Thursday, June 21, 2012

Spectroscopes then and now

The WYSIWYG principle myBlog is so crucial for understanding the advances of space sciences from the times of Galileo Galilei on.

But there is also another principle - DYUWYS or Do You Understand What You See?

Here is an example of this principle - there is only about 150 years between the making of the two instruments depicted. But while the first one has been of fundamental importance to the history of science the second one is "just one among many" modern spectroscopes and is filling in the - many - missing details.

We wish plenty of people with positive DYUWYS will benefit from the Italian marvel. But do not despair if you do not have access to such tools or the budget to get your own Echelle. For It is not only in the power of the instruments and sharpness of eyes but also in what is between the ears of the viewer.

Kirchhoffs firrst spectroscope (1896)

There has been some progress in the making of these instruments since Kirchhoff's times as seen, for example, in the impressive tool installed in Campo Dei Fiori (Varese).

Schiaparelli Observatory Spectrograph (2008)
An Echelle Spectrograph is installed at Cassegrain F20 focus of the 0.6m reflector. It has been completely designed and built by Paolo Valisa and took first light on sept 2008.

It is equipped with a 2192x1472 SBIG XME CCD Camera.

Echelle grating is an R2 79 lines/mm and with 100mm camera lens gives 0.15 (bin 1) or 0.3 (bin 2) A/pixel dispersion at Halfa.

Cross disperser is a 300 l/mm transmission grating and from order 57 to order 26 covers the 3900-8600 range.

Spectral resolution is usually 12'000 (with 2.5 arcsec slit) but can attain 18'000 for bright sources (1 arcsec slit).

Radial velocity measurements routinely attain 1 Km/sec precision with a RMS error of 0.7 Km/sec.
Schiaparelli Observatory

No comments:

Post a Comment