Imaging System Analysis
The Imaging System Analysis page defines a quantifiable and systematic procedure to collect the data necessary to analyze your digital imaging system with the goal of producing “quality” images with minimal tracking error.
Since the Paramount’s began shipping in 1996, many users, from expert to novice, have concluded that their Paramount mount is “not able to track accurately” or “the sidereal tracking rate is wrong” or the mount is “not able to point accurately” or “the periodic error of the mount is above specification.”
With respect to the Paramount, Software Bisque has found that the imaging system components that produce poor tracking or poor pointing are generally caused by one or more of the following (but not necessarily limited to):
One such experienced non-technical astronomer was considering returning his Paramount because his imaging system was producing “elongated stars.” After following the procedures below (and with some guidance from Software Bisque), he was able produce quality images that not only exceeded his personal expectations, but enabled him to capture an APOD.
What Tools to Use?
There is a great deal of confusion and misinformation among amateurs about how to analyze your imaging system’s tracking to produce a “quality” image (specifically, symmetrical stars).
The tools that can be used to analyze your imaging system’s tracking and pointing include:
Where to Start?
If you are having difficulty getting “acceptable tracking or pointing performance”, and need a procedure that will help objectively analyze your imaging system, here’s the place to start…
Imaging system diagnosis is a time consuming, and can be a painstaking process. Unfortunately, Software Bisque does unable to provide free consulting to all mount owners.
Our hope is that, by using the systematic procedure below, you’ll be able to quantify, identify and isolate the problems so that you can use your imaging system to produce tracking and pointing performance that meets or exceeds the Paramount published specifications.
Step 1: Acquire Digital Photographs of your Imaging System
Step 2: Quantify your Imaging System Configuration
Step 3: Send your TPoint Model
Step 4: Collect Tracking Log Data With and Without Periodic Error Correction
Step 5: Collect a Series of Short, Back to Back Photos
Step 6: Collect Unguided Images of Various Lengths
The purpose of this step is to analyze the physical setup of your imaging system. You must scrutinize every mechanical component and mounting interface to ensure there is no “slop” or “play” that might cause pointing and/or tracking errors. This includes the earth to pier, pier to mount, mount to OTA, OTA mirror mounting, OTA to camera/focuser/filter wheel/rotator/AO mounting.
Please share the following information.
If you have hired Software Bisque to analyze your system, please send this information, do not proceed to Step 2 until a Software Bisque engineer has instructed you to do so.
The purpose of this step is to determine the image scale of your imaging system. Image scale is the metric that you can use to quantify tracking errors on your images. Once the the magnitude of the tracking error is quantified (by measuring the “width” of the elongated stars), then the “rate” of tracking error can be computed and compared to the sidereal tracking rate. This will help determine where the tracking error is coming from.
For the purposes of this analysis, please use a single optic, imaging camera, and accessory configuration. That is, do not change anything equipment-wise during the analysis.
Do not proceed to Step 3 until a Software Bisque support staff member has instructed you to do so.
TPoint pointing data reveals problems or errors with the imaging system, and is very important to this analysis.
TPoint Settings Overview
The TPoint settings (specifically, a file with the extension .tptx that is generated by TheSky Professional Edition and saved to the TPoint folder in TheSky’s Settings folder.
Do not proceed to Step 4 until a Software Bisque support staff member has instructed you to do so.
The purpose of this step is to quantify the mount’s periodic error before and after periodic error correction (PEC) is applied. All mounts that use worm gears have periodic error, and, with periodic error correction disabled, this error produces elongated stars on in photos. The mount’s peak-to-peak periodic can be approximated by measuring the angular size of a star’s elongation.
If your imaging system is producing elongated stars, you can determine if the elongated stars are due only to periodic error, or periodic error plus other sources of tracking factor (such as tube flexure).
If you have hired Software Bisque to help you analyze your system, do not proceed to Step 5 until a Software Bisque support staff member has instructed you to do so.
The purpose of this step is to acquire images in an optimal part of the sky to measure tracking accuracy with no tracking, no guiding, and no periodic error correction enabled.
Look at the resulting photos to determine the quality of stars on the images. Stars in the photo should be round, and should not move significantly between successive photos. Otherwise, the stability/rigidity of the system comes into question or there may be a bad guider cable, or the wrong tracking rate is being applied.
Do not proceed to Step 6 until a Software Bisque support staff member has instructed you to do so.
The purpose of this step is to acquire images in an optimal part of the sky to access tracking accuracy over various exposure lengths, but no guiding, and no periodic error correction enabled. Analyze the resulting images to determine how the mount tracks without any corrections.
Paramount worm periods are listed in the Paramount User Guide. Compare the elongation of stars for each set of data to determine the magnitude of tracking errors.
Using the same setup parameters as in Step 5:
FITS Image Distribution Options
FITS Image Notes:
The above data should be sufficient to characterize the tracking of your mount and help isolate most any kind of tracking issue. Some experience is required to know if there are egregious issues with the raw data, significant enough that cannot be corrected by Software Bisque technologies.
If the raw data is reasonable, Steps 5 and 6 above can be repeated with, for example, the Apply PEC checkbox turned on (or ProTrack enabled, or while autoguiding). The resulting photo must be better than the photo with the Apply PEC checkbox turned off (or ProTrack disabled, or not autoguiding).
By comparing the raw data collected to the same data collected with a particular technology turned on, its possible to isolate where a tracking error is being introduced.
Software Bisque, at its discretion, may need to obtain additional information as required.
Software Bisque understands that troubleshooting issues with imaging systems is not always a simple task. Successful remote troubleshooting imaging system performance requires patience, cooperation, and clear communication between everyone involved. We thank you in advance for your help collecting clear and informative photos of your imaging system, TPoint calibration data, PE tracking logs, well-focused, high signal, low noise FITS photos and the detailed information about the steps taken to resolve the unexpected behavior.
We will try our best to help you determine what’s wrong with your imaging system.