The split depends on what you intend to do, and there are really only two intentions.
If you intend to look
Aperture and steadiness, in that order. A Dobsonian puts almost everything into the mirror and needs nothing else to work; the money left over goes to a collimation tool, a low-power eyepiece and a red torch.
If you intend to photograph
The mount takes the largest share, and it is not close. A modest tube on a capable mount produces images; a large tube on a marginal mount produces discarded frames. The camera can wait; the mount cannot be worked around.
What to buy in the first month either way
A collimation tool if the telescope has mirrors, a low-power eyepiece with a wide field, a red torch judged on how dim it goes, and a planisphere or a chart. Together they cost a fraction of the telescope and change more than an upgrade would.
What to buy in the first year
A better eyepiece at whichever end you use most, a Barlow if the gaps warrant it, and a chair. The chair is the purchase most experienced observers name and most beginners skip.
What can wait indefinitely
Filters beyond a broadband nebula filter, a second telescope, and anything that promises to fix a problem you have not yet had.
The questions that keep arriving
Is it worth buying second-hand?
Optics age well and mounts age less well, so a used tube is usually a better risk than used electronics. Check a reflector for coating condition and a focuser for slop before anything else.
What should I definitely not buy yet?
A full filter set, a second Barlow, and anything bought because it completes a range. Each of those is better bought after a specific evening made you want it.
Last reviewed 17 September 2026