How long should I image the M55 with the Vespera 3 from a Bortle 6 sky?

About 13 min of total integration for a solid image, or 53 min for a showpiece. A quick look takes 3 min.

How many subs is that on the Vespera 3?

At the default 10 s sub length, 79 subs for a solid image from Bortle 6 and 37 from Bortle 3.

Does a dual-band filter help on the M55?

No. The M55 is a broadband target and a dual-band filter blocks most of its light. Shoot without a filter.

How long to image the M55 with the Vaonis Vespera 3

From a Bortle 6 suburban sky, the Vaonis Vespera 3 needs about 13 min (79 subs of 10 s) for a solid image of the M55. A quick look takes 3 min; a showpiece 53 min. Under a Bortle 3 rural sky the solid figure drops to 6 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 22% of the frame’s short side.

M55 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	2 min10 subs	5 min33 subs	22 min131 subs
Bortle 2Typical dark site	2 min10 subs	6 min35 subs	23 min137 subs
Bortle 3Rural	2 min10 subs	6 min37 subs	24 min147 subs
Bortle 4Rural / suburban transition	2 min11 subs	7 min44 subs	29 min174 subs
Bortle 5Suburban	2 min14 subs	9 min54 subs	36 min215 subs
Bortle 6Bright suburban	3 min20 subs	13 min79 subs	53 min316 subs
Bortle 7Suburban / urban transition	5 min32 subs	21 min128 subs	1 h 25 min509 subs
Bortle 8City	8 min51 subs	34 min203 subs	2 h 15 min809 subs
Bortle 9Inner city	15 min91 subs	1 h362 subs	4 h 01 min1,448 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 17 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 M55 is 19′ across. The Vespera 3 frames 2.60° × 1.46° at 2.44″ per pixel, so it fills 22% 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	6 min37 subs	9 min54 subs	21 min128 subs
20 s	10 min30 subs	10 min30 subs	21 min62 subs
30 s	15 min30 subs	15 min30 subs	20 min41 subs

About the M55

A large, loose globular that resolves easily but sits low for northern imagers.

NGC 6809 · Globular cluster in Sagittarius · magnitude 6.3 · 19′ · best in Jun, Jul, Aug. 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 M55 with your Vespera 3? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the M55 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 M55 · All targets for the Vespera 3