1
$\begingroup$

I have a Celestron Astromaster 130Eq. I saw all the planets in our solar system and quite satisfied. Now I am in the hunt for DSOs, but living in a city is a disaster for tracking some good-for-observation deep sky objects. At the moment, I have only observed the Orion nebula (which was elegant) and nothing else. Any tips for how to track them?

$\endgroup$
4
3
$\begingroup$

When you say "track" I think you mean "track down", or - simply - "find".

Living in a city, you're going to have trouble seeing a lot of DSOs. Most galaxies will be out of the question. You'll have to understand the limitations of your environment and the aperture of your telescope and choose your targets accordingly.

The objects you should choose are the brighter nebulae, open clusters, and double stars. Some of the brighter globular clusters might be visible, too.

Star hopping

In order to find the more elusive targets you'll need a map and to learn how to star-hop: to jump from star to star in order to point your telescope in the right place.

As you're in the city, you'll never become fully dark-adapted, so you'll be fine using a phone application to help you find things. The best star maps on a phone, in my opinion, are SkySafari 6 Plus, Stellarium +, and SkEye. Enable the "dark mode" on the application you use - although your eyes may never completely adjust to the dark in the city, you'll want to help them do the best that they can, and that means not blinding them with the screen of a phone.

SkEye lets you mark a target and when you move the map an arrow will appear that points to your target. With two fingers you can rotate the view so it appears as it does through your eyepiece.

Find the nearest star to your target which is visible to your naked eye. Point your telescope at that star, and move the star map to the same star. Use your lowest-power eyepiece to slowly move the telescope and the star map towards the target, following the arrow on the screen.

Use the brightest stars on your journey to guide your way. Look for shapes: triangles of stars of a similar brightness make great signposts.

If you find that you can see more stars in the eyepiece than the star map is showing you, then you might want to change to one of the other applications. SkEye is free and has a limited catalogue. The other two are not free but have more extensive catalogues.

A great desktop application for this is KStars: it has a star hopping tool which will generate set of instructions, given a start point, and end point, and an eyepiece.

I find star hopping to be a fun way to hunt down targets in the sky. For me it makes the sense of discovery even sweeter. Other people find it dull and would rather use a Go-To mount to do the work for them.

Give it a try and find out which type of person you are - either way is perfectly valid :-)

Filters

In a comment, D.Halsey suggests using a light pollution filter. Unfortunately these are less useful than they were. These days many cities have 'upgraded' to LED lighting, which has the unfortunate side-effect of casting light which covers the full visible spectrum. Light pollution filters worked by filtering out the yellow light given off by the old sodium street lights. Against modern LED lights they don't do very much. If you're fortunate then you might live in an area which hasn't yet changed the street lighting over from sodium to LED - in which case go ahead with the light pollution filter!

Filters which do work - on certain nebulae at least - are the O-III (doubly ionised oxygen) and Ha (hydrogen alpha) filters, or one of the several "nebula filters" which allow both of these bands through.

They don't make the objects brighter - they work by making everything else darker. But they do work. I've seen several nebulae from the city which were impossible to see without them.

Just bear in mind that, because they work by dimming everything except the nebula, they're best used with your lowest power eyepiece: the one that gives the biggest exit pupil, and therefore the brightest view.

Aperture and/or darker skies

If you're stuck in the city, and you have the space to use it and to store it, then a larger aperture telescope will gather a lot more light and make it a lot easier to find things. An 8-, 10-, or 12-inch (200, 250, or 300mm) Dobsonian is a fine budget telescope for city use, depending on your budget, of course!

But there's nothing like really dark skies. If you're able, then get out of the city as much as possible to observe. (I personally have two telescopes: a large aperture one which I use from home in the city, and a small aperture one which I use when travelling to dark places. The best thing is when I can take my large telescope to a dark place, but that only happens once a year)

A small telescope under dark skies will show more than a large telescope under heavy light pollution.

$\endgroup$
1
  • 1
    $\begingroup$ Very useful and detailed answer, thanks $\endgroup$
    – Prallax
    Aug 16 at 10:32

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.