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

About 23 h of total integration for a solid image, or 93 h for a showpiece. A quick look takes 5 h 49 min.

How many subs is that on the Vespera Pro?

At the default 10 s sub length, 8,366 subs for a solid image from Bortle 6 and 3,348 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 23 h to 16 h.

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

From a Bortle 6 suburban sky, the Vaonis Vespera Pro needs about 23 h (8,366 subs of 10 s) for a solid image of the Thor's Helmet. A quick look takes 5 h 49 min; a showpiece 93 h. Under a Bortle 3 rural sky the solid figure drops to 9 h 18 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 8% of the frame’s short side.

Thor's Helmet with the Vaonis Vespera Pro: 10 s subs.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	1 h 59 min715 subs	7 h 56 min2,859 subs	32 h11,436 subs
Bortle 2Typical dark site	2 h 06 min757 subs	8 h 25 min3,028 subs	34 h12,112 subs
Bortle 3Rural	2 h 19 min837 subs	9 h 18 min3,348 subs	37 h13,392 subs
Bortle 4Rural / suburban transition	2 h 52 min1,031 subs	11 h4,124 subs	46 h16,493 subs
Bortle 5Suburban	3 h 43 min1,338 subs	15 h5,352 subs	59 h21,406 subs
Bortle 6Bright suburban	5 h 49 min2,092 subs	23 h8,366 subs	93 h33,462 subs
Bortle 7Suburban / urban transition	9 h 48 min3,528 subs	39 h14,109 subs	160+ h56,434 subs
Bortle 8City	16 h5,757 subs	64 h23,026 subs	260+ h92,102 subs
Bortle 9Inner city	29 h10,511 subs	120+ h42,043 subs	470+ h168,170 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 30 h of run time. That is more than one night: over 5 nights, about 6 h 03 min each. The Vespera Pro’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 Pro frames 1.62° × 1.62° at 1.65″ per pixel, so it fills 8% 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	9 h 18 min3,348 subs	15 h5,352 subs	39 h14,109 subs
20 s	7 h 33 min1,359 subs	13 h2,360 subs	37 h6,739 subs
30 s	6 h 58 min836 subs	13 h1,504 subs	37 h4,423 subs

With and without the dual-band filter

Solid quality, default sub length.
Filter	Bortle 3	Bortle 5	Bortle 7
No filter	9 h 18 min3,348 subs	15 h5,352 subs	39 h14,109 subs
dual-band (Dual Band filter), clip-on	12 h4,311 subs	14 h4,924 subs	21 h7,605 subs

The Vespera Pro has no built-in dual-band filter. Optional clip-on Vaonis filters: dual-band, light-pollution (CLS) and solar. 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 Pro

The square-sensor Vespera with 2 µm pixels. Higher resolution than the II, and correspondingly slower per pixel: expect around double the time for the same per-pixel SNR. Run-out in 2026 and replaced by the Vespera Pro 2.

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.

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 Pro? 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 Pro? 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 Pro