Asteroids

JPL Small-Body Database Browser – NASA/JPL’s authoritative lookup for every known asteroid or comet, giving orbital elements, physical parameters, ephemerides, and 3-D orbit visualisations. 

Minor Planet Center – Database Search – The IAU clearing-house for asteroid and comet observations; provides discovery details, updated orbits, and ephemeris tables on demand. 

NASA “Eyes on Asteroids” – Interactive 3-D web app that lets you track thousands of asteroids and comets in real time, replay past fly-bys, and preview future close approaches. 

NASA CNEOS / Asteroid Watch – Center for Near-Earth Object Studies portal with daily close-approach tables, impact-risk lists, and news on planetary-defense research. 

NEODyS-2 – European Near-Earth Object Dynamic Site offering continuously updated orbits, impact-risk pages, and custom ephemerides for every NEA. 

In-The-Sky.org — Asteroids – Automatically generated list of the brightest asteroids currently visible, with finder charts tailored to any location. 

Heavens-Above — Asteroids – Under “Astronomy → Asteroids” you can create personalised ephemerides and sky charts for major asteroids alongside the site’s satellite tools. 

Asteroid Lightcurve Database (LCDB) – NASA-PDS repository of 34 000+ published rotation light-curves and derived spin/shape data for asteroid research and amateur photometry projects. 

Astronomical League – Asteroid Observing Program – Step-by-step visual/CCD observing award that teaches amateurs how to identify, track, and record asteroid positions and light-curves. 

NEO Earth Close Approaches – Daily-updated list of upcoming near-Earth asteroid fly-bys with size estimates, miss distances, and quick-link orbit visualisers. 

Boosk on Astrophotographic Target Selection

The 100 Best Astrophotography Targets by Ruben Kier - This excellent list of classic targets is a great resource when trying to pick what you are going to shoot next. (Thanks to Vaughn Payne for suggesting this one!)

Comets

NASA Science – Comets – Plain-language primer on what comets are, where they come from, and why they sprout glowing comae and tails, with links to current research and missions. 

JPL Small-Body Database Browser – The authoritative NASA tool for up-to-date orbital elements, physical parameters, ephemerides, and 3-D orbit diagrams of every numbered or provisional comet. 

Minor Planet Center – Comet Database Search – IAU clearing-house where discovery details, designation history, and continuously updated orbits for all known comets are published. 

Comet Observation Database (COBS) – Global hub for amateur + professional observers to upload magnitude estimates and light curves; includes searchable reports and automatically generated graphs. 

Weekly Information about Bright Comets – Seiichi Yoshida – Long-running weekly digest forecasting brightness trends, visibility maps, and discovery news for comets down to mag 14. 

TheSkyLive – Comets – Real-time table of the brightest observable comets, updated several times per day and linked to interactive finder charts for any location. 

In-The-Sky.org – Current Comets – Continuously updated listing of upcoming perihelia, perigees, and peak-brightness dates, each with custom altitude/time plots. 

Sky & Telescope – Comet Observing – Magazine portal offering observing guides, monthly highlights, and expert tips on tracking or photographing the latest comets. 

Comet Chasing – Skyhound – Up-to-date finder charts, visibility forecasts, and observing advice aimed squarely at backyard comet hunters. 

AstroBackyard – “How I Photographed the Green Comet” – Practical, step-by-step imaging tutorial (gear, settings, processing) that doubles as a general guide to photographing any bright comet. 

ESA Rosetta Image Archive – Full, high-resolution dataset from Rosetta’s rendez­vous with Comet 67P, ideal for studying comet geology and activity. 

Cometography (Gary Kronk) – Extensive historical catalogue weaving together centuries of observations and stories of every significant periodic or great comet. 

Deepsky Object Catalogs

Overview of Deepsky Catalogs

Messier & Other Catalogs – Paris Observatory – Handy table summarising all major deep-sky catalogs.

SIMBAD Dictionary of Nomenclature – Master lookup of every published designation for celestial objects

Messier Catalog

NASA / Hubble Messier Catalog – High-resolution Hubble images and object facts for all 110 Messiers.. NASA does the Messier list with some of the best images ever taken of each object! Descriptions and some finder charts (somewhat crude but useful).

Seasky.org – Messier Guide – Descriptions, finder charts, and observing tips.

Go-Astronomy – Messier Objects – Whole-sky map with images, data, and cross-references. - nice whole sky map, descriptions, and images.

Spanel Planetarium Messier List – Illustrated Messier tour from Western Washington University.

SEDS Messier Database – Classic Messier pages with images, discoverer notes, and catalog cross-links.

in-the-sky.org – In-The-Sky.org’s interactive Messier catalog with data, coordinates, and visibility charts for all 110 Messier objects (filterable by constellation, object type, etc.).

skyatnightmagazine.com – BBC Sky at Night magazine’s complete Messier Catalogue, including images, descriptions, magnitudes and coordinates for finding each object 

Messier Catalog – AstroPixels – Comprehensive table listing all Messier objects with classifications, magnitudes, and coordinates, plus links to a photo gallery project.

Messier Catalogue – FreeStarCharts – Overview of all 110 Messier objects, including descriptions and observing tips for amateur astronomers.

NGC/IC Catalogs

Wikipedia – Full NGC List – Clickable master list with basic data and images.

In-The-Sky.org – Interactive NGC Catalog – Object data plus visibility charts for your location.

SEDS NGC/IC Database – Searchable NGC/IC entries with historical notes. cross-links to more data.

Sky-Map.org – IC Image Browser – IC catalog list linked to multi-survey images.

Emil Ivanov – NGC Photo List – Amateur images and notes for many NGC objects.

Emil Ivanov – IC Photo List – Companion gallery for IC objects.

News@Sky-Map – IC Image Browser – IC catalog entries linked to multi-survey images.

ngcicproject.observers.org – The NGC/IC Project (archived): a comprehensive database aiming to correctly identify all original NGC and IC objects, with collected images and detailed data for each entry 

NGC 2000.0 – HEASARC – Modern compilation of the New General Catalogue and Index Catalogues with updated positions and corrections.

NGC / IC Catalogues – FreeStarCharts – Detailed information on the NGC and IC catalogs, including object types and historical context.

Arp Catalog

NASA/IPAC – Arp Atlas of Peculiar Galaxies – High-resolution scans of Halton Arp’s 1966 atlas with notes on each interacting or disturbed system.

https://arpgalaxy.com/ - A great overview of the ARP’s Catalog and some great cross-links to images and more info.

Bernards Catalog

https://in-the-sky.org/data/catalogue.php?cat=Barnard&const=1&sort=0&view=0&page=2 in-the-sky.org has an online listing of Barnard objects - one of the very few that I have seen.

saguaroastro.org – Saguaro Astronomy Club: “The Best of Barnard’s Dark Nebulae” observing list, featuring data and notes for many of the most famous dark nebulae from E.E. Barnard’s catalog 

Barnard Catalog – In-The-Sky.org – Interactive listing of Barnard catalog objects with data and visibility charts.

Barnard Dark Nebulae Catalogue – DeepSkyCorner – Detailed descriptions and data for Barnard dark nebulae, including object numbers and coordinates.

DWB Catalog

http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1969A%26A.....1..270D&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf - Paper covering the emission nebula in Cygnus X, including a catalog of emission object studied.

Caldwell Catalog

NASA / Hubble Caldwell Catalog – Stunning Hubble views of the 109 Caldwell objects with finder info.

Wikipedia – Caldwell Catalogue – Table with object data, discovery details, and links.cccc

in-the-sky.org – In-The-Sky.org’s interactive listing of the 109 Caldwell objects, with data on each object and tools for viewing visibility from different locations. 

Caldwell Catalog – AstroPixels – Detailed table of all Caldwell objects with classifications, magnitudes, and coordinates, plus links to a photo gallery project.

Caldwell Catalogue PDF – Scribd – Downloadable PDF listing all Caldwell objects with descriptions and observing data.

Herschel Catalog

“The Herschels and Their Catalog” (PDF) – Illustrated history of William & Caroline Herschel’s surveying work.

Wikipedia – Herschel 400 Catalogue – Detailed object table with cross-references to Messier & NGC.

Go-Astronomy – Herschel 400 List – Online reference with sortable data and sky map.

Herschel’s General Catalogue (1864) – Archive.org – Original scanned catalog of nebulae and clusters.

Royal Society – Herschel Catalog Scans – PDF facsimiles of Herschel’s 1786, 1789, 1802 nebulae papers. The complete online text of “A general catalogue of nebulæ and clusters of stars, arranged in order of right ascension and reduced to the common epoch 1860.0 (with precessions computed for the epoch 1880.0)” by Herschel, John F. W. (John Frederick William), Sir, 1792-1871

Catalogue of One Thousand New Nebulae & Clusters (1786 PDF) – William Herschel’s first great nebula catalog (Philosophical Transactions vol. 76 pp. 457-499) scanned in full! A downloadable Scan of "Catalogue of One Thousand New Nebulae and Clusters of Stars" (PDF). By William Herschel. Philosophical Transactions of the Royal Society of London. 76: 457–499. Bibcode:1786RSPT...76..457H

Catalogue of a Second Thousand of New Nebulae (1789 PDF) – Herschel’s follow-up paper adding another 1 000 objects and remarks on the heavens’ structure. A downloadable scan of the "Catalogue of a Second Thousand of New Nebulae and Clusters of Stars; with a Few Introductory Remarks on the Construction of the Heavens", by William Herschel. Philosophical Transactions of the Royal Society of London. 79: 212–255. Bibcode:1789RSPT...79..212H. doi:10.1098/rstl.1789.0021.

Catalogue of 500 New Nebulae & Clusters (1802 PDF) – Third installment listing 500 more nebulae, including planetary nebulae, with construction-of-the-sky commentary. A downloadable scan of "Catalogue of 500 New Nebulae, Nebulous Stars, Planetary Nebulae, and Clusters of Stars; with Remarks on the Construction of the Heavens", By William Herschel. Philosophical Transactions of the Royal Society of London. 92: 477–528. Bibcode:1802RSPT...92..477H. doi:10.1098/rstl.1802.0021.

https://ia903207.us.archive.org/20/items/jstor-106639/106639.pdf - Anotehr PDF of “Catalogue of One Thousand New Nebulae and Clusters of Stars. By William Herschel, LL.D. F. R. S.”. This one is a little cleaner.

Second-Thousand Catalogue (clean scan, PDF) – High-resolution copy of the 1789 paper suitable for printing or detailed study. his a clener downloadbale PDF of “Catalogue of a Second Thousand of New Nebulae and Clusters of Stars; With a Few Introductory Remarks on the Construction of the Heavens. By William Herschel, L L. D. F. R. S.” from Herschel, William, Public domain, via Wikimedia Commons.

Catalogue of Nebulae & Clusters of Stars (1863 PDF) – Sir John Herschel’s consolidated catalog (2 510 objects) that became the basis for the NGC; full 1863 scan.

Herschel 400 Guide – Part I (PDF) – Observing charts and object notes for the first 134 entries of the Astronomical League’s Herschel 400 program.

Herschel 400 Guide – Part II (PDF) – Continuation covering objects 135-267 with finder charts and data.

Herschel 400 Guide – Part III (PDF) – Final volume (objects 268-400) completing the full Herschel 400 observing guide.

Astronomical League – Herschel 400 Program – the official observing program page for the Herschel 400, providing the full list of 400 deep-sky objects (a subset of the Herschels’ discoveries ) along with program details and resources for observers.

Herschel 400 Observing Guide – Cambridge University Press – Guidebook providing detailed information and observing tips for the Herschel 400 catalog.

Hickson Compact Groups

HCG List – Wikipedia – Table of all 100 Hickson groups with positions, redshifts, and member counts.

LBN Catalog

http://cdsads.u-strasbg.fr/cgi-bin/nph-iarticle_query?1965ApJS...12..163L&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf - This is a link to the original paper written by Beverly T. Lynds on the Catalog of Bright Nebulae.

LDN Catalog

Go-Astronomy – LDN List – Complete coordinates and sizes for all 1,700 Lynds Dark Nebulae

PGC / LEDA

HyperLeda Database – Search 3 million galaxies by name, position, redshift, or diameter; returns detailed photometry and morphology.

Quasars

https://en.wikipedia.org/wiki/List_of_quasars -A list of Quasars in Wikipedia

https://heasarc.gsfc.nasa.gov/W3Browse/all/milliquas.html - MILLIQUAS: The Million Quasars Catalog, Version 8

Sharpless Catalog

SharplessCatalog.com – Dedicated site with data, images, and observing notes on all Sh-objects.

GalaxyMap – Sharpless Objects – Interactive Milky Way map with Sharpless nebulae.

PDF Atlas of the Sharpless Catalog – 200-page atlas of Sh objects with charts and survey plates.

Neutral.org – Sharpless Comprehensive List – Data table with alternate IDs and images

http://astro.neutral.org/sharpless/sharpless-catalogue-list.html - This is a great comprehensive list of the Sharpless Catalog.

en.wikipedia.org – Wikipedia overview of Stewart Sharpless’s catalog of 313 H II regions (emission nebulae), with a list of all Sharpless objects and their basic data .

In-The-Sky.org – Sharpless Catalog – Interactive list of 313 H II regions with visibility charts for any observing site.

The Sharpless Catalog – Adventures in Deep Space – Overview and selection of notable Sharpless catalog objects with descriptions and observing notes.

The Local Group

https://www.faintfuzzies.com/Files/LocalGroup%20v2.pdf - The galaxies consisting of our own Local Group!

Uppsala General Catalogue (UGC)

UGC Online (PDF Scans) – Digitised pages of the 12 921-object UGC with positions, sizes and magnitudes for northern galaxies.

vdB Catalog

http://www.emilivanov.com/CCD%20Images/Catalog_VdB.htm - Emil Ivanov’s vdB list - nice reference

vdB Catalog – Wikipedia – Table of 158 reflection nebulae with positions, magnitudes and cross-IDs.

Wolf-Rayet Stars

http://www.pacrowther.staff.shef.ac.uk/WRcat/ An online catalog of all of the known examples of these massive stars!

Quasars

Wikipedia – Quasar – Detailed reference on quasar properties, discovery, and cosmological relevance.

RASC – Visually Observing Quasars (PDF) – Guide to identifying and observing bright quasars with amateur gear.

Wikipedia – List of Quasars – Catalog of notable quasars with coordinates and finder info.

Supernova

Rochester Astronomy – Bright Supernovae – Daily-updated list of current supernova discoveries with finder charts. Unique resource on the latest Supernova reports

IAU Transient Name Server (TNS) – Official, up-to-the-minute database of newly discovered supernovae and other transients.