Two Pole Master Questions

[Gordy]

I am seeking advice on the following two questions about setting up the PM.



The manual states that the correct setup for the PM is having the connecting socket on the left side when standing in front and looking at the unit (not the exact words). I presume this means in the southern hemisphere the socket is on the west side of the mount. (Why don't they just say this and make it clear?)





The manual also states that the unit does not have to be placed at the exact centre of rotation of the RA axis. I wonder just how far from the centre of rotation the unit can be before it affects accurate polar alignment? I am making a bracket for my mount and would like to know what I can get away and still have good polar alignment.

[The_bluester (Paul)]

I had that discussion around the traps when I started using one. To make it even less clear the early instructions were different and I think specified east not left (Which is the same thing in the Northern hemisphere) I concluded pointing left was the way to go and stuck with that, but the only time I could see it making any difference would be if you turned on the atmospheric refraction correction (I never did) as if you had it wrong it would correct the wrong way.

By what I have seen they can be a long way off center. Mine is on axis but I have seen them on brackets mounted to the telescope dovetail bar and the EQ8 bracket looks like it places the camera a good 300mm off axis. It will introduce a little parallax but finding the center of rotation will still work fine.

[bojan]

Originally Posted by The_bluester

... By what I have seen they can be a long way off center. Mine is on axis but I have seen them on brackets mounted to the telescope dovetail bar and the EQ8 bracket looks like it places the camera a good 300mm off axis. It will introduce a little parallax but finding the center of rotation will still work fine.

There will not be any parallax error... 300mm is way smaller than radius of Earth orbit around the Sun - and even that is not enough in most cases

[Nikolas (Nik)]

You keep the usb plug facing East so that it is on the right when you are looking at the camera face on.
That is the correct orientation for the southern hemishpere

[Nikolas (Nik)]

https://www.youtube.com/watch?v=R_LgUFZLqIM


This is the best video explaining it all

[The_bluester (Paul)]

Originally Posted by Nikolas

You keep the usb plug facing East so that it is on the right when you are looking at the camera face on.
That is the correct orientation for the southern hemishpere

The original instructions I saw which were northern hemisphere specific specified east. This snip is from another (Northern hemisphere specific set) specifies both East and left for Northern hemisphere use. The current instructions on the QHY site specify pointed left but no compass directions.

With your mount in the park position (weights down, telescope pointing up), stand to
the north of the mount facing south. Insert the quick install plate into the base mount
adapter ensuring that the USB socket faces to the left (east). This position aligns the
PoleMaster’s sensor correctly and makes azimuth and altitude adjustments during
polar alignment more intuitive as the up/down directions on the image will be the
mount's elevation angle directions and the left/right directions will the azimuth angle
directions without there being too much adverse interaction between the two.
Furthermore, when carrying out the atmospheric refraction calibration, which is
required for locations with a latitude of below 40 degrees, this orientation is vital

[The_bluester (Paul)]

For some reason I can't edit the last post to add this. As far as I am aware, what I wrote the first time is correct, apart form the directions of movement being different, the only time the direction of the USB port will make a difference is if you use the atmospheric dispersion correction, which I have never done.

[Nikolas (Nik)]

It works perfectly for me each time oriented to the right as shown in the youtube video

[The_bluester (Paul)]

Do you use the atmospheric refraction correction? I don't, I should do an alignment then look at the altitude setting via drift aligning in PHD2, then do it again with atmospheric refraction correction switched on, check again with PHD2, then flip the Polemaster and do the same again and see what difference it makes. The "Left" instruction was the first one I found when I bought the camera so I have always done it that way.

[Gordy]

Thanks everyone for your advice and info. I now will put it all into effect on the next clear night.