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Challenge #1 – M14, Globular Cluster in Ophiuchus

TargetTypeR. A.Dec.ConstellationMagnitudeSize
M14 (NGC 6402)Globular Cluster17h 37m 36s-03° 14′ 45″Ophiuchus7.5911.0 arcmins

Overview

Contrary to what it’s statistics suggest, M14 turns in a pleasing view at the telescope. It is not visible to the naked eye (but is readily found with binoculars), is relatively small, and is tricky to track down… but it is worth doing!

This cluster was first discovered by Charles Messier in June 1764, he called it a ‘nebula without a star’. Almost twenty years later, William Herschel resolved Messier’s apparition into a cluster of 300 stars.

Only 13,000 light-years from the galactic center, this cluster is some 33,000 light-years away from us and receding at a rate of 41 miles per second. It is about 100 light-years wide but its brightest individual stars shine at magnitude 14, just about within reach of moderate backyard telescopes.

In total, we believe M14 contains several hundred thousand stars. Indeed, its absolute magnitude of -9.12 suggests a brightness of 400,000 suns. In reality, this cluster is much brighter than M10 and M12, also in Ophiuchus, but appears dimmer to us due to its greater distance.

M14, a fairly loose globular cluster (source)

Finder Charts

This cluster is highest in the sky around 8 pm in the middle of October, which is what the first sky chart shows below. There are no planets shown on any of the charts so they can be used at any time of year, and stars are shown to magnitude 5.0. The charts all from SkySafari 6.

This first chart shows you where M14 is located. You can see it about a third of the way towards the zenith (overhead) above the southwest horizon.

The lack of bright stars in this region makes tracking down M14 a trickier prospect than most but it’s decent magnitude means it can be spied in magnifying finderscopes and binoculars.

Our first step is to identify the barn side which is Ophiuchus and its brighter stars, which we’ll do in the second chart.

[M25-1] Locate the Teapot asterism (circled orange) to begin your hunt for M25. Click for full-screen.

We now zoom in to show stars to magnitude 6.5. M14 lies on the line joining Nu and Kappa Ophiuchi, as shown by the orange arrow, below. The cluster is just to east of the line connecting Cebrali to Sabik. All of these stars are magnitude 3 or brighter.

Pay special attention to the magnitude 4.5 star HR 6493 because this is quite close to our cluster.

[M14-2] Use connections between the bright stars of Ophiuchus to refine your search location. Click for full-screen.

This last star chart shows the stars to magnitude 10. See that Nu Ophiuchi is still visible and we’ve shown HR 6493 as the start point for a hop to the cluster. The blue circles are each a 1° field of view and it’s less than 5° northeast from HR 6593 to M14.

In reality, M14 is bright enough to identify visually if you’re looking in the correct part of the sky with a magnifying finderscope.

[M14-3] When you’re centered on the star HR 6493, a 5° star hop northeast brings M14 into view. Click for full-screen or download the pdf below.

Now you have this cluster in your eyepiece, what should you expect to see?

Individual Telescope Views

The following views will help you find M14 in different telescope types by presenting the images as your telescope will show them. The first image is with a black sky and white stars, the second picture is the same image but presented in inverse monochrome. Black stars on a white background is often easier to use at the telescope. Stars are shown to magnitude 12.0. Each image can be clicked on for a full-screen version.

Upright View – This is what your eyes see unaided and through a reflex or red-dot finderscope

[M14-4]
[M14-5]

Upside-down view – This is what reflectors and magnifying finders show, and refractors / Cassegrains without a star diagonal

[M14-6]
[M14-7]

Mirrored View – Refractors and Cassegrain models with a star diagonal show this view

[M14-8]
[M14-9]

Observation

In smaller telescopes, we see this cluster with no definition as a typical hazy glow. It is helped to stand out by the fact the field around it is sparse, we see mostly darkness and dim stars in the eyepiece. With time and averted vision, you should distinguish a softer halo around a denser core. However, it’s not possible to tease out individual stars.

Pushing a higher magnification reveals a handful of individual stars, if the seeing is good enough and your optics sound.

Seeing individual stars is an easier proposition in a moderately large telescope with better resolving power. You’ll notice them nestled in the halo surrounding a core which we can see as gradually brightening towards its center. The very brightest star is magnitude 12.8 but we need to resolve magnitude 14 to see a good number more.


PDFs for Printing

Each of the star maps above is reproduced as a pdf below. Each star map has a number in [square brackets] beneath it which corresponds to the file number below. If you want image [M48-1], for example, click the ‘download’ button next to it below and you’ll be able to open it as a printable pdf.

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