How long should I image the M68 with the Vespera 3 from a Bortle 6 sky?

About 30 min of total integration for a solid image, or 2 h 01 min for a showpiece. A quick look takes 8 min.

How many subs is that on the Vespera 3?

At the default 10 s sub length, 182 subs for a solid image from Bortle 6 and 80 from Bortle 3.

Does a dual-band filter help on the M68?

No. The M68 is a broadband target and a dual-band filter blocks most of its light. Shoot without a filter.

How long to image the M68 with the Vaonis Vespera 3

From a Bortle 6 suburban sky, the Vaonis Vespera 3 needs about 30 min (182 subs of 10 s) for a solid image of the M68. A quick look takes 8 min; a showpiece 2 h 01 min. Under a Bortle 3 rural sky the solid figure drops to 13 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 13% of the frame’s short side.

M68 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	3 min18 subs	12 min70 subs	46 min277 subs
Bortle 2Typical dark site	3 min19 subs	12 min73 subs	48 min291 subs
Bortle 3Rural	3 min20 subs	13 min80 subs	53 min317 subs
Bortle 4Rural / suburban transition	4 min24 subs	16 min95 subs	1 h 03 min380 subs
Bortle 5Suburban	5 min31 subs	20 min121 subs	1 h 20 min481 subs
Bortle 6Bright suburban	8 min46 subs	30 min182 subs	2 h 01 min727 subs
Bortle 7Suburban / urban transition	12 min75 subs	50 min299 subs	3 h 19 min1,196 subs
Bortle 8City	20 min121 subs	1 h 20 min481 subs	5 h 20 min1,923 subs
Bortle 9Inner city	36 min218 subs	2 h 25 min869 subs	9 h 39 min3,476 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 39 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 M68 is 11′ across. The Vespera 3 frames 2.60° × 1.46° at 2.44″ per pixel, so it fills 13% 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	13 min80 subs	20 min121 subs	50 min299 subs
20 s	12 min35 subs	18 min56 subs	48 min145 subs
30 s	15 min30 subs	18 min36 subs	48 min96 subs

About the M68

A loose globular in Hydra, low from the UK but easy from lower latitudes.

NGC 4590 · Globular cluster in Hydra · magnitude 7.8 · 11′ · best in Mar, Apr, May. 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 M68 with your Vespera 3? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the M68 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 M68 · All targets for the Vespera 3