Affiliation
American Association of Variable Star Observers (AAVSO)
Tue, 03/11/2014 - 21:01
Here are the transformation coefficients for TMO61:
Tv_bv = -0.075 +/- 0.004
Tv_vi = -0.065 +/- 0.007
Ti_vi = 0.029 +/- 0.009
Tbv = 1.273 +/- 0.022
Tvr = 1.004 +/- 0.014
Tri = 0.816 +/- 0.011
Tvi = 0.911 +/- 0.008
Note that Tbv is quite large. The KAF8300 does not have very good blue response, which shows up when you are transforming. I did not see any nonlinearity in Tbv over the color range of standard stars that I was using, but when the coefficient gets large, it is usually useful to think about a quadratic fit rather than a pure linear fit.
Arme
Quadratic terms are obviously the next step, but it is useful to remember that cool-enough stars can have huge molecular absorption bands which can only be roughly approximated by the next term in a polynomial expansion.
There is a qualitative difference between how well one can expect a very-reddened star to be transformed relative to a very cool star.
Cheers,
Doug
Attached are updated transform coeffs from images collected on 190108..
description= TG - Version TG_V7.3 beta 5, Telescope= TM061, Time created (UT) = 2019_02_26_21:39:02
[Coefficients]
Tbv= 1.043
Tb_bv= 0.024
Tv_bv= -0.019
Tvr= 0.997
Tv_vr= -0.031
Tr_vr= -0.051
Tri= 1.032
Tr_ri= -0.049
Ti_ri= -0.034
Tvi= 1.005
Tv_vi= -0.017
Ti_vi= -0.014
Tr_vi= -0.028
[Error]
Tbv= 0.015
Tb_bv= 0.013
Tv_bv= 0.012
Tvr= 0.034
Tv_vr= 0.020
Tr_vr= 0.028
Tri= 0.029
Tr_ri= 0.028
Ti_ri= 0.071
Tvi= 0.017
Tv_vi= 0.011
Ti_vi= 0.033
Tr_vi= 0.017
[R Squared Values]
Tbv= 0.984
Tb_bv= 0.083
Tv_bv= 0.106
Tvr= 0.970
Tv_vr= 0.082
Tr_vr= 0.141
Tri= 0.952
Tr_ri= 0.094
Ti_ri= 0.142
Tvi= 0.988
Tv_vi= 0.083
Ti_vi= 0.126
Tr_vi= 0.102
TMO61 now uses a QHY600 camera. New coefficients have been generated. The infrared filter is a Sloan i' filter but the coeffs provided below transform the infrared magnitudes to a Cousins I magnitude.
[Setup]
description= TG - Version 6.8, Telescope= TMO61_QHY600, Time created (UT) = 2022_04_19_01:06:57
[Coefficients]
Tbv= 1.372
Tb_bv= 0.156
Tbr= 1.239
Tb_br= 0.104
Tb_bi= 0.082
Tbi= 1.190
Tv_bv= -0.098
Tvr= 1.039
Tv_vr= -0.185
Tr_vr= -0.218
Tri= 1.047
Tr_ri= -0.281
Ti_ri= -0.331
Tvi= 1.036
Tv_vi= -0.104
Ti_vi= -0.142
Tr_vi= -0.122
[Error]
Tbv= 0.016
Tb_bv= 0.015
Tbr= 0.011
Tb_br= 0.010
Tb_bi= 0.008
Tbi= 0.012
Tv_bv= 0.015
Tvr= 0.014
Tv_vr= 0.030
Tr_vr= 0.035
Tri= 0.025
Tr_ri= 0.041
Ti_ri= 0.056
Tvi= 0.015
Tv_vi= 0.016
Ti_vi= 0.026
Tr_vi= 0.019
[R Squared Values]
Tbv= 0.996
Tb_bv= 0.691
Tbr= 0.998
Tb_br= 0.693
Tb_bi= 0.691
Tbi= 0.996
Tv_bv= 0.432
Tvr= 0.990
Tv_vr= 0.398
Tr_vr= 0.435
Tri= 0.969
Tr_ri= 0.516
Ti_ri= 0.377
Tvi= 0.988
Tv_vi= 0.428
Ti_vi= 0.336
Tr_vi= 0.465