Aligning the mount

Alignment – sounds more astrology than astronomy!

In order for the go-to systems to work, you need to ensure that they are aligned both to the sky map that they have in their “brains”, but also, for one of the types of mount, aligned to the pole star (polaris) too.

Before I get into this, mounts come in two different forms – Alt/Azimuth mounts (why they can’t be called up/down left/right mounts is beyond me – oh I know, so it sounds just that little bit more inaccessible!). These are easy to use mounts for visual observing, but no good for long exposure astro-photography due to a thing called field rotation – I won’t attempt to describe that here, so either google it or just take it as read that you can’t!

The other type of mount is the Equatorial (or German Equatorial, or GEM, or Centre Equatorial, sometimes called Chinese Equatorial or CEM – see, I said this was confusing) mount. This is great for astrophotography but does your head in trying to work it out, and also trying to work out how the scope is actually going to move when you press one of the direction buttons on the handset…. It still comes as a bit of a surprise to me today..Rather than up/down left/right, these move in Right Ascension  and Declination. I’m sure you’ll agree these are common, everyday words that need no further explanation…. Yeah right! (Wikipedia is your friend) – furthermore the units used for these (and other bits of location information) are degrees minutes and seconds – good old base 60 number system.

With these two co-ordinates you can locate anything in the sky – fortunately, with a goto / push-to system you don’t have to.

BUT (and it’s a big but), as I mentioned earlier the goto / push-to systems need to be aligned.

Alignment is a complicated procedure for the novice, but I promise you it does become easier the more you do it. In order to get good alignments I would really recommend getting an illuminated eyepiece (sometimes called a reticle or reticule or illuminated reticule eyepiece – you get the picture) – these aren’t that expensive but do make a significant difference to the accuracy of your goto alignment. You see, it allows you to accurately position the objects you need to tell the goto system the location of right in the centre of the field of view. It does this by projecting an illuminated crosshair in the eyepiece. Put the required object on the cross and you know it’s slap bang in the centre! My goto accuracy has increased and much lower frustration levels experienced since using one of these eyepieces,

The goto alignment procedure is different for all mounts – I’m familiar with the Celestron AVX mount, and it’s pretty straight forward, even if I do have to refer to my iOS device to confirm the location of some of the objects. On the Celestron mount, the handset gives you the option of doing a number of different alignment routines, some more accurate than others. The most accurate one is the Two-Star Align followed by 4 calibration stars. Once I’ve done this I’ve found the pointing accuracy to be spot on. It regularly and frequently puts objects in the centre of a 14mm eyepiece on my C8 Edge HD

Of course… that’s not the end of it! As I mentioned at the start of this post – you have to make sure the mount is aligned with polaris (the ‘north’ star in the Northern Hemisphere). The way this has to be done with many mounts is using a polar scope and (frankly) some magic and a following wind. I’ve never had to do this – google it – it looks bloody complicated, but is essential if you want to do any astrophotography. For visual work, a rough (i.e. “it’s pointing roughly north”) seems to be good enough.

Fortunately modern mounts (incl my AVX) have software routines on the handsets to help you conduct this process. Celestron call it All Star Polar Align – you may see it shortened to ASPA or even ASA on various forums. I’ve not done this procedure myself yet, but plan to if I ever get any fine weather which doesn’t correspond with me working a night shift.

Why isn’t there some technological way of automating this?

Great question. I know Celestron are trying to sort this out with their StarSense product. StarSense is essentially a digital camera that you connect to the telescope and to the mount handset. The system then goes through a plate solving routine to work out where it is and what it’s pointing at. People are reporting limited success with the product (well actually, it seems to vary between great success even under moderate cloud to not working at all!) At the time of writing, it still doesn’t help at all with the polar alignment bit, although Celestron are working on it.

I do wonder with the processing power in modern smart phones why there isn’t a bracket you can get to mount your iPhone on the scope and it uses it’s camera to do this plate solving and sends the data via Bluetooth 4 to the handset… Probably because they couldn’t charge the best part of £300 for this solution.

Come on manufacturers – be brave – develop a game changing device in this area – you’ll take the market.

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