4 Results of the first experimental run

This seeing monitor has been tested on the nights of January 15, 16 and 17 at the Astrophysical Observatory of Asiago. During the same night, the images of the edge of the Moon where collected in two or more runs, separated by an amount of time greater than the typical e-folding time of the atmospheric perturbations (Racine 1996).
The results obtained from the collected data are summarized in Table 2.

  

Table 2: Measured values for the isokinetic patch and for the Fried parameter during the three nights of the test. The last two columns represent mean values for the same night

As previously explained with this experiment one can simultaneously get both the value of the isokinetic angle, $\theta_0$ (in the third column) and of the Fried parameter, r₀, (fourth column) but the latter is not measured directly.
It is then possible, with the following equation, to recover from r₀ the value of the seeing, here and in the following denoted as $\delta_{\rm sm}$, during the night of test (last column):

$$\delta_{\rm sm} \approx 206265 \left({\lambda \over r_0}\right) \ \ {\rm [arcsec]},$$ (7)

It has not been possible to compare the results of the experiment with other seeing monitors. Nevertheless, during the same nights, astronomers at the Cima Ekar Telescope in Asiago gave an estimate to the seeing from the FWHM of the lines of the Echelle Spectrograph along the spatial scale. A comparison with their estimates (Fig. 6) shows consistency of the data obtained with this experiment, provided that one sums quadratically a blurring effect $\delta_0$ to the seeing measured with our seeing monitor, $\delta_{\rm sm}$:

$$\delta_{\rm ekar} = \sqrt{\delta_0^2 + \delta^2_{\rm sm} }.$$ (8)

The blurring term, $\delta_0$, includes both the effects of dome seeing, of jittering and tracking and of the optical aberrations of the 1.82 m telescope. Unfortunatly we could not measure directly r₀ with our seeing monitor and this is the only way we had to compare our results with an independent estimation.

  

Figure 6: The seeing measured at the Echelle spectrograph of Cima Ekar during the nights of the test is compared to the results obtained with the seeing monitor. The difference observed can be ascribed to dome seeing

A further relation has been searched using the data collected during the experiment. We said that one can partially ascribe to dome seeing and to errors introduced by the telescope the difference observed between the seeing monitor and the Cima Ekar telescope. The mean thermal gradient between the inside and the outside of the dome at Cima Ekar, measured during the three nights of the test, when compared to the difference in the seeing, $\delta_0$, approximatively follows a law of this kind:

$$\delta_0 \approx 0.25 \Delta T.$$ (9)

With three available points, one for each night, it is only possible to show the proportionality between $\Delta T$ and $\delta_0$: a comparison with other "seeing/temperature" relations, as reported for example by Lowne (1979) and by Bridgeland & Jenkins (1997), shows that the data collected with this experiment may fall in the range of values given by those authors.