How long should I image the Ghost of Cassiopeia with the Seestar S30 from a Bortle 6 sky?

About 2 h 06 min of total integration for a solid image, or 8 h 23 min for a showpiece. A quick look takes 31 min.

How many subs is that on the Seestar S30?

At the default 10 s sub length, 755 subs for a solid image from Bortle 6 and 562 from Bortle 3.

Does a dual-band filter help on the Ghost of Cassiopeia?

Yes. It is an emission-line object; from Bortle 6 the filter cuts the solid-image time from 2 h 59 min to 2 h 06 min.

How long to image the Ghost of Cassiopeia with the ZWO Seestar S30

From a Bortle 6 suburban sky, the ZWO Seestar S30 needs about 2 h 06 min (755 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the Ghost of Cassiopeia. A quick look takes 31 min; a showpiece 8 h 23 min. Under a Bortle 3 rural sky the solid figure drops to 1 h 34 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 14% of the frame’s short side.

Ghost of Cassiopeia with the ZWO Seestar S30: 10 s subs with the built-in dual-band (LP filter) filter.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	23 min136 subs	1 h 30 min543 subs	6 h 01 min2,169 subs
Bortle 2Typical dark site	23 min138 subs	1 h 31 min549 subs	6 h 06 min2,196 subs
Bortle 3Rural	23 min141 subs	1 h 34 min562 subs	6 h 14 min2,245 subs
Bortle 4Rural / suburban transition	25 min148 subs	1 h 38 min591 subs	6 h 34 min2,364 subs
Bortle 5Suburban	27 min160 subs	1 h 46 min639 subs	7 h 06 min2,554 subs
Bortle 6Bright suburban	31 min189 subs	2 h 06 min755 subs	8 h 23 min3,019 subs
Bortle 7Suburban / urban transition	41 min245 subs	2 h 43 min977 subs	11 h3,905 subs
Bortle 8City	55 min331 subs	3 h 40 min1,321 subs	15 h5,281 subs
Bortle 9Inner city	1 h 26 min514 subs	5 h 42 min2,054 subs	23 h8,215 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 2 h 44 min of run time. The Seestar S30’s battery (rated about 6 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 power bank 10000mAh 5V 3A6,000 mAh inside; a 10,000 mAh 5 V 3 A bank roughly doubles a session.
Amazon UK Amazon US
Seestar S30 dew shieldHeater is built in; a cheap shield reduces dew and stray light.
Amazon UK Amazon US
red LED head torchRed light keeps your night vision; white light costs you twenty minutes of dark adaptation every time.
Amazon UK Amazon US

Affiliate links: the retailer pays us a small commission and you pay the same price. These are search links to the named product, not endorsements of a particular listing; check the listing matches your model.

Everything that fits the Seestar S30 →

How it frames

The Ghost of Cassiopeia is 10′ × 3′ across. The Seestar S30 frames 2.13° × 1.20° at 3.99″ per pixel, so it fills 14% of the frame’s short side.

Longer subs

10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, which needs the TH10 head. Time for a solid image by sub length:

Sub length	Bortle 3	Bortle 5	Bortle 7
10 s	1 h 34 min562 subs	1 h 46 min639 subs	2 h 43 min977 subs
20 s	1 h 05 min194 subs	1 h 17 min233 subs	2 h 14 min402 subs
30 s	55 min110 subs	1 h 08 min136 subs	2 h 04 min249 subs
60 s	45 min46 subs	58 min59 subs	1 h 54 min115 subs

With and without the dual-band filter

Solid quality, default sub length.
Filter	Bortle 3	Bortle 5	Bortle 7
UV/IR-cut (no light-pollution filter)	1 h 13 min441 subs	1 h 56 min694 subs	4 h 59 min1,797 subs
dual-band (LP filter)	1 h 34 min562 subs	1 h 46 min639 subs	2 h 43 min977 subs

About the Ghost of Cassiopeia

A small emission and reflection wisp being eroded by the star Gamma Cassiopeiae. Keep the bright star's glare under control.

IC 63 · Emission nebula in Cassiopeia · magnitude 10.0 · 10′ × 3′ · best in Sep, Oct, Nov. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.

Emission nebulae glow in a few narrow lines, mostly hydrogen-alpha (deep red) and doubly ionised oxygen (teal). A dual-band filter passes those lines and blocks most skyglow, which is why it cuts the time needed from a suburban sky so dramatically. Use it. From a genuinely dark site the gain is smaller because there is less skyglow to block, and read noise becomes the limit, which is where longer subs (EQ mode, or Expert Mode on a Vespera) earn their keep.

Stars lose colour through a dual-band filter; a short broadband stack blended in fixes that if you care.

About the ZWO Seestar S30

Wider and lighter than the S50 with the same 2.9 µm pixels, so its per-pixel speed on extended targets is close despite the smaller aperture. Ideal for big nebulae.

10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, which needs the TH10 head. Built-in UV/IR-cut, dual-band (OIII 30 nm / Hα 20 nm) and dark filters.

Longer subs matter most under dark skies, where read noise rather than skyglow sets the floor. From a city the difference between 10 s and 60 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 Seestar S30ZWO store Direct Amazon UK Amazon USThe ZWO 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 Ghost of Cassiopeia with your Seestar S30? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the Ghost of Cassiopeia from a Seestar S30? Email it with your total time and sky to [email protected] and it goes here, credited.

Same target, other telescopes

All telescopes for the Ghost of Cassiopeia · All targets for the Seestar S30