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SIPS v2.4.1 released (updated)
 SIPS version 2.4 implements two most often requested functions. The first one is dithering—the capability to shift guiding star position among individual exposures of the main imaging camera to be able to eliminate image artifacts (hot pixels, bad columns) during image stacking. The second one is the ability to save (and load) defined exposure series to files. Although these updates look like a minor ones, it was necessary to completely overhaul the camera user interface to implement them. The original Camera control tool was split into Imaging Camera tool and new Guiding Camera tool. This new tool contains all necessary guiding controls on single place and offers more interactivity and provides better feedback to the user, which makes guiding setup much simpler task. What's more, all the work done on v2.4 allows adding of new features planned for v2.5.

The Camera user's interface overhaul is probably the most significant change from introduction of the SIPS version 2.

SIPS now offers separate Imaging Camera tool and Guiding Camera tool windows

SIPS now offers separate Imaging Camera tool and Guiding Camera tool windows

Hint:

New version of SIPS also contains updated documentation, describing all new features and updates. The documentation is accessible from the SIPS main menu Help -> Contents...

Imaging Camera tool

Changes of the Imaging Camera tool are relatively minor. Both guiding-related tabs were removed and because there are more tools handling more cameras, also the camera selection and configuration is different. Instead of “interactive” tree showing current state of all connected cameras, a modal dialog box for camera selection was introduced (the same dialog box, but selecting guiding camera instead of imaging camera, is used in the Guiding Camera tool). The Camera tab of the Imaging Camera tool shows information about the active imaging camera, beside the camera selection button.

Camera tab of the Imaging Camera tool window

Camera tab of the Imaging Camera tool window

Another change to Imaging Camera tool is the ability to save and load defined series of exposures.

Series tab of the Imaging Camera tool window

Series tab of the Imaging Camera tool window

Series description is saved into simple text file, which can be easily edited by any text editor, providing the changes follow the syntax rules.

SIPS Exposure Series File
list
  repeat_num = 1
  repeat_period = 1
  item
    exp_type = dark
    exp_time = 3E+2
    filter_index = 0
    binning_x = 1
    binning_y = 1
    repeat_num = 5
    repeat_period = 1000
  end_item
  item
    exp_type = dark
    exp_time = 3E+2
    filter_index = 0
    binning_x = 2
    binning_y = 2
    repeat_num = 5
    repeat_period = 1000
  end_item
  list
    repeat_num = 10
    repeat_period = 1000
    item
      exp_type = light
      exp_time = 3E+2
      filter_index = 0
      binning_x = 1
      binning_y = 1
      repeat_num = 2
      repeat_period = 1000
    end_item
    item
      exp_type = light
      exp_time = 3E+2
      filter_index = 1
      binning_x = 2
      binning_y = 2
      repeat_num = 1
      repeat_period = 1000
    end_item
    item
      exp_type = light
      exp_time = 3E+2
      filter_index = 2
      binning_x = 2
      binning_y = 2
      repeat_num = 1
      repeat_period = 1000
    end_item
    item
      exp_type = light
      exp_time = 3E+2
      filter_index = 3
      binning_x = 2
      binning_y = 2
      repeat_num = 1
      repeat_period = 1000
    end_item
  end_list
end_list

Guiding camera tool

The Guiding Camera tool user interface was programmed from the ground up. There were two tabs covering guiding in the Camera tool in the previous SIPS version. But these tabs somewhat artificially divided the guiding functionality into two separate parts. They were also full of controls and adding anything new was close to impossible in the given area.

Images, read from the guiding camera, were handled similarly to the images read from the main imaging camera, which could cause some confusion (if guiding camera image has to be displayed in the new window, it could overwrite last downloaded imaging camera etc.). All these problems lead to new design of Guiding Camera tool, which contains all necessary controls in the single window as well as panes displaying guiding camera image, history charts and log of all actions performed by the Guiding Camera tool.

Warning:

Due to large number of controls and thus great vertical size of the Guiding Camera tool window, it was necessary to leave out some functions when SIPS runs on displays with vertical resolution 768 or less pixels. Unfortunately this modification caused instability of the SIPS version 2.4. Upgrade to version 2.4.1, which fixed this problem, please.

Guiding Camera tool window

Guiding Camera tool window

Because guiding is based on the ability to find star(s) on the guiding camera image, the Guiding Camera tool helps to tune parameters, used for star searching, by indicating of all found stars on every read image.

Many other functions are available, like guider calibration, altering of guiding parameters on declination change or GEM pier swap, alarms on star lost or too long correction pulses, guiding to fixed position or dithering while guiding. Dithering is just opposite of fixed star position guiding. This mode is used mainly by astrophotographers and its main purpose is to spread hot pixels, possible bad columns and other artifacts around defined area of the acquired images instead of keeping them on constant position. This allows removing of artifacts during final stacking of individual exposures by some statistical method, rejecting extreme values (e.g. sigma clipping).

Guiding Camera tool demonstrates dithering

Guiding Camera tool demonstrates dithering

The guiding history chart on the image above shows how reference position is moved by 2 pixels in R.A., then a 2 pixels shift in Dec. (move to next line) appears together with long move in R.A. (move to beginning of the line). The main imaging camera exposure time was set to 15 seconds only and the guiding camera exposure time was 5 seconds for demonstration purposes only. So the guider was able to perform only a few exposures on each offset and the shift to next position occurred, because imaging camera exposure finished. Such arrangement was chosen to show the shifts on guiding chart history. In reality, imaging camera exposures are way longer (many minutes) compared to guiding camera exposure time.

The following image demonstrates effect of dithering.

Effect of regular dithering on stacked images without matching (left) and after matching (right)

Effect of regular dithering on stacked images without matching (left) and after matching (right)

Stacking without mutual image shifts keep all hotpixels on exactly the same position and individual stars create a grid, which demonstrate dithering offsets. When properly stacked with mutual matching of stars, S/N naturally significantly increases and detector artifacts disappear.

Hint:

The Guiding Camera tool has its own chapter in the SIPS documentation. There is a guiding tutorial, explaining calibration, regular guiding and other special functions in detail.

Other new features

Many new features, despite not as fundamental as introduction of new Guiding Camera tool, were added to SIPS v2.4. These enhancements include enhancements to Telescope Control tool to control many features of the mount (e.g. the pier side control of the German Equatorial Mounts).

Enhanced Telescope Control tool window

Enhanced Telescope Control tool window

More small updates include keeping of the pixel under mouse position while zooming of the image by mouse wheel (providing the geometry of the displayed image allows it), adding the ability to maximize zoomable tool windows (and keeping the Maximized state between SIPS sessions), automatic identification of the Gx Camera Ethernet Adapter within the IP network (no longer necessary to manually enter of the adapter IP address) etc.

There is one more new tool added to SIPS—the Photometry. This is rather complex tool, maybe the most complex one in SIPS. But the Photometry in SIPS v2.4 is only experimental with some features not finished yet. Also the documentation for this tool is still not ready. So take the Photometry tool like indication of things to come.

Photometry tool is still in the experimental stage in SIPS v2.4

Photometry tool is still in the experimental stage in SIPS v2.4

SIPS is a freeware and can be downloaded from the Download section of this web site.

 
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