Hello Jasem and INDI guru's,

Peter Polakovic got a new version of the INDI Server to me tonight, and indeed, the dome now frequently rotates! Solved - thank you!

However, telescope pointing is off everywhere but the South East quadrant. I suspect something may be wrong with the units in the Dome Parameters. My carefully measured values are here:

Inches Meters
Radius 45 1.14
Width 25 0.64
N -2.75 -0.07
E -0.75 -0.02
Up - 3.75 -0.10
OTA 15 0.38

To test the parameters, I set the scope to pointing due north, and rotated it so the GEM weight bar was flat, with the weights in the East, then later in the West. I set the meridian appropriately for each case. With the scope in the East, the scope optical axis was aligned with the east-side dome slot edge, partially occluding it's view (it looked like my 11" scope could move at least 7" to the West to get it closer to centered). With the scope in the West, the scope top was aligned with the west edge, enabling a view, but was still very close to the dome slot (it looked like it should move 3" towards the East).

This suggested to me that OTA offset was too small (even though it was carefully and easily measured from the intersection of RA and DEC to the optical axis), as well as there being an E-W offset, in the W direction, of about 4". I increased the OTA offset to 0.5m, which resulted in the western side scope being nearly centered in the dome slot, and the eastern side scope position being just inside the east edge of the dome. I don't understand how this could be the case though, as the size of the offset is clearly smaller than 0.5m.

Next I tried offsetting the E-W dome parameters 4" to the east (-0.13m total). The dome didn't move at all with this change. I then tried -0.5m. This led to a small positional change, but not enough to center the scope in the slot. Finally, I tried a -1m change. The dome moved noticeably, but still not far enough. This doesn't make much sense, as a 1m move of the pier in a small 8' dome is huge!

Is it possible that the units are not all in meters? For example, these observations make sense if the Radius and width are in meters, but the N, E, and Up are in centimeters. I don't yet understand the OTA offset value, unless it is from the DEC-RA to the far side/top of the scope. 0.38 to 0.5 made a noticeable difference in dome position, in the right direction, and I think adding a little more would help. It is almost like it needs to be 1.5X to 2X the distance between the RA-DEC intersection and the optical axis.

Does any of this sound like a known issue?

As always, big thanks,

Scott

Read More...