Title:              Solar Astrometry with Pinholes
Authors:            Sigismondi, Costantino; Ludovico, Cesario
Affiliation:        AA(ICRA International Center for Relativistic 
                    Astrophysics), AB(University of Rome ""La Sapienza"" 
                    Solar Physics Laboratory)
Publication:        Effective Teaching and Learning of Astronomy, 25th 
                    meeting of the IAU, Special Session 4, 24-25 July, 
                    2003 in Sydney, Australia, meeting abstract
Publication Date:   00/2003
Origin:             IAU
Bibliographic Code: 2003IAUSS...4E..39S

                               Abstract
A flat mirror projects sunlight onto a framed pinhole. The pinhole 
produces the solar disk's image of diameter Di on a screen 
parallel to the frame posed at focal distance f better in a room. For an 
ideal point-like pinhole the angular solar diameter is tan(D)=Di/f and 
can be measured: 

1.	like Kepler comparing the disk with pre-drawn disks of known 
diameter; 2.	 measuring Di on the image (possible errors: identifying 
the true diameter among chords; problems due to the motion of the image; 
limb darkening); 3.	timing the passage of the disk perpendicularly to a 
profile posed before the screen (error sources: not perpendicular path; 
uncertainty on the limb's contact times). 4.	Using two equal 
pinholes built on the same frame at distance d between centers measuring 
the focal fc where the disks are in contact; tan(D)=d/fc (main error 
source: fc uncertainty). 

All methods have to deal with systematic errors due to diffraction and 
to the finite opening of the pinhole. The data analysis is discussed in 
the four methods. 

They are experiments with easy to find and low cost material good to 
make indoor demonstrations offering to students different levels of 
complexity in setup strategies and data analysis. 




Title:              Pinhole Solar Monitor to Detect 0.01''RADIUS 
                    Variations
Authors:            Sigismondi, Costantino; Contento, Carla
Affiliation:        AA(ICRA International Center for Relativistic 
                    Astrophysics), AB(University of Rome ""La Sapienza"" 
                    Solar Physics Lab. G28)
Publication:        Solar and Solar-Like Oscillations: Insights and 
                    Challenges for the Sun and Stars, 25th meeting of 
                    the IAU, Joint Discussion 12, 18 July 2003, Sydney, 
                    Australia
Publication Date:   00/2003
Origin:             IAU
Bibliographic Code: 2003IAUJD..12E..16S

                               Abstract
The Pinhole Solar Monitor (PSM) is a small space-device with two 
pinholes projecting two identical images on the focal plane. It has the 
advantage to be an astigmatic heliometer without optics compact without 
need of accurate pointing and costless. On the payload of a satellite 
PSM exploits the side facing the Sun and monitors the secular variations 
of the angular solar diameter D. 

Two pinholes of equal radius r are built on the same rigid platform at 
distance d between the centers; they project two images on the focal 
plane a flat screen parallel to the platform at distance f. When those 
images are in contact tan(D)=d/f. 

The contact between the two solar limbs is simulated with a raytracer 
and studied numerically. 

The focal length of contact about 1 meter can be measured with a system 
of encoder-actuators within 10 micron of precision. Although d and r are 
measurable within a micron of accuracy they introduce errors in the 
calculation of D which are systematic due to thermal stability in the 
space. 

With such a compact device an accuracy of 0.01 arcseconds is expected 
evaluating the variations of the mean angular solar radius D/2~960 
arcseconds.