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

About 45 min of total integration for a solid image, or 2 h 59 min for a showpiece. A quick look takes 11 min.

How many subs is that on the Draco?

At the default 30 s sub length, 90 subs for a solid image from Bortle 6 and 36 from Bortle 3.

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

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

How long to image the Whale Galaxy with the DwarfLab Draco

From a Bortle 6 suburban sky, the DwarfLab Draco needs about 45 min (90 subs of 30 s) for a solid image of the Whale Galaxy. A quick look takes 11 min; a showpiece 2 h 59 min. Under a Bortle 3 rural sky the solid figure drops to 18 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 21% of the frame’s short side.

Whale 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	1 h120 subs
Bortle 2Typical dark site	5 min10 subs	16 min32 subs	1 h 04 min128 subs
Bortle 3Rural	5 min10 subs	18 min36 subs	1 h 11 min142 subs
Bortle 4Rural / suburban transition	5 min11 subs	22 min44 subs	1 h 27 min175 subs
Bortle 5Suburban	7 min15 subs	28 min57 subs	1 h 54 min228 subs
Bortle 6Bright suburban	11 min23 subs	45 min90 subs	2 h 59 min359 subs
Bortle 7Suburban / urban transition	19 min38 subs	1 h 16 min152 subs	5 h 03 min607 subs
Bortle 8City	31 min63 subs	2 h 04 min249 subs	8 h 16 min993 subs
Bortle 9Inner city	57 min114 subs	3 h 47 min454 subs	15 h1,816 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 58 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 Whale Galaxy is 15.5′ × 2.7′ across. The Draco frames 1.66° × 1.24° at 1.46″ per pixel, so it fills 21% 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	18 min36 subs	28 min57 subs	1 h 16 min152 subs
60 s	30 min30 subs	30 min30 subs	1 h 14 min74 subs
120 s	1 h30 subs	1 h30 subs	1 h 12 min37 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 Whale 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 Whale Galaxy

A distorted edge-on galaxy with a small companion on its back, and the Hockey Stick (NGC 4656) in the same wide field.

NGC 4631, Caldwell 32 · Galaxy in Canes Venatici · magnitude 9.2 · 15.5′ × 2.7′ · 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 Whale Galaxy with your Draco? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

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