Aligning with N.I.N.A. using Plate Solving

Alignment by the use of the program "N.I.N.A." by means of Plate Solving

The free program N.I.N.A. can be used to align the telescope to Polaris without a clear view. By rotating the right ascension axis, the software moves to three points and takes an image, which is adjusted via 'Plate Solving' by the theoretical position at the given rotation. Prerequisite is a previously executed "Star Alignment" (Easy Align) and a focusing (see menu item 'Proceeding' - 'Focusing with the Bahtinov-mask').

Information about Plate Solving:

'Plate Solving' is a very useful function especially for beginners in the field of astrophotography. Thereby the software creates an image of the starry sky, which is currently imaged on the chip, and compares this star image with a database. If the ASTAP database is used, it can be stored locally on the computer, so that no internet is needed. The program and the database can be downloaded from https://www.hnsky.org/astap.htm.

After selecting the program for the corresponding operating system, it is sufficient if only the 'H18' database is downloaded for the moment. This is installed in the installation folder of the ASTAP program.

Afterwards, it must be set in N.I.N.A. that this database is to be accessed during plate solving. For this the following settings are to be made under the point 'Options' at 'Plate Solving:

Based on the comparison with the star bank images, the software determines to which point the telescope is currently aligned. This knowledge is not only important for the 'Three Point Polar Alignment', but especially for finding the deep sky objects. After the initial determination of the coordinates, the software can specify exactly which travel distance is required again to correctly center the target object on the chip in the event of a deviation.

An important prerequisite is the correct setting of the focal length of the telescope (additional elements such as reducers or barlow must be included here) and the specification of the pixel size of the camera. Only with this information a proper evaluation during plate solving is possible.

To align the telescope with N.I.N.A., the plugin 'Three Point Polar Alignment' must be installed.

After installation, a new icon will appear in the top right corner of the program under 'Tools'.

By activating this icon, a new tab will appear in the image display window and you can start the alignment.

Step	Description	Illustration
(1a)	Manual Mode' remains set to 'OFF'. The three celestial coordinates required for alignment are to be approached automatically.
(1b)	The distance of the approached points is entered via 'Measure Point Distance'. It has to be taken care that after the first capturing the next two points after the rotation show a sky picture without obstacles (trees, houses, ...). In this case the third point is 20° away.
(1c)	Via 'Telescope Move Rate' the speed is defined, with which the three sky sections are approached. This can also be increased depending on the mount properties.
(1d)	The direction of rotation of the right ascension axis is defined via 'Direction East'. With 'ON' the telescope rotates in direction East, with 'OFF' in direction West.
(1e)	The next line specifies the starting point. Either the point where the mount is currently located can be used, or a point can be specified manually. Here it is advisable to move the telescope with the hand control box to a suitable place with free sky and to set the point 'Start from current position' to 'ON'.
(1f)	In the last line, the exposure inputs are to be defined. Here, a possible filter is defined and the exposure time of the single image. If possible, no narrowband filter should be installed in the beam path. This would greatly increase the exposure time and make it more difficult to adjust the axes quickly and easily.
(1g)	To the right, the camera settings are entered. The binning remains unchanged. In this case, a high value can be selected for the gain. The image quality is not important. Only the recognition of the stars is important.
(1h)	The 'Solver Search Radius' can be left as it is. If there is no match, the program moves the search field in a square spiral and increases the distance from the starting position to the specified radius. The start button can now be clicked.
(2)	After starting, the software automatically moves to the three points, takes a picture at each point and compares it with the database.	Approaching the three points for plate solving [1]
(3)	The deviations are calculated from the theoretical values of the database and the real values, which were created by the rotation. Depending on the entered exposure time, new images are created one after the other, during which the deviation is corrected by turning the azimuth screw and adjusting the pole height in the specified direction.	Deviations calculated from plate solving [1]
(4)	If the deviation is small enough (e.g. < 1'), the alignment is complete and capturing can begin.	Values corrected by turning the azimuth screw and pole height adjustment [1]

Source:
[1] https://www.youtube.com/watch?v=JI1tzoBhkH8