How long should I image the Sombrero Galaxy with the Draco from a Bortle 6 sky?

About 39 min of total integration for a solid image, or 2 h 34 min for a showpiece. A quick look takes 10 min.

How many subs is that on the Draco?

At the default 30 s sub length, 78 subs for a solid image from Bortle 6 and 33 from Bortle 3.

Does a dual-band filter help on the Sombrero Galaxy?

No. The Sombrero Galaxy is a broadband target and a dual-band filter blocks most of its light. Shoot without a filter.

How long to image the Sombrero Galaxy with the DwarfLab Draco

From a Bortle 6 suburban sky, the DwarfLab Draco needs about 39 min (78 subs of 30 s) for a solid image of the Sombrero Galaxy. A quick look takes 10 min; a showpiece 2 h 34 min. Under a Bortle 3 rural sky the solid figure drops to 16 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 12% of the frame’s short side.

Sombrero Galaxy with the DwarfLab Draco: 30 s subs.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	5 min10 subs	15 min30 subs	56 min113 subs
Bortle 2Typical dark site	5 min10 subs	15 min30 subs	59 min119 subs
Bortle 3Rural	5 min10 subs	16 min33 subs	1 h 05 min131 subs
Bortle 4Rural / suburban transition	5 min10 subs	20 min40 subs	1 h 19 min158 subs
Bortle 5Suburban	6 min13 subs	25 min51 subs	1 h 41 min202 subs
Bortle 6Bright suburban	10 min20 subs	39 min78 subs	2 h 34 min309 subs
Bortle 7Suburban / urban transition	16 min33 subs	1 h 04 min129 subs	4 h 17 min514 subs
Bortle 8City	26 min52 subs	1 h 44 min208 subs	6 h 56 min832 subs
Bortle 9Inner city	47 min95 subs	3 h 09 min378 subs	13 h1,510 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 50 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.
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How it frames

The Sombrero Galaxy is 9′ × 4′ across. The Draco frames 1.66° × 1.24° at 1.46″ per pixel, so it fills 12% 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	16 min33 subs	25 min51 subs	1 h 04 min129 subs
60 s	30 min30 subs	30 min30 subs	1 h 02 min63 subs
120 s	1 h30 subs	1 h30 subs	1 h 01 min31 subs
300 s	2 h 30 min30 subs	2 h 30 min30 subs	2 h 30 min30 subs

Leave the dual-band filter out for the Sombrero Galaxy. 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 Sombrero Galaxy

The bright bulge and knife-edge dust lane are obvious within an hour. Low from northern Europe, so catch it near the meridian.

M104, NGC 4594 · Galaxy in Virgo · magnitude 8.0 · 9′ × 4′ · 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.

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Imaged the Sombrero Galaxy with your Draco? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the Sombrero Galaxy from a Draco? Email it with your total time and sky to [email protected] and it goes here, credited.

Same target, other telescopes

All telescopes for the Sombrero Galaxy · All targets for the Draco