 18 min (276 subs of 30 s) for a solid image of the M99. A quick look takes 34 min; a showpiece 9 h 12 min. Under a Bortle 3 rural sky the solid figure drops to 53 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 7% 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 | 11 min23 subs | 45 min90 subs | 2 h 58 min357 subs |
| Bortle 2Typical dark site | 12 min24 subs | 47 min95 subs | 3 h 10 min380 subs |
| Bortle 3Rural | 13 min27 subs | 53 min106 subs | 3 h 31 min423 subs |
| Bortle 4Rural / suburban transition | 16 min33 subs | 1 h 06 min132 subs | 4 h 24 min528 subs |
| Bortle 5Suburban | 22 min44 subs | 1 h 27 min174 subs | 5 h 47 min695 subs |
| Bortle 6Bright suburban | 34 min69 subs | 2 h 18 min276 subs | 9 h 12 min1,104 subs |
| Bortle 7Suburban / urban transition | 59 min118 subs | 3 h 55 min471 subs | 16 h1,883 subs |
| Bortle 8City | 1 h 37 min194 subs | 6 h 26 min773 subs | 26 h3,092 subs |
| Bortle 9Inner city | 2 h 57 min355 subs | 12 h1,418 subs | 47 h5,671 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 2 h 59 min of run time. The Draco’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 PD power bank 20000mAhRated 5 h on its 10,000 mAh battery. DwarfLab has not published the charging input, so check PD support before relying on it mid-session.
- 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 Draco →
How it frames
The M99 is 5.4′ × 4.8′ across. The Draco frames 1.66° × 1.24° at 1.46″ per pixel, so it fills 7% of the frame’s short side.
Longer subs
Auto Mode picks the exposure; Pro Mode allows up to 300 s, held by built-in guiding and field derotation. The 30 s default here is our assumption. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 30 s | 53 min106 subs | 1 h 27 min174 subs | 3 h 55 min471 subs |
| 60 s | 46 min46 subs | 1 h 20 min80 subs | 3 h 48 min229 subs |
| 120 s | 1 h30 subs | 1 h 16 min39 subs | 3 h 45 min113 subs |
| 300 s | 2 h 30 min30 subs | 2 h 30 min30 subs | 3 h 42 min45 subs |
Leave the dual-band filter out for the M99. It is a galaxy, 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 M99
A face-on spiral with one arm flung out by an encounter. Small but distinctive.
NGC 4254, Coma Pinwheel · Galaxy in Coma Berenices · magnitude 9.9 · 5.4′ × 4.8′ · best in Mar, Apr, May. 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 DwarfLab Draco
DwarfLab’s big scope: 90 mm of folded f/3.8 optics, the most aperture of any Seestar or DWARF, a narrow 13 nm dual-band filter and 300 s subs with built-in guiding. A small-target scope; big nebulae need its mosaic mode.
Auto Mode picks the exposure; Pro Mode allows up to 300 s, held by built-in guiding and field derotation. The 30 s default here is our assumption. Built-in Hα + OIII dual-narrowband filter, 13 nm per line; the SHO Edition adds an SII option.
Longer subs matter most under dark skies, where read noise rather than skyglow sets the floor. From a city the difference between 30 s and 300 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 M99 from a Draco? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M99 with the ZWO Seestar S50: 2 h 48 min from Bortle 6
- M99 with the ZWO Seestar S50 Pro: 3 h 04 min from Bortle 6
- M99 with the ZWO Seestar S30: 2 h 56 min from Bortle 6
- M99 with the ZWO Seestar S30 Pro: 3 h 15 min from Bortle 6
- M99 with the DwarfLab DWARF 3: 4 h 04 min from Bortle 6
- M99 with the DwarfLab DWARF mini: 2 h 47 min from Bortle 6
- M99 with the DwarfLab DWARF II: 9 h 34 min from Bortle 6
- M99 with the Vaonis Vespera II: 2 h 48 min from Bortle 6
- M99 with the Vaonis Vespera Pro: 6 h 16 min from Bortle 6
- M99 with the Vaonis Vespera 3: 2 h 40 min from Bortle 6
- M99 with the Vaonis Vespera Pro 2: 5 h 58 min from Bortle 6
- M99 with the Unistellar eQuinox 2: 2 h 32 min from Bortle 6
- M99 with the Unistellar Odyssey: 12 h from Bortle 6
- M99 with the Celestron Origin: 44 min from Bortle 6
- M99 with the Celestron Origin Mark II: 1 h 01 min from Bortle 6