Challenge #1 – C45, Spiral Galaxy in Boötes
| Target | Type | R. A. | Dec. | Constellation | Magnitude | Size |
| C45 (NGC 5248) | Spiral Galaxy | 13h 37m 32s | +08° 53′ 07″ | Boötes | 10.1 | 4.1×2.4 arcmins |
Overview
C45 is a gorgeous view in the image below from Hubble and, although it’ll never be so gorgeous in our backyard telescopes, it is worth hunting down, even if it is much more challenging than you might expect.
This compact barred-spiral galaxy was discovered by William Herschel in April 1784.
It’s around 70 million light-years away from us, although there is still some debate about that figure between astronomers.
This galaxy is part of its own group of galaxies which is, in turn, part of the Virgo Supercluster.
Learn how to find this lovely galaxy with your telescope.
Finder Charts
This first sky chart, from SkySafari 6, which shows the sky looking south at 10:00 p.m. in mid-April. The green oval marked NGC 5248 is our galaxy and you should note its proximity to the bright stars Arcturus and Spica, as well as the Big Dipper (Plough), which is marked with an orange oval.
Stars on this chart are shown to magnitude 5.0 and the moon and planets are not shown.
This is a tricky object to tie down. The first step is to imagine a line between the stars Vindemiatrix and 109 Virginis. Our galaxy is very close to this line in the vicinity of the fainter stars (but still just about visible to the naked eye) 71 Virginis and HR 5138.
In this third chart, stars are shown to magnitude seven, comfortably visible in binoculars and magnifying finderscopes. We can still see 71 Virginis and HR 5138 but we can now also see fainter stars to help with the location. The blue circle is a 1.5° field of view.
Now you have this galaxy in your eyepiece, what should you expect to see?
Individual Telescope Views
The following views will help you find C45 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 10.0 and the bright star diagonally opposite the North bearing of the 1.5° fov circle is HR 5138, shown above.
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
Upside-down view – This is what reflectors and magnifying finders show, and refractors / Cassegrains without a star diagonal
Mirrored View – Refractors and Cassegrain models with a star diagonal show this view
Observation
Although magnitude 10 is not particularly dim for a galaxy, the light is spread over a large area and this makes identifying and certainly observing C45 a real challenge.
We always say that dark skies are the best and this is particularly true now!
That said, even at low magnitude the brighter core is distinctly surrounded by a fainter outer outer halo oriented east-west.
More power helps to brighten the scene but there’s just not enough light coming in to determine structure. Use averted vision to tease out mottling in the glow but this is a tricky beast under less than perfect conditions.
Much higher power is useless because on the galaxy’s low surface brightness. Any detail chased by strong magnification vanishes like a magician’s rabit.
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 [C45-1], for example, click the ‘download’ button next to it below and you’ll be able to open it as a printable pdf.