Re: EXOS 2 GT Payload Capacity

Bill Black

Hi All,
I have a data point to share in this thread.
I use an older Celestron 8" SCT (NexStar 8SE orange tube) modified with an electric crayford focuser and flocking in the tube.
I have my 80mm APO piggyback mounted on top of the SCT, so I have both wide angle and tight field going at the same time.
I'm using a Losmandy D-style rail on the SCT with Farpoint clamps to keep the whole thing sturdy on the EXOS II puck.

The set-up is about 27 lbs and I have 27 lbs of counterweight on the mount as well. Similar to Vince, I get a total RMS error in the 0.6 to 0.8 arcsec range on an average night reported by PHDII.
On a night of good seeing, I can get a total RMS error of about 0.5 arcsec and on a bad night I've seen it climb as high 1.3 arcsec.
In PHD II shift clicking the guide button to force a recalibration is a must anytime I change something with the set-up. Then a little trial and error to go through fine-tuning the guiding algorithms.

Here's a pic of my current set up and some results.
The image of M51 is a stack of 4 5-minute exposures shot through the SCT+0.63 reducer/flattener using a ZWO ASI294MCPro camera.


Location: Dallas, GA
 Celestron C8, AstroTech 80mm APO

Mounts: EXOS II PMC-Eight, LXD75

Cameras: ZWO ASI294MCPro, ASI385

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