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M65 and M66, Spiral Galaxies in Leo

TargetTypeR. A.Dec.ConstellationMagnitudeSize
M65 (NGC 3623)
M66 (NGC 3627)
Spiral Galaxies11h 18m 56s
11h 20m 15s
+13° 05′ 35″
+12° 59′ 30″
Leo+9.1
+8.9
7.6×2.0 arcmin
10×4.6 arcmin

Overview

We’re taking these two galaxies together because they’re so close to each other. Along with a third galaxy, NGC 3628, they are known as the Leo Triplet of galaxies.

Charles Messier discovered both M65 and M66 on the same day in March 1780. He noted them to be nebulae because, at the time they were discovered, we didn’t know of the existence of galaxies.

M66 is the bigger galaxy, covering 80,000 light-years and is 37 million light-years away from us. M65 is 42 million light-years away. Both galaxies shine at about magnitude 9 and so are comfortably within reach of our backyard scopes. Both can be seen in the same 1° field of view, along with NGC 3628.

As with most galaxies, M65 and M66 are moving away from us at an incredible speed. For M66 that’s 700 km/s and, for its neighbor, the speed is 800 km/s.

The spiral galaxy M65, as imaged by the Hubble Space Telescope (source)

Finder Charts

In the first star chart (from SkySafari 6) you can see that M65 (green circle) is close to the Sickle asterism, which is inside the smaller orange oval. The larger oval shows Boötes, including the bright star Arcturus, which can help to locate the Sickle.

This is the view in mid-April at 10 pm, when the galaxies are two-thirds of the way over the horizon in the southeast. Stars in the chart are shown to magnitude 5.0 and the moon and planets are not shown.

[M65-1] Find the Sickle asterism to begin your hunt for the Leo Triplet (shown as M65 in this chart). Click for full-screen.

When you’ve found the Sickle, we need to work our way to the triangle of stars formed by Zosma, Chertan, and Denebola. The Triplet is nearest to Chertan, midway between it and the magnitude four star Iota Leonis.

[M65-2] Track down Chertan and Iota Leonis to find the Leo Triplet. Click for full-screen.

Stars are now shown to magnitude 7.0. See that M65 is almost exactly midway between Chertan and Iota Leonis and that both galaxies will comfortably fit inside the same 1° field of view.

[M65-3] In this last chart, we can see the relative positions of M65 and M66. Click for full-screen.

In the last section, you’ll discover what you should expect to see of these galaxies once you’ve got them in your eyepiece.

Individual Telescope Views

The following views will help you find M65 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. Stars are shown to magnitude 10.0. The large circle is a 1° field of view and Chertan is shown in all images.

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

[M65-4]
[M65-5]

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

[M65-6]
[M65-7]

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

[M65-8]
[M65-9]

Observation

There’s no escaping that your view of these three will be better under a dark sky. Under less than perfect conditions you will struggle to see NGC 3628 even if you find M65 and M66. Even so, they are both visible in binoculars under darkness.

As an aid to seeing the faintest of these three galaxies, assume that M65 and M66 are the corners at the base of a narrow but tall triangle. NGC 3628 is at the top point of that triangle.

To identify which galaxy is which in your eyepiece, M65 is not quite as large or bright as M66. If you can see any level of detail you should be able to note that M65 is more of a cigar-shape, whilst M66 is more rounded. You’ll pick up a brighter core when your eyes are well adjusted to the darkness.

Remember, familiarity is your friend with these large but faint objects. Revisit them over a few nights and you’ll be able to pick out more detail than if you visit once and don’t return for a long time.

I hope you enjoy having three galaxies in one eyepiece!


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 [M65-1], 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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