Mississauga Centre RASC

106th Meeting

                                                      Members’ Night 

Day:                Friday May 23, 2008

Chair:               Randy Attwood

Speakers:          Randy Attwood

                         Chris Malicki

                          William Callahan

                          Roy Swanson

                         Bob Anderson

The Sky for June 2008

Randy Attwood demonstrated the sky for June 2008 using Starry Night Pro software.  He showed how Mars would pas through the beehive cluster M44 in cancer, and he demonstrated Saturn near Regulus.   The Big Dipper is a guidepost for other stars and  constellations as well as to Polaris, the North Star.  Polaris is not the brightest star in the sky but due to its position near the North Pole, has other stars rotating around it.   The arc of the Dipper’s handle goes to Arcturus and further on to Spica.  Randy noted that the ISS passes through the bowl of the Big Dipper on this evening  

 He also described Vega, Deneb and Altair as the Summer Triangle and their respective constellations.

Astrophotography with a Digital SLR

Chris Malicki recently purchased a Canon XTi, a camera recommended by SkyNews for astrophotography.  He showed a number of his unguided images including the Moon, Mars in the Beehive Cluster and the rising full Moon over Lake Ontario.  He encouraged others with digital cameras to take astroimages. 

Telescopes

William Callahan spoke about different types of telescopes.  A telescope is an engineered system and each type has its strengths and weaknesses.  A telescope is a combination of mirrors and lenses. 

The first telescope was made by Hans Lipperby in 1608 as a machine for seeing things close than they are.  The actual name “telescope” was given to Galileo’s instrument and means “far seeing”.    

The refractor has a glass lens to bend incoming light and includes binoculars.  It has the highest performance per inch of aperture and its high contrast makes it best for planetary observing.  Stars are sharp to the edge of the field.  The disadvantages are highest price per inch, need for collimating using a star test, and susceptibility to dewing.  It often has an inconvenient observing position and is susceptible to dewing.

The reflector uses mirrors to bring light to a common point.  Reflectors are either  obstructed or un-obstructed and come in many different subcategories.  They have the lowest price per inch of aperture.  Large sizes are easy to produce and are readily available.  They are not as susceptible to dewing  and have convenient viewing positions. 

Obstructed designs have the disadvantage of lower contrast; the telescopes can be bulky to transport; the open tube makes the mirror susceptible to dirt.  They also re3quire regular collimation.  Short focal length scopes also have chromatic aberration at the edge of the field. 

Catadioptric telescopes have lenses and mirrors enabling a compact design.  This is a good general purpose telescope, fashionable for astrophotography, holding its collimation well and requiring little maintenance.  There is however a very high obstruction ratio and small field of view with a long focal ratio as well as proneness to dewing and high cost. 

In conclusion, the best telescope is the one used on a regular basis, size does matter and binoculars are essentially two little telescopes. 

The Sky in June

Roy Swanson described the constellations visible in June including Ursa Major and Ursa Minor and the pointers to Polaris as well as the Big Dipper’s arc going to Arcturus and Spica.  The main highway in the sky is the ecliptic where Jupiter is now visible and where the Moon occults stars.  During the solstices , the Sun is overhead at the Tropic of Cancer or Capricorn.  This would have been fine over 2,000 years ago, but at present the Sun is overhead in Taurus during the solstice. Roy asked what the southern tropic should be called correctly. 

Astroimages

Bob Anderson described the software of his observatory and demonstrated it in real time.  He showed images of M51 and M3

After the meeting, many members observed a bright pass of the International Space Station form the parking lot at UTM.

 Submitted by Chris Malicki, Secretary  Chris Malicki, Secretary                               back to Miss Centre. meeting reports page
Mississauga Centre RASC