How long should I image the Cocoon Nebula with the Vespera Pro from a Bortle 6 sky?

About 11 h of total integration for a solid image, or 43 h for a showpiece. A quick look takes 2 h 42 min.

How many subs is that on the Vespera Pro?

At the default 10 s sub length, 3,893 subs for a solid image from Bortle 6 and 1,579 from Bortle 3.

Does a dual-band filter help on the Cocoon Nebula?

Yes. It is an emission-line object; from Bortle 6 the filter cuts the solid-image time from 11 h to 7 h 38 min.

How long to image the Cocoon Nebula with the Vaonis Vespera Pro

From a Bortle 6 suburban sky, the Vaonis Vespera Pro needs about 11 h (3,893 subs of 10 s) for a solid image of the Cocoon Nebula. A quick look takes 2 h 42 min; a showpiece 43 h. Under a Bortle 3 rural sky the solid figure drops to 4 h 23 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.

Cocoon Nebula with the Vaonis Vespera Pro: 10 s subs.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	56 min339 subs	3 h 45 min1,353 subs	15 h5,411 subs
Bortle 2Typical dark site	1 h358 subs	3 h 58 min1,431 subs	16 h5,723 subs
Bortle 3Rural	1 h 06 min395 subs	4 h 23 min1,579 subs	18 h6,313 subs
Bortle 4Rural / suburban transition	1 h 21 min484 subs	5 h 23 min1,936 subs	22 h7,743 subs
Bortle 5Suburban	1 h 44 min626 subs	6 h 57 min2,503 subs	28 h10,009 subs
Bortle 6Bright suburban	2 h 42 min974 subs	11 h3,893 subs	43 h15,570 subs
Bortle 7Suburban / urban transition	4 h 33 min1,636 subs	18 h6,542 subs	73 h26,165 subs
Bortle 8City	7 h 24 min2,664 subs	30 h10,654 subs	120+ h42,616 subs
Bortle 9Inner city	13 h4,857 subs	54 h19,425 subs	220+ h77,700 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 14 h of run time. That is more than one night: over 3 nights, about 4 h 41 min each. The Vespera Pro’s battery (rated about 11 h) should cover each night; 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 20000mAh 30WExtends the 11 h battery; 30 W PD per Vaonis.
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 Vespera Pro →

How it frames

The Cocoon Nebula is 12′ across. The Vespera Pro frames 1.62° × 1.62° at 1.65″ per pixel, so it fills 12% of the frame’s short side.

Longer subs

10 s subs by default; Expert Mode manual targets allow 1 to 30 s. Alt-azimuth only, no EQ mode. Time for a solid image by sub length:

Sub length	Bortle 3	Bortle 5	Bortle 7
10 s	4 h 23 min1,579 subs	6 h 57 min2,503 subs	18 h6,542 subs
20 s	3 h 34 min644 subs	6 h 08 min1,106 subs	17 h3,125 subs
30 s	3 h 18 min397 subs	5 h 52 min705 subs	17 h2,051 subs

With and without the dual-band filter

Solid quality, default sub length.
Filter	Bortle 3	Bortle 5	Bortle 7
No filter	4 h 23 min1,579 subs	6 h 57 min2,503 subs	18 h6,542 subs
dual-band (Dual Band filter), clip-on	5 h 39 min2,037 subs	6 h 27 min2,320 subs	9 h 53 min3,556 subs

The Vespera Pro has no built-in dual-band filter. Optional clip-on Vaonis filters: dual-band, light-pollution (CLS) and solar. On an emission target like this it is the single biggest upgrade you can make.

About the Cocoon Nebula

A round emission and reflection nebula at the end of a long dark lane. Mixed light, so a broadband stack keeps the blue.

IC 5146, Caldwell 19 · Emission nebula in Cygnus · magnitude 7.2 · 12′ · best in Jul, Aug, Sep. 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 Vaonis Vespera Pro

The square-sensor Vespera with 2 µm pixels. Higher resolution than the II, and correspondingly slower per pixel: expect around double the time for the same per-pixel SNR. Run-out in 2026 and replaced by the Vespera Pro 2.

10 s subs by default; Expert Mode manual targets allow 1 to 30 s. Alt-azimuth only, no EQ mode. Optional clip-on Vaonis filters: dual-band, light-pollution (CLS) and solar.

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 30 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 Vespera ProAmazon UK Amazon USAffiliate links: As an Amazon Associate I earn from qualifying purchases, at no cost to you.

Imaged the Cocoon Nebula with your Vespera Pro? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the Cocoon Nebula from a Vespera Pro? Email it with your total time and sky to [email protected] and it goes here, credited.

Same target, other telescopes

All telescopes for the Cocoon Nebula · All targets for the Vespera Pro