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Mohammed,
Are you asking about portable trackers for eclipse chasing / photography or for astrophotography more generally?
Drive precision and PE specs for eclipse photography are pretty irrelevant. If you use 70-80mm diameter f6-f8 refractors, or a 4-5" f12.5 mak, the longest exposures are only 1-2s for such optics. Even 200" PE won't affect such a short exposure.
During a total eclipse, the primary job of the drive is to keep the image centered and by using an equatorial mount, no rotatation is required later when processing, aligning and stacking images. There are no stars to register on in the short exposures and the moon moves relative to the corona so you can't use the moon.
If you are asking the question for longer exposure astrophotography more generally, then Pete's advice holds. Also read Phil Hart's SW Star Adventurer review. The Star Adventurer has an autoguider ST4 connector which can take input from a SW Synguider.
You could also consider building a compact lightweight double arm Trott type 4 barn door.
Joe
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