type : AstroArt plugin

author : Patrick Mergan

version : 1.01

install : simply copy pineutback.dll onto your AstroArt directory

This plugin adjusts the color balance of an image by making the background neutral. First, select a (small) rectangle on the image, on a place where there is only background ( no stars! ), then call the plugin.

The plugin first reads the R, G and B values of all the pixels inside the selected rectangle. Then, it calculates the mean of all R, G and B values. Then it calculates the offsets needed in order to bring the background neutral. Finally, it applies those offsets to all pixels of the image.

Click here to download the plugin.

Neutral Back

Type : AstroArt plugin

Author : Patrick Mergan

Version : 1.01

install : simply copy pimeas.dll onto your AstroArt directory

This plugin calculates the angular separation and the position angle of 2 points in an astrometric calibrated image.

1. •first, perform an astrometric calibration on your image (refer to the help function in Astroart ). Use at least 7 or 8 stars for good results.
   

2. •select 2 points on your image ( for instance the centers of 2 stars in a binary star system )
   

3. •call the plugin
   

To calculate the angular separation, the routine will first retrieve the right ascension and declination of both points.

Then, it calculates the angular separation by means of the 'haversine' method as described on page 111 of "Astronomical Algorithms" of Jean Meeus. This method yields accurate results from 180 degrees down to exactly 0 degrees. Also, the position angle is calculated ( in degrees ).

The plugin is useful for

1. •measuring the separation and position angle of binary stars
   

2. •measuring the (angular) size of any astronomical object in your image
   

3. •finding the separation of any 2 stars
   

4. •etc.
   

Click here to download the plugin.

Measure

type : AstroArt plugin

author : Patrick Mergan

version : 1.01

install : simply copy pidrawline.dll onto your AstroArt directory

With this plugin, you can draw a line on an image.

First, select 2 points in your image. Then, call the plugin.

1. •On a (jpg) color image, a green line will be drawn. The plugin assumes a color image when the value of the first selected pixel < 256
   

2. •On a monochrome 16 bit fits image, the value of the first selected pixel will usually be > 255. Then, a white line will be drawn.
   

This plugin is useful if you want to mark a specific point or object in your image, for instance by drawing a line that points to it. You can draw multiple lines in order to construct an arrow or a rectangle if you like.

Click here to download the plugin.

Drawline

type : AstroArt plugin

author : Patrick Mergan

version : 1.01

install : simply copy piundonut.dll onto your AstroArt directory

Did you ever discover a large donut on your image due to a dust particle the day after you made a long exposure? This is a problem, especially if you don't have a matching flat field to remove it. Or maybe you made a flat field, but the dust particle wasn't there when you made it.

This plugin will try to 'remove' such a donut, or at least it will try to improve the situation so that the image can be stretched deeper before the donut becomes visible.

Do not expect some kind of miracle from this plugin. However, it can be the last straw to grasp when everything else failed. So give it a try ...

Maybe the donut will not become completely invisible, but in most cases the situation improves quite a lot.

We will consider 3 zones of a donut :

1. •the 'core zone' : this is the central part of the donut
   

2. •the 'ring zone': this is the darker zone around the core that has the typical donut shape.
   

3. •the 'outer zone' : this is a zone of 10 pixels thick around the donut. It represents the pixels outside the donut.
   

First, you will have to select 3 points:

1. 1.the center of the donut
   

2. 2.a point at the inner edge of the ring zone
   

3. 3.a point at the outer edge of the ring zone
   

Then : ... call the plugin.

From the 3 points, the radius of the inner and outer edges of the ring zone will be calculated. The plugin will then calculate the mean value of all the pixels in the 'core zone' (m1), the mean value of all the pixels in the 'ring zone' (m2) and the mean value of all the pixels in the 'outer zone' (m3). Then it will apply offsets to the pixels of the core zone and the ring zone to match the mean value of the outer zone.

Remarks :

1. •The selection of the 3 points is quite critical. You can try more than once to obtain the best results.
   

2. •The presence of a bright star in one of the zone can influence the results and can result in overcorrection or undercorrection in some cases. Don't worry: you can always use F9 to undo the corrections.
   

Click here to download the plugin.

Undonut

type : AstroArt plugin

author : Patrick Mergan

version : 2

install : simply copy piundonut2.dll onto your AstroArt directory

This is a new version of the 'undonut' plugin (see above), but with the following improvements:

1. 1.After correcting the donut, the routine will also soften the edges. This will make these edges less visible.
   

2. 2.The plugin now works with a form. First, it will try to correct the donut as good as it can. If you are happy with the result, just click 'accept'.
   Otherwise, you can use the sliders to adjust the inner and/or outer zone.
   

Click here to download the plugin.

Undonut 2

type : AstroArt plugin

author : Patrick Mergan

version : 1

install : simply copy pifalsecolor.dll onto your AstroArt directory

This plugin will create a false color image from a monochrome image.

Once the image is converted to color, you can further use 'color balance' in Astroart to adjust your (false) colors.

Click here to download the plugin.

False Color

type : AstroArt library file

author : Patrick Mergan

version : 1

install : simply copy aafocus.dll onto your AstroArt directory

Whenever you are focusing, you can use the focus window in AstroArt to

do this. You can look at the size of the star displayed, or use the

'focus' or 'FWHM' readings at the bottom of the focus window.

However, whatever you are looking at, you always have to take a look

at the screen of the computer.

Unless your pc is quite close to your telescope, this can be quite

cumbersome. Indeed, oftenly you have to run back and forth between

your telescope and your pc.

This small tool can be a solution : simply copy the file AAfocus.dll

onto your AstroArt directory.

As soon as you start 'focus', the routine will sound a beep after every

new frame. The frequency (tone) of the beep is related to the 'focus'

value.

The first time it is called, the frequency will be 800Hz. During the next

cycles the frequency will be recalculated and a new tone will be produced.

Now it is easy : just stay at the focus knob of your telescope and

listen to the focus. The higher the tone, the better !

Remarks :

-If you started far away from the best focus, it can happen that the tone

becomes too high at a certain moment. Don't worry : stop the focus window

and start again. The routine will then start again from 800 Hz.

-Even when you do not touch your focus knob, you will usually notice that the

frequency changes from frame to frame. This is due to the seeing conditions.

In fact, by listening to the 'melody' it is playing, you can have an idea of

the current seeing conditions ....

-Maybe your neighbours will wonder about hearing some strange beeping sounds

at night. Or maybe your neighbour will tell you next day : " Hey, you achieved

quite a good focus last night ... ".

Of course, you could also use headphones as well.

If you want a whole star party to enjoy your focusing efforts, connect a 100 Watt

amplifier and two large speakerboxes.

Click here to download the plugin.

AAfocus.dll

type : AstroArt plugin

author : Patrick Mergan

version : 1.01

install : simply copy bottomtext.dll onto your AstroArt directory

With this plugin, you can write a text string below your image. This can be used to put some information of your image or it can serve as a caption.

The plugin will first open a form to enter the string that you want below your picture. Then click OK.

A new image is then created which is the same as your original image, but with an extra zone where the string will be written.

Click here to download the plugin.

Bottomtext

type : AstroArt plugin

author : Patrick Mergan

version : 1.01

install : simply copy label.dll onto your AstroArt directory

With this plugin, you can write a text string in your image.

1. •First, select a point in the image, where you want the string to be written.
   

2. •Call the plugin.
   

3. •A form will open to enter the string that you want to write.
   

4. •then click OK
   

With a monochrome image, the intensity of the string will be the same as the maximum pixel value in your image.

With a color image, the maximum value of the green pixels will be used.

This plugin can be useful to put a string like 'NGC1234' close to an astronomical object in your picture, to label binary stars with 'A' and 'B' or to put any string at any place you want. If you want your string outside your picture, you can add an extra zone at the bottom or the top using 'border'. After that, put your string in the extra zone.

Click here to download the plugin.

Label

type : AstroArt plugin

author : Patrick Mergan

version : 1

install : simply copy pihammer.dll onto your AstroArt directory

Let's count a little bit on our imagination. The background of an image could be seen as some kind of aluminium plate on which our (oftenly very faint) objects are scattered like sand.

If you want to 'stretch' your visualisation as much as possible in order to make the fainter parts of an object visible, it is important that your background is very flat. Of course, the best way to make your background flat is to use a good 'flat field' image.

The 'flat field' will:

1. •help to eliminate the 'pixel to pixel' noise coming from the fact that each pixel has not exactly the same sensitivity
   

2. •remove gradients resulting from 'vignetting', especially if you use a focal reducer
   

3. •remove gradients caused by anything which might be in your light path
   

4. •eventually remove dust donuts ( but it is better to keep the dust away !! )
   

However, there are still other things to consider. Also stray light, ( from overall light pollution or even light from nearby street lamps ) can bounce on the inside of your dew cap and bounce around in the interior of your scope. As the telescope moves over a considerable angle during a long exposure, this effect can change over time. It's not always easy to make a good 'flat field'. We also found out that the 'color temperature' of the light used to make the flat is important as well. Flats made with a 'light box' having ordinary bulbs are oftenly useless, because their spectrum is totally different. For that reason, twilight flats are usually the best ones.

Now, suppose you have done everything you can, but the background still has some nasty 'hill'...

What would you do if your background was indeed an aluminium plate ?

Well, you would probably take a hammer and try to knock it down ....

This is exactly what this little plugin will try to do.

The plugin will have an effect on a circular area of your image. First, select a point which is the center of the 'hill'. Then, select a point on the edge of the 'hill'. After that, call the plugin. The 3 boxes at the bottom of the form will tell you :

1. •the ADU value of the center
   

2. •the ADU value of the edge
   

3. •the maximum step used to knock down the center of the hill. This will be 10% or 1% of the difference between the center and the edge, depending on the setting.
   

You can also select the type of curve which is used during hammering :

1. •Cos : a cosine function like 0.5*(cos(dtc*pi/rad)+1) , where dtc = distance to center, rad = the radius of the circular area. At the center, the full step will be used, at the edge it will be zero.
   

2. •Cos2 : a cosine function like cos(dtc*pi/(rad*2)). This is like a cosine from 0 to 90 degrees.
   

3. •Gauss : a curve like a Gauss function ( probability function with a sigma from 0 up to 4 )
   

4. •Lin : a simple linear function.
   

5. •Flt : a curve which is flat until 75% of the radius and then follows a cosine down to zero.
   

Now, each time you push the 'down' button, your hammer will hit the center of the hill .... Bang ... bang ... bang ...

Hope you will succeed in making it flatter...

Click here to download the plugin.

Hammer

type : AstroArt plugin

author : Patrick Mergan

version : 1.01

install : simply copy picrop.dll onto your AstroArt directory

AA4 has a crop function, while AA3 has not. With this little plugin you can crop an image using AA3. Drag a rectangular area in your image and then call the plugin. A new image will be created containing the selected area.

Click here to download the plugin.

Crop

type : AstroArt plugin

author : Patrick Mergan

version : 1.01

install : simply copy piswap.dll onto your AstroArt directory

This plugin will swap the even and odd lines of your image. It can be useful when an exposure has been made with the wrong setting of "swap fields".

Click here to download the plugin.

Swap Fields

type : AstroArt plugin

author : Patrick Mergan

version : 1.01

install : simply copy pispect.dll onto your AstroArt directory

This plugin will help elaborating a spectrum. First, drag a rectangle around the area you want to investigate. Then call the plugin. The plugin will create a new image with the same size as the selected area. However, every pixel in x of the new image will contain the average of all pixels in y. After that, you can adapt the visualisation ( logarithmic) and apply high pass filter if you like. The resulting image can then be used as an input for another program such as Vspect.

Click here to download the plugin.

Spectrum

Listen to the focus!

Index