Craig's advice is spot on, the only change in the order I'd make is to put the mount first, it is going to be your path to fun or frustration - once you get past Milky Way shots you are going to need a driven mount that will counteract the Earth's rotation (OTOH there is some good work that has been created on the brighter objects with a ILC/DSLR, tripod and software stacking. For Deep Sky objects you really want a driven mount, probably with Goto. Roland Christensen of Astro-Physics says the three most important things in astroimaging are the mount, then the mount, then the mount....
Start with a short refractor, say 60-100mm aperture (objective size) and 300-600mm focal ratio - so that would put you somewhere between F4-F7, here faster is better since it can have a dramatic effect on exposure time). On the simple end of a mount is a star tracker - like the Skywatcher Star Adventurer and a solid tripod. In the middle is a German Equatorial Mount (GEM) something like the EQ6R as mentioned by Craig. I've had okay luck with a Celestron AVX, better luck with a Vixen SXD2 and the best of all luck with my Astro-Physics Mach2 (big bucks though). Software Bisque makes great mounts (My-T) and when I lived in Boulder I used to hang out with the Bisque clan (they were in Golden, CO).
Another approach to the mount is both easy and complex (at the same time), what is called a driven alt-az mount, this avoids polar alignment (still needs to be aligned on typically two stars) BUT at the expense of something called field rotation (everything in the view spins over time) so you need to do special processing to register (align) the images, stack them and your images will essentially be cropped. There are solutions to this such as the Track The Stars Panther TTS-160 mount which rotates the entire camera and telescope tube - it works really well, and it is a blast to take on camping trips but it is a different kind of complexity. It packs down tiny so fits in the camper van easily. I'll try and find some examples to post, I never seem to have good luck posting images here
The next decision is are you going to do One Shot Color or Monochrome?
On the camera front you can use a DSLR or an ILC, I did a lot of work with a Fuji XT-2 and XT-3, and don't forget the Nikon D810a or the Canon modified equivalent, this is all called one shot color since you are shooting a color image (the CFA impacts exposure and you have to limit exposure time based on sky condition, I found 30-45 seconds worked fine, take a lot of images, use software to register (align) and then stack them. The next step up, as Craig suggests, is a monochrome camera, and better yet one that is cooled electronically. Vendors include SBIG (who kinda started it all), FLI, ATIK, ZWO, QHYCCD, QSI, and more I can't remember right now. SBIG and FLI the premium brands, however its getting really complex with the move from CCD to CMOS (you should hear the arguments in the astro circles, it puts the photographers to shame
ZWO deserves special mention since they also make a device Craig referenced - called the ASIAir, which is a tiny computer (Raspberry Pi) designed specifically for astronomy and controlled by your iPad - it is all in one and has become quite capable, it can help with polar alignment, focusing, guiding (another whole subject), taking images, running the filter wheel (if you are doing monochrome you will want a filter wheel and filters), etc.. The ASIAir is a fantastic device, however it only supports ZWO cameras, ZWO guide cameras, ZWO focus motors and ZWO filter wheels, however it is the quickest path to astroimaging with a dedicated astro camera. Highly recommended especially to get started. I still use it all the time unless I'm trying to collect exposure time for a group project - then the big guns get deployed.
One thing with the ASIAir and iPad that is really fun is to use live stacking and registration for sharing the night sky with a group, it is awe inspiring to see the image unfold as more images are stacked - I will usually have another telescope setup so folks can try to see the same thing with their own eyes - something I've never tired of!
A ZWO cooled monochrome micro4/3 or APS-c sized imager can be had used for $600 or so and up to the ZWO ASI6200mm for $5K, the latter being 60 megapixel full-frame. I always recommend either micro4/3 or APS-c to get started, full-frame increases the cost of everything like filters and telescopes that can cover full-frame can get really, really expensive. So a ZWO ASI1600mm (monochrome) or a ZWO ASI294MC (color) are incredible entry points and will keep you busy for years and years.
So lets say you decide monochrome, then you need a filter wheel and filters - ah and yet another decision - broadband (LRGB) or narrowband (SHO)? Broadband takes exposures through four filters, clear (Luminance), red, green and blue and you composite the images in post to make a color image. Exposure times are "relatively" short BUT you need a relatively dark site to do good work. Narrowband takes three or four images, clear (Luminance), Sodium2, Hydrogen Alpha and Oxygen3 - these filters have very narrow passbands and thus exposures get long quick, however you can image from the middle of a big city. Ray Gralak and Robert Gendler first introduced me to narrowband imaging long ago, look up their work - Ray used to image from his driveway under street lamps in urban San Jose.
Get a seven position filter wheel, since if you "get hooked" you can have LRGBSHO filters all loaded and ready to go - and yes they are expensive, so another reason to keep sensor size to micro4/3 or APS-c, cost goes up geometrically
Although it is a tough decision, I'd probably suggest starting with a one shot color (ZWO ASI294mc) and a light pollution filter maybe? I'd start with a 80-90mm refractor, you really want to stay with an Apochromatic (either a doublet or a triplet). Mount wise gets harder, I never had a lot of luck or fun with the star trackers, however many people (like Don) have had good luck. I'd go for a GEM and just learn how to polar align, the ASIAir can make it simpler. I'd go with the ASIAir and an iPad. I'd get either a Bahtinov mask for manual focusing or a ZWO EAF focus motor (this can be a pain to get mounted properly depending on your telescope). So mount wise I'd spend as much as you can, so either used or new if you can - the trade off is stability versus weight versus cost. There are definitely bargains to be found, folks get into and out of the hobby on a regular basis. For many years my "compact" kit was a Vixen SXD2 mount with their tripod (today there are better choices), a Takahashi FSQ 85mm telescope and a variety of cameras including long ago a SBIG STL11000, SBIG 8300, later ZWO ASI294mc and later a ZWO ASI1600mm with 7 position filter wheel and an ASIAir using an iPad.
Cloudy Nights is a great website for classified, forums, opinions, etc......
Yes this can be a money pit and a time pit and a learning journey as well as training in patience! Dante loves astrophotographers even more than s/he loves medium format photographers!
Kind regards, Glenn