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SP-2526: community.lsst.org/t/10769 (Update DP1 astrometry notebook tutorial) #53

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Merged
plazas merged 3 commits into from
Aug 18, 2025
Merged

SP-2526: community.lsst.org/t/10769 (Update DP1 astrometry notebook tutorial) #53

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718d278
Add reference to DP1 paper / technical note
Aug 14, 2025
06db163
Remove references to WCS functions that should not be called
Aug 14, 2025
76a0e5c
Change warning and clear outputs
Aug 15, 2025
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106 changes: 9 additions & 97 deletions DP1/200_Data_Products/204_Calibrations/204_3_Astrometric_calibration.ipynb
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Original file line number Diff line number Diff line change
Expand Up @@ -67,9 +67,10 @@
"* [Data Management Technical Note - 266: Astrometric Calibration in the LSST\n",
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"Pipeline](https://dmtn-266.lsst.io/DMTN-266.pdf)\n",
"* [PSTN-019: The LSST Science Pipelines Software: Optical Survey Pipeline Reduction and Analysis Environment](https://pstn-019.lsst.io/)\n",
"* [RTN-095: The Vera C. Rubin Observatory Data Preview 1](https://rtn-095.lsst.io/)\n",
"* [AST: A library for modeling and manipulating coordinate systems](https://ui.adsabs.harvard.edu/abs/2016A%26C....15...33B/abstract)\n",
"\n",
"**Related tutorials:** The Monster reference catalog is covered in another tutorial in this series."
"**Related tutorials:** The Monster reference catalog is covered in another tutorial in this series (200)."
]
},
{
Expand Down Expand Up @@ -264,104 +265,23 @@
"wcs = visit_image.getWcs()"
]
},
{
"cell_type": "markdown",
"id": "c5ae6005-3ec5-4d5b-83cf-b728a5885392",
"metadata": {},
"source": [
"Get the pixel origin, in pixels. "
]
},
{
"cell_type": "code",
"execution_count": null,
"id": "4fd499a8-d71a-4f6d-9083-f266ee5aeb58",
"metadata": {},
"outputs": [],
"source": [
"pixel_origin = wcs.getPixelOrigin()"
]
},
{
"cell_type": "code",
"execution_count": null,
"id": "0a8c5a4c-2662-41b4-8e45-512eea89e929",
"metadata": {},
"outputs": [],
"source": [
"print(pixel_origin)"
]
},
{
"cell_type": "markdown",
"id": "2050eae7-7a18-4a46-9ebb-d2f118482a28",
"metadata": {},
"source": [
"Get the sky origin, in degrees. It will be the same for all detectors of a given visit."
]
},
{
"cell_type": "code",
"execution_count": null,
"id": "7e1b052b-5082-475a-a251-76f12a4ea4c5",
"metadata": {},
"outputs": [],
"source": [
"wcs.getSkyOrigin()"
]
},
{
"cell_type": "markdown",
"id": "cd991686-0b61-4a8a-bf69-9a6b6dddc6dd",
"metadata": {},
"source": [
"### 2.1. Pixel scale\n",
"### 2.1. Pixel scale at a particular point.\n",
"\n",
"Get the pixel scale, in arcseconds per pixel. With no argument, `wcs.getPixelScale()` gives the pixel scale at the sky origin, which is the center of the focal plane, and is the same for all detectors."
]
},
{
"cell_type": "code",
"execution_count": null,
"id": "fecddbf9-5543-488a-b384-24a6d30d5e3b",
"metadata": {},
"outputs": [],
"source": [
"wcs.getPixelScale().asArcseconds()"
"Use the bounding box (`bbox`) information for the `visit_image` to get the pixel scale, in arcseconds, at the center of the detector.\n",
"The pixel scale can be calculated at different points, and it may differ across the focal plane."
]
},
{
"cell_type": "markdown",
"id": "30b3da16-23ef-4dff-b498-ca28737a44b4",
"id": "d51b0fe1-3801-4a89-9a4b-f09dcddd6bc3",
"metadata": {},
"source": [
"The pixel scale can be calulated at different points, and it may differ across the focal plane."
]
},
{
"cell_type": "markdown",
"id": "fb8ea629-3350-4b2e-a210-0f3929fe33fa",
"metadata": {},
"source": [
"Get the pixel scale, in arcseconds, at the pixel origin."
]
},
{
"cell_type": "code",
"execution_count": null,
"id": "c3e70c74-2e86-4b08-82c6-5104672046b1",
"metadata": {},
"outputs": [],
"source": [
"wcs.getPixelScale(lsst.geom.Point2D(pixel_origin)).asArcseconds()"
]
},
{
"cell_type": "markdown",
"id": "d07a01dc-aab6-4583-ba12-5e4c15313bc0",
"metadata": {},
"source": [
"Use the bounding box (`bbox`) information for the `visit_image` to get the pixel scale, in arcseconds, at the center of the detector."
"> **Warning**: Avoid calling `wcs.getPixelScale()` without an argument; the implicit reference point may not suit your use case."
]
},
{
Expand Down Expand Up @@ -409,7 +329,7 @@
"outputs": [],
"source": [
"del query, bind, visitimage_refs\n",
"del visit_image, wcs, pixel_origin, bbox"
"del visit_image, wcs, bbox"
]
},
{
Expand Down Expand Up @@ -777,16 +697,8 @@
"\n",
"For **external consistency**, the median separation between sources *not* included in the astrometric fit and their associated counterparts in **Gaia DR3** is within **5 milliarcseconds**—well below the main survey’s design requirement of 50 milliarcseconds. Remaining residuals are due to distortions not yet included in the LSSTComCam astrometric model (but planned for future inclusion), such as **atmospheric**, **camera**, and **detector-level distortions**. \n",
"\n",
"For more details, see Section 5.3 on Astrometry in the DP1 paper."
"For more details, see Section 5.3 on Astrometry in the [DP1 paper](https://rtn-095.lsst.io/)."
]
},
{
"cell_type": "code",
"execution_count": null,
"id": "5d804a96-d993-4bec-808c-be066c03f157",
"metadata": {},
"outputs": [],
"source": []
}
],
"metadata": {
Expand Down