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

About 3 h 47 min of total integration for a solid image, or 15 h for a showpiece. A quick look takes 57 min.

How many subs is that on the Draco?

At the default 30 s sub length, 454 subs for a solid image from Bortle 6 and 160 from Bortle 3.

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

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

How long to image the Pinwheel Galaxy with the DwarfLab Draco

From a Bortle 6 suburban sky, the DwarfLab Draco needs about 3 h 47 min (454 subs of 30 s) for a solid image of the Pinwheel Galaxy. A quick look takes 57 min; a showpiece 15 h. Under a Bortle 3 rural sky the solid figure drops to 1 h 20 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 39% of the frame’s short side.

Pinwheel 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	16 min33 subs	1 h 06 min132 subs	4 h 22 min525 subs
Bortle 2Typical dark site	18 min36 subs	1 h 11 min142 subs	4 h 42 min565 subs
Bortle 3Rural	20 min40 subs	1 h 20 min160 subs	5 h 20 min640 subs
Bortle 4Rural / suburban transition	26 min52 subs	1 h 43 min206 subs	6 h 51 min822 subs
Bortle 5Suburban	35 min70 subs	2 h 19 min278 subs	9 h 15 min1,110 subs
Bortle 6Bright suburban	57 min114 subs	3 h 47 min454 subs	15 h1,816 subs
Bortle 7Suburban / urban transition	1 h 39 min198 subs	6 h 35 min791 subs	26 h3,163 subs
Bortle 8City	2 h 44 min329 subs	11 h1,314 subs	44 h5,254 subs
Bortle 9Inner city	5 h 04 min608 subs	20 h2,429 subs	81 h9,713 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 4 h 55 min of run time. The Draco’s battery is rated at about 5 h, which is cutting it fine; take a power bank. (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 Pinwheel Galaxy is 29′ × 27′ across. The Draco frames 1.66° × 1.24° at 1.46″ per pixel, so it fills 39% 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	1 h 20 min160 subs	2 h 19 min278 subs	6 h 35 min791 subs
60 s	1 h 08 min68 subs	2 h 06 min127 subs	6 h 23 min383 subs
120 s	1 h 01 min31 subs	2 h61 subs	6 h 17 min189 subs
300 s	2 h 30 min30 subs	2 h 30 min30 subs	6 h 13 min75 subs

Leave the dual-band filter out for the Pinwheel 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 12 times slower.

About the Pinwheel Galaxy

Big, face-on and faint. Its total magnitude is flattering; spread over half a degree the arms are dim and demand hours, especially from suburban skies.

M101, NGC 5457 · Galaxy in Ursa Major · magnitude 7.9 · 29′ × 27′ · best in Apr, May, Jun. 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 Pinwheel Galaxy with your Draco? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

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