| Telescope | MDM 1.3m |
| Date | 9/26/95 |
| Instrument | Nellie |
| Filter | V |
| Exposure Time |
900 sec |
Problem:Large dewar windows (which are especially cold) can have condensation forming at the center of the window whenever the humidity starts to rise. Different telltale symptoms can show up. One giveaway is more pronounced (darker) dust rings in the center. Other possibilities are the sudden appearance of filamentary structure or bright 'explosions' in the center of the image due to light from bright stars being dispersed by the dew. In some cases, the condensation on the dewar window may freeze, causing frost on the dewar window. |
Fix:Fix depends on the observatory but may include dewar window heating or blowing dry nitrogen into the setup. |
Smoke-like, bright feature on the image after filling dewar