unexpected mosaicing behaviour
Posted: Tue Oct 15, 2013 1:27 pm
I am not quite sure how to describe the problem, but here goes...
We took some L-band data for C2290 last year in two configurations:
In May we did EW352 and then in July we did 750A. The observations consisted of mosaicing 24 pointings. The setup for each run was identical, just the array was different.
We've processed the July 750A data and it all looks very good. But we are having problems with the May EW352 data. The first 9 pointings in the mosaic look fine and combine well with the other data. However, the rest of the pointings look like a mess with emission where we don't expect to see it. In fact, you can look at images of the pointings separately and see that in overlap areas the emission does not match up. It is like the telescope was pointing at the wrong place.
But I have checked the mosaic file used in SCHED with the header information in the individual pointings and they agree well. So I would guess the telescope was pointing in the right direction for each position. But we have no idea why the emission we see in these data does not match what we expect. Furthermore, it appears that we can manually apply offsets to the individual pointings and get a reasonably good match of the emission. That suggests the mosaic positions were wrong. But, as I said, the mosaic file checks out with the headers.
I realise this is probably not enough information to diagnose a problem, but I am hoping to at least get the ball rolling with this post.
Later. Andrew xxx
We took some L-band data for C2290 last year in two configurations:
In May we did EW352 and then in July we did 750A. The observations consisted of mosaicing 24 pointings. The setup for each run was identical, just the array was different.
We've processed the July 750A data and it all looks very good. But we are having problems with the May EW352 data. The first 9 pointings in the mosaic look fine and combine well with the other data. However, the rest of the pointings look like a mess with emission where we don't expect to see it. In fact, you can look at images of the pointings separately and see that in overlap areas the emission does not match up. It is like the telescope was pointing at the wrong place.
But I have checked the mosaic file used in SCHED with the header information in the individual pointings and they agree well. So I would guess the telescope was pointing in the right direction for each position. But we have no idea why the emission we see in these data does not match what we expect. Furthermore, it appears that we can manually apply offsets to the individual pointings and get a reasonably good match of the emission. That suggests the mosaic positions were wrong. But, as I said, the mosaic file checks out with the headers.
I realise this is probably not enough information to diagnose a problem, but I am hoping to at least get the ball rolling with this post.
Later. Andrew xxx