ENR CTIO 1.5-m 2025-02-26

1. R. Hernandez came to understand the pointing issue in the beginning of the night. The plumb is good. We first did the zpoint, but slewing to the next three bright stars is not successful and they are no where to be seen in the guider. We take some time check the plumb and zpoint again. The offset to the first science star is more than 5 arcmins in the south. 

2. Around mid-night, the guider can't guide the telescope and can't keep a star in the center of the guiding box in the N-S direction. Even using hand paddle can't move the telescope in the N-S direction. The flashing "GUIDE N' or 'GUIDE S' is on the TCS screen, but nothing moves. After about 5 mins attempts by pressing the SET+N/S or N/S buttons, the telescope finally can move in the N-S direction with the guider off. Then, the guider operates as it should be.

For the first half of the night, the zpoint offset is mostly in the N-S direction with offsets about a few arcmins. For the second half of the night, after doing another zpoint on Omega CMa, the offset is generally in the E-W direction but the offset shrinks to about ~20 arcsecs, regardless of the DEC. It is not clear what improves the pointing accuracy.

>>>> If possible, please check the balance, especially in the DEC. <<<<

3. The ThAr mean counts in slicer mode in the last four frames are lower than other frames taken earlier in the night, including the evening calibration frame. These four frames are visibly faint in DS9. 

#               IMAGE      NPIX      MEAN    STDDEV       MIN       MAX
  chi250226.1003.fits   5751066     1063.     26.56     1000.     1181.
  chi250226.1117.fits   5748601     1062.     26.27      999.     1181.
  chi250226.1118.fits   5748926     1064.      26.9     1002.     1184.
  chi250226.1120.fits   5748375     1063.     26.33      990.     1183.
  chi250226.1122.fits   5747889     1063.     26.32     1000.     1183.
  chi250226.1124.fits   5747554     1063.     26.38     1004.     1184.
  chi250226.1128.fits   5747986     1063.     26.75     1002.     1185.
  chi250226.1129.fits   5747836     1063.     26.54     1005.     1184.
  chi250226.1131.fits   5747134     1062.     26.18     1001.     1182.
  chi250226.1133.fits   5747339     1063.     26.68      997.     1185.
  chi250226.1135.fits   5746510     1062.     26.31      992.     1183.
  chi250226.1136.fits   5746892     1063.     26.67     1006.     1184.
  chi250226.1138.fits   5747922     1063.     26.77      997.     1184.
  chi250226.1140.fits   5746999     1063.     26.73     1003.     1184.
  chi250226.1142.fits   5746933     1063.     26.26     1001.     1184.
  chi250226.1143.fits   5747503     1062.     26.41     1005.     1183.
  chi250226.1145.fits   5748300     1063.     26.75     1006.     1184.
  chi250226.1147.fits   5748225     1062.     26.48      998.     1182.
  chi250226.1149.fits   5746408     1062.     26.21     1000.     1183.
  chi250226.1151.fits   5745583     1063.     26.82      998.     1186.
  chi250226.1153.fits   5746093     1062.     26.96      997.     1186.
  chi250226.1155.fits   5745665     1062.     26.57     1001.     1185.
  chi250226.1157.fits   5746026     1062.     26.48     1001.     1184.
  chi250226.1162.fits   5828773     1048.     22.19     1003.     1119.
  chi250226.1163.fits   5826002     1048.      22.1      998.     1120.
  chi250226.1165.fits   5826391     1047.     22.38     1001.     1120.
  chi250226.1166.fits   5825055     1047.      22.3      997.     1119.