Synthesizing Ti-poly stray light images.

[Analysis by tipl_sl_components.pro, tipl_disk_comp.pro, etc.]

15-May-2014 18:25:03

Stray light components:

1. Wood Grain pattern.

Extracted by subtracting the smoothed image.

Wood grain image. [stray light] - [wood grain]

There found a destorsion in the solar disk profile.

Vertical profile of the disk Horizontal profile of the disk

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

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

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

4. Example of synthesizing..

Example of synthesizing.

synthesized disk component. [syn-disk]*[v-filt]*[h-filt]+[wdg]

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.

observedsynthesized vertical profileshorizontal profiles

[memo]