At first I thought the battery was expensive for 7Ah but then I noticed it is the newer technology Lithium. The Nexstar cord seems expensive but it will give you the correct plug but the polarity is still dependent on you connecting correctly to the battery and provided the female cigarette socket is correctly wired.
I’m not familiar with the telescope you have or it’s power polarity requirements, i.e. centre positive or centre negative. Get a pocket multimeter, cheapest you can find and that way once you connect the cords to the battery first test the voltage and see if it is generating centre pos or centre neg. It needs to match your telescope requirements. If opposite, reverse the connection at the battery.
It is probably reasonable to assume the cigarette socket is correctly wired as would be the Celestron cord but better safe than sorry.
This is the battery cord you need. (Link below). See if you can find one that has fully insulated alligator clips to avoid accidental shorting of the battery terminals. I use this battery for all my telescopes that need 12V. It’s nothing special but it works. If I need a reverse polarity I use a different cord.
See
https://www.jaycar.com.au/cigarette-...clips/p/PP2007
Perhaps others who have a similar telescope can chime in with what they use. I use a 12V 9Ah SLA and similar cords that I hand made. I use an OzCharge 8A charger set at 2A and keep the battery connected to the charger when not in use.