Separate the power requirements of the laptop from the rest of the gear.
Find out the peak amp draw of your gear, aka the mount when it's slewing in both axis, dew heaters on highest setting, etc. This will give you an idea of how many amp hours you need to get through your typical session. It's best to use a meter, but you can go by Output listed on any AC adapters.
For example: My mount, 2 dew straps (main/guide), focuser, rotator, and camera never draw more than 2amps peak, and most of the time (not slewing) it is much less (1.2amp). I use the Suaoki Lithium Power, it will run my gear all night easily, and often two nights. Small, lightweight, delivers consistent voltage and can use the whole thing (Lead Acid should only be discharged to 50%)
Your laptop is a whole other beast entirely, and depends on the make/model of laptop. Many laptops require 15-19volt, and inverter losses take a significant toll. Older laptops may have batteries that no longer perform like they once did. Maybe a new replacement internal battery will get through the night (for an old battery scenario). Your laptop may have an external "clip on" battery designed specifically for it, check your make/model. In any case, I would divide and conquer, most astro gear doesn't draw much power and is quite happy with small, lightweight lithium packs/batteries. Keep your 12-volt needs separate from your laptop needs, or at least explore the possibility, sometimes solving 2 power needs is easier/cheaper and more elegant than combining into 1 solution.
I keep my system ultra-light and ultra-portable without compromising any functionality, so I use a Microsoft Surface Pro laptop, which is very happy running on 12-volt(2.5amps). Not only does the battery last 12 hours, but I can charge it from the same Suaoki Lithium Power if I need using the common 5.5x2.1 DC plug (doing this will reduce the Suaoki to just one night of operation) Not all laptops can do this, and my point is, know your gear and what it needs, designing a solution is far better than just throwing lead acid amp hours at it (your back and legs and arms will thank you!)
Those "portable jump starters" are terrible for what your doing. They are designed to deliver a lot of power all at once (Cold Crank Amps), discharging quickly... yes you can plug AC into them because they have a built in inverter, but it's meant for emergency use, and it's extremely inefficient. These are not meant for sustained draw, steady discharge, like true deep cycle. If you must use a lead acid battery for your AC plug laptop, then get a true deep cycle (not a marine), and a small inverter, you'll get much more mileage out of it (mind the 50% discharge limit).
Edited by davidparks, 22 July 2019 - 02:06 PM.