Three Fundamental “Sciences”
• Measuring “Distance”, Position & “Scale” Astrometry
• Measuring Brightness and Intensity Photometry
• Measuring “Colour” Spectroscopy
Exciting science that you can do from the back yard!
Astrometry
How big are the lunar features in this image?
August 29, 2012H-alpha filter0.001 s exposureED80Atik 314L+ cameraTKUCO
Some Math …
RS
The Small Angle Formula R = S where:• R = distance from object• = angle that the object subtends in the sky• S = distance across the object
* Angle in radians
The Scale of Your Telescope• Scale in (seconds of arc)/mm found by:
• In the previous image a ED80 telescope was used so the scale is (206265)/(600 mm) = 343.8 “/mm
• The Atik 314L+ has 6.45 m pixels, so each pixel has a scale of 342.8”/mm × 0.00645mm/px = 2.22 “/px when used with the ED80
• By measuring the number of pixels you can measure the angle that an object or feature subtends
scalefocal length206,265
850 px = 3457 km(0.5% error)
304 px = 1236 km
Distance = 0.002524 AUs r
pxs AU 149 598 000 km/AU)
s km px
2.2"/(0.002524 )(
206265"4.027 /
Some other images…
• Capuanus Crater:– December 26,2009– C14, f/11 – Imaging source DMK2104 – 2000 frames– Distance = 0.002523 AU– Scale = 0.20”/px = 0.37 km/px
• Apennines (Eratsothenes, Archimedes)
– March 1, 2012– C14, f/7– Atik 314L+– 20 frames (0.005 s)– Scale = 0.52”/px– Distance = 0.00262 AU
• Jupiter– November 5, 2011– Distance = 3.98101 AU– C14, f/11– Imaging Source DMK2104– LRGB (~2000 frames each)– Scale = 0.29”/px =
837 km/px 170 px =142 000 km
159 px = 133 000 km
Oblateness = (142 -133)/142 = 6.3%
• M57– August 26, 2011– C14 f/7– ST7E– LRGB– Distance = 2300 ly– Scale 1.49”/px =
0.017 ly/px
160 px = 2.7 ly
• M15– August 21, 2011– C14 f/7– ST7E– LRGB– Distance = 33 Kly– Scale 1.49”/px =
0.238 ly/px
534 px = 127 ly
Photometry – Measuring Changes in Brightness
• Intrinsic Variables– Scuti– SX Phe
• Novae and Supernovae• Cataclysmic Variables
Consumer grade CCD cameras…• Capable of doing excellent science!• Modest cost (< $2000)• Excellent software support• Monochrome with no anti-blooming is
preferred• Pixel size should be carefully matched
to image scale – need to oversample• Capable of milli-magnitude precision
photometry
Atik 314L+
SBIG ST7E
SX Phoenicis Variables
• BL Camelopardalis– Average mag 13.1 – Period
• 0.0389d• 56 minutes – this is
an exciting system to watch!!
40 s integration, C14 f/7ST7E camera – KAF400 detector
November 9, 2009
The Light-Curve…
November 9, 2009, (C2-C1) = 0.007 mag
BL CamTeff 7730 KAge ~4GaMetal poorPeriod shows a Small change over time!
DY Pegasi … A Nice Intro to SX Phe
• A great star!– Bright (m = 10.3)– Excellent Check and
Comparison stars– Well placed for fall
observations
Data collected with 8” Newtonian and SpectraSource Lynxx (TC211)
Cataclysmic Variable Stars
• Binary stars that are exchanging mass
• One of the stars is compact• Hot spot forms on accetion
disk• Accretion disk around
compact star produces variability
• A rewarding study for amateurs!
Two exemplar CVs…• DW Uma
– Period (d) 0.136606– Mag 14 - 18
TKUCO 120 s image 0.32 f/4.8
• GK Persei– Period (d) 1.996803 d– Mag 11.5 - ?
TKUCO 60 s image 0.32 f/4.8
Other Photometric Delights!• Novae and Supernovae• Algol systems• Asteroids
September 29, 2004SN 2004ET0.32 f/4.8 Newtonian ST7E camera
NGC 694630s exposure
Spectroscopy
• Broad and Narrow band filter imaging• Low Resolution Spectroscopy• Medium – High Resolution Spectroscopy
Broadband Colour Imaging
L
R
G
B
M27 LRGB, August 2011, C14 f/7ST7E
Narrow Band Imaging
• H• H• SII• OIII
H S II O III
C14 f/7Atik 314L+March 1, 2012
LRGB image of central region of M51 C14 f/7 ST7E
L filter with H overlay showing star forming regions along spiral arms
C14 f/7 Atik 314L+
Stellar Spectra (Low R)
• Remarkably easy to do – even with modest equipment!– Small telescope w/wo tracking– CCD or DSLR– Rainbow Optics or Star Analyzer grating
• Introduces a fascinating new direction for amateurs
Some samples… (trailed images with Atik 314L+, Orion 80 mm ED)
Vega, Teff = 9600 K
Altair, Teff = 6900 K – 8500 K
Altair is a very fast rotator and is squished like a football!
Hotter at the poles by about 20%
Ca II line
Note Deneb’s narrow lines!
Other Interesting Stars…
T = 31 000 K
T = 7 100 K
T = 8 400 K A5
F2
B0.5e
Be Star with disk
Which is these is the hottest star?
Planetary Nebulae
The “Eskimo” – NGC 2392C14 f/7 10 minutesApril 21, 2011
The reason nebula filters work!
Measuring the Expansion of the Universe!
3C273 C14 f/7 60 minutesST7E April 5, 2011
Rest Frame (A)
Measured (A)
z
H 4860 5666 806 0.166
H 6563 7562 990 0.151
z
Zaverage = 0.159
Universal Expansion
• What does z = 0.159 mean?– Apparent recessional velocity is 0.159C = 47 700 km/s!– Hubble expansion law:– Hubble’s constant H = 70 km/s/Mpc– R = 681 Mpc = 2.2 billion light years!
v HR
Medium/High Resolution Spectroscopy• For more advanced work• Requires robust mount and
tracking• Need as much aperture as
possible• BUT – still well within the
reach of advanced amateurs and astronomy clubs!
The L200 Littrow Configuration
• Can resolve to about 1 A (R = 3000)• Built from a kit, cost ~$1000• Capable of useful research on Be, WR and
Algol type stars (and much more!)
The Solar Spectrum
ST7E on C14
Altair
Homebrew for under $200!
And it Works!
The Magnesium Triplet…
R > 5000!
Some References…
• Christian Buil - http://www.astrosurf.com/buil/
• Tom Field - RealTimeSpectroscopy (RSPEC) http://www.rspec-astro.com
• Rainbow Optics Spectroscopes http://www.starspectroscope.com/
• Center for Backyard Astrophysics (CBA) http://cbastro.org/