How to use plate solver in AstroImager/AstroDSLR 4.x

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Peter Polakovic
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How to use plate solver in AstroImager/AstroDSLR 4.x

Post by Peter Polakovic »

Plate solving in AstroImager or AstroDSLR is intended to speed up mount alignment and/or to do it automatically (e.g. for automated meridian flip).

Since build 4.0_580 it supports 3 different modes - public or local WEB service and astrometry agent.

Public WEB service

This mode uses public web service like nova.astrometry.net, so you need to have an account on such portal and you need to know your API key (see API section of the portal).
  1. capture a preview frame (select a camera, set exposure time, get a single exposure preview),
  2. open plate solver panel,
  3. select "Use public WEB service option", make sure the service URL is correct and API key is entered,
  4. in case of public WEB service is image always converted to JPEG format to save bandwidth, but you can control the scale (e.g. to 50% or even 25%) to speed up the transfer and the solving and it may be useful to crop the image (e.g. to 80%) if your lens or telescope doesn't provide really flat field,
  5. optionally enter some configuration parameters and hints for plate solver: downsample (downsample the image before extracting star coordinates) or parity (image orientation, it is better to start from "any" unless you don't know it). If AstroTelescope or another mount agent is running and selected as "related mount agent" in the main window, the current coordinates are filled in and you can set radius to narrow the search,
  6. click "solve" button to submit the job to a remote service and wait until done (or failed), it may take even couple of minutes,
  7. if successfully done, click either "sync" button (to tell AstroTelescope or other mount agent to SYNC its current position to the computed center of the image) or "sync & center" (to SYNC first and then slew to the selected target again).
Local WEB service

This mode uses local web service provided by Astrometry for macOS application. You can download it for free from its product page.
  1. Make sure Astrometry for macOS is running and has a proper indexes installed (read astrometry.net README file to identify what index files you really need)
  2. capture a preview frame (select a camera, set exposure time, get a single exposure preview),
  3. open plate solver panel,
  4. select "Use local WEB service option" and make sure the service URL is correct,
  5. in case of local WEB service is image optionally converted to JPEG format to save bandwidth and you can control the scale (e.g. to 50% or even 25%) to speed up the transfer and the solving and it may be useful to crop the image (e.g. to 80%) if your lens or telescope doesn't provide really flat field,
  6. optionally enter some configuration parameters and hints for plate solver: downsample (downsample the image before extracting star coordinates), parity (image orientation, it is better to start from "any" unless you don't know it), depth (the number of top brightest star to take into account) or CPU limit (solving will fail if not finished within the time limit). If AstroTelescope or another mount agent is running and selected as "related mount agent" in the main window, the current coordinates are filled in and you can set radius to narrow the search,
  7. click "solve" button to submit the job to a remote service and wait until done (or failed), it may take even couple of minutes,
  8. if successfully done, click either "sync" button (to tell AstroTelescope or other mount agent to SYNC its current position to the computed center of the image) or "sync & center" (to SYNC first and then slew to the selected target again).
Local or remote astrometry agent

This mode uses astrometry agent running on the same INDIGO server as currently selected imager agent (nevertheless, mount agent can run on the same or any other server). No image transfer is involved, so it is much more efficient than web service.

In case you want to use local astrometry agent (built-in into AstroImager or AstroDSLR), make sure you have Astrometry for macOS version 2.1 or later and it is running.
  1. open any INDIGO control panel, navigate to the agent you want to use and make sure a proper indexes are installed (in case of local agent you can do it in Astrometry for macOS Index manager as well).
  2. select a camera and set exposure time,
  3. open plate solver panel,
  4. select "Use astrometry agent" option,
  5. optionally enter some configuration parameters and hints for plate solver: downsample (downsample the image before extracting star coordinates), parity (image orientation, it is better to start from "any" unless you don't know it), depth (the number of top brightest star to take into account), CPU limit (solving will fail if not finished within the time limit) or the index file to use (select "any" to use all installed index files). If AstroTelescope or another mount agent is running and selected as "related mount agent" in the main window, the current coordinates are filled in and you can set radius to narrow the search,
  6. click "solve" button to solve the image only, "sync" button (to solve the image and then tell AstroTelescope or other mount agent to SYNC its current position to the computed center of the image) or "sync & center" (to solve and SYNC first and then slew to the selected target again).
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