Validation of the Photometric Method Used for Micropipette Calibration

There are two methods generally used for calibration of micropipettes: the gravimetric method described in ISO 8655-6:2002 and the photometric method described in ISO 8655-7:2005. In order to validate the photometric method, several micropipettes of different capacities from 0.1 µL to 1000 µL were calibrated using both methods (gravimetric and photometric) in two different laboratories, IPQ (Portuguese Institute for Quality) and Artel. These tests were performed by six different operators. The uncertainty for both methods was determined and it was verified that the uncertainty component that has a higher contribution to the final uncertainty budget depends on the volume delivered. In the photometric method for small volumes, the repeatability of the pipette is the largest uncertainty component, but for volumes, larger than 100 µL, the photometric instrument is the most significant source of uncertainty. Based on all the results obtained with this study, one may consider the photometric method validated.

Detection of an optical halo surrounding the spiral galaxy NGC 4565

A halo surrounding the edge-on Sb giant spiral galaxy NGC 4565 has been detected in the spectral band 3800–8600 A using a new photometric instrument, an annular scanning photometer. the halo is brightest close to the galactic nucleus and decreases in brightness until it reaches a level of 1 part in 1000 of the sky at a galactic radius of 6.1 arc minutes or 43 kpc from the galactic center. Because the scan path of the ASP is circular, this point corresponds to a distance of 34 kpc from the galactic plane. For comparison, the Holmberg radius of NGC 4565 is equal to 7 arc minutes or 50 kpc. Preliminary V-I photometric data indicate that the halo becomes redder with increasing galactic radius, exceeding V-I = 1.9. Based on a variety of possible origins for the light, it is concluded that the light is due to stars.

Colorimetry of Martian features by means of area scanning

The contrast between light and dark areas on Mars has been the subject of two photoelectric studies by Younkin (1966) and McCord (1969), both of which were somewhat limited in scope. Younkin's data are based on one night's observations. McCord had a more suitable instrument for making a comparison between two areas on Mars, but still used only six nights. The agreement between these two studies is excellent. However, there is ample evidence from photographs that there are short-term changes in the contrast and brightness of Martian surface features, especially in the case of blue clearing. Visual observations are unsuitable for investigating these changes, due to the limited wavelength range of the eye's sensitivity, as well as the poor accuracy of the eye as a photometric instrument. Even photography is of limited usefulness when high accuracy is desired. Consequently, a program of continuous photoelectric observation of Mars was set up for the 1969 opposition. The technique of area scanning was chosen as the best method of recording the contrast of Martian surface features.