TSX Bisque TCS Periodic error – The West check box

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When training Periodic Error Correction on a Paramount using the Bisque TSC – Periodic Error Correction – Compute PEC Curve tab, the West check box can be confusing.

For the West box if your mount is pointing East with the camera at 0° position angle (PA) and you flip the mount (with no rotation of the image train) to collect data West of the meridian the camera is now at 180° PA (upside down).  In this case you would check the West box when you save the fit data to the mount.

If you’re on the West side but the camera is at 0° PA (not upside down) you would not check the West box.

Basically 0° camera PA no West check box

180° camera PA check the West box, regardless of pier side.

The exception to this is if your system produces a mirror image, this is why checking camera PA with image link is important, it tells you if the image is mirrored or not.  If mirrored you basically reverse the above.

If you find the PEC has doubled the box is most likely the problem.  In this case you would just do the opposite and re save the log and grab another correction log to confirm.

Notes: for a raw PE tracking log the West box does not matter, only when you save to mount as the box is telling the control system if the curve is inverted or not.

Camera position angle is very important when collecting data for the PE curve, the camera must be at an angle of either 0° or 180° give or take a degree or so.

Ti Pro Dome shutter wind restraint mod

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This is a mod for the wind restraint system on the Ti Pro dome. The cables keep the middle shutter (which uses gravity only to stay on the dome unless in the fully closed position in which case it is locked in) in place during windy conditions during a close. I say during a close as you should not be opening the dome if its too windy. Sometimes wind does kick up during the night and the weather sensor (Boltwood, SkyAlert, AAG CloudWatcher) initiates the shut down command. The wind restraint does its job well but over the years we’ve had some issues as it wears.

What happens is as the shutter is opened and closed over many nights the cables eat in to the aluminum cable guides. Here is a image of the cable guides with cable doing their thing.

After a few hundred open / close cycles you can get wear on the guides from the cable dragging over them. There is no pressure as the cables are loose but the open / close action of the aluminum guides with the cable running through them as the shutter moves wears out a small channel in the guide as seen here.

If the cable happens to catch in the worn out channel on shutter close you can, depending on which shutter control you have, either snap a cable (new shutter control as of 2014) or pull (stretch) the close spring (right side front, looking in from home position) and rat nest the windlass screw on the old system. Here are before and after images of the spring on the old style windlass system.

Here is the close spring on the old windlass system in good condition.

This is a the result of the wind restraint catching and the close spring stretching.

On the new system the (one of two) cable snaps but the shutter still gets closed however on the old system once the spring is 4+ feet long (see image above) the windlass lose its tension and you get the rat nest with the shutter stuck about a foot from closed. Not good if you are remote and a long way away. Replacing the guides with regular maintenance works for the most part but we’ve been caught out with both shutter systems when it seemed we had a few months to go before guide replacement was required on the domes.

The mod is (at least for our domes) to use Polyurethane tubing and replace the guides with snug fit clamps. In our testing it will take many years for the cable to wear through the tubing if it ever does.

The clamps are 1/4″ ID and fit the tubing snugly. Going bigger does not seem to be an issue, 1/2″ or 5/8″ ID would be good as well (with the appropriate OD tubing). The clamps run a bit closer to the shutter lip but there is plenty of clearance and so far it is running smoothly.

This is 1/4″ OD x 5/32 ID Polyurethane tubing in white, very flexible and can handle -40 F ~ 160 F temps so weather should not be a problem.

Here is the shutter all together with the wind restraint mod.