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+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Widget Example Using bqplot"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "See https://astrowidgets.readthedocs.io for additional details about the widget, including installation notes."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from astrowidgets.bqplot import ImageWidget"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# from ginga.misc.log import get_logger\n",
+    "\n",
+    "# logger = get_logger('my viewer', log_stderr=True,\n",
+    "#                     log_file=None, level=30)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "w = ImageWidget()"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "For this example, we use an image from Astropy data repository and load it as `CCDData`. Feel free to modify `filename` to point to your desired image.\n",
+    "\n",
+    "Alternately, for local FITS file, you could load it like this instead:\n",
+    "```python\n",
+    "w.load_fits(filename, numhdu=numhdu)\n",
+    "```    \n",
+    "Or if you wish to load a data array natively (without WCS):\n",
+    "```python\n",
+    "from astropy.io import fits\n",
+    "# NOTE: memmap=False is needed for remote data on Windows.\n",
+    "with fits.open(filename, memmap=False) as pf:\n",
+    "    arr = pf[numhdu].data.copy()\n",
+    "w.load_array(arr)\n",
+    "```"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "filename = 'http://data.astropy.org/photometry/spitzer_example_image.fits'\n",
+    "numhdu = 0\n",
+    "\n",
+    "# Loads NDData\n",
+    "# NOTE: Some file also requires unit to be explicitly set in CCDData.\n",
+    "from astropy.nddata import CCDData\n",
+    "ccd = CCDData.read(filename, hdu=numhdu, format='fits')\n",
+    "w.load_nddata(ccd)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Ginga key bindings documented at http://ginga.readthedocs.io/en/latest/quickref.html . Note that not all documented bindings would work here. Please use an alternate binding, if available, if the chosen one is not working.\n",
+    "\n",
+    "Here are the ones that worked during testing with Firefox 52.8.0 on RHEL7 64-bit:\n",
+    "\n",
+    "Key | Action | Notes\n",
+    "--- | --- | ---\n",
+    "`+` | Zoom in |\n",
+    "`-` | Zoom out |\n",
+    "Number (0-9) | Zoom in to specified level | 0 = 10\n",
+    "Shift + number | Zoom out to specified level | Numpad does not work\n",
+    "` (backtick) | Reset zoom |\n",
+    "Space > `q` > arrow | Pan |\n",
+    "ESC | Exit mode (pan, etc) |\n",
+    "`c` | Center image\n",
+    "Space > `d` > up/down arrow | Cycle through color distributions\n",
+    "Space > `d` > Shift + `d` | Go back to linear color distribution\n",
+    "Space > `s` > Shift + `s` | Set cut level to min/max\n",
+    "Space > `s` > Shift + `a` | Set cut level to 0/255 (for 8bpp RGB images)\n",
+    "Space > `s` > up/down arrow | Cycle through cuts algorithms\n",
+    "Space > `l` | Toggle no/soft/normal lock |\n",
+    "\n",
+    "*NOTE: This list is not exhaustive.*"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "A viewer will be shown after running the next cell.\n",
+    "In Jupyter Lab, you can split it out into a separate view by right-clicking on the viewer and then select\n",
+    "\"Create New View for Output\". Then, you can drag the new\n",
+    "\"Output View\" tab, say, to the right side of the workspace. Both viewers are connected to the same events."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 5,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "446131d7e9a24639b5a1be203c32e159",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "ImageWidget(children=(_AstroImage(children=(Figure(axes=[Axis(scale=LinearScale(allow_padding=False, max=1025.…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
+   "source": [
+    "w"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "This next cell captures print outputs. You can pop it out like the viewer above. It is very convenient for debugging purpose."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 6,
+   "metadata": {},
+   "outputs": [
+    {
+     "ename": "AttributeError",
+     "evalue": "'ImageWidget' object has no attribute 'print_out'",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-6-190c878d19a7>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;31m# Capture print outputs from the widget\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0mdisplay\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mw\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mprint_out\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;31mAttributeError\u001b[0m: 'ImageWidget' object has no attribute 'print_out'"
+     ]
+    }
+   ],
+   "source": [
+    "# Capture print outputs from the widget\n",
+    "display(w.print_out)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "The following cell changes the visibility or position of the cursor info bar.\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 6,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "top\n"
+     ]
+    }
+   ],
+   "source": [
+    "w.cursor = 'top'  # 'top', 'bottom', None\n",
+    "print(w.cursor)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# 👆 ~FAILURE ABOVE~ FIXED! 😃 -- cursor does not move"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "The rest of the calls demonstrate how the widget API works. Comment/uncomment as needed. Feel free to experiment."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 7,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# Programmatically center to (X, Y) on viewer\n",
+    "w.center_on((1, 1))"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 8,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# Programmatically offset w.r.t. current center\n",
+    "w.offset_by(10, 10)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 9,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from astropy.coordinates import SkyCoord\n",
+    "\n",
+    "# Change the values here if you are not using given\n",
+    "# example image.\n",
+    "ra_str = '01h13m23.193s'\n",
+    "dec_str = '+00d12m32.19s'\n",
+    "frame = 'galactic'\n",
+    "\n",
+    "# Programmatically center to SkyCoord on viewer\n",
+    "w.center_on(SkyCoord(ra_str, dec_str, frame=frame))"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# 👆 ~FAILURE ABOVE~ 😕 -- issue is that the test image is in Galactic coordinates so either the frame needs to be galactic here or a different center is needed -- image moves completely out of view"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 10,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from astropy import units as u\n",
+    "\n",
+    "# Change the values if needed.\n",
+    "deg_offset = 0.1 * u.deg\n",
+    "\n",
+    "# Programmatically offset (in degrees) w.r.t.\n",
+    "# SkyCoord center\n",
+    "w.offset_by(deg_offset, deg_offset)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 11,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "0.4878048780487805\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Show zoom level\n",
+    "print(w.zoom_level)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# 👆 ~FAILURE ABOVE~ 😃 fixed! -- zoom_level should never be zero!"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 12,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "w.zoom_level = 1"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# 👆 ~FAILURE ABOVE~ -- setting zoom_level to 1 took image out of view -- 😕 now it works, but not sure what I did to fix it\n",
+    "\n",
+    "with X: -349501.59 Y: -186964.83\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 13,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# Programmatically zoom image on viewer\n",
+    "w.zoom(2)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 14,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# Capture what viewer is showing and save RGB image.\n",
+    "# Need https://github.com/ejeschke/ginga/pull/688 to work.\n",
+    "w.save('test.png', overwrite=True)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# 👆 FAILURE ABOVE -- saving *downloads* the image but does not put it in the directory notebook is in"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 19,
+   "metadata": {},
+   "outputs": [
+    {
+     "ename": "AttributeError",
+     "evalue": "'ImageWidget' object has no attribute 'stretch_options'",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-19-6635fee50c41>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;31m# Get all available image stretch options\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mw\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mstretch_options\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;31mAttributeError\u001b[0m: 'ImageWidget' object has no attribute 'stretch_options'"
+     ]
+    }
+   ],
+   "source": [
+    "# Get all available image stretch options\n",
+    "print(w.stretch_options)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# 👆 FAILURE ABOVE -- There should be stretch_options"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 14,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Get image stretch algorithm in use\n",
+    "print(w.stretch)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 15,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "histeq\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Change the stretch\n",
+    "w.stretch = 'histeq'\n",
+    "print(w.stretch)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# 👆 ~FAILURE ABOVE~ -- changing stretch does not change display -- 😕 the change looks terrible but it does change"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 26,
+   "metadata": {},
+   "outputs": [
+    {
+     "ename": "AttributeError",
+     "evalue": "'ImageWidget' object has no attribute 'autocut_options'",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-26-dee3c74378f7>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;31m# Get all available image cuts options\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mw\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mautocut_options\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;31mAttributeError\u001b[0m: 'ImageWidget' object has no attribute 'autocut_options'"
+     ]
+    }
+   ],
+   "source": [
+    "# Get all available image cuts options\n",
+    "print(w.autocut_options)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# 👆 FAILURE ABOVE -- There should be autocut options I guess"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 14,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "<astropy.visualization.interval.AsymmetricPercentileInterval object at 0x1441e4b80>\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Get image cut levels in use\n",
+    "print(w.cuts)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# 👆 FAILURE ABOVE -- this isn't *wrong* but maybe a __str__ would be nice"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 15,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "(10, 15)\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Change the cuts by providing explicit low/high values\n",
+    "w.cuts = (10, 15)\n",
+    "print(w.cuts)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# 👆 ~FAILURE ABOVE~ -- yeah, it is a failure...works now, though 🤷‍♂️ HA HA HA NO -- fails again, WTF? -- AAAH, the issue was with whether the stretch had been set to something."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 16,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "w.stretch = 'log'"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 24,
+   "metadata": {},
+   "outputs": [
+    {
+     "ename": "ValueError",
+     "evalue": "Cut levels must be given as (low, high).zscale is not a valid value. cuts must be one of None, an astropy interval, or list/tuple of length 2.",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mValueError\u001b[0m                                Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-24-eaaf453adbcd>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;31m# Change the cuts with an autocut algorithm\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0mw\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcuts\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;34m'zscale'\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      3\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mw\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcuts\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/miniconda3/envs/awid-jlab3/lib/python3.9/site-packages/traitlets/traitlets.py\u001b[0m in \u001b[0;36m__set__\u001b[0;34m(self, obj, value)\u001b[0m\n\u001b[1;32m    602\u001b[0m             \u001b[0;32mraise\u001b[0m \u001b[0mTraitError\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'The \"%s\" trait is read-only.'\u001b[0m \u001b[0;34m%\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mname\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    603\u001b[0m         \u001b[0;32melse\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 604\u001b[0;31m             \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mset\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mobj\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    605\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    606\u001b[0m     \u001b[0;32mdef\u001b[0m \u001b[0m_validate\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mobj\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/miniconda3/envs/awid-jlab3/lib/python3.9/site-packages/traitlets/traitlets.py\u001b[0m in \u001b[0;36mset\u001b[0;34m(self, obj, value)\u001b[0m\n\u001b[1;32m    576\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    577\u001b[0m     \u001b[0;32mdef\u001b[0m \u001b[0mset\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mobj\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 578\u001b[0;31m         \u001b[0mnew_value\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_validate\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mobj\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    579\u001b[0m         \u001b[0;32mtry\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    580\u001b[0m             \u001b[0mold_value\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mobj\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_trait_values\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mname\u001b[0m\u001b[0;34m]\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/miniconda3/envs/awid-jlab3/lib/python3.9/site-packages/traitlets/traitlets.py\u001b[0m in \u001b[0;36m_validate\u001b[0;34m(self, obj, value)\u001b[0m\n\u001b[1;32m    610\u001b[0m             \u001b[0mvalue\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mvalidate\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mobj\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    611\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0mobj\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_cross_validation_lock\u001b[0m \u001b[0;32mis\u001b[0m \u001b[0;32mFalse\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 612\u001b[0;31m             \u001b[0mvalue\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_cross_validate\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mobj\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    613\u001b[0m         \u001b[0;32mreturn\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    614\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/miniconda3/envs/awid-jlab3/lib/python3.9/site-packages/traitlets/traitlets.py\u001b[0m in \u001b[0;36m_cross_validate\u001b[0;34m(self, obj, value)\u001b[0m\n\u001b[1;32m    616\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mname\u001b[0m \u001b[0;32min\u001b[0m \u001b[0mobj\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_trait_validators\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    617\u001b[0m             \u001b[0mproposal\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mBunch\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m{\u001b[0m\u001b[0;34m'trait'\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'value'\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'owner'\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mobj\u001b[0m\u001b[0;34m}\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 618\u001b[0;31m             \u001b[0mvalue\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mobj\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_trait_validators\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mname\u001b[0m\u001b[0;34m]\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mobj\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mproposal\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    619\u001b[0m         \u001b[0;32melif\u001b[0m \u001b[0mhasattr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mobj\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'_%s_validate'\u001b[0m \u001b[0;34m%\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mname\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    620\u001b[0m             \u001b[0mmeth_name\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;34m'_%s_validate'\u001b[0m \u001b[0;34m%\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mname\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/miniconda3/envs/awid-jlab3/lib/python3.9/site-packages/traitlets/traitlets.py\u001b[0m in \u001b[0;36m__call__\u001b[0;34m(self, *args, **kwargs)\u001b[0m\n\u001b[1;32m    973\u001b[0m         \u001b[0;34m\"\"\"Pass `*args` and `**kwargs` to the handler's function if it exists.\"\"\"\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    974\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0mhasattr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'func'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 975\u001b[0;31m             \u001b[0;32mreturn\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mfunc\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m*\u001b[0m\u001b[0margs\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m**\u001b[0m\u001b[0mkwargs\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    976\u001b[0m         \u001b[0;32melse\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    977\u001b[0m             \u001b[0;32mreturn\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_init_call\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m*\u001b[0m\u001b[0margs\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m**\u001b[0m\u001b[0mkwargs\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/development/astronomy/astrowidgets/astrowidgets/bqplot.py\u001b[0m in \u001b[0;36m_validate_cuts\u001b[0;34m(self, proposal)\u001b[0m\n\u001b[1;32m    578\u001b[0m                 \u001b[0mlength\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mlen\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mproposed_cuts\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    579\u001b[0m                 \u001b[0;32mif\u001b[0m \u001b[0mlength\u001b[0m \u001b[0;34m!=\u001b[0m \u001b[0;36m2\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 580\u001b[0;31m                     raise ValueError('Cut levels must be given as (low, high).'\n\u001b[0m\u001b[1;32m    581\u001b[0m                                         + bad_value_error)\n\u001b[1;32m    582\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;31mValueError\u001b[0m: Cut levels must be given as (low, high).zscale is not a valid value. cuts must be one of None, an astropy interval, or list/tuple of length 2."
+     ]
+    }
+   ],
+   "source": [
+    "# Change the cuts with an autocut algorithm\n",
+    "w.cuts = 'zscale'\n",
+    "print(w.cuts)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# 👆 FAILURE ABOVE -- yeah, it is a failure..."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 19,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# This enables click to center.\n",
+    "w.click_center = True"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Now, click on the image to center it."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {
+    "tags": []
+   },
+   "source": [
+    "# 👆 ~FAILURE ABOVE~ -- clicking does nothing -- FIXED 😃\n",
+    "\n",
+    "Actually, I knew this would be the case...."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 20,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# Turn it back off so marking (next cell) can be done.\n",
+    "w.click_center = False"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 16,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "True\n"
+     ]
+    }
+   ],
+   "source": [
+    "# This enables marking mode.\n",
+    "w.start_marking()\n",
+    "print(w.is_marking)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# 👆 ~FAILURE ABOVE~ 😃 Fixed -- yeah, it is a failure..."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Now, click on the image to mark a point of interest."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 17,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "False\n"
+     ]
+    }
+   ],
+   "source": [
+    "# When done, set back to False.\n",
+    "w.stop_marking()\n",
+    "print(w.is_marking)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 21,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "   X        Y             Coordinates         \n",
+      "  119.00   242.00 01h13m23.32s +00d12m37.8s\n",
+      "  691.00   209.00 01h12m37.56s +00d11m58.2s\n",
+      "  710.00   305.00 01h12m36.04s +00d13m53.4s\n",
+      "   68.00   291.00 01h13m27.4s +00d13m36.6s\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Get table of markers\n",
+    "markers_table = w.get_all_markers()\n",
+    "\n",
+    "# Default display might be hard to read, so we do this\n",
+    "print(f'{\"X\":^8s} {\"Y\":^8s} {\"Coordinates\":^28s}')\n",
+    "for row in markers_table:\n",
+    "    c = row['coord'].to_string('hmsdms')\n",
+    "    print(f'{row[\"x\"]:8.2f} {row[\"y\"]:8.2f} {c}')"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 55,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# Erase markers from display\n",
+    "w.remove_all_markers()"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "The following works even when we have set `w.is_marking=False`. This is because `w.is_marking` only controls the interactive marking and does not affect marking programmatically."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 44,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stderr",
+     "output_type": "stream",
+     "text": [
+      "/Users/mattcraig/miniconda3/envs/awid-jlab3/lib/python3.9/site-packages/traittypes/traittypes.py:97: UserWarning: Given trait value dtype \"int32\" does not match required type \"float64\". A coerced copy has been created.\n",
+      "  warnings.warn(\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Programmatically re-mark from table using X, Y.\n",
+    "# To be fancy, first 2 points marked as bigger\n",
+    "# and thicker red circles.\n",
+    "w.marker = {'type': 'circle', 'color': 'red', 'radius': 50,\n",
+    "            'linewidth': 2}\n",
+    "# 👇👇👇👇👇👇 HAD TO ADD DIFFERENT MARKER NAMES FOR THIS TO WORK 👇👇👇👇\n",
+    "w.add_markers(markers_table[:2], marker_name='first')\n",
+    "# You can also change the type of marker to cross or plus\n",
+    "w.marker = {'type': 'cross', 'color': 'cyan', 'radius': 20}\n",
+    "w.add_markers(markers_table[2:], marker_name='second')"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## 👆 FAILURE -- first two are not showing up as big red circles"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 37,
+   "metadata": {},
+   "outputs": [
+    {
+     "ename": "TypeError",
+     "evalue": "'NoneType' object is not subscriptable",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-37-1f3ff6ff43a4>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      3\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      4\u001b[0m \u001b[0;31m# Programmatically re-mark from table using SkyCoord\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 5\u001b[0;31m \u001b[0mw\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0madd_markers\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mmarkers_table\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0muse_skycoord\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;32m~/development/astronomy/astrowidgets/astrowidgets/bqplot.py\u001b[0m in \u001b[0;36madd_markers\u001b[0;34m(self, table, x_colname, y_colname, skycoord_colname, use_skycoord, marker_name)\u001b[0m\n\u001b[1;32m    680\u001b[0m                                  'world coordinates for markers.')\n\u001b[1;32m    681\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 682\u001b[0;31m             \u001b[0mx\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0my\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_wcs\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mworld_to_pixel\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mtable\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0mskycoord_colname\u001b[0m\u001b[0;34m]\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    683\u001b[0m         \u001b[0;32melse\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    684\u001b[0m             \u001b[0mx\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mtable\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0mx_colname\u001b[0m\u001b[0;34m]\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;31mTypeError\u001b[0m: 'NoneType' object is not subscriptable"
+     ]
+    }
+   ],
+   "source": [
+    "# Erase them again\n",
+    "w.remove_all_markers()\n",
+    "\n",
+    "# Programmatically re-mark from table using SkyCoord\n",
+    "w.add_markers(markers_table, use_skycoord=True)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# Start marking again\n",
+    "w.start_marking()\n",
+    "print(w.is_marking)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# Stop marking AND clear markers.\n",
+    "# Note that this deletes ALL of the markers\n",
+    "w.stop_marking(clear_markers=True)\n",
+    "print(w.is_marking)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "The next cell randomly generates some \"stars\" to mark. In the real world, you would probably detect real stars using `photutils` package."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 53,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "  x     y  \n",
+      "----- -----\n",
+      "141.0 451.0\n",
+      "941.0 239.0\n",
+      "195.0 321.0\n",
+      "327.0 287.0\n",
+      "108.0 101.0\n",
+      "919.0 352.0\n",
+      "331.0 194.0\n",
+      "533.0 464.0\n",
+      "322.0 298.0\n",
+      "853.0 398.0\n",
+      "  ...   ...\n",
+      "697.0  47.0\n",
+      "437.0 327.0\n",
+      "138.0 393.0\n",
+      "420.0 335.0\n",
+      "744.0 445.0\n",
+      "964.0 480.0\n",
+      "769.0 340.0\n",
+      "149.0 302.0\n",
+      "979.0 399.0\n",
+      "478.0 423.0\n",
+      "789.0 153.0\n",
+      "Length = 482 rows\n"
+     ]
+    }
+   ],
+   "source": [
+    "import numpy as np\n",
+    "from astropy.table import Table\n",
+    "\n",
+    "# Maximum umber of \"stars\" to generate randomly.\n",
+    "max_stars = 1000\n",
+    "\n",
+    "# Number of pixels from edge to avoid.\n",
+    "dpix = 20\n",
+    "\n",
+    "# Image from the viewer.\n",
+    "img = w._data #w.viewer.get_image()\n",
+    "\n",
+    "# Random \"stars\" generated.\n",
+    "bad_locs = np.random.randint(\n",
+    "    dpix, high=img.shape[1] - dpix, size=[max_stars, 2])\n",
+    "\n",
+    "# Only want those not near the edges.\n",
+    "mask = ((dpix < bad_locs[:, 0]) &\n",
+    "        (bad_locs[:, 0] < img.shape[0] - dpix) &\n",
+    "        (dpix < bad_locs[:, 1]) &\n",
+    "        (bad_locs[:, 1] < img.shape[1] - dpix))\n",
+    "locs = bad_locs[mask]\n",
+    "\n",
+    "# Put them in table\n",
+    "t = Table([locs[:, 1], locs[:, 0]], names=('x', 'y'), dtype=('float', 'float'))\n",
+    "print(t)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# 👆 FAILURE ABOVE -- to be fair, this is relying on an implementation detail of ginga\n",
+    "\n",
+    "Fixed temporarily by changing `img`"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 56,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stderr",
+     "output_type": "stream",
+     "text": [
+      "/Users/mattcraig/miniconda3/envs/awid-jlab3/lib/python3.9/site-packages/traittypes/traittypes.py:97: UserWarning: Given trait value dtype \"int32\" does not match required type \"float64\". A coerced copy has been created.\n",
+      "  warnings.warn(\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Mark those \"stars\" based on given table with X and Y.\n",
+    "w.add_markers(t)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# 👆 ~FAILURE ABOVE~ 😃 fixed! -- Really?! Does anything in here work?! This _should_ have been caught by the tests.... 😃 it is now!"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "The following illustrates how to control number of markers displayed using interactive widget from `ipywidgets`."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 58,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# Set the marker properties as you like.\n",
+    "w.marker = {'type': 'circle', 'color': 'red', 'radius': 10,\n",
+    "            'linewidth': 2}\n",
+    "\n",
+    "# Define a function to control marker display\n",
+    "def show_circles(n):\n",
+    "    \"\"\"Show and hide circles.\"\"\"\n",
+    "    w.remove_all_markers()\n",
+    "    t2show = t[:n]\n",
+    "    w.add_markers(t2show)\n",
+    "    with w.print_out:\n",
+    "        print('Displaying {} markers...'.format(len(t2show)))"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "We redisplay the image widget below above the slider. Note that the slider affects both this view of the image widget and the one near the top of the notebook."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 59,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "446131d7e9a24639b5a1be203c32e159",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "ImageWidget(children=(_AstroImage(children=(Figure(axes=[Axis(scale=LinearScale(allow_padding=False, max=1022.…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    },
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "51d32b6b02de4103b39e2ef757e3bc49",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "interactive(children=(IntSlider(value=0, continuous_update=False, description='n', max=482), Output()), _dom_c…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
+   "source": [
+    "from IPython.display import display\n",
+    "\n",
+    "import ipywidgets as ipyw\n",
+    "from ipywidgets import interactive\n",
+    "\n",
+    "# Show the slider widget.\n",
+    "slider = interactive(show_circles,\n",
+    "                     n=ipyw.IntSlider(min=0,max=len(t),step=1,value=0, continuous_update=False))\n",
+    "display(w, slider)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Now, use the slider. The chosen `n` represents the first `n` \"stars\" being displayed."
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.9.5"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 4
+}