Markarian's Chain — M84, M86 & the Eyes
Virgo · Askar FRA400 · ToupTek ATR585M · Sky-Watcher AZ-EQ6 PRO · 2026-03-25
Acquisition
| Filter | Exposures | Sessions |
|---|---|---|
| Luminance | 84 × 120s | 6 |
| Red | 35 × 180s | 6 |
| Green | 35 × 180s | 6 |
| Blue | 35 × 180s | 6 |
Total integration: 8h 03m
Astrometric Data
Field Center
12h 28m 52.6s
+13° 22′ 59″
Pixel Scale
0.746 ″/px
Orientation
-92.11°
Field Radius
0.880°
Objects in Field
Main Challenges
The Virgo Cluster is a galaxy processing problem. The field contains objects ranging from the bright, compact cores of M84 and M86 to the faint outer halos of the same galaxies, the diffuse tidal debris of NGC 4438's interaction with M86, the dust lane of edge-on NGC 4402, and background field galaxies at various depths. The dynamic range between the saturated cores and the faint periphery is wide. The luminance channel carries most of the structural weight — without it, the halos, the interaction features, and the background galaxies collapse into noise.
From the Field
Six sessions across nine nights, running 21:25 to 00:09 — after the Leo Triplet's evening window closed and before the sky gave out. NINA sequenced both targets the same nights: Leo first, Markarian's Chain second. The field transits at 53–58 degrees from Torria, noticeably higher than the Leo Triplet's 44-degree ceiling, and the longer accessible arc shows in the session length — 2 to 2.5 hours per night versus Leo's cramped 90 minutes. The best session, March 23, ran past midnight to 00:09 and reached 58 degrees altitude.
Opening session. Guide RMS 0.30″ — clean night. All 48 frames used.
Worst session. Guide RMS 0.73″ — 3× the run average. Most of the L, R, G, B rejections trace back here. Best altitude of the early run, worst guiding.
Guide RMS 0.25″ — full recovery from March 18. Clean session, all 48 frames used.
Best session. Guide RMS 0.24″, peak altitude 58.1°, airmass 1.18 — the cleanest geometry of the run. Ran past midnight.
27-minute session before conditions ended. Guide RMS 0.22″ — excellent, but short.
Mirror of March 24 — same window, same frame count, guide RMS 0.24″. Two short sessions that together added one full LRGB cycle to the stack.
Process Notes
Sixty-five million light-years away — roughly where the observable universe starts to feel large — a cluster of more than a thousand galaxies occupies a region of sky about eight degrees across in Virgo. The Virgo Cluster is the gravitational anchor of the Local Supercluster, the structure our own galaxy falls toward. Markarian's Chain is the visual spine of it: a curved arc of galaxies, photographically coherent but physically real, stretching across the cluster's core.
This image captures the western end of the chain — M84 and M86 at the anchor, NGC 4438 and NGC 4435 forming the Eyes, NGC 4402 edge-on in the foreground, and a dozen fainter cluster members filling the background. The full chain extends further east than the FRA400's 0.88-degree field radius allows. What fits here is the densest, most visually complex portion of it.
What's in the Frame
M84 (NGC 4374) and M86 (NGC 4406) are the pair that define the chain's western terminus — two giant ellipticals close enough on the sky that they share the same field in most amateur images. M84 is relatively relaxed; M86 is moving toward us at 244 km/s, notably blueshift for a galaxy in a cluster where most members are redshifting with the expansion of the universe. M86 is falling into the Virgo Cluster from our side.
NGC 4438 and NGC 4435 — the Eyes — are the most dramatic pair in the field. NGC 4438 is being actively stripped: tidal interaction with M86 (which it passed close to perhaps 100 million years ago) pulled out a stream of material still visible as extended emission between the two galaxies. Its core is disturbed, its outer regions stretched. NGC 4435 is more intact but shows signs of the same event. Together they stare back from the image with an unsettling symmetry that earned them the name.
NGC 4402 is an edge-on spiral sitting in the foreground of the cluster, its dust lane cutting across the disk — a sharp-edged structure against the diffuse glow of the ellipticals behind it.
Why Luminance Matters Here
A galaxy cluster is not a single object. The Virgo Cluster field is a superposition of structures at different distances, different surface brightnesses, and different angular scales — from the bright, almost star-like cores of M84 and M86 to their faint outer halos extending well beyond their visible boundaries, to the gossamer tidal stream connecting NGC 4438 to M86, to the background field galaxies at distances that make 65 million light-years look nearby.
The luminance channel is what allows all of these to coexist in a single image. Shot at 120 seconds per frame — shorter than the RGB exposures — the luminance accumulates signal in a wideband pass that the narrower colour channels can't match for sensitivity. 84 frames of luminance, stacked carefully, captures the halo extent of M84 and M86 that 35 frames of any single colour filter simply cannot. The RGB channels provide the colour overlay — the warm amber cores of the ellipticals, the bluer tint of star-forming regions in the disturbed galaxies, the neutral tone of edge-on NGC 4402's disk. But without the luminance foundation, the faint periphery vanishes and you are left with bright cores and nothing else.
For this specific field — dense, high dynamic range, structurally complex — the luminance is not an optional enhancement. It is the image.
Software
Stacked and processed in PixInsight. Acquisition managed with N.I.N.A., autofocus via ZWO EAF through the ToupTek AFW-M 8-position filter wheel.
Behind the Scenes
Markarian's Chain shared its nights with the Leo Triplet. On March 17, 19, 23, 24, and 25, NINA ran the Leo Triplet in the evening window (19:35–21:30) and switched to M86 once Leo dropped toward the horizon limit. Same mount, same sequence, two targets per night. The Chain's higher transit altitude — 53 to 58 degrees versus Leo's 44-degree ceiling — meant longer accessible windows and better airmass for the second half of the night.
Sessions
| Date | Frames | Filters | Window | Alt range | Guide RMS | Focus drift |
|---|---|---|---|---|---|---|
| 2026-03-17 | 48 | 21×L + 9×R + 9×G + 9×B | 21:36–23:45 | 34.5°–53.6° | 0.30″ | 8 steps |
| 2026-03-18 | 41 | 21×L + 8×R + 6×G + 6×B | 21:50–23:41 | 37.5°–53.9° | 0.73″ | 8 steps |
| 2026-03-19 | 48 | 21×L + 9×R + 9×G + 9×B | 21:25–23:33 | 33.9°–53.5° | 0.25″ | 8 steps |
| 2026-03-23 | 48 | 21×L + 9×R + 9×G + 9×B | 22:01–00:09 | 42.6°–58.1° | 0.24″ | 8 steps |
| 2026-03-24 | 11 | 5×L + 2×R + 2×G + 2×B | 21:05–21:32 | 33.9°–38.7° | 0.22″ | 8 steps |
| 2026-03-25 | 11 | 5×L + 2×R + 2×G + 2×B | 21:01–21:28 | 33.8°–38.6° | 0.24″ | 8 steps |
What Got Rejected
207 NINA frames in, 189 published — 18 rejected (8.7%). The luminance took the hardest hit: 94 frames captured, 84 used (10.6%). Red lost 4 of 39 (10.3%). Green and Blue each lost 2 of 37 (5.4%).
March 18 is the session to look at. Guide RMS of 0.73 arcseconds — three times the run's average of 0.24″ — on an otherwise good night at good altitude. The 41 frames from that session produced most of the rejected luminance. The calibration routine flagged the elongated stars before they reached the stack.
Post-mortem
The same bad night that damaged the Leo Triplet's luminance (March 19 for Leo, March 18 for the Chain — one night apart) cost this project 10 luminance frames. It is a reminder that the guide RMS is not a cosmetic metric. The session notes look identical: same mount, same setup, consistent focus drift, consistent temperature. But 0.73 arcseconds versus 0.24 arcseconds is the difference between frames that integrate and frames that don't. The March 19 recovery session (0.25″) and March 23's best-of-run performance (0.24″ at 58 degrees altitude) compensated. The final stack is clean because four good nights outvoted one bad one.