Theatre Hipparchus

CCDWare is writing some nifty code.

Periodic Error Correcting (PEC) my new LXD 75 was made easier with the software program PEMPRO. I have to compliment the authors at CCDWare. The interfaces and set up wizards made it easy for me to get started.

Here is the step by step process I used to measure the PEC data for LXD 75. First the conditions:

It is a beautiful clear night but a bit colder at -22C than I like. There is no room for this set up in the observatory so the pool deck will have to do. No wind. I was using battery power for the laptop with the 1200W unit pictured on the bottom left. Smaller units under the tripod power the CCD imager and scope for extended periods of time on a full charge even at these temperatures. Using a Stellarvue AT1010 and a Starlight Express H9C imager.

I used Markab in Pegasus the the entire evening. Apparent magnitude 2.46 and at a altitude that didn't cause stress on the AT1010 focuser. This is the Nighthawks standard focuser and under the weight of a H9C there is slippage when pointing near the zenith. I think there are some simple mods for this.

The Program  

I tried Pempro on evaluation and took an immediate liking to it. How simple to use. After entering some data to the set up wizards, plug your stuff in and start firing.

This is the curve that is created after several 12 minute runs of the LXD 75. The periodic error on average was +13.9/-12.3. This curve is played back into the mount with the appropriate settings on the autostar handpaddle.

Here you see the yellow band playing back into the mount. Of note: on the LXD 75 the PEC Train is reflected in "counts" of 150. Rather than seconds like some other mounts the autostar had a count up to 150. I timed it and it was 12 minutes.

The Anomaly

On December 13 under similar conditions I did an run using the same settings and image scales and for a period of over thirty minutes and had this result.

This was obviously a mistake. During the December 21 run, there were periods of very low periodic error but nothing sustained like the 30 minutes above. I think the error was in my settings but I have to do more investigation to sort it out. When I originally posted this on Cloudy Nights, the graph met with some scepticism including my own.   

I think the numbers +13/-13 from the trials I did last December 21 night are in line with what this mount's PE actually is. 

Imaging with the LXD 75 and Stellarvue Nighthawk. Here is 40 at 60 seconds unguided.

The Equipment  

I have to tip my hat to the equipment. These were difficult conditions, Check out the Nighthawk at the end of five hours worth.

In summary:

I plan to do more testing on all of my mounts with the idea of improving periodic error. I do think the equipment is superior to mounts of even five years ago and I wanted to know more about the periodic error for each.

Please feel free to leave comments, experiences or advice in the section below.

Best,

David