Sedgwick Telescope sees first light on site

The Sedgwick telescope has now had first light at its site.  The telescope is not robotically controllable yet and does not have a full set of instrumentation installed or commissioned on it. This trip was was to check and calibrate the optics on a dark sky, before commissioning can continue.The weather had been sunny all day, with a medium breeze, with thunderhead clouds to the east during late afternoon. Slight breeze until about 9pm, then still for rest of night. Later in the night it turned a bit hazy, with low clouds near the mountains to the south. Not perfect astronomical observing conditions but more than good enough.

Observatory was open and airy all afternoon, with the open shutter facing away from the sun. Had the building been closed all day the telescope would have been cooler at sunset. Ideally we want the telescope and the air inside the observatory to be at the same temperature as the outside air. If there is a difference, you get air currents which makes the stars twinkle more than usual and diffuse objects even fuzzier.

The first step was to test the telescope collimation. This is an important stage in the commissioning process, which checks the alignment of the optics of the telescope. The secondary mirror was adjusted to make sure it gives the best image quality, although it still needs some final tweaking for smooth operation

By 9pm or so we had the telescope on the visual binary star Castor, in the constellation Gemini, which was well placed high in the sky. The image was quite poor and unresolved, although we could tell that it was a double star. The seeing was terrible, boiling with a mix of atmosphere and mirror thermals. The out of focus image indicated the primary mirror needed some alignment tweaking. Once we had done that the image quality improved considerably, so we decided to put the telescope axes through their paces and start slewing around.

By about 10pm we turned the telescope to Saturn, which was well placed near the meridian. With the telescope thermalized a little more, and the atmosphere steadier, Saturn was a pretty nice sight. Several of its satellites were visible, and the thin shadow of the rings was quite dark and obvious running across the globe. The rings are nearly edge-on to our line of sight and very thin, but during moments of steadier seeing we could intermittently see the gap between the inner part of the rings and the edge of the planet. We then looked at M51, the Whirlpool Galaxy. It was quite bright in the eyepiece, and no averted vision was needed to see the spiral structure and knots in the spiral arms.

All in all not a bad first light.

LCOGT staff present: John Hygelund, Derek Johnson , Jon De Vera , and John Martinez (provided the unedited copy)

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