How long should I image the Thor's Helmet with the Vespera 3 from a Bortle 6 sky?

About 9 h 53 min of total integration for a solid image, or 40 h for a showpiece. A quick look takes 2 h 28 min.

How many subs is that on the Vespera 3?

At the default 10 s sub length, 3,559 subs for a solid image from Bortle 6 and 1,267 from Bortle 3.

Does a dual-band filter help on the Thor's Helmet?

Yes. It is an emission-line object; from Bortle 6 the filter cuts the solid-image time from 9 h 53 min to 5 h 56 min.

How long to image the Thor's Helmet with the Vaonis Vespera 3

From a Bortle 6 suburban sky, the Vaonis Vespera 3 needs about 9 h 53 min (3,559 subs of 10 s) for a solid image of the Thor's Helmet. A quick look takes 2 h 28 min; a showpiece 40 h. Under a Bortle 3 rural sky the solid figure drops to 3 h 31 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 9% of the frame’s short side.

Thor's Helmet 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	43 min261 subs	2 h 54 min1,043 subs	12 h4,172 subs
Bortle 2Typical dark site	47 min281 subs	3 h 07 min1,121 subs	12 h4,481 subs
Bortle 3Rural	53 min317 subs	3 h 31 min1,267 subs	14 h5,065 subs
Bortle 4Rural / suburban transition	1 h 08 min406 subs	4 h 30 min1,621 subs	18 h6,481 subs
Bortle 5Suburban	1 h 31 min546 subs	6 h 04 min2,182 subs	24 h8,726 subs
Bortle 6Bright suburban	2 h 28 min890 subs	9 h 53 min3,559 subs	40 h14,233 subs
Bortle 7Suburban / urban transition	4 h 18 min1,546 subs	17 h6,182 subs	69 h24,727 subs
Bortle 8City	7 h 07 min2,564 subs	28 h10,255 subs	110+ h41,019 subs
Bortle 9Inner city	13 h4,736 subs	53 h18,942 subs	210+ h75,766 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 13 h of run time. That is more than one night: over 2 nights, about 6 h 25 min each. The Vespera 3’s battery (rated about 11 h) should cover each night; a power bank still keeps the phone running the app alive. (Bortle 6, solid image; we allow 30% over the integration time, and 30% off the battery for a January night.)

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How it frames

The Thor's Helmet is 8′ across. The Vespera 3 frames 2.60° × 1.46° at 2.44″ per pixel, so it fills 9% 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	3 h 31 min1,267 subs	6 h 04 min2,182 subs	17 h6,182 subs
20 s	2 h 57 min531 subs	5 h 29 min988 subs	17 h2,988 subs
30 s	2 h 45 min331 subs	5 h 18 min636 subs	16 h1,969 subs

With and without the dual-band filter

Solid quality, default sub length.
Filter	Bortle 3	Bortle 5	Bortle 7
No filter	3 h 31 min1,267 subs	6 h 04 min2,182 subs	17 h6,182 subs
dual-band (Dual Band filter), clip-on	3 h 59 min1,432 subs	4 h 45 min1,713 subs	8 h 09 min2,937 subs

The Vespera 3 has no built-in dual-band filter. Optional clip-on Vaonis filters: dual-band, light-pollution (CLS) and solar. The new optical baffle is not a substitute for a CLS filter. On an emission target like this it is the single biggest upgrade you can make.

About the Thor's Helmet

A Wolf-Rayet bubble with wings, strong in OIII. Small and faint; dual-band is essential and a bigger scope helps.

NGC 2359 · Emission nebula in Canis Major · magnitude 11.5 · 8′ · best in Dec, Jan, Feb. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.

Emission nebulae glow in a few narrow lines, mostly hydrogen-alpha (deep red) and doubly ionised oxygen (teal). A dual-band filter passes those lines and blocks most skyglow, which is why it cuts the time needed from a suburban sky so dramatically. Use it. From a genuinely dark site the gain is smaller because there is less skyglow to block, and read noise becomes the limit, which is where longer subs (EQ mode, or Expert Mode on a Vespera) earn their keep.

Stars lose colour through a dual-band filter; a short broadband stack blended in fixes that if you care.

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.

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Imaged the Thor's Helmet with your Vespera 3? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the Thor's Helmet 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 Thor's Helmet · All targets for the Vespera 3