Contents - Index

Filter Factors

There are some differences between the three focus programs that are described here.

FocusMax, Maxim  and PlaneWave Filter Factors





There will be as many entries here as you have defined filters in your camera server program.


Focus Offset: enter how many counts you wish your focuser to move for a given filter. Normally one filter would be the reference and the others would move an amount, either + or -, relative to that reference.  The reference filter should be the filter you select for plate solving - usually a clear or luminance filter.  If your filters are parfocal, i.e. they all focus at the same focuser position, you would enter 0 for all the filter offsets. The button at the top sets all filter offsets to the same value as that of the first filter entry.  If some filters, typically some Halpha filters, are sufficiently non-parfocal, you can speed up the active focusing method considerably by entering the offset.  That way, automatic focusing will start closer to the ultimate focus position. Focus Offsets can be measured automatically using the wizard described here.  When using focus offsets, be sure the system is in focus at the start of the session. A good way to do this is to use CCDAutoPilot's Focus Before Target Run Start as described here.
  • Focus Exposure: As mentioned above, these fields provide a convenient entry point for the FocusMax and Maxim starting exposure.  With most systems, the shortest exposure is suitable for focusing through the clear filter and the exposure time should be increased for less transparent filters.  For example, you might set a 1 sec. exposure for color filters and a 2 - 4 second exposure for narrow band filters such as Halpha or OIII. If the exposure is set to 0, the FocusMax base exposure or the AutoFocus exposure length specified in the PlaneWave control application will be used.


    CCDSoft and TheSkyX Camera Add On @Focus2 Filter Factors



    There will be as many entries here as you have defined filters in your camera server program.

    Focus Offset: enter how many counts you wish your focuser to move for a given filter. Normally one filter would be the reference and the others would move an amount, either + or -, relative to that reference.  The reference filter should be the filter you select for plate solving - usually a clear or luminance filter.  If your filters are parfocal, i.e. they all focus at the same focuser position, you would enter 0 for all the filter offsets. The button at the top sets all filter offsets to the same value as that of the first filter entry.  If some filters, typically some Halpha filters, are sufficiently non-parfocal, you can speed up the active focusing method considerably by entering the offset.  That way, automatic focusing will start closer to the ultimate focus position. Focus Offsets can be measured automatically using the wizard described here.  When using focus offsets, be sure the system is in focus at the start of the session. A good way to do this is to use CCDAutoPilot's Focus Before Target Run Start as described here.

  • Calibration Exposure: This is the exposure time in seconds required to achieve a peak count of 20,000 ADU for the corresponding stellar magnitude below. These values must be set for successful @Focus2 operation. See CCDSoft/TheSkyX Camera Add On documentation for more details.
  • Calibration Magnitude: This is the stellar magnitude required to achieve a peak count of 20,000 ADU for the corresponding exposure. These values must be set for successful @Focus2 operation. See CCDSoft/TheSkyX Camera Add On documentation for more details.