How long should I image the M4 with the Vespera II from a Bortle 6 sky?

About 1 h 14 min of total integration for a solid image, or 4 h 57 min for a showpiece. A quick look takes 19 min.

How many subs is that on the Vespera II?

At the default 10 s sub length, 446 subs for a solid image from Bortle 6 and 176 from Bortle 3.

Does a dual-band filter help on the M4?

No. The M4 is a broadband target and a dual-band filter blocks most of its light. Shoot without a filter.

How long to image the M4 with the Vaonis Vespera II

From a Bortle 6 suburban sky, the Vaonis Vespera II needs about 1 h 14 min (446 subs of 10 s) for a solid image of the M4. A quick look takes 19 min; a showpiece 4 h 57 min. Under a Bortle 3 rural sky the solid figure drops to 29 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 42% of the frame’s short side.

M4 with the Vaonis Vespera II: 10 s subs.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	6 min38 subs	25 min149 subs	1 h 39 min595 subs
Bortle 2Typical dark site	7 min40 subs	26 min158 subs	1 h 45 min632 subs
Bortle 3Rural	7 min44 subs	29 min176 subs	1 h 57 min701 subs
Bortle 4Rural / suburban transition	9 min55 subs	36 min217 subs	2 h 25 min868 subs
Bortle 5Suburban	12 min71 subs	47 min284 subs	3 h 09 min1,133 subs
Bortle 6Bright suburban	19 min112 subs	1 h 14 min446 subs	4 h 57 min1,784 subs
Bortle 7Suburban / urban transition	31 min189 subs	2 h 06 min756 subs	8 h 24 min3,024 subs
Bortle 8City	52 min310 subs	3 h 26 min1,238 subs	14 h4,950 subs
Bortle 9Inner city	1 h 34 min566 subs	6 h 17 min2,264 subs	25 h9,056 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 1 h 37 min of run time. The Vespera II’s battery (rated about 4 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 30WOnly four hours inside; Vaonis specifies a 30 W PD source. C-to-C cable not included.
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Vaonis Vespera hygrometer sensorTriggers the built-in demister automatically; the correct dew accessory for the II.
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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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Everything that fits the Vespera II →

How it frames

The M4 is 36′ across. The Vespera II frames 2.55° × 1.44° at 2.39″ per pixel, so it fills 42% 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	29 min176 subs	47 min284 subs	2 h 06 min756 subs
20 s	25 min75 subs	43 min129 subs	2 h 02 min366 subs
30 s	24 min48 subs	42 min84 subs	2 h241 subs

About the M4

The loose globular next to Antares. Low in the sky from the UK, so image it near transit.

NGC 6121 · Globular cluster in Scorpius · magnitude 5.9 · 36′ · 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 II

A 50 mm quadruplet on an 8 MP sensor with Vaonis’s mosaic mode for wide fields. Same optics class as the Seestar S50, four times the pixels.

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; the app detects which is fitted.

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 IIVaonis 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 M4 with your Vespera II? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the M4 from a Vespera II? Email it with your total time and sky to [email protected] and it goes here, credited.

Same target, other telescopes

All telescopes for the M4 · All targets for the Vespera II