UFOCapture Night Sky Observation Guide V2.0


4. Post processing

4.1 Object Analysis

Step 20 Installation of UFOAnalyzer

Step 21 Profile setting

Profile setting is the most important and most difficult step. You should set your observation conditions as correct as possible to get most accurate results.

To set parameters, you need at least one fine and clear night's observation results of UFOCaptureV2 including *.xml *M.bmp and *P.jpg or *P.bmp.

You are recommended to use clips that contains famous fixed star or constellation , because you must know the direction of camera by degrees. And the elevation of camera is recommend to be medium, because it is very difficult to distinguish direction error or rotation error around zenith.

All parameters effects each other. There is no straight way. Try and error is needed. Do not change many parameters at once or you will be in chaos. Most of the parameters depend on camera and lens, so advice from someone who uses same equipments will be great help.

Once you have decided your profile parameter, you can use same parameter as long as you use same equipments and direction.

Profile parameters are below.

Step 21-1 (initial setting)

Step 21-2 (rough setting FOV)

Step 21-3 (rough setting of distortion)

Step 21-4 (fine tuning)

This is a sample of successful tuning result.

All star image(blue circle) are match to reference star which are calculated from star map data(yellow dot).

You can tune number of reference stars by changing Display Mag .

There are still stand alone blue circles. They may be dim star, planets, hot spot of CCD, clouds or ground objects.

This sample show the case when Altitude(G0) is a bit small.

All blue circles are equally below the yellow dots.

This means actual FOV was a little above the Altitude data.

This sample show the case when Direction(S0) is a bit small ( this is northern view).

All blue circles are equally a bit left of yellow dots.

This means actual FOV was a little right of the Direction data.

This sample show the case when Rot(deg) is a bit small.

All blue circles are equally rotated from the yellow dots.

This means actual FOV was a little rotated.

This sample show the case when FOV H&V(deg) is a bit small.

All blue circles comes a bit inside of yellow dots.

This means actual FOV was a little larger.

This sample show the case when FOV V(deg) is fair but H is a bit large.

Horizontally, all blue circles comes a bit inside of yellow dots. But vertical positions are fair.

These phenomena happened when the captured pixel was not true square.

In this case a pixel has a bit shorter horizontal edge than vertical edge.

Do not tune FOV H, but Set X/Yratio a bit smaller than it is.

This sample show the opposite case of previous one. This sample shows when only FOV H is a bit large.

Horizontally, all blue circles comes a bit outside of yellow dots. But vertical positions are fair.

In this case a pixel has a bit longer horizontal edge than vertical edge.

Do not tune FOV H or V, but Set X/Yratio a bit larger than it is.

This sample shows the case when Lens k2 is too small.

Blue and yellow meets near edge of the FOV, but blue come equally inside in the center area of FOV.

Try increase Lens k2 a bit.

The position of yellow dots are calculated by the equation of

R = k3*r*r*r + k2*r*r + (1-k3-k2)r

where r is the distance from the optical center position, and R is compensated distance from the optical center position to the star position.

This sample shows the case when Lens k3 is too small.

Blue and yellow meets near edge of the FOV, but blue come inside.

The difference becomes smaller when the star is near the center.

Try increase Lens k3 a bit.

This sample shows the case when the true optical center position is a bit right .

Compensation of k2 and k3 differs its effect between left half and right half.

Try increase center offset x a bit .

This sample shows the case when the true optical center position is a bit low .

Compensation of k2 and k3 differs its effect between upper half and lower half.

Try increase center offset y a bit .

Step 22 Manual measurement

You can measure the direction and altitude of every pixel manually when profile setting has been done.