Synthesizing Ti-poly stray light images.
[Analysis by tipl_sl_components.pro, tipl_disk_comp.pro, etc.]
| 15-May-2014 18:25:03 |
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Stray light components:
- Disk component.
- Wood Grain pattern.
- Horizontal bias.
- Vertical bias.
1. Wood Grain pattern.
Extracted by subtracting the smoothed image.
| Wood grain image. |
[stray light] - [wood grain] |
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There found a destorsion in the solar disk profile.
| Vertical profile of the disk |
Horizontal profile of the disk |
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Determining the Vertical and Horizontal bias
using the limb-pointed stray light images.
| 8-Aug-2014 19:11:24 |
8-Aug-2014 22:29:05 |
13-May-2015 17:46:46 |
13-May-2015 22:41:45 |
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The
raw value of the k-factor (to correct accumlating dusts) :
2014/05/15 : 1.00
2014/08/08 : 0.99 <--- correction negligible for V-profile.
2015/05/13 : 1.13 <--- correction needed for deriving H-profile.
2. VERTICAL variation of background intensity.
The limb profiles from the N- and S-pole pointed images
also have destortion.
A combination of "slope" and "gaussian" filter was derived in vertical
direction, so that the intensity levels of DC and Polar limb profiles
match after correction.
| Vertical filter profile |
Vertical filter image |
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This vertical filter provides the model (i.e., non-destorted) disk profile,
that is used for generating disk component of stray light pattern.
3. HORIZONTAL variation of background intensity.
Horizontal background was determined by comparing the model disk profile
(derived from the vertical variation study) with the disk profiles
from the disk-center, W-limb and E-limb images.
The conversion factors (from observed profiles to the model) tend to
diverge where the intensity level is low.
So, the good S/N part of each pointing was conbined.
| Horizontal filter profile (raw) |
Horizontal filter profile (conbine & fit) |
Horizontal filter image |
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4. Example of synthesizing..
Example of synthesizing.
| synthesized disk component. |
[syn-disk]*[v-filt]*[h-filt]+[wdg] |
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The
raw value of the k-factor
(to correct accumlating dusts) at the time of observation :
0.89 (@ 2012/09/28).
[stray_light_image @2012/09/28] = [stray_light_image @2014/05/15] * 0.89
Intensity profiles of the sample image
(before/after subtracting synthesized stray light image).
Varification: synthesizing stray light images for the known pointings.
| observed | synthesized |
vertical profiles | horizontal profiles |
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[memo]
- near disk center : intensities are well reproducted (~10% error).
- near the limbs : not very good (~20% error)
- East limb pointing : poor reproduction.
