NEO Planner V4.5 - CCD / CMOS Parameters - Explanations
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These settings are the fifth and last step in getting NEO Planner up and running.
Finally you define
some CCD / CMOS parameters for the planning process.
Some parameters relating to your
CCD / CMOS 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 in the past!
Tycho Tracker by
Daniel Parrott is now the state-of-the-art program for astrometricians.
The active observatory is displayed.
The CCD / CMOS 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 for N.I.N.A.'s advanced sequencer.
Resolution CCD in arcsec/pixel:
Enter the resolution of the CCD chip in arcsec/pixel 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.
In order to determine the best exposure time for each object, NEO Planner requires an
FWHM value that allows 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 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) / velocity in s/min * 60
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 primarily on the aperture or the 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 more difficult to
find weak objects in the stacked images.
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.
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.
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:
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 ensures that at least the
specified number of images are used in the planning list, regardless of whether they are
actually needed for a measurement or not.
If you intend to search for new
objects in the planning list using the Synthetic Tracker,
we recommend entering at least 36 images at this point, based on the experience
of our users.
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 measurements (stacks) / 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 group value manually in the planning list in the Revise Window.
This parameter defines the time the telescope needs to move to the next
object and to lock in.
This can also be the time in seconds that elapses on average for
manual work between observing two objects.
Waiting period after the swing:
Use this time span in seconds to give the guider enough time to activate himself after panning the telescope.
If in the settings of N.I.N.A. autofocus parameters are activated, you can enter the corresponding period of time in seconds here.