PROMPT 5 Down

PROMPT 5 has gone down temporarily. The seal on the camera has finally failed (we knew it would eventually) and we had rather large amounts of ice forming. The camera has been sent back to Apogee for repair. P3’s camera recently arrived back from Apogee and is on its way to Chile now. The current plan is to put it onto P5 to bring it back into service.

Recent PROMPT 5 Issues

We recently noticed that PROMPT 5 is having a problem with its filter wheel. Until we get it all sorted out, please be very skeptical of what fitler is used on P5. Right now, we think that the wheel is stuck and is not changing filter properly, so the filter recorded in the header may be incorrect.

–Aaron

Pointing Problem, Redux

The same problem (here) seemed to reassert itself on March 11/12 with all of my images, though everything seemed to function fine for me on March 10/11.  I’m using P4.  An example would be obs 1281 on Mar 11/12 — the image is some field I don’t recognize.  On March 10/11 the same object (obs 1253) lists the same RA and DEC in the image header but this time the object I wanted is present in the field.  Same for other pairs of images from these two nights (i.e. 1253 is fine on Mar 10/11, but points to some other field for obs 1279 on Mar 11/12).

Image Headers

None of my images last night (March 7/8) contained the specified fields (at least on P4).  Do the FITS headers properly list the telescope position?  Any idea what the cause was and whether it will be with us for a time?

Tracking problems

As you may have noticed, I submit rather long runs of time-series images on eclipsing binaries. I finally found time to reduce a several hour long run and found a huge amount of drift on PROMPT 4 — about 20 – 25% of the field! It is large both in dec and right ascension so there is obviously a large polar alignment error on this scope. I am lucky that my comparison stars stayed on the chip. Has anybody else found problems on other scopes? This would normally be of little concern to GRB event observers but is annoying for long runs on one object.

Telescope pointing

I’m wondering about the pointing accuracy of the telescopes. So far I’ve been working with Prompt4 and 2. Prompt4 points pretty accurately in most cases: the object can be off by 100-200 pixels, but usually it is near the image center. Prompt2 seems to point with a lower accuracy. Sometimes the object is near the edge, while in some cases I am not able to identify the area. It’d be helpful to analyse the situation taking into account pointing dependence on the hour angle, air mass, and object coordinates, but it is hard to do without the corresponding information in the image headers.

Trailed Images

What are the conditions underwhich images are trailed? I’ve mostly taken images with PROMPT 4 and most are trailed. I don’t seem to see a strong correlation (as I’d expect from telescope tracking error) with length of exposure, though I haven’t looked exhaustively at this (for example, 40 s, 60 s and 80 s exposures seem roughly trailed to the same extent).