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This stack sat in my archive for almost four months. I captured the Leo Triplet on the night of February 14th, ran it through Stellar Studio and Snapseed within a few days, looked at the result, and filed it under good but not finished. Then galaxy season got busy. M101 got six hours, M106 got fifteen and a half, and M51 ended up spread across three sessions. The Triplet got one night and a note to come back.

This is the writeup of that one night, because the data holds up better than I gave it credit for in February.

Three galaxies, one telephoto frame

M65, M66, and NGC 3628 sit about 35 million light-years away in Leo, close enough together on the sky that all three fit inside the DWARF 3’s telephoto field with room to spare. That is the reason to point this telescope at them. At 150mm of focal length, no single member of the group resolves the way it would through a long focal length instrument. What you get instead is the group as a scene: two spirals at different tilts plus an edge-on disk, all in one exposure.

They are easy to tell apart once the stack is stretched. M65 is the restrained one, smooth and elongated. M66 beside it shows real structure, with brightness knots along the arms and a slightly bent look that comes from its interaction with its neighbors. NGC 3628 sits apart from the pair, a flat sliver with a dark dust lane running the full length of the disk. It carries no Messier number because Messier missed it, which still seems odd given how close it sits to the other two.

Run Card

Target	Leo Triplet: M65, M66, NGC 3628
Type	Galaxy group
Constellation	Leo
Distance	About 35 million light-years
Telescope	DwarfLab DWARF 3
Mode	Guided EQ
Filter	Astro
Sub-exposure	60 seconds
Gain	50
Subs stacked	278
Stacked integration	4h 38m
Run time	About 5 hours
Polar alignment	1° deviation
Moon	Waning crescent, ~9%, rose after midnight
Sky conditions	Bortle 6, mid-February
Processing	Stellar Studio stack, Snapseed finish

The capture

The settings were the standard galaxy preset from my settings and calibration guide: EQ mode, Astro filter, 60-second subs at gain 50. The same configuration that produced M101 and M63.

Polar alignment came in at 1 degree of deviation, which is looser than I normally accept. I left it. At 60 seconds the stars stayed round anyway, and this was logged as a quick run from the start.

Darks were temperature-matched within about a degree of ambient. After what a single bad dark did to my M13 stack, I no longer treat that step casually.

The moon cooperated by being nearly gone. February 14th had a waning crescent around 9 percent illuminated that did not rise until after midnight, so the useful evening hours were effectively moonless. Out of roughly five hours of run time, 278 subs survived to the stack for 4 hours 38 minutes of integration. The gap between run time and stacked time was overhead and a modest pile of rejected frames. Nothing dramatic.

One filter note, since the question comes up: this is broadband galaxy light. The Duo-Band filter would throw most of it away. Astro filter, every time.

What the frame shows

All three galaxies resolved with the features that make them recognizable. M66 shows its knots. M65 stays smooth.

And the NGC 3628 dust lane, the feature I rated most likely to fail from a suburban sky, is plainly there. It cuts the disk end to end with the brownish tone intact, and there is a hint of the flared tips at both ends. That lane is low-contrast structure, and an aggressive stretch will bury it in background noise faster than it will brighten it. The restrained stretch won.

There is a fourth galaxy in the frame too: a small edge-on streak in the lower right that I have not plate-solved yet. The M81 project taught me to go hunting for these after the fact. UGC 5210 turned up at magnitude 14.88 in that field, so I expect this one has a catalog number waiting.

My one complaint is with my own processing. The background may be a touch darker than the data deserves. Snapseed makes it easy to pull the sky toward pure black, and pure black looks clean on a phone screen while it costs you faint signal at the edges of the galaxies. With 4h 38m of integration there was not much faint signal to protect. With ten hours there would be.

Why it gets a second visit

The plan that night was to confirm the framing and check whether the dust lane was reachable from Bortle 6. It was, on both counts. By the time I circled back in April, Leo was past its best evening hours and M51 had taken over the schedule, so I let the Triplet go for the season.

It goes back on the list for next galaxy season with the same 60-second, gain 50 configuration and a target of ten-plus hours across multiple nights, the multi-session approach that worked on M106. The open question is whether tripling the integration buys a visibly cleaner dust lane and a background I can afford to leave brighter, or whether 4h 38m already captured most of what this field offers at this focal length. I do not know yet. That comparison is the follow-up post.

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