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What is new in SIPS v3.9
 New SIPS version brings numerous minor changes and improvements, some of which considerably enhance user's convenience and program reliability. Ability to automatically connect to predefined camera, introduced in SIPS v3.7, is now extended to all devices controlled by SIPS (telescopes, focusers, domes, ...). However, the most important change remains invisible to the users — new SIPS redefined the telescope driver interface to make host PC and telescope controller communication more efficient and less bandwidth demanding.

Automatically connect to selected driver

When SIPS is used to control a fixed observing setup, it is convenient if it loads all drivers automatically upon startup and the user needs not to take care about selection of appropriate drivers. This functionality was added for all connected cameras earlier, version 3.9 introduces this feature also for other drivers.


Please note also drivers have to support this functionality and not all drivers do it yet. Telescope mount drivers work OK in version 3.9. If some other driver does not support this function, it will be updated in the subsequent SIPS versions.

Calibrate “in situ” option

SIPS uses image sets each time it has to process multiple images at once. Handling all images in RAM leads to much faster processing compared to disk-oriented operations. On the other side, a lot of memory is needed to keeping many multi-megapixel images.


The 64 bit version of SIPS comes handy here, as it is not limited to 2 GB of memory accessible to 32 bit applications. All modern PCs are equipped with 8 or 16 GB RAM and 64 bit SIPS can use it all.

The most memory intensive operation is calibration, which creates set of calibrated images in memory in addition to already loaded raw images. Raw images can be removed from memory immediately after calibration finishes, but memory consumption doubles during calibration itself.

New “in situ” option of the Calibration tool allows it just to replace original raw image with calibrated one. The memory footprint remains exactly the same. So, new SIPS version can handle almost twice as big image sets on the same computer compared to previous versions.


Because original raw images are modified (replaced with calibrated versions), any Save operation on individual image or on the whole set replaces the original raw image file(s) with calibrated one and original data are lost.

Repeated exposures with main imaging camera

While both Guider and Context camera tools offered the possibility to perform exposures with defined parameters until user stops it, the main imaging camera control tool relied on defined number of exposures to be performed. If the user needed to performing of repeated exposures, it was necessary to enter some big number into cont box labeled “Repeat”, which was not so convenient.

Adding a function to repeat “indefinitely” is not difficult to program, but it was difficult to find some place for a GUI control, allowing this functionality, within already stuffed “Exposure” tab of the Imager control window. Hopefully SIPS v3.9 solved this problem by intuitive and elegant way.

The “Repeat” label was replaced with a check-box control. If the check-box is unchecked, the tool works exactly like in previous versions — “Start Exp” button performs exposure and if the Repeat control contains number > 1, it is decreased and new exposure begins. This repeats until the Repeat number reaches 1.

Now if the Repeat check-box is checked, number of exposures control is disabled and exposures are repeated indefinitely (the Repeat control number is not decreased). Un-checking the check-box resumes decreasing of the number of exposures until number reaches 1.

Photometry tool updates

Photometry tool underwent numerous bug fixes between version 3.8 and 3.9. These bugs occurred in very specific situations only, which is why such long time was necessary to fix them. Majority of users never met a problem, which makes locating of the bug causes particularly difficult (if the developer cannot reproduce the error, it is virtually impossible to fix it). Either way, we have no knowledge about any stability issues in the current version.

Matching images from arbitrary reference image

New function introduced in Photometry tool is the ability to choose any image within the processed image set to be a reference image to which other images are aligned. Prior versions always used the first image of the set.


The image set alignment code is used also in other tools, e.g. Image Add or Image Blink. Changes described here apply also to these tools.

Using of the first image as reference worked well when the observing session started well after twilight, when sky was dark and the first image quality was generally the same like quality of the following images. But in situations when observing started at twilight (or was affected by clouds, thick air-mass close to horizon, light pollution etc.) and first image was of poor quality, matching of later images to such low-quality first image could cause problems.

SIPS v3.9 starts matching of image set from the image actually selected in the image set (such image is usually displayed in the panel and its name is highlighted in the list box with image names). Only if no image is selected (highlighted), the first image is taken as reference.

Other Photometry enhancements

  • When the Field description is sorted according to variable name, the simple string comparison was replaced with “intelligent” comparison, which users know e.g. from Windows Explorer. In standard string comparison the name “var2” is located after the name “var10” because character on the same position “2” is after the character “1”. The new algorithm recognizes when the name ends with number and if the name prefix text equals, number values are used for sorting, so “var2” is located before the “var10”, because 2 is less than 10.

  • Automatically calculated apertures now cannot be arbitrary small. If the calculated automatic aperture is less than smallest defined fixed aperture, the smallest defined aperture is used instead.

  • When the alignment was invoked on set with one image only, the OK button remained disabled and the operation has to be canceled even after the single image was processed. Despite aligning single image has no sense (only stars are found within the single image, there is nothing to align), the operation now performs correctly.

  • The option “Calculate next image stretch using histogram auto type” sometimes worked unreliably.

  • When anther image is selected, the field description table is updated to show whether stars in the field description were found on newly selected image (stars not found on active image are listed in red instead of black color).

General updates and bug fixes

Small updates include:

  • Numerous parameters of every new image (image opened from file or read from camera) are calculated prior to its display (e.g. mean value, standard deviation, extreme pixel values, low and high stretch limits according to selected Auto type and image histogram is also calculated). When exposures are take with exposure time counted in seconds or minutes, time needed to handle every image is negligible. But if fast camera is used for video-like observing, time needed to handle every frame limits frame rate.

    While SIPS is not designed to achieve high frame rates, at last some overhead reduction was introduced when the Histogram and Stretch tool “Auto type” is se to “Keep current”. No image statistics is calculated in such case and frame rate is somewhat higher. Still, some time-demanding operation must be performed either way (e.g. calculation of histogram).

  • The “Save As” option of image set allowed storing all images under different name as FITS files or exporting them into common format (PNG, JPG, TIFF, ...). SIPS v3.9 added a possibility to export whole set also to 16 bit PNG and TIFF formats (only 8 bit PNG and TIFF were supported by previous versions).


    Single image could be exported to 16 bit PNG or TIFF also in previous SIPS versions, the new functionality affects only the export of the whole image set.

  • The reworked Context camera handling, which kept capturing parameters like binning and sub-frame between sessions, sometimes lead incorrect image width and depth of 1 pixel only. Version 3.9 fixes this problem.

  • ASCOM telescope driver was updated to better cooperate with common drivers (for instance EQMOD). ASCOM standard sometimes allows usage of different functions for the same task (e.g. stop movement in particular axis), but not all drivers allow usage of all specified functions. This is why the direction buttons in the Telescope control tool could not work properly in previous versions.

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

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