NEO Planner V4.3  -  CCD Parameter  -  Explanations


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Within the picture, click on the zone that you want to be explained: (not in all browsers available)

 

These settings are the fifth and last step in getting NEO Planner up and running.  

Finally you define some CCD parameters for the planning process.
Some parameters relating to your CCD camera and the behavior of your mount are required.
They are primarily required to calculate the exposure times, the number of exposures and the timing during the night of observation.
Correct entry of these parameters is crucial for the usability of the planning results.

Plausibility checks or actions are usually only carried out after leaving the cursor in the input field.

The Astrometrica program mentioned in the description was written by Herbert Raab from Austria. At this point, too, my sincere thanks for the opportunity to use his program!

IAU Observatory Code:

The active observatory is displayed.

Camera selection:

The CCD parameters can be entered individually for up to 5 cameras/equipment. By clicking in the selection menu, the camera settings are displayed and can be adjusted.
At the same time, the active camera used in Execute Planning or Execute Search is determined by clicking on it. The active camera is displayed in the relevant windows.

Binning XML and JSON for N.I.N.A.:  

Binning is required for the XML and JSON transaction files.

Resolution CCD in arcsec/pixel:  

Enter the resolution of the CCD chip in arcsec/pixel chip here. If you are observing with e.g. 2 * 2 or 3 * 3 binning, multiply the basic resolution value with 2 or 3.

Resolution FWHM in arcsec/pixel:

The FWHM is a frequently discussed value among observers. Everyone would like to emphasize the particularly good seeing of their location.
But let's just be realistic when entering this value. A good starting point is the indication of the seeing value in the .log files of Astrometrica.
To determine the best exposure time for each object, NEO Planner requires an FWHM value that enables precise measurement based on the movement of the objects.
So it is best to enter a value that roughly corresponds to the best FWHM that the location historically provides, according to the value in Astrometrica .log file.
In this way, NEO Planner can largely ensure that an object is not exposed for too long in order to obtain its position measurement in Astometrica as reliably as possible.

Use resolution CCD (C) or FWHM (F):

The choice of which kind of resolution you use for calculating the exposure time is up to you and your experience with your equipment.
Either enter C for CCD resolution or F for the seeing value FWHM.

The formula for calculating the exposure time of an object is:

exposure time (sec) = best FWHM (or Resolution CCD) * 60 / velocity in s/min

whereby the maximum exposure time is not exceeded. The exposure time is calculated and used to the nearest tenth of a second, and it is, as can easily be seen,
dependent solely on the resolution of the CCD camera or the measured best FWHM and the relative speed of the object and not on the aperture or type of your telescope.

For amateur telescopes, the use of the FWHM value is generally sufficient,
because otherwise exposure times that are too short would make it difficult to find weak objects in the stacked images.

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sky background mag/arcsec2:    

My former programs, which did the planning for the objects, related to my equipment alone.
The particular challenge was therefore to calculate the correct number of images for a single stack for other equipment as well.
After a few days of thinking, I got the idea to include the value of the sky background in the calculation.

Because the combination of local conditions, CCD sensitivity and telescope aperture ultimately results in the achieved sky background value
represented in the .log files of ADES Astrometrica.
The sky background in mag/arcsec2 is now used as an individual quality value for calculating the number of images required for a single stack.
In fact, this value is the most important during planning.

Equipment calibration: Technique of calculating the sky background with ADES Astrometrica:

Creation of some well-focused and calibrated light images (bias, dark, flat) with an exposure time of 10 seconds and an altitude of approx. 55 degree.
which are won on moonless nights around the meridian.
Avoid bright stars in and around the FOV and regions of the Milky Way. It doesn't matter using the best sky for the measurements, rather average nights.

Each of the images is measured with Astrometrica and the usual settings and set the value 3 in the Aperture Radius.
After the data reduction, click on a star-free field and astrometry.
For the "Object verification" select any proposed asteroid and confirm (Accept).
Then select "View Log File" via the File tab and search for "Sky Background". Make a note of this value.

If you like, calculate the sky background average from the images obtained from different nights.
This average value is then entered in the settings.

The calculation of the sky background with the above method determines a good comparison value for all possible combinations of CCD cameras and telescopes
of all sizes and types in relation to the reference value of the sky background I gained with my equipment under the mentioned conditions.

Astrometrica or Tycho may show an SB value that is too high or too low for images obtained with CMOS chips.
The calibration value of NEO Planner refers to CCD chips and therefore you have to enter a lower or higher value in the settings in this case.
Therefore you have to approach the value through experiments.

Observe the sum of exposures per group calculated by the NEO planner and adjust the sky background value in the settings,
if the
sum of exposures per stack (group) seem too low or too high to you. Then lower or higher the sky background value.

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Sky Background:

Compute SB: Technique of calculating the sky background with Tycho:

For Tycho users, the sky background can be calculated using two values.
On the one hand, the zero point of a recording is required, and on the other hand, the ADC value of a star-free area of the image is required.

The technique is initially similar to the Astrometrica method:

Creation of some well-focused and calibrated light images (bias, dark, flat) with an exposure time of 10 seconds and an altitude of approx. 55 degree.
which are won on moonless nights around the meridian.
Avoid bright stars in and around the FOV and regions of the Milky Way. It doesn't matter using the best sky for the measurements, rather average nights.
 

Then do the following in Tycho:

Load the 10 second image(s) from the Image Manager and List tab.
Align and plate solve the calibrated images over the "Action" tab. Then push there "View Images". On the Image Viewer "File" tab  run "Load Star Catalog".
Then push the "Photometry" tab and compute MZERO. Record this value as the zero point.

Then move the cursor to a star-free place in the image. Note the ADU value, which is displayed at the bottom in the Image Viewer.
Repeat this method with other images and form an ADU mean.

The example shown is not the 10 seconds reference image from K87.

The sky background is then calculated using the following formula: SB = Zero Point - 2.5 * LOG10 (ADU)
Reference of the formula: Rainer Kracht, Astronomer:
Die Messung der Himmelshelligkeit. (rkracht.de)
 

 

Calculation method of the number of images per stack:

Let's go into the depth of the calculation.

The reference values come from an image with a sky background value of 18.74 mag = RefSB on K87.
An asteroid was photographed with 16.6 arc seconds / min = Refvelo and a brightness of 19.4 mag = Refmag.
50 stacked images = Refimg were necessary so that the asteroid could be measured reliably.
I use exactly these reference values on K87 to calculate the number of necessary images for all objects for my equipment.

Some basics first:

The difference between two integer magnitudes means a reduction or increase in brightness of 2.512 times
The formula for exponential growth or decay is then 2.512difference  

 

First step for calculation the number of images for one stack according to the brightness in mag of the object:

dmag (Difference) = Refmag  - Vmag(Object)

The number of images increases or decreases exponentially by 2.512 dmag

Number of images (1) = Numimg1 according to the reference value of Refimg:

Exponential factor (with negative value of dmag = growth)
Exponential divisor (with positive value  of dmag = decay)

Growth:  Numimg1 = Refimg * 2.512 dmag   * -1
Decay:    Numimg1 = Refimg / 2.512 dmag   

 

Second step for calculation the number of images for one stack according to the velocity of the object:

Number of images (2) = Numimg2  according to the reference value of Refvelo:

Numimg2 = Numimg1 * Objvelo / Refvelo

I use exactly rounded Numimg2 on K87 for the number of images for a single stack.

Third step for calculation the number of images for one stack according to the sky background for any equipment:

SBdiff (Difference) = RefSB - settingsSB

Exponential divisor (with negative value of SBdiff = growth) !
Exponential factor (with positive value  of SBdiff = decay)    !

Growth:  Numimg3 = Numimg2 / 2.512 SBdiff  * -1
Decay:    Numimg3 = Numimg2 *2.512 SBdiff   

The minimum number of images per stack is 1.

 

This method made it possible to calculate the necessary image sequences independently of the equipment.
 

I would like to add one important hint. Objects of the solar system, regardless of their type, have different albedos due to their chemical and physical properties.
So it is perfectly normal that a carbon-rich asteroid is harder to astrometry than a ferrous one.
The same is true for highly condensed comas in comets as compared to less strongly condensed comas.
However, NEO Planner cannot know the albedo of the individual objects. Therefore everyone has to expect that the observation can go wrong due to too few images in the stack.

For years I have been observing NEO and comets with my formula and have achieved useful results.
Both the reference data and the formulas therefore have a certain practical value, and by no means a scientific one.

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FoV calculation:

If desired, by entering the field of view (FoV) of the CCD or CMOS chip, the number of groups (stacks) can be automatically recalculated
with a simultaneous increase in the recording positions for each planning, if the object threatens to leave the FoV during the exposure series.

The path length of an object through the FoV is calculated based on the movement of the object in arcsec/min, its position angle,
the exposure times including download load times and the number of exposures per series.

Allocation of positions per object:
Normal planning takes place first, then the excesses of the FoV are determined for objects, which leads to a recalculation of the planning in terms of time and content.
The procedure is as follows:

First, it is checked whether the movement of the object is greater than the maximum path according to the number of shots and the groups set (3 or 4 or 11, etc.).
If not, the position remains as it is.
If so, the position needs to be adjusted. There are several options for reacting to exceeding the maximum path length.
In order to simplify the complexity, the number of groups is reduced to 1 in this case and the positions are supplemented by the number of groups originally required.
This means that, for example, a series of recordings per object is divided from the original 4 groups to 4 x 1 group.
In the revise, there are then, for example, four positions for such objects instead of one, including a repositioning and complete recalculation of all parameters for NINA.

However, new groups only if the CCD FOV is filled in the settings and the number of groups is > 1.

In addition, width and height are essential for the Execute Mosaic Search.

 

Width of the camera field in arcmin:

Total width of the FoV

Height of the camera field in arcmin:

Total height of the FoV.

Maximum path of the object trail:

Maximum path that an object is allowed to travel from the center of the image to the edge during a series of exposures.
The maximum path of 100% is automatically determined by the FoV and can be reduced by entering a percentage.
90% means that the maximum path length of the FoV is shortened by 10%, 80% means that the maximum path length is shortened by 20%.
This ensures that the object is not recorded up to the edge.

If it is found in a series of recordings that the maximum permissible path is exceeded, the planner splits the observation of the object into several positions.
At the same time, the number of groups (stacks) per position is reduced to 01.
For each object position, R.A. and decl. and all exposure values and observation times are recalculated.

The division into several positions can then be adjusted manually in the revise window.
You can delete too many positions there or adjust the number of groups (stacks) as you like.
In the case of planning, the maximum path length is always recalculated if the number of groups is > 01.

 

 

Calculation of recordings:

Minimum number of images:

At least three images are required for the required three measurements per object and night.
As a rule, this value of 03 should therefore be set here. This applies to all surveying programs such as Astrometrica or Tycho etc.
However, there are at least two cases where the minimum number of images should or must be increased.

1th For observations around the full moon time +/- 3-4 days you should at least double the value.

2nd When using Tycho's Synthetic tracker for astrometry, Tycho requires at least 11 images.
        This value does not play a role when calculating the number of total images, but it does play a role in determining the number of images in the final planning in the Revice Window.
        NEO Planner then ensures that at least 11 images are used in the planning list, regardless of whether they are actually needed for a measurement or not.

 

Maximum exposure time in seconds:

After calculating the exposure time, a check is made to determine whether the maximum exposure time set here has been exceeded. If so, this time is used.
You can find information about the exposure time here

Download time of one image in seconds:

The download time for each individual image is a very important value.
Especially with fast objects with short exposure times and many images per stack, the download time plays an important role in calculating the total exposure time of an object.
This value should be specified to the second.

Number of groups (stacks) of exposures/object:

The group value basically means how many measurements for each single object should be sent to the MPC.
After planning, you can increase this value
for each object in the Revise Window if you want.

This sensitive value is based on the rules of the MPC, which determine the quality of the measurements.
In order to meet the requirements of independent stacks and at least two or three measurements per object,
this parameter ensures that enough recordings per object are always suggested in the planning.
Three measurements per object should be mandatory. It can happen that the MPC rejects two measurements per object.
For a measurement that complies with the rules, NEO Planner calculates, on the one hand, the number of recordings per individual stack using the sky background,
and on the other hand, the number of groups ensures that enough stacks are available for the measurement.
With bright objects or with a deep sky background, individual unstacked images can of course also be measured if the quality is available.

NEO Planner calculates all the necessary planning data for the measurement of NEO and comets according to the individual settings of each observer.
However, the suggested values are not compulsory and it is up to the observer to evaluate the images.

In the case of a group value of <6, the following applies:

Neo Planner uses the entered value from the settings at speeds of the object greater than 3 arcsec / minute.
At speeds less than 3 arcsec / min. the value is multiplied by 2, at speeds less than 1 arcsec / min. the value is multiplied by 3 and at speeds less than 0.1 by 5.

Automatic increase at lower s/min  Y/N:

If the checkbox is set, the group (stack) value per object is automatically increased based on the speed, as described above. If not, there is no automatic increase.
You can edit the value manually in the planning list in the Revise Window.

 

Swing time of the telescope:

On K87, a program-generated script for Orchestrate takes over the job of controlling the telescope throughout the night.
This parameter now includes the time the telescope needs to move to the next object and to lock in.
Since my focuser is temperature-controlled, there is no need to focus on the K87 after panning. Guiding is also automatic.

If the equipment does not have a fully automatic control and has to be refocused,
you should enter the time in seconds that elapses on average for manual work between observing two objects.

Waiting period after the swing:

I use this time span in seconds on K87 to give the guider enough time to activate himself after panning the telescope.

 

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Copyright: The author of NEO Planner and all sites of this web is Bernhard Haeusler, Dettelbach, Germany, all rights reserved