Celestial hemisphere:  Northern  ·  Constellation: Draco (Dra)  ·  Contains:  NGC 5976  ·  NGC 5981  ·  NGC 5982  ·  NGC 5985  ·  NGC 5989  ·  PGC 214405  ·  PGC 2581886  ·  PGC 2583116  ·  PGC 2583846  ·  PGC 2584354  ·  PGC 2584799  ·  PGC 2585105  ·  PGC 2586109  ·  PGC 2586286  ·  PGC 2586355  ·  PGC 2587066  ·  PGC 2587426  ·  PGC 2587777  ·  PGC 2587800  ·  PGC 2588841  ·  PGC 2588984  ·  PGC 2589408  ·  PGC 2590275  ·  PGC 2590383  ·  PGC 2590542  ·  PGC 2590679  ·  PGC 2591169  ·  PGC 2591563  ·  PGC 2591991  ·  PGC 2592514  ·  And 27 more.
Getting plate-solving status, please wait...
NGC 5985, 5982, 5981 (Draco Triplet) & Vicinity in LRGB, Ben Koltenbah
NGC 5985, 5982, 5981 (Draco Triplet) & Vicinity in LRGB, Ben Koltenbah

NGC 5985, 5982, 5981 (Draco Triplet) & Vicinity in LRGB

Getting plate-solving status, please wait...
NGC 5985, 5982, 5981 (Draco Triplet) & Vicinity in LRGB, Ben Koltenbah
NGC 5985, 5982, 5981 (Draco Triplet) & Vicinity in LRGB, Ben Koltenbah

NGC 5985, 5982, 5981 (Draco Triplet) & Vicinity in LRGB

Equipment

Loading...

Acquisition details

Loading...

Description

========== Hardware and Image Overview ==========

This is an LRGB image of the Draco Triplet taken with my new TS 130/910 APO refractor. This was an ambitious (perhaps somewhat foolish) choice of target so close to the last Full Moon, but this time of year I need to grab any precious clear nights I can get, moon or not. I only got two nights out, but at least I was able to devote the entire imaging time to the Triplet. Another challenge for my light polluted skies was that these galaxies are, at their brightest core, magnitude 9.4, with structure detail at much fainter magnitude and therefore even lower SNR. Seeing conditions were average at best for me these two nights.

Although this scope and camera combination makes for a nice intermediate-sized field of view, it is not my favorite choice for smaller galaxy imaging. Even so, I got adequate resolution for the purpose of investigating and annotating this region of sky. I have been contemplating pairing the TS 130/910 with a smaller pixel camera, perhaps one of the new CMOS sensors, but that possibility will have to wait until the future.

I'm mostly satisfied with the performance of this scope. I already owned a Moonlite CFL 2.5" focuser for an older refractor that was easily fitted on this scope with new upper flange. One issue I ran into was the need to flock the interior of the drawtube as the original paint was glossy and bright. I am still facing some internal reflection issues that may require more flocking. And I am suspicious that the focuser drawtube is too long for this configuration. I'm reluctant to hacksaw it shorter, however, until I've truly determined whether or not this really is an issue.

In the final image (Rev. E) I've added an enlarged inset of the Triplet against the wider field of view for better viewing. I have also, as usual, included a detailed annotated image (Rev. D). I very much enjoy researching the various targets in my images, and for those interested, I've included some notes below.

Thank you for your attention. Your comments and suggestions are very welcome!

========== Draco Triplet ==========

Here is some data and description of each member of the triplet. Links are to the CDS Portal, data from NED.

I wanted to quote consistently derived distances. These are derived from the redshift data using the Galactocentric GSR method. Follow the links to NED if you are interested in the details. The varying redshifts and calculated distances indicate that, although visually appearing close to one another, the galaxies are likely quite separated and do not in actuality form an interacting group. Traveling towards the central NGC 5982 (I'm reminded of Carl Sagan's Ship of the Imagination from the old Cosmos Series.), we would first pass NGC 5981 on the right, then NGC 5985 on the left, and then arrive at NGC 5982, almost twice as far away as the first from our galaxy. (Be sure to imagine Vangelis playing in the background the whole time we travel. The 8-track tape is stuck in the player.)

NGC 5985

Seyfert Galaxy, SBbc (Barred Spiral, moderately loose arms)

z = 0.008396, Distance = 36.7 ± 2.6 Mpc

Apparent Size = 5.5' x 3.0'

This is (to me) the most visually interesting of the three members of the triplet. I admit to some color tweaking of the image for the purpose of emphasizing blueish arms and yellowish central core. Seyfert galaxies have active cores, similar to quasars, but closer, less luminous, and the host galaxy is visible. They are powered by super massive black holes with accretion discs, bright even more so in UV.

NGC 5982

LINER-type Active Galaxy Nucleus, E (Elliptical, bright nucleus, amorphous)

z = 0.010064, Distance = 43.6 ± 3.1 Mpc

Apparent Size = 2.26' x 1.39'

Of the three members of the triplet, this one is the brightest given its luminous central core. LINER refers to Low-Ionization Nuclear Emission-Line Region, characterized by emission lines of weakly ionized or neutral atoms.

NGC 5981

Sab (Tightly-bound spiral seen edge-on)

z = 0.005884, Distance = 26.4 ± 32.11 Mpc

Apparent Size = 2.8' x 0.5'

Not surprisingly, the morphology of this one is not nailed down well since it's seen edge-on. But even in my relatively low resolution image, it hints at a central bulge with well-defined disk, perhaps even with outer rim of dust. Redshift implies this one is quite a bit closer to us than the other two.

========== Other Notable Galaxies in Field ==========

I selected a couple more to research because they were to me visually interesting. Most of the PGC galaxies annotated are too far away to show any real detail, but I'm continually amazed at the ability of digital imaging to at least pick them out of the horribly bright suburban sky background.

NGC 5976

SA0 (Lenticular Galaxy, in between Elliptical and Spiral)

z = 0.010170, Distance = 44.0 ± 3.1 Mpc

Apparent Size = 0.9' x 0.4'

This one is found continuing on to the right and a little beyond the Triplet. Interestingly, its distance is comparable to that of middle Triplet member NGC 5982. If that's true, then they may be in interaction with one another, with this one being a possible satellite. I measured an angular separation from center to center between the two galaxies to be 14.5', and using an equal distance of 44 Mpc, these could be at minimum 186 kpc apart from one another. In comparison, the Andromeda Galaxy is 778 kpc distance from the Milky Way. Looks like their proximity and interaction is plausible.

NGC 5989

SAc (Lenticular Galaxy, Closer to Spiral than Elliptical)

z = 0.0096, Distance 41.7 ± 2.9 Mpc

Apparent Size = 0.9' x 0.9'

This one is left and above the Triplet in my image. This may also be interacting with NGC 5982, although less convincingly than the previous. The formless but discernible tightly-wound arms caught my attention, and sure enough it is classified as Lenticular, a morphological form between Elliptical and Spiral, with this one edging more towards Spiral in the spectrum. A higher resolution image would draw out more interesting features here.

Comments

Revisions

  • NGC 5985, 5982, 5981 (Draco Triplet) & Vicinity in LRGB, Ben Koltenbah
    Original
  • NGC 5985, 5982, 5981 (Draco Triplet) & Vicinity in LRGB, Ben Koltenbah
    B
  • NGC 5985, 5982, 5981 (Draco Triplet) & Vicinity in LRGB, Ben Koltenbah
    C
  • NGC 5985, 5982, 5981 (Draco Triplet) & Vicinity in LRGB, Ben Koltenbah
    D
  • Final
    NGC 5985, 5982, 5981 (Draco Triplet) & Vicinity in LRGB, Ben Koltenbah
    E

B

Description: Luminance Image

Uploaded: ...

C

Description: Inverted Luminance Image

Uploaded: ...

D

Description: Annotated LRGB Image

Uploaded: ...

E

Description: LRGB Image with Enlarged Draco Triplet Inset

Uploaded: ...

Sky plot

Sky plot

Histogram

NGC 5985, 5982, 5981 (Draco Triplet) & Vicinity in LRGB, Ben Koltenbah