Tripod help , ultimate novice here

[TwinkleTwinkle]

I have an 8se with the tripod that came with it, but a couple of month ago I bought a preowned celestron cg-5-GT , as i thought it tracked stars with dslr ( yeah that's what I thought, how daft)

Now iv not set up the cg-5-GT yet, and wondering if iv dropped a clanger , and maybe I should sell it as it's the same but older and more complicated version of the SE mount. Please help!

Many thanks !

[nightfisher]

The CG5 GT is a good mount and worth using

[michael.h.f.wilkinson]

Both mounts track, but the SE is alt-azimuth, which means it is less good for imaging, because although the centre object stays in place while tracking, the rest of the image rotates around it. The CG is an equatorial mount, which automatically keeps the image orientation constant.

[TwinkleTwinkle]

Many thanks for your replies , I have auto guide ports on both mounts , what is this for, if the CG tracks stars why would this be needed.

Sorry if I'm sounding simple

[TwinkleTwinkle]

Iv realised its the advanced GT I'm not sure if that makes any difference

[Scott]

there's quite a difference between tracking and guiding. tracking will follow a star as best it can but things like polar alignment (or slight errors in it) and periodic error means that it will never be 100%. With guiding (in conjunction with tracking) the guide camera tells the mount if there is any minor drift and the mount corrects this.

This is a very basic breakdown and it'd probably be helpful if you could purchase "Making Every Photon Count". It's a brilliant book for those of us starting out in astrophotography.

Edit, this said, if you are using a camera and camera lens at short focal lengths then tracking will be sufficient to get very nice pics. It's mainly when your focal length increases that guiding starts to become necessary.

[cjdawson]

Here's my breakdown....

Alt-Az mount will get you daytime style photos.  Moon, possibly saturn and Jupiter.

Using an EQ mount, you'll be able to take some long exposures.

Tracking - as built into practially every goto telescope will attempt to follow the sky as it rotates.  For a tracking mount, the motion is an approximation.  It can be accurate over a long period but it's a guess based on some fairly simply maths.  There are various things that can get in the way of tracking an object perfectly.   These include Periodic error (an inconsistency in the mechanics of the mount), polar alignment not being perfect - this will cause image rotation, and atmospheric conditions.

A guide camera can help to compensate for the above issues.  note I said compensate, not correct.  A bad polar alignment will ruin any image, a close polar alignment shouldn't need much in the way of correction.  Periodic error is just inconvenient, and atmospheric conditions are never going away.

A guide camera needs to have a view of the night sky, it needs to be able to lock onto a star, so that it can track the movements.   On my scope, I have a guide camera attached to a small (80mm) telescope which is mounted on top of my main scope.  This camera is used keep an eye on the sky as seen through the 80mm scope.  With that it will keep the guide star that it's locked onto in the same place.  It does this by issuing commands to the telescope mount via the auto-guiding port.  This will make the telescope move slowly (about 2/3 of the normal star movement rate) to compensate for errors in the telescope mounts tracking ability.

Using this technique, you can then achieve much longer exposure times on each sub frame, longest that I've done so far is a single frame of 10 mins.  But theoretically it can go for the whole night.