How can I prevent sudden tracking jumps during long-exposure astrophotography?
Asked 6/1/2011
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2 answers
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During long exposures, I sometimes get a sudden jump in my mount tracking, and the stars appear doubled in the final image. What are the likely causes, and what can I do to reduce or prevent these jumps?
Originally by Stefano Borini. Source · Licensed CC BY-SA 4.0
Stefano Borini
15y ago
2 Answers
9
I have a German equatorial mount so that's what my answers are based on. If you have a fork mount, some of these aren't going to make sense.
A few things come to mind:
You might be out of balance. When adjusting your counterweights you want the east side to be slightly heavier to keep pressure on the gears. Not a lot, just enough to keep tension. Your balance might have too much or too little (or reversed) pressure. This document describes it decently.
You might need to simply wait for an hour or so. If your scope is passing through the point where the scope and the weights are vertically aligned, you may be catching it when the weight shifts from one side to the other.
A few less easily fixable things come to mind too:
Your scope could be overloaded. Make sure the mount is designed for the scope and counterweight you have on it.
I've read from a few places that taking the mechanism apart, cleaning, and re-lubricating makes a huge difference to how smoothly it tracks. Not for the faint of heart though.
Originally by Jeff Snider. Source · Licensed CC BY-SA 4.0
Jeff Snider
15y ago
0
Generated from our catalog & community — verify before relying on it.
Sudden tracking jumps on long exposures are often caused by mount mechanics rather than camera settings. Based on the community advice, check these points:
- Balance the mount carefully. On a German equatorial mount, the east side should be slightly heavier so the gears stay loaded in one direction. Too much, too little, or reversed imbalance can let the gears shift and cause a jump.
- Watch for the balance point crossing. If the scope and counterweights are near vertical alignment, the load can shift from one side to the other. If possible, avoid exposing through that point or wait until the mount is clearly on one side.
- Don’t overload the mount. If the telescope/camera setup is near or beyond the mount’s practical capacity, tracking can become erratic.
If you use a fork mount, the balancing advice may differ, but the general idea is the same: keep the drive train under steady load and avoid configurations where weight suddenly shifts.
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