Software Bisque
Imaging System Analysis

   

Imaging System Analysis

 
 

The purpose of this web page is to define a quantifiable and systematic procedure to collect data necessary to analyze your CCD imaging system with the goal of producing "quality" images with minimal tracking error.

 

Background

 

Since the Paramount ME began shipping in early 2002, many users, from expert to novice, have came to the conclusion that their Paramount ME 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".

 

To date, after careful, objective, scientific, systematic analysis of their entire imaging system, every single Paramount ME that Software Bisque has analyzed met or exceeded specification with regard to tracking and pointing performance.

 

With respect to the Paramount ME, 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):

  • Inadequate, unstable or improperly mounted piers

  • Piers with sympathetic frequencies that produce vibration from an external source

  • Optical tube assemblies that have mirror flop

  • Excessive tube flexure from optical tube assemblies that create a measurable "non-sidereal tracking rate" (and other errors)

  • Poorly mounted CCD cameras that introduce random pointing and tracking errors

  • OTAs mounted using a dovetail mounting that flex

One such experienced non-technical astronomer was considering returning his Paramount ME 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:

 

  • TPoint Telescope Modeling and Analysis Software for Windows (to quantify and optimize polar alignment and improve all sky pointing)

  • ProTrack (modeled tracking using a TPoint model)

  • Periodic Error Correction (PEC) and PrecisionPEC

  • Autoguiders

  • AO-7 devices.

 

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 not have the manpower to provide free consulting to Paramount ME 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 ME's published specifications.

 

If you have hired Software Bisque to help you analyze your system, please send the information requested below.  Otherwise, you can follow the steps below to help diagnose potential sources of tracking error in your imaging system.

 

Step 1: Acquire Digital Photographs of your Imaging System

 

Step 1 Details

 

Step 2: Quantify your Imaging System Configuration

 

Step 2 Details

 

Step 3: Send your Sky Document that includes your TPoint Document

 

Step 3 Details

 

Step 4: Collect and Send your Tracking Log Data

 

Step 4 Details

 

Step 5: Acquire and Send CCD Images

 

Step 5 Details

 

Step 6: Send Unguided CCD Images

 

Step 6 Details

 

Step 1: Details for Sending Software Bisque Digital Photographs of your Imaging System

 

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" 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 CCD Camera/Focuser/Filter wheel mounting.

 

If you have hired Software Bisque to help you analyze your system, please send this information.

 

  1. Take five digital photographs the imaging system.
    1. Two “wide field” views showing the pier, mount and optical tube assembly from two different angles.
    2. A photograph of the pier-to-earth interface.
    3. A photograph of the camera to optical tube assembly interface.
    4. A photograph of the Versa-Plate to OTA interface.
  2. Create a "zip" file named ISAPhotographs.zip that contains each photograph, and email the zip file to support at bisque.com. The subject of the email must read "ISA Step 1 <Your Last Name Here>". Where <Your Last Name Here> should be replaced by your surname. For example, John Smith's subject would be "ISA Step 1 Smith".

If you have entered a consulting contract with 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.

 

Step 2: Details for Sending Software Bisque your Imaging System Configuration

 

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 CCD 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, CCD imaging camera, and accessory configuration. That is, do not change anything equipment-wise during the analysis.

 

If you have entered a consulting contract with Software Bisque to analyze your system, please compile the follow information and email it to support at bisque dot com. The subject of the email must read "ISA Step 2 <Your Last Name Here>". Where <Your Last Name Here> should be replaced by your surname. For example, John Smith's subject would be "ISA Step 2 Smith"

  1. The make and model of the optical tube assembly used to acquire CCD images. If you own multiple OTAs, please use one, and only one OTA during this analysis.

  2. The make and model of the CCD camera used to acquire CCD images. If you own multiple CCD cameras, please use one, and only one camera during this analysis.

  3. A detailed description of all auxiliary devices being used on the system (specifically, the make and model of any/all motorized focusers, filter wheels, AO-7 devices, focal reducers, field flatteners, Barlow lens, field rotators, etc.).

Do not proceed to Step 3 until a Software Bisque engineer has instructed you to do so.

 

Step 3:  Details for Sending Software Bisque your Current TPoint Document

 

TPoint pointing data reveals problems or errors with the imaging system, and is very important to this analysis.

  1. If you have entered a consulting contract with Software Bisque to analyze your system, please email Software Bisque your TPoint Document (with 100 data points, minimum), either as a file with the extension ".TPT", or a Sky Document (.SKY) file that includes a TPoint model, and email this file to support at bisque.com. The subject of the email must read "ISA Step 3 <Your Last Name Here>". Where <Your Last Name Here> should be replaced by your surname. For example, Jim Smith's subject would be "ISA Step 3 Smith".

TPoint Document Overview

 

The TPoint document (that is, a file with the extension .TPT that is generated by TPoint for Windows) includes the pointing or "mapping" data, as well as the terms you've added to the TPoint model.  If you've inserted a TPoint model into TheSky6, then the Sky Document (that is, a file with the extension .SKY that is generated by TheSky6) contains the TPoint model, as well as your current TheSky6 settings.

 

Do not proceed to Step 4 until a Software Bisque engineer has instructed you to do so.

 

Step 4: Details for Sending Software Bisque your Tracking Data

 

The purpose of this step is to quantify your mount's periodic error before and after Periodic Error Correction (PEC) is applied. Mounts that use worm gears all have periodic error, and, with periodic error correction disabled, this error will produce elongated stars on your CCD images.

 

If your imaging system is producing elongated stars, you can determine if the elongated stars are due only to PE, or PE and some other factor (such as tube flexure).

  1. Install the latest versions of TheSky6 and CCDSoft (from www.bisque.com/download).

  2. If you have hired Software Bisque to help you analyze your system: email Software Bisque 10 minutes of tracking data acquired with your system. Please see the Collect Periodic Error Data topic in the PrecisionPEC Help file for step-by-step procedure to do this task. Please do not send tracking data acquired using any software other than CCDSoft. The subject of the email must read "ISA Step 4 <Your Last Name Here>". Where <Your Last Name Here> should be replaced by your surname. For example, Jim Smith's subject would be "ISA Step 4 Smith".

If you have hired Software Bisque to help you analyze your system, do not proceed to Step 5 until a Software Bisque engineer has instructed you to do so.

 

 

Step 5: Details for Sending Software Bisque A Series of CCD Images

 

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 enable. Analyze the resulting images to determine the quality of stars on the images. These images should have nice, round stars. If not, there may be a bad guider cable, or the wrong tracking rate is enabled.

  1. Collect a series of CCD images without any tracking corrections. Please see Step 1 in the Collect Periodic Error Data topic in the PrecisionPEC Help file for step-by-step procedure how to configure the mount, TheSky and CCDSoft.

  2. Using TheSky6, slew the telescope near declination 0 degrees, near the meridian (within 5 degrees or so).

  3. Use CCDSoft to acquire a series of 15, 10 second images in succession (1 x 1 binning on the larger detector if the camera has two detectors).  Do not perform any image processing on any images (dark frame removal is okay).

  4. If you own a large format camera, the images may be large and difficult to send via the internet. So, either email to support at bisque dot com, place on web site and provide a URL, or burn to a CD-ROM and mail the unprocessed, 16-bit FITS files to Software Bisque. The subject of the email, or any other written correspondence must read "ISA Step 5 <Your Last Name Here>". Where <Your Last Name Here> should be replaced by your surname. For example, Jim Smith's subject would be "ISA Step 5 Smith".

If you have hired Software Bisque to help you analyze your system, do not proceed to Step 6 until a Software Bisque engineer has instructed you to do so.

 

Step 6: Send Unguided CCD Images

The purpose of this step is to acquire images in an optimal part of the sky to measure tracking accuracy with tracking turned on, but no guiding, and no periodic error correction enable. Analyze the resulting images to determine how the mount tracks without any corrections.

 

The period of the Paramount ME's worm is 2.5 minutes. 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:

  1. Acquire 1, one-minute "raw" image. Specifically, unguided, un-pec corrected, no TPoint, no ProTrack, no AO-7 guiding, no guider cable plugged in, no joystick plugged in, 1x1 binned image using the larger detector if the camera has two detectors.
  2. Acquire 1, 2.5 minute "raw" image. Specifically, unguided, un-pec corrected, no TPoint, no ProTrack, no AO-7 guiding, no guider cable plugged in, no joystick plugged in, 1x1 binned image.
  3. Acquire 1, five-minute "raw" image. Specifically, unguided, un-pec corrected, no TPoint, no ProTrack, no AO-7 guiding, no guider cable plugged in, no joystick plugged in, 1x1 binned image.

If you have hired Software Bisque to help you analyze your system:

If you own a large format camera, the images may be large and difficult to send via the email.

FITS Image Distribution Options

  • Email the images to support at bisque.com.
  • Place the images on a web server, and then email Software Bisque the URL to download them.
  • Burn them to CD or DVD media and mail them to Software Bisque.

Notes:

  • The images must be unprocessed, 16-bit, grayscale FITS files.
  • The subject of the email, or any other written correspondence must read "ISA Step 6 <Your Last Name Here>". Where <Your Last Name Here> should be replaced by your surname. For example, Jim Smith's subject would be "ISA Step 6 Smith".
 

The above data should be sufficient to characterize the tracking of your mount.

If you have entered a consulting contract with Software Bisque to analyze your system, once Steps 1 through 6 have been successfully accomplished, Software Bisque can begin its analysis of your imaging system.

Software Bisque, at its discretion, may need to obtain additional information as required.

 

 


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