How long should I image the Cocoon Nebula with the Vespera Pro 2 from a Bortle 6 sky?

About 10 h of total integration for a solid image, or 41 h for a showpiece. A quick look takes 2 h 35 min.

How many subs is that on the Vespera Pro 2?

At the default 10 s sub length, 3,710 subs for a solid image from Bortle 6 and 1,487 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 10 h to 7 h 09 min.

How long to image the Cocoon Nebula with the Vaonis Vespera Pro 2

From a Bortle 6 suburban sky, the Vaonis Vespera Pro 2 needs about 10 h (3,710 subs of 10 s) for a solid image of the Cocoon Nebula. A quick look takes 2 h 35 min; a showpiece 41 h. Under a Bortle 3 rural sky the solid figure drops to 4 h 08 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 2: 10 s subs.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	53 min318 subs	3 h 32 min1,270 subs	14 h5,080 subs
Bortle 2Typical dark site	56 min337 subs	3 h 44 min1,345 subs	15 h5,380 subs
Bortle 3Rural	1 h 02 min372 subs	4 h 08 min1,487 subs	17 h5,947 subs
Bortle 4Rural / suburban transition	1 h 16 min458 subs	5 h 05 min1,830 subs	20 h7,320 subs
Bortle 5Suburban	1 h 39 min594 subs	6 h 36 min2,375 subs	26 h9,497 subs
Bortle 6Bright suburban	2 h 35 min928 subs	10 h3,710 subs	41 h14,837 subs
Bortle 7Suburban / urban transition	4 h 21 min1,564 subs	17 h6,254 subs	69 h25,013 subs
Bortle 8City	7 h 05 min2,551 subs	28 h10,203 subs	110+ h40,812 subs
Bortle 9Inner city	13 h4,657 subs	52 h18,627 subs	210+ h74,507 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 13 h of run time. That is more than one night: over 2 nights, about 6 h 42 min each. The Vespera Pro 2’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 30WExternal bank extends the 11 h battery.
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How it frames

The Cocoon Nebula is 12′ across. The Vespera Pro 2 frames 1.65° × 1.65° at 1.68″ 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; CovalENS mosaic gives 3.2° × 3.2° at 50 MP. Time for a solid image by sub length:

Sub length	Bortle 3	Bortle 5	Bortle 7
10 s	4 h 08 min1,487 subs	6 h 36 min2,375 subs	17 h6,254 subs
20 s	3 h 23 min609 subs	5 h 51 min1,053 subs	17 h2,993 subs
30 s	3 h 08 min377 subs	5 h 36 min672 subs	16 h1,965 subs

With and without the dual-band filter

Solid quality, default sub length.
Filter	Bortle 3	Bortle 5	Bortle 7
No filter	4 h 08 min1,487 subs	6 h 36 min2,375 subs	17 h6,254 subs
dual-band (Dual Band filter), clip-on	5 h 16 min1,897 subs	6 h 01 min2,169 subs	9 h 19 min3,356 subs

The Vespera Pro 2 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 2

The square-sensor 2026 Vespera with 2 µm pixels. Sharper than the Vespera 3 on small targets and correspondingly slower per pixel; the 12.5 MP square frame suits galaxies and planetaries.

10 s subs by default; Expert Mode manual targets allow 1 to 30 s. Alt-azimuth only; CovalENS mosaic gives 3.2° × 3.2° at 50 MP. 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 Pro 2Vaonis store Direct Amazon UK Amazon USThe Vaonis 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 Cocoon Nebula with your Vespera Pro 2? 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 2? 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 2