Transcript
EQUATORIAL (EQ) MOUNTS If you’ve bought an astronomical telescope, the likelihood is it’s come with a tripod and an “equatorial mount “ If you are not familiar with equatorial mountings, setting up and aligning one these for the first time can seem a little bit daunting. It’s very difficult to show clearly on a printed page how to do this, which is why many of the instruction books often don’t seem to make sense. Don’t panic. You can still use your telescope even without the mount properly aligned, and when you feel ready it’s worth taking a little bit of time to make the alignments, you’ll get even more enjoyment out of your telescope. Essentially the EQ mount is designed the allow the telescope to track the apparent movement of objects in the sky as the earth turns. Our earth turns around a north/south axis making one rotation per day, so stars, which are to all intents and purposes fixed in the sky, appear to move in an arc across the sky. A correctly set up and aligned EQ mount allows the telescope to follow this movement easily. To set up the EQ mount correctly it must be aligned towards the north celestial pole ( the mount must be aligned, not necessarily the telescope ) This means turning the mount so it points north, perhaps using a compass and then tilting the mount to match latitude of your observing position. Most EQ mounts have a scale for this. Latitudes here in the UK are between around 52 - 57 degrees and you’ll need to check the precise latitude for your location. Some EQ mounts have a built in polar alignment scope - Here in the northern hemisphere we are fortunate to have the POLE STAR which is just about on the north celestial pole, if your EQ mount has a polar scope it can be quicker to align using this. Bear in mind that the pole star isn’t exactly on the pole, so for very precise alignment there are more adjustments to make. It all depends how exacting you want to be in your observations. For most casual observations an EQ mount roughly aligned to the pole star will be good enough and provide a great deal of enjoyment. It is very difficult to describe this properly here, it really needs to be demonstrated. Many dealers have staff who can explain this to you, but please bear in mind that not all store assistants are experts in astronomy. For a great guide to setting up an EQ mount, please visit the astronomy section of our website www.opticalhardware.co.uk/astronomy Scroll down the links on the right hand side and click on “ setting up your astronomical telescope and equatorial mount “ This links to Richard McDonalds website and pages who kindly allowed us to use the link. Here you’ll find a full description complete with some moving graphics, much better than trying to show this on paper. Once the mount is aligned there are only two actions you need to use. These are the DECLINATION (measured in degrees) and the RIGHT ASCENSION (measured in hours) The declination is the angle from the north celestial pole that a star occupies. You can find this in any of the night sky reference guides. You turn the declination control so that the pointer indicates the correct setting. The right ascension is then its position as the earth turns. Once you have set the declination for a particular object, this does not need to be changed, and you only need movement on the right ascension to find and track your subject. By convention, an object at the north celestial pole (pole star ) has a declination of +90, an object on the celestial equator has a declination of 0. Please note however that the scales on astronomical mounts are rarely perfectly set up by the factory and if you intend using these it’s worth taking a little bit of time to position the indicators correctly. You’ll need to align on a known object and then reposition the scale or the scale marker. Mostly these are affixed with light adhesive, they can be removed and refixed.
The scales on some typical EQ mounts
The scale markers are often not accurately positioned. Once you have aligned on a known object, some scales will rotate to allow repositioning or you can remove the marker and reposition it , fixing it with a spot of glue
DECLINATION R/A LATITUDE
Markers usually only attached with glue but some may be screwed into place, Check with your dealer if you are unsure
DECLINATION R/A Ostara astronomical products and good advice is available from :
LATITUDE
DECLINATION R/A LATITUDE If no dealer is shown here, please visit www.opticalhardware.co.uk/astronomy
