There are so many things one needs besides the scopes and eyepieces ... One can keep buying and still there are useful things to buy . This page was initially covering all my equipment but it grew too big as my equipment inventory increased over time.
The equipment not needing more in-depth coverage is mentioned below, the other stuff is described in the following sections: eyepieces, CGE1400 specific equipment, clothes, chairs, binoviewer and the whole group of imaging equipment with its subsections.
A very useful thing to have around on an observing session is an observing table for keeping eyepieces, maps, books etc. It should be light and possibly foldable, so it can be taken for a trip to a dark site. I bought an Orion foldable observing table - I can unscrew the legs, remove frame and roll it into a small package. I don't do it often, it usually sits assembled inside my observatory, and I just take it out to the deck when needed. Don't forget about red light - an observer needs red light to look at notes, maps and work around the scopes. The best ones are the ones that you don't need to keep in hand - the ones that are attached to head band. I bought online a bunch of red LED lights used for outdoors, each has three red LEDs and is powered by 3 AAA batteries (picture below). They are very comfortable, but a bit too bright. So I took one and painted the glass with a red nail polish, and now I have two: bright one for setting up and a dim one for later once my dark adaptation kicks in. I have also a LightWedge - a flat source of red light ideal for maps and observing lists. Especially useful when there is some wind, it keeps sky charts, notes and lists in place.
Another must-have accessory are narrowband filters for visual use. I mean by that nebula filters like Orion UltraBlock Narrowband filter or Orion OIII filter: I have both in 2" size. Some nebulae are much better with them, especially all the emission nebulae glowing in OIII like supernova remnants (e.g. Veil Nebula in Cygnus) or planetary nebulae (e.g. Dumbbell Nebula M27 in Vulpecula). Sometimes I can't see anything without such a filter, and definitively I can see way more details with them. These filters work by allowing only selected narrow band (in wavelength) to go through that corresponds to wavelength in which these nebulae are bright, they eliminate all other light and therefore increase contrast a lot. The work best on larger scopes, the narrower band the large scope needed, i.e. UltraBlock is OK on smaller telescope than OIII.
I do not recommend wideband light pollution filters - they have too wide pass band (let too much "unrelated" light through) and I can't see much effect at all. Maybe they would be better in light pollution worse than mine. I don't also recommend any "galaxy" filters since they don't work at all - galaxies emit light mostly as sets of stars, i.e. in continuous spectrum and one can't enhance it by cutting pieces of spectrum out.
I started my practical astronomy using my scopes on my backyard deck, and I needed to screen myself from some neighborhood lights. I have build removable screens using black plastic trash bags and 1x2's that attach to the railing with Velcro. Works very well and is fast to deploy (and take down). It can withstand surprisingly strong wind if it is attached by Velcro at the bottom as well so it can't slide on the floor.
A very important accessory for a Newtonian owner is a laser collimator. I got a simple one when I bought 10" Antares Dob, and then i upgraded it to more precise barlowed laser when buying Obsession. It really simplifies Newtonian collimation and I can't imagine not having one. But it won't work for a Schmidt-Cassegrain (SCT) scope!
I always wanted to know what is really the quality of my night sky and how the light pollution affects my observing and photography. There are visual tricks (like checking the visibility of stars in Little Dipper) that allow to estimate limiting magnitude, but nothing beats the measurement. Unihedron Sky Quality Meter makes such measurements possible, I bought the SQM-L version with a lens which has smaller filed of view than a non-lens one, what allows measuring different parts of the sky. The unit is small, uses one 9V battery, and can be taken anywhere. I measured light pollution in several places around Ithaca and put the measurements on local light pollution map.