Your garden variety electronic solder with rosin core isn't agressive enough to solder NiChrome. You would need acid based flux as sheetmetal workers use, you can get it at Napa or HomeDepot.
That stuff happily will destroy almost anything electronics related. Like copper wire, PVC wire insulation, most plastics. So its at most good enough for a few hours lifetime
Another thing is heat. An even just moderately hot heater wire will over time degrade your solder contact. So you will at least want to use a higher temp silver solder. And now you think - I'm not using it to get THAT not. Well, the wire has a very small surface area and even at quite low energy densities it does get quite warm ... in particular at the ends where its not having a good heat sinking for it.
So in reality - you crimp/compression contact NiChrome wire, only. Use a copper or brass ferrule or some wire clamps.
I do use NiChrome wire for the corrector plate of my 6" Mak. Its directly wound onto the glass, with thermal paste and all held in place with Capton adhesive tape, which is very heat resistant. Some 1-2 watts is enough to keep the somewhat big thing just at ambient temperature or a tad above. You really just want to replace the radiative lost heat.
And that is why you want MUCH finer control than just a series/parallel connection of two resistive loads. Most dew heater controllers use some PWM circuit to adjust the average power. I'll nowadays would just get some step-down buck converter module to supply it with a lower and variable voltage.
Edited by triplemon, 08 November 2023 - 04:36 AM.