How long should I image the M4 with the Vespera 3 from a Bortle 6 sky?

About 1 h 11 min of total integration for a solid image, or 4 h 44 min for a showpiece. A quick look takes 18 min.

How many subs is that on the Vespera 3?

At the default 10 s sub length, 426 subs for a solid image from Bortle 6 and 166 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 3

From a Bortle 6 suburban sky, the Vaonis Vespera 3 needs about 1 h 11 min (426 subs of 10 s) for a solid image of the M4. A quick look takes 18 min; a showpiece 4 h 44 min. Under a Bortle 3 rural sky the solid figure drops to 28 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 41% of the frame’s short side.

M4 with the Vaonis Vespera 3: 10 s subs.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	6 min36 subs	23 min141 subs	1 h 34 min562 subs
Bortle 2Typical dark site	6 min38 subs	25 min150 subs	1 h 39 min597 subs
Bortle 3Rural	7 min42 subs	28 min166 subs	1 h 51 min664 subs
Bortle 4Rural / suburban transition	9 min52 subs	34 min206 subs	2 h 17 min824 subs
Bortle 5Suburban	11 min68 subs	45 min270 subs	3 h1,079 subs
Bortle 6Bright suburban	18 min107 subs	1 h 11 min426 subs	4 h 44 min1,704 subs
Bortle 7Suburban / urban transition	30 min181 subs	2 h 01 min724 subs	8 h 02 min2,895 subs
Bortle 8City	49 min297 subs	3 h 18 min1,186 subs	13 h4,744 subs
Bortle 9Inner city	1 h 30 min543 subs	6 h 02 min2,172 subs	24 h8,688 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 1 h 32 min of run time. The Vespera 3’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 30WVaonis says an external bank extends sessions; 30 W PD as for the II and Pro.
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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 M4 is 36′ across. The Vespera 3 frames 2.60° × 1.46° at 2.44″ per pixel, so it fills 41% 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 widens the field to 4.3° × 2.4°. Time for a solid image by sub length:

Sub length	Bortle 3	Bortle 5	Bortle 7
10 s	28 min166 subs	45 min270 subs	2 h 01 min724 subs
20 s	24 min72 subs	41 min124 subs	1 h 57 min351 subs
30 s	22 min45 subs	40 min80 subs	1 h 55 min231 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 3

The 2026 Vespera: same 50 mm quadruplet class as the II on an 8 MP IMX585, with a 24 MP mosaic mode and 11 hours of battery. Per pixel it behaves like a Seestar S50 Pro without the built-in dual-band filter.

10 s subs by default; Expert Mode manual targets allow 1 to 30 s. Alt-azimuth only; CovalENS mosaic widens the field to 4.3° × 2.4°. Optional clip-on Vaonis filters: dual-band, light-pollution (CLS) and solar. The new optical baffle is not a substitute for a CLS filter.

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 3Vaonis 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 3? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the M4 from a Vespera 3? 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 3