Neo Planner V2.3  -  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

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:     Attention: When using a CMOS chip, please ask!

My old 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 CCD sensitivity and telescope aperture ultimately results in the achieved sky background value of each recording 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.

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.
 

Calculation method of NEO Planner:

The reference values come from an image with the sky background value of 18.74 mag = RefSB on K87, an asteroid with 16.6 arcsec / 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

But, if the maximum exposure time in the CCD settings was set below 60 seconds and a single exposure therefore takes exactly this time, the following will be corrected:

Numimg2 = Numimg2 * 60 / maximal exposure time   to bring the number of shots to a realistic level.

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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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 of exposures/object:

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 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.

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.

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