Tools
What you want within reach before you take the instrument out: the vocabulary, the catalogues, and where to look elsewhere.
Every technical term used on this site leads to its glossary entry. So does integration time, dual-band, magnitude.
Temps d'intégration : the total exposure time, the sum of every exposure stacked on an object. Filtre duo-bande : it lets through only the two colours of emission nebulae.
Before you go out
The one thing nobody tells you about and everybody does: charge it the night before.
The equipment photographs on this site are mine. The device they show is not named, and it will not be named until it is established: the brands were erased when the album was sorted, and the inventory file does not say which of the 12 devices is in the frame. I do not guess it, any more than I guess a field of view. The dates are the dates of the files.
Catalogues
One and the same nebula often carries three names. They are not synonyms: they are three surveys made in three different periods, with three different aims. Each prefix leads to its glossary entry.
Ciel profond : everything outside the solar system, the nebulae, the galaxies and the clusters.
110 objects
Drawn up in the 18th century so as not to mistake these smudges for comets. Messier published 103 of them, taken to 110 in the 20th century. It remains the best list to start with: everything in it is within reach of a small instrument.
Glossary entry
7,840 objects
New General Catalogue, 1888. The reference catalogue of the deep sky, the one you come across most often in the apps.
Glossary entry
5,386 objects
Index Catalogue, a supplement to the NGC published in 1895 and 1908. Objects that are generally fainter.
Glossary entry
109 objects
The bright objects Messier had left aside, listed by Patrick Moore in 1995. The natural next step after the Messiers.
Glossary entry
313 regions
Regions of ionised hydrogen. Very large and very faint: the home ground of the dual-band filter and of wide fields.
Glossary entry
86 nebulae
Faint planetary nebulae. End of the road targets, which ask for hours of integration.
Glossary entry
Maps
The brief asked for three maps: the Moon, Mars, Earth. All three live in the same place, in the “Space” panel of Google Maps, and that is just as well: one thing to understand, one detour to put up with. Because there is one, and it is better known before you click.
From Europe, all three addresses open a Google cookie consent form first, in French. The map comes afterwards. Nothing is loaded from this site until you have clicked: these maps refuse to be displayed inside a third-party page, and I do not try to get around that refusal.
Images ©2026 NASA
The globe seen from the satellite, turned with a finger and taken all the way down to your own street. It is the Earth tab of the same panel, the one you go through to reach the other worlds.
Open on Google Maps
Images ©2026 NASA
The seas and the craters, from Mare Imbrium to Mare Tranquillitatis, from Clavius to Montes Apenninus. The formations keep their Latin names, the rest of the map is in French.
Open on Google Maps
Images ©2026 NASA
The whole planet, from Acidalia Planitia to Hellas Planitia, with Cydonia and Syrtis Major Planum. Same image base, same panel, same credit.
Open on Google Maps
The same panel opens 21 bodies in all, every one of them named in French, from Mercure to Charon: the four moons of Jupiter, seven moons of Saturn, Vesta and Ceres. The names of the formations, for their part, stay in Latin on every map.
Two services show the same worlds with no cookie form, but they are in English, which is worth knowing before you send somebody there: Stellarium Web, a planetarium that runs in the browser, and NASA Eyes, the solar system in three dimensions, which covers Earth, the Moon and Mars on its own.
Links
None of these links earns a commission, and none of these channels has anything to do with selling the devices. The channels cited are French language and follow the subject of smart telescopes or astronomy news; the list is not exhaustive.
Manufacturer sites
French language channels and sites
2 of these 7 channels carry their address: those are the ones that have been opened and checked. The other 5 are waiting for theirs, one at a time: no dead links on this site. The names are given as they stand, with no ranking and no recommendation.
The glossary is the only place on the site where a word is defined. The product entries, the deep sky catalogue and the home page link back to it. None of them redefines the same term in its own way.
