Is there a reason to go with DSLR instead?
There might be a slight one, depending on exactly what type of astrophotography you're planning on doing.
The sensor is on and energized the entire time a mirrorless cameras is turned on. This creates heat that can affect the amount of camera generated "read noise."
A DSLR's sensor is energized only when actually ...
Not true. I have a Tamron pair of lenses that are trash at staying clean. The dust is on the back 50% of the elements inside so it's impossible for me to clean and not worth paying for it for $100 lenses.
My d7000 really shows the dirt exactly like this in the same conditions. My d7500 seems to be more immune to this issue but it still shows up.
DSLR or mirrorless, either works just fine. Mirrorless will eventually displace DSLR, but then again DSLR lenses can be used for mirrorless cameras so you won't lose anything if you buy now the old technology. (Vice versa, mirrorless lenses can't be used on DSLRs.)
For astrophotography, the answer is: yes! Yes! If you can afford it, full frame is really ...
I agree with mattdm, dust in images are usually found on or near the sensor. They are usually visible at small apertures, like F16-32. Some thoughts and points to consider on this topic:
You can avoid problem apertures with aperture priority. Dust usually isn't visible in photos taken with apertures larger than about F8.
Check for dust proportional to how ...
The dust isn't on the lens — it's on the sensor. Dust on the lens will not resolve so clearly.
To check for it quickly, set your aperture to the smallest your lens can support. (Small apertures have large f-numbers, like f/22.) This will keep the light striking the sensor to a straighter angle, which in turn will make the dust (which sits on filter layer ...
What do you think the mirrorless RP can do for the type of photography you do that your current 6D Mark II can not?
If you can't answer that question then you don't need to upgrade anything.
If you are dissatisfied with your current photos and think that a change in gear will make you a better photographer, please see:
Does the camera matter?
When should ...
I would say probably not. You should wait until they release a mirrorless camera with better specs. For example, the EOS RP has quite slow burst rate, and in burst, you only see the images and nothing about what happens between the images. (There is a high speed display option for showing what happens between the images, but that's only available for RF ...
I have the RF 24-240 lens for my EOS RP. I also have EF 24-105 f/4L mk1 lens. I don't have the RF 24-105 f/4L lens.
The RF 24-240 lens has several quirks you need to know:
Lack of weather sealing
Lens hood needs to be bought separately
Manual focus switch is missing and you need to set it in the camera menu
The focus/control rings are combined into one
How important is "image quality" to you (sharpness, aberrations, distortion, light falloff, flaring, etc)? You can compare the lenses at The Digital Picture.
Are more versatile. They cover a greater focal length range.
Are more convenient. You don't have to change lenses.
Are more fun. You can take pictures without worrying about ...