Latest Tass Observations

Back to the APL Astronomy Club Web Page LATEST TASS OBSERVATIONS

October 29, 1998

The JHU/APL Tass Observatory collected data last night as part of a VCO setting evaluation. A new version of the Linux Data Collection software was provided by Chris Albertson and installed on out data collection system. The new version prints out the data collection time interval. Since we are able to command the linux version from our solaris computer, we set up a series of vco setting commands, changing the vco setting every 15 minutes throughout the evening. Although there were problems around 3:00am (The Linux system seemed to be unable to fork a new process), sufficient data was collected through the normal operating region. Data collection began around 6:15pm. The VCO settings were changed at 7:00pm, and were programmed to change every 15 minutes until the last command at 5:00am. The vco settings studied were from 9700 to 10500. Due to the process failure, the last setting was 10340.

The following are the measured average times for each VCO setting.

VCO   Average Time
9700      0.972033
9720      0.971461
9740      0.968872
9760      0.965540
9780      0.965124
9800      0.962854
9820      0.959804
9840      0.958696
9860      0.957135
9880      0.95396
9900      0.95181
9920      0.950979
9940      0.948256
9960      0.94544
9980      0.944135
10000     0.942767
10020     0.939897
10040     0.937895
10060     0.936758
10080     0.934154
10100     0.931591
10120     0.930498
10140     0.928728
10160     0.926010
10180     0.924324
10200     0.922932
10220     0.920662
10240     0.918040
10260     0.916842
10280     0.914946
10300     0.912303
10320     0.910986
10340     0.908543

Note that the images included in this web page represent settings:

9700         First setting
10080       Best Setting for CCD 1 and CCD 2
10200       Best Setting for CCD 0
10280       Optimum Measured Interval
10340       Last Setting for run.

Note that all images were obtained prior to the VCO change (i.e. VCO was now stable and output image represents that VCO setting). All images are raw (no dark current and flat field correction).

Analysis:
TASS Technote 26, (General Considerations for Drift Scanning) suggest that an optimum interval for a telescope pointing at 0 degrees declination should be 0.91416. That corresponds to VCO setting 10280. As can be seen by the data, the performance is not optimum. One possible reason is that the alignment of all three cameras are not the same. CCD1 and CCD2 are slightly more out of alignment than CCD0. It is quite possible that by adjusting the vertical alignment of all three cameras, we can get them to perform at a high quality level at the same VCO setting. It remains to be seen if we should attempt to adjust all three cameras so that the measured time interval matches the target of 0.91416. During the next hands on session, the alignment will be adjusted, and then a sequence of VCO measures will be retaken.

Images:

VCO Setting 9700
CCD0

CCD1

CCD2