Your astrophotography copilot
Balancing your mount: RA and Dec
Balancing means arranging the weight so each axis stays put when you let go. It takes about five minutes, and it decides how smoothly your mount tracks and how calm your guiding is. Try it in the demo, then follow the steps.
Smoother tracking
A mount tracks by turning a gear at a very steady rate. If the load is lopsided, the gear is pushed unevenly as it turns, and the motion gets slightly jerky. Round stars need a smooth motion.
Easier guiding
A guider can only correct small errors. When the mount is well balanced, the errors are small and the guide graph stays calm. A badly balanced mount makes the guider work much harder.
Less strain on the motors
A heavy side that is not balanced makes the motors lift the load all night. It uses more battery and wears the gears, and it can make the mount stall or slip.
Safer slews and flips
A balanced load swings over the top evenly. An unbalanced one can drop suddenly when a clutch is loosened, or swing too fast in a slew.
Drag the slider and watch the load tip. Add a camera and guide scope and the balance point moves, which is why you balance with everything on.
Simplified drawing. Real mounts differ in detail, but the idea is the same: the heavier side drops until the load is equal on both sides.
The heavy side drops the moment the clutch is released. The motor has to fight it, so expect jerky tracking, poor guiding and extra wear.
The weight side is heavy: move the weight in.
On a real mount, hold the tube or bar with one hand before you loosen the clutch, so a badly balanced load cannot swing.
RA axis (the counterweight)
- 1
Load everything you will use
Mount the scope, camera, guide scope, finder, dew heater and cables first. Balance with the real load, not a bare tube.
- 2
Make the counterweight bar level
Loosen the RA clutch and swing the bar so it points out to the side, level with the ground. The scope is then on the opposite side.
- 3
Hold on, then release carefully
Keep a hand on the bar or tube. If you let go and one side drops, it is out of balance. Slow, gentle release is safest.
- 4
Slide the counterweight until it stays level
Move the weight along the bar until the assembly stays put when you let go. A heavier counterweight sits closer in, and a lighter one farther out.
- 5
Lock the counterweight and the clutch
Tighten the counterweight lock and the RA clutch. Then do the Dec axis.
Dec axis (the scope in its clamp)
- 1
Do RA first and lock its clutch
Keep the RA axis fixed so the tube cannot swing around while you work on Dec.
- 2
Make the tube level
Loosen the Dec clutch and turn the tube until it is level with the ground, then hold it.
- 3
Release slowly and watch which end drops
If the front sinks, the scope is front-heavy. If the rear sinks, it is rear-heavy.
- 4
Slide the scope in the dovetail clamp
Loosen the clamp a little while holding the scope, slide it toward the lighter end (if the front sinks, slide the scope back), and tighten. Never loosen the clamp without a hand on the tube.
- 5
Check it pointing at the sky too
Balance changes when the camera angle or a heavier accessory changes. Check again after adding a camera, filter wheel or guide scope.
Mounts differ in how their clutches and locks work, so check your own manual for the exact controls and the maximum payload. Small trackers have fewer adjustments but the same idea.
- Balancing without the camera, guide scope or cables on, then adding them later.
- Letting go of the tube with the clutch loose and no hand ready. Always hold it first.
- Balancing only one axis. Both RA and Dec need it.
- Using the clutch to hold an imbalance. The clutch is for locking, not for carrying the load.
- Forgetting to rebalance after changing gear, such as a heavier camera, a dew shield or a filter wheel.
- Leaving too little cable slack, so a cable pulls on the camera and quietly changes the balance as the mount turns.
- What does it mean to balance an equatorial mount?
- It means arranging the weight so the mount holds the load without help from the motors or clutches. On the RA axis you slide the counterweight along its bar, and on the Dec axis you slide the telescope in its clamp, until each axis stays level when you let go.
- Should I leave the mount perfectly balanced or a little off?
- Perfect balance is a fine goal for a short session without guiding. For guided imaging many people leave RA a little heavy on the east side, so the gears stay pressed together rather than rattling as the load flips from one side to the other. Keep it small, and keep it the same all night. Check what your mount's maker recommends.
- Do I need to rebalance after a meridian flip?
- Not usually, since the load is the same and only its side changes. But any small imbalance you left on purpose switches sides after the flip, so watch the guiding graph. Also check that the cables still have enough slack.
- How do I balance a small star tracker like a Star Adventurer?
- The idea is the same, with fewer adjustments. Trackers usually motorize only the RA axis, and the camera head has its own ball head or clamp. Use the counterweight shaft and kit if you have one, and slide the load in the clamp so the head stays put when you release it. Follow your tracker's manual for its payload and balance advice.
- How often should I balance?
- Every time the load changes, and a quick check at the start of each session. If you always mount the same gear, you will find the positions repeat, and a mark on the bar saves time.
Next in the night: polar alignment, the night checklist and the meridian flip.