GardenAstronomy

What can you see?

It may be strange to start off the pages in this section by referring you to another site, but most of what I have said in this section is better expressed - did he read my site?! - with visual comparisons at this Stargazers Lounge Forum.   But when you return here you should find additional information which will be useful.

 

It really is a very good idea to try to plan what you are going to look at.  There is so much to see and often limited time.  As well as 'normal' light pollution there is the Moon.  On nights leading up to and beyond the full Moon, its light will be such that you will not be able to see the fainter objects like Galaxies and Nebulae. That is the time to look at the planets, if they are around, or double stars, but probably not the Moon itself.  The best time to look at the Moon is usually during the first or last quarters.

 

There are useful books and programs available which can be used to plan your viewing.  Particularly useful are those which categorise objects according to whether they are easy, medium or hard to see.  A program which enables you to create lists is the NexStar Observor List.   Although designed especially for the Celestron NexStar series it can still be used to simply create observor lists of Double Stars, Galaxies, Nebulae, Clusters, etc.  And for those who have something like a Telrad finder or the small refractor kind of finderscope, Sky  & Telescope's 'Pocket Sky Atlas' is a useful way of finding your way around the sky.

 

One particular aspect of viewing which beginners often don't appreciate relates to the magnitude of objects. This is calculated assuming that they are points of light.  This is true of stars but not of galaxies and nebulae which can be as much as 3 or more degrees in diameter, like the Andromeda Nebula. Thus a galaxy with a designated magnitude of 8,  which is well within the range of most small scopes, may have an actual surface brightness of perhaps 12 or 13 rendering it totally invisible in these scopes.

 

Dark Adaptation: It takes time for our eyes to adjust to darkness when we step outside.  After 10 minutes you will find that you can see better and your ability will continue to improve for several hours - if you stay out that long and can avoid bright lights!  Indeed, any bright light  will destroy your dark adaptation, especially normal torch-light or the orange of street-lights.  Red light has the least effect, which is why astronomers use red light torches - they should not be too bright either.

 

Another factor which affects how well you see and which you can do nothing about is your age. The older you are the smaller the maximum aperture of your pupils and hence the less light your eyes can gather. And obviously clean optics is another essential as is a dew shield for catadioptrics.

 

Averted Vision: A seemingly daft idea based on the physical structure of the eye where you look to one side of an object - to the right if you use your right eye, your left with the left eye, up with binoculars. This brings the more sensitive monochromatic rods in your eye into play so that you should see fainter objects.  It does need practice.

 

Tapping the Telescope: This may enable you to detect a faint object.  Why?  Because we sense motion more easily than a stationary object - think of a  rabbit in a field which we don't see until it moves.

 

Magnification: There is usually a best magnification for any object, depending on the viewing conditions.   It makes no sense to up the magnification if the end result is a fuzzy, wobbly object.  Start off with the low power magnification 25 or 26mm eyepiece which usually comes with most small telescopes, then move on to higher magnifications if the conditions allow - see zoom eyepieces on the Accessories page

 

Obviously what you can see this will depend on the time of year - not to mention the weather! But let us look at the different types of objects and consider how visible the main ones might be from typical suburban back garden using a small telescope - say 6 inch (150mm) or less.  Of necessity this only a very, very brief guide and is restricted to objects visible from the Northern Hemisphere, particularly the UK.

 

The Solar System

 

The Stars

 

Clusters, Galaxies and Nebulae