GardenAstronomy

Most of what has been said on the previous page also applies there.  Having a computerised GOTO Telescope doesn't mean that you won't have the same problems in adjusting to life in the dark.  So do practice and familiarise yourself with your scope as much as possible before you attempt to do any 'serious' viewing - you won't if the weather is cloudy when you get your scope, but maybe afterwards!

 

The theory behind GOTO telescopes is very good and, once you have successfully and accurately aligned your telescope, you  should be able to find whatever you want depending, of course, on  viewing conditions and the aperture of your telescope.

 

Before using your scope it really is worth reading the manual.  If you haven't got one then go online and do a search.  Most manufacturers have download sections where you can get the manual you require.  What follows here are a few tips which may help specifically relating to the initial alignment of the smaller telescopes.

 

If we ignore the older versions which can only be obtained second-hand and the recent more expensive  'automatic' systems like the Celestron SkyProdigy, there are essentially 3 systems: the Meade AutoStar, the Celestron SkyAlign and the Skywatcher SynScan.  All 3 systems require your location (latitude and longitude), time and date.   Google Earth is excellent for finding your latitude and longitude and, for the UK use Universal Time or, for the summer months Daylight Saving.  Although Celestron, for instance, will tell you that you can use the nearest city for your location, the more accurate you can be the better - similarly with the time.

 

If you have an Equatorial mount and are going to use your scope in one particular place in your garden, then try to level that spot out and mark the direction of north.  And make some marks on the scope to indicate where you need to clamp the tube so you don't have to rebalance it every time you use it.  The next all-important action is the initial alignment for which you will then need to choose your alignment stars.    

 

All 3 systems have a variety of methods, but the most accurate usually involves choosing 2 stars with the Meade AutoStar or 3 stars with the Celestron and SynScan scopes.  Both the SynScan and AutoStar systems present you with lists of stars, whilst the Celestron system asks you to choose 3 bright stars without necessarily knowing their names - or you can even use the planets and the Moon.  However, it is not easy to precisely centre the Moon and the planets don't always work, so stick to the stars.  And it really does help if you know which stars you are looking at.  So, for all systems a little knowledge of the night sky is really essential.  Fortunately, with a program like Stellarium set up for your location, time and date, it is possible to see exactly what is in your sky.

 

Which alignment stars should you choose? In all cases there are online programs or lists of suitable stars.  They have to be bright, well separated stars preferably on opposite sides of the Meridian - and avoid any near the horizon.  The Celestron NexStar Resource site have a very useful free, downloadable utility which enables you to choose the best 2 stars, depending on your location, time and date - and these will probably work well for the other systems.  With Celestron the 3rd star is simply used to 'verify' the others - but do choose a star which is in their list.

 

With all systems the better you centre the stars, the better the subsequent GOTO accuracy.  Judging this is not that easy. Assuming that you only have the one eyepiece, a 25mm or 26mm, then the best way to centre is to do defocus the start so that it is a relatively large circle. This is much easier to centre than a dot.  If you have a higher magnification 10mm then you may switch to that and do the same for even greater accuracy.  Better still, get a Reticule eyepiece such as the 12.5mm Skywatcher and center the stars on the crosshairs.

 

Once you have aligned on the 2 or 3 stars the computer will tell you if you have been successful.  With Celestron you can find out which 3 stars you have aligned on and, having personally had Mars identified as Betelgeuse it is worth doing!  The other systems will have used the stars from their lists.

 

From then on you should be able to GOTO any object which your scope is capable of viewing and, depending on viewing conditions, it should be visible somewhere in the eyepiece.  This where a good finderscope can be an additional help, particularly with stars and planets as, if you can't see it in the scope eyepiece you should, in most cases, be able to see it in the wider view of your finderscope and slew the scope in the right direction.  One further point - if you have the Celestron Hibernate or the Skywatcher and Meade Park function, which allows you to power off whilst retaining its position, it is important to  be accurate time-wise when you next power up and re-enter the time and date.

 

And finally, to reiterate what is perhaps the most important point.  

 

Even though you are using a very clever computerised system,  it is not infallible and neither are you.  As with a calculator, where you need to know that 2 + 2 doesn't equal 5, you do need knowledge of, or access to knowledge of the sky either with a star chart or a computer program.  Noone will mistake the Moon for a star, but most stars look pretty much the same and even the planets Uranus and Neptune show very small discs.

 

Postscript: If you are only intending to look at a relatively small portion of the sky, then one star alignment can work well.  Indeed at times I have found it just as good as the 3 star alignments over quite a wide area.   For Astrophotography where you require greater accuracy in finding often very faint objects the trick is to find a bright star nearest that object and then use the Sync facility (available on many scopes).  When you then move to your desired object it should be centered  

Using GOTO Telescopes