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SIPS v2.4.9 released
 SIPS went through many incremental enhancements and introduced new features from version 2.4.0 to current 2.4.9. It also polished these function and fixed some problems, which surfaced as new advanced image analysis tools like astrometry reduction and photometry light curve analysis are used by more and more users.

New functions and tools introduced in versions 2.4.x

SIPS is continuously evolved with respect to its user community, comprising of both amateur and professional astronomers. This evolution affects almost every part of the system, like introduction of new FITS headers, toolbar arrangement, enhancement of various tools and dialog boxes etc. Another examples are for instance the ability to select images in sets according to used filter, automatic choosing of the fastest camera read mode when focusing, moving of guiding calibration parameters to a separate dialog box not to occupy precious space of the guider tool, saving and loading defined exposure series etc. Some enhancements introduced in versions 2.4.x are more substantial, so they deserve to be named explicitly.

New Guider tool for automatic guiding

Version 2.4.0 introduced new Guider tool window and removed the Guider/Guider Setup tabs from the Camera control tool window (this Camera tool window become Imager tool beginning with this version). Splitting of imaging and guiding functionality allowed introduction of new guiding capabilities, like image dithering etc.

Guiding camera handling was moved into independent SIPS tool to allow implementation of new functionality

Guiding camera handling was moved into independent SIPS tool to allow implementation of new functionality

Later a new Simple mode of the Guider tool was introduced, hiding the advanced features not necessary for basic guiding tasks. This simplified life especially to beginners, just gathering astro-imaging experience, as well as saved screen area and allowed more tools to be visible at once.

Advanced (left) and Simple (right) mode of the Guider tool


When the Guider tool is in the Simple mode, the advanced parameters still work, only the corresponding GUI controls are not displayed. So it is possible to switch to Advanced mode, set required parameters and then switch back to Simple mode just to preserve display space.

Inter-image guiding

This new feature is designed for modern mounts, which are precise enough to keep tracking with sub-pixel precision through the single exposure, and irregularities only appear on the multiple-exposure time-span. Inter-image guiding then performs slight mount position fixes between individual exposures of the main camera, which eliminates “traveling” of the observed objects through the detector area during observing session.

Inter-image guiding controls are available in the newly introduced Guiding tab of the Imager tool window

Inter-image guiding controls are available in the newly introduced Guiding tab of the Imager tool window

Context camera tool

This new tool allows handling of the third camera (in addition to the main Imaging camera and Guiding camera), which can be used e.g. like wide-field viewer/finder on the telescope or context camera showing the telescope and dome interior etc.

Context camera tool used to show observatory dome interior during observing session

Context camera tool used to show observatory dome interior during observing session

Observatory hardware tools

Tool controlling motorized focusers and telescope mounts we also enhanced with numerous new features. Focuser tool now supports absolute positions as well as temperature compensations. Telescope control tool was continuously evolved to incorporate more and more features, supported by modern mounts and the version 2.4 added support for pier-side control of the German Equatorial Mounts (GEM).

Updated Focuser (left) and Telescope (right) tools

Astrometry tool

While the astrometry tool was present in SIPS for a while, it was significantly enhanced recently. It now supports UCAC4 catalog beside the USNO-A2.0. The catalog matching is much faster (several orders of magnitude faster).

SIPS Astrometry tool

SIPS Astrometry tool


The UCAC4 catalog, offered for download by the very popular planetarium program Cartes du Ciel (or Sky Charts in English), is a modified (shrunk) catalog version, not the original catalog with all information for every star available. We can argue whether shrinking of the catalog from original approx. 8.4 GB to approx. 6 GB was worth the introduction of the new, incompatible catalog version. Either way, SIPS needs the original UCAC4 catalog files, it does not work with modified version used by CdC.

The Astrometry tool now supports the field curvature modeling. This feature is especially useful when a wide-field, highly corrected optics is used. Such optics almost never keeps the ideal tangential projection of the celestial sphere to the detector plane, so the star catalog cannot me matched with stars on the image as star centroids are shifted by many pixels in different parts of the image. Here comes the ability of the SIPS Astrometry tool to fit the field curvature with polynomial surfaces independently for the X and Y axes to allow proper match of such images. Curvature description is included into FITS headers so the match can be performed anytime later.

Photometry tool

The Photometry tool was experimentally added in the version 2.3, but it become properly functional tool allowing light cure photometry analysis only in the version 2.4.9. This tool is rather complex and it is still evolving with new features added with every minor SIPS update.

SIPS Photometry tool

SIPS Photometry tool

Bug fixes

SIPS version 2.4.x fixed same bugs, already present in the older versions, but discovered only recently.

  • Because the Series tab defines only some exposure parameters (exposure time, filter and binning), other parameters are used as defined in the Exposure tab for individual exposure types. And while the Series tab allows taking of various exposure types (light, dark, ...), the parameters defined in the Exposure tab were not used according to exposure type defined in the series table, but according to exposure type currently selected in the Exposure tab.

  • The Flat field application could provide wrong results when 32-bit flat was applied to 32-bit image.

However, majority of fixes are related only to the newly introduced features.

  • SIPS v2.4.2 replaced the DATE-OBS and TIME-OBS FITS header with single DATE-OBS header containing both date and time, as the TIME-OBS header is not defined in the official FITS keyword dictionary. Unfortunately the prolonged DATE-OBS string could be damaged by a header comment until version 2.4.7.

  • Omitting of the TIME-OBS header caused problem with some FITS files, created by programs still using this keyword. So SIPS v2.4.8 can read and properly handle this header, despite it is no longer used when a new FITS is created.

  • The astrometry using UCAC4 catalog could wrongly determine the catalog identifier (catalog star number) of the matched stars up to version 2.4.8.

  • The newly introduced Guider camera tool could cause hang-ups when this large window was opened on screens with vertical resolution 768 or less pixels (fixed in SIPS version 2.4.1).

  • Whole image set calibration was reimplemented to utilize all available CPU cores (and thus to run much faster on multi-core processors). However, up to version 2.4.2 some images could be omitted (skipped) in this case.

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

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