How long should I image the Cone and Christmas Tree with the DWARF 3 from a Bortle 6 sky?

About 4 h 52 min of total integration for a solid image, or 19 h for a showpiece. A quick look takes 1 h 13 min.

How many subs is that on the DWARF 3?

At the default 15 s sub length, 1,169 subs for a solid image from Bortle 6 and 686 from Bortle 3.

Does a dual-band filter help on the Cone and Christmas Tree?

Yes. It is an emission-line object; from Bortle 6 the filter cuts the solid-image time from 9 h 34 min to 4 h 52 min.

How long to image the Cone and Christmas Tree with the DwarfLab DWARF 3

From a Bortle 6 suburban sky, the DwarfLab DWARF 3 needs about 4 h 52 min (1,169 subs of 15 s with the built-in dual-band filter) for a solid image of the Cone and Christmas Tree. A quick look takes 1 h 13 min; a showpiece 19 h. Under a Bortle 3 rural sky the solid figure drops to 2 h 51 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 61% of the frame’s short side.

Cone and Christmas Tree with the DwarfLab DWARF 3: 15 s subs with the built-in dual-band filter.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	40 min160 subs	2 h 40 min639 subs	11 h2,555 subs
Bortle 2Typical dark site	41 min164 subs	2 h 44 min655 subs	11 h2,620 subs
Bortle 3Rural	43 min172 subs	2 h 51 min686 subs	11 h2,743 subs
Bortle 4Rural / suburban transition	48 min191 subs	3 h 10 min761 subs	13 h3,041 subs
Bortle 5Suburban	55 min220 subs	3 h 40 min879 subs	15 h3,514 subs
Bortle 6Bright suburban	1 h 13 min293 subs	4 h 52 min1,169 subs	19 h4,673 subs
Bortle 7Suburban / urban transition	1 h 48 min431 subs	7 h 10 min1,721 subs	29 h6,881 subs
Bortle 8City	2 h 41 min645 subs	11 h2,578 subs	43 h10,310 subs
Bortle 9Inner city	4 h 35 min1,102 subs	18 h4,406 subs	73 h17,624 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 6 h 20 min of run time. The DWARF 3’s battery is rated at about 5 h 30 min, less near freezing, so the session needs an external power bank. (Bortle 6, solid image; we allow 30% over the integration time, and 30% off the battery for a January night.)

USB-C PD power bank 20000mAh 18W18 W PD input and it runs while charging; needs a C-to-C cable for PD.
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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 Cone and Christmas Tree is 60′ × 30′ across. The DWARF 3 frames 2.93° × 1.65° at 2.75″ per pixel, so it fills 61% of the frame’s short side.

Longer subs

Auto mode caps subs at 15 s; 30 s and longer need EQ mode, and 60 s is the ceiling on the tele camera. Time for a solid image by sub length:

Sub length	Bortle 3	Bortle 5	Bortle 7
15 s	2 h 51 min686 subs	3 h 40 min879 subs	7 h 10 min1,721 subs
30 s	2 h 24 min288 subs	3 h 12 min384 subs	6 h 42 min805 subs
60 s	2 h 10 min130 subs	2 h 58 min178 subs	6 h 28 min389 subs

With and without the dual-band filter

Solid quality, default sub length.
Filter	Bortle 3	Bortle 5	Bortle 7
Astro (no light-pollution filter)	3 h722 subs	5 h 38 min1,351 subs	17 h4,101 subs
dual-band	2 h 51 min686 subs	3 h 40 min879 subs	7 h 10 min1,721 subs

About the Cone and Christmas Tree

A bright cluster shaped like a tree with the faint Cone Nebula at its tip and the Fox Fur beside it. The cluster is easy; the nebulosity is not.

NGC 2264 · Emission nebula in Monoceros · magnitude 3.9 · 60′ × 30′ · 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 DwarfLab DWARF 3

Small pixels on a 35 mm f/4.3 lens give a sharper image than its aperture suggests, and EQ mode with 60 s subs makes it the read-noise winner in dark skies.

Auto mode caps subs at 15 s; 30 s and longer need EQ mode, and 60 s is the ceiling on the tele camera. Three built-in filters: VIS, Astro (430 to 690 nm) and dual-band Hα 656 nm / OIII 501 nm.

Longer subs matter most under dark skies, where read noise rather than skyglow sets the floor. From a city the difference between 15 s and 60 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 Cone and Christmas Tree with your DWARF 3? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the Cone and Christmas Tree from a DWARF 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 Cone and Christmas Tree · All targets for the DWARF 3