I drove up to New York and picked up all of the electronics, cabinets, etc for completing the installation of telescopes into the observatory.
Got everything installed, and began to discover various issues. I will deal with each issue in detail in separate posts.
First, using a dome brings in a number of problems. First, the telescope stack is big – everything just fits inside the dome. The top Tak is within a foot of the dome wall. This makes it tricky to see out of the slit, especially to the South and North. The scope looks out the slit at a very oblique angle.
My existing equipment will not work in the dome. Specifically, I had previously had the Tak and William Optics Guide scope mounted on the sides of the Edge11. This does not work in the dome – first, the geometry requires the scope to be centered over the RA/Dec axes. It cannot be offset to the side, the calculations do not take that into account. Thus, a side positioned scope will often not be able to look out the slit.
This implies the William Optics cannot be used, I can’t mount three scope vertically, because a) I do not have the hardware to do it, b) if I managed it, flexure would be terrible, c) the stack will not fit inside the dome, and d) I can’t get two scopes to look out the slit. Well, I might be able to get the Tak and WO, but not the WO and E11.
I got an ST-i guide scope and lens kit, which is supposed to provide a very small, lightweight guiding option. Had problems getting it to work; somehow the Windows system was not properly handling the USB drivers. Eventually I ran Windows Update, did a bunch of updates, and the ST-i started working. Now I find that in fact, the ST-i is not usable as a guide scope. It has an image scale of 15.2 arcseconds per pixel, which is way too big for guiding the Sky90 accurately, much less the E11. It sounds like the camera itself is nice, but the lens piece is not appropriate at all. I don’t know what SBig is intending with this setup.
So, the Tak will need to guide using the internal ST2K chip. Alternatively, if I can get the Paramount set up accurately enough, maybe the ProTrack system will remove any need for guiding.
The Edge11? Once I decided to remove the WO guide scope, I had intended to guide using the sky90. However, this doesn’t look feasible – I don’t think I can get both scopes to look out the dome at the same time. I think I will need an Off Axis Guider (OAG) to guide the E11. I will use the ST-i on the OAG, once I figure out which one to get.
OK, other issues.
It has been a real pain getting the Dome shutters to work. See separate post. They still do not work correctly; I have to be there to close the shutters because they physically do not close right. The software is wacky, has a poorly designed interface and various bugs. I am currently working with a beta version of 2.1.3. It is impossible to get hold of Stan, their forum has very little traffic.
See separate posts.
1. The initial setup has strange flexure? issues – the TPoint scatterplot has a very distinct N/S distribution. I suspect the various counterweights, which are necessary because the focuser is attached to the rings, which means I cannot rotate the scope. The camera is all threaded connections, resulting in the camera being sideways (assymetric to the scope stack). This in turn requires significant counterweights (about 12 pounds) to balance the scope. I’m not convinced it is well balanced in the end anyway, and probably leads to flexure issues.
2) Odd thing, if the scope is just tracking without any guiding, then both the RA and Dec positions steadily drift over time. Guiding will remove this, but clearly ProTrack does not handle it. I tested both with and without ProTrack running and the results were identical. Bisque thinks this is also due to flexure? They clearly don’t like my setup and will blame it for all problems.
3) I still do not have a perfect polar alignment. I doubt the slight offset from the pole is enough to cause the drift I am seeing, but I want to get it more accurate. It seems like every time I run a TPoint it changes the offset instructions. I don’t know if a 25 point run gives the same results as a 50 point run as a 300 point run. I guess I need to test some of these options to get a better feel for the results.