How long should I image the Hercules Cluster with the Vespera Pro from a Bortle 6 sky?

About 16 min of total integration for a solid image, or 1 h 05 min for a showpiece. A quick look takes 4 min.

How many subs is that on the Vespera Pro?

At the default 10 s sub length, 98 subs for a solid image from Bortle 6 and 53 from Bortle 3.

Does a dual-band filter help on the Hercules Cluster?

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

How long to image the Hercules Cluster with the Vaonis Vespera Pro

From a Bortle 6 suburban sky, the Vaonis Vespera Pro needs about 16 min (98 subs of 10 s) for a solid image of the Hercules Cluster. A quick look takes 4 min; a showpiece 1 h 05 min. Under a Bortle 3 rural sky the solid figure drops to 9 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.

Hercules Cluster 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	2 min12 subs	8 min48 subs	32 min191 subs
Bortle 2Typical dark site	2 min13 subs	8 min50 subs	33 min197 subs
Bortle 3Rural	2 min14 subs	9 min53 subs	35 min209 subs
Bortle 4Rural / suburban transition	2 min15 subs	10 min60 subs	39 min237 subs
Bortle 5Suburban	3 min18 subs	12 min71 subs	47 min281 subs
Bortle 6Bright suburban	4 min25 subs	16 min98 subs	1 h 05 min389 subs
Bortle 7Suburban / urban transition	6 min38 subs	25 min149 subs	1 h 39 min596 subs
Bortle 8City	10 min58 subs	38 min230 subs	2 h 33 min917 subs
Bortle 9Inner city	17 min101 subs	1 h 07 min401 subs	4 h 27 min1,601 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 21 min of run time. The Vespera Pro’s battery (rated about 11 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 20000mAh 30WExtends the 11 h battery; 30 W PD per Vaonis.
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red LED head torchRed light keeps your night vision; white light costs you twenty minutes of dark adaptation every time.
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How it frames

The Hercules Cluster is 20′ across. The Vespera Pro frames 1.62° × 1.62° at 1.65″ per pixel, so it fills 21% 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	9 min53 subs	12 min71 subs	25 min149 subs
20 s	10 min30 subs	11 min33 subs	24 min72 subs
30 s	15 min30 subs	15 min30 subs	24 min48 subs

About the Hercules Cluster

The great northern globular, a few hundred thousand stars in a ball a third the Moon's width. Quick and always satisfying.

M13, NGC 6205 · Globular cluster in Hercules · magnitude 5.8 · 20′ · best in May, Jun, Jul. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.

Globular clusters are point sources packed tight, so they come quickly: the core resolves into stars within a handful of minutes on any smart scope. More time deepens the halo and pulls in the faint outer members. Use short subs so the core does not saturate into a white blob, and no filter.

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.

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

Have an image of the Hercules Cluster 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 Hercules Cluster · All targets for the Vespera Pro