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

About 48 min of total integration for a solid image, or 3 h 12 min for a showpiece. A quick look takes 12 min.

How many subs is that on the Draco?

At the default 30 s sub length, 97 subs for a solid image from Bortle 6 and 39 from Bortle 3.

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

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

How long to image the Whirlpool Galaxy with the DwarfLab Draco

From a Bortle 6 suburban sky, the DwarfLab Draco needs about 48 min (97 subs of 30 s) for a solid image of the Whirlpool Galaxy. A quick look takes 12 min; a showpiece 3 h 12 min. Under a Bortle 3 rural sky the solid figure drops to 19 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 15% of the frame’s short side.

Whirlpool 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	17 min34 subs	1 h 06 min133 subs
Bortle 2Typical dark site	5 min10 subs	18 min36 subs	1 h 10 min141 subs
Bortle 3Rural	5 min10 subs	19 min39 subs	1 h 17 min155 subs
Bortle 4Rural / suburban transition	6 min12 subs	24 min48 subs	1 h 35 min191 subs
Bortle 5Suburban	8 min16 subs	31 min62 subs	2 h 03 min247 subs
Bortle 6Bright suburban	12 min25 subs	48 min97 subs	3 h 12 min385 subs
Bortle 7Suburban / urban transition	20 min41 subs	1 h 21 min162 subs	5 h 24 min648 subs
Bortle 8City	33 min66 subs	2 h 12 min264 subs	8 h 48 min1,056 subs
Bortle 9Inner city	1 h121 subs	4 h 01 min482 subs	16 h1,926 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 1 h 02 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 Whirlpool Galaxy is 11′ × 7′ across. The Draco frames 1.66° × 1.24° at 1.46″ per pixel, so it fills 15% 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	19 min39 subs	31 min62 subs	1 h 21 min162 subs
60 s	30 min30 subs	30 min30 subs	1 h 19 min79 subs
120 s	1 h30 subs	1 h30 subs	1 h 17 min39 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 Whirlpool 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 Whirlpool Galaxy

The classic face-on spiral with its companion tugging at one arm. Small in a smart scope but bright; the arms appear within an hour, the tidal bridge needs several.

M51, NGC 5194 · Galaxy in Canes Venatici · magnitude 8.4 · 11′ × 7′ · 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.

Where to buy the DracoDwarfLab store UK DwarfLab store US Amazon UK Amazon USThe DwarfLab store link is a plain link; the others are affiliate links. As an Amazon Associate I earn from qualifying purchases, at no cost to you.

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

Have an image of the Whirlpool 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 Whirlpool Galaxy · All targets for the Draco