Matching Stars
• Have to find the minimum distance between all stars that are input and the candidate stars
• Set star-finding threshold to 1*Sigma to include as many stars as possible
• Distances between true (i) and candidate stars (j):

• Chose a 3 pixel separation as the limit for matching stars between the input simulated data and candidate data
Star Finding Threhold

• Plotted fraction of stars matched in the simulated Double Cluster with varying threshold values
• Appears 5*Sigma is an appropriate choice

Scaling Correction

• Goal: correct the scaling error for the real HR diagram (from 20170119 meeting)
• Get Aladin coordinates of 2 bright stars for the Visual and Blue images used to make HR
• Double Cluster blue frame in Aladin indicating 2 coordinates:

• Converting RA/DEC to pixel coordinates:
• Transformation Equation:
• Where (x,y) is the transformed coordinate, m is the transformation matrix, (x,y) is the reference pixel obtained from the header of the new fits file from Astrometry.net, and (delta_x,delta_y) is the reference pixel converted from RA/DEC.
•  Visual Blue Cental Coord RA: 02h 22m 05.712sDec: +57° 11' 09.516"Degrees (35.524, 57.186) RA: 02h 22m 06.101sDec: +57° 11' 07.288"Degrees (35.525, 57.185) Reference Coord (deg) (delta) (35.5401978009, 57.173493981) (35.5475695422, 57.1718325267) Reference Pixel (v) (710.564499521, 582.921770788) (691.959394509, 588.543775601) TransformationMatrix [[-0.000168531158698, -5.13170131402E-06] [4.85829972477E-06, -0.000168690594262]] [[-0.000168632203737, -5.10181679782E-06] [4.90637384969E-06, -0.000168703688821]] Inverted Matrix [[-5938.8289203, -180.66387345][171.03864644, 5933.21591892]] [[-5924.85229703, 179.17516318][-172.31123147, -5922.34174989]

• Converted Reference coordinate into pixel coordinates the same way Aaron did for simulation
• Reference Coord into Pixel coordinates (delta) = (818.31717994, 435.103886)
• (v)' = (710.42435476, 582.99914435)
• vstar1: [[ 171.87468786][ 80.055386 ]]
vstar1_prime: [[ 171.73454309][ 80.13275956]]
vstar2: [[ 957.24304638][ 93.475386 ]]
vstar2_prime: [[ 957.10290161][ 93.55275956]]
Error Propagation
• Calculated flux as sum over pixels, subtracting background:
• : pixel ADU. Assume Poisson distributed, hence
• : background value. Determined, along with error, via filter method.
• Therefore variance of flux given by:
• Magnitude calculated using equation:
• Therefore magnitude variance given by:
• Errors shown on zoomed section of simulated candidate HR diagram:

Astrometry files

-- AaronAndrews - 30 Jan 2017

Topic attachments
I Attachment History Action Size Date Who Comment
png CodeCogsEqn_1.png r1 manage 1.8 K 31 Jan 2017 - 21:47 AnishaVadher Transformation Equation
png DistancesBetweenStars.png r1 manage 28.7 K 01 Feb 2017 - 10:52 AnishaVadher Distances between true (i) and candidate stars (j)
png DoubleCluster_40s_blue_5_ASTRO_Aladin_Annotated.png r1 manage 1994.6 K 31 Jan 2017 - 14:44 AnishaVadher Double Cluster blue frame in Aladin indicating 2 coordinates
png HR_Errors1.png r1 manage 28.8 K 30 Jan 2017 - 14:54 AaronAndrews HR with errors, simulated double cluster
png HR_Errors2.png r1 manage 31.1 K 30 Jan 2017 - 14:54 AaronAndrews HR with errors, simulated double cluster (zoomed)
png Hist_dij_InputOutput_1Sigma_20.png r1 manage 31.9 K 31 Jan 2017 - 15:21 LauraBevilacqua distances between all input and output stars
png Hist_dij_InputOutput_2000.png r1 manage 38.0 K 31 Jan 2017 - 15:22 LauraBevilacqua distances between all input and output stars
png Transform.png r1 manage 51.2 K 31 Jan 2017 - 21:33 AnishaVadher Converting RA/DEC to pixel coordinates
png fractionStarsMatched.png r1 manage 32.9 K 31 Jan 2017 - 15:18 LauraBevilacqua fraction of stars matched as a function of threshold

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Topic revision: r8 - 01 Feb 2017 - LauraBevilacqua

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