Good advice here... all around.
Tough issue to resolve, since there are many more factors than eyepiece focal length that determine upper magnification limit. Some that come immediately to mind are double star attributes, optics collimation, target altitude, mirror thermal stability, mirror quality and focal ratio, natural/artificial seeing impediments (mountain/upper atmosphere driven currents, radiating surfaces like roofs, roads, etc.), time of observation (late night/early morning being generally better) and eyepiece design/execution characteristics (the reality that none do everything optimally).
I had a good 10” f/5 reflector and still own a fairly solid Celestron C-8 Edge HD, which in theory would allow me to get to higher than 200x. But in practice, all the other factors along with seeing typically limited me to 200x. My 3 and 4” refractors deliver very tight stars, but are limited in aperture and my 150mm Mak-Cass delivers almost the same caliber of pinpoint stars as my apo and occasionally allows higher magnification (300x, via a 6mm Delos). But to your point/question, once you’ve mitigated all the other factors, backing off on magnification is generally the only recourse... along with trying other EPs in your arsenal; e.g., orthos versus wide field varieties (I have both).
With my outstanding 3” and 4” apos, I’m limited to about 160 and 200x, respectively before I start running out of brightness for dimmer targets. With my 150mm Mak-Cass and 200mm C-8, I’m generally limited to 200x. I am roughly 25 mi north of San Diego with mountains about 2 miles to the east... along with a not-too-infrequent marine layer intrusion (fog) coming in from the west; so what the light pollution and fog does to me gets supplemented by winds transiting over mountains whose rocks are also radiating their daytime heat into the sky at night. Persistence is a worthy attribute in this hobby. As is the use of a comfortable adjustable observing chair, in what otherwise can prove to be uncomfortable circumstances which impede capturing subtle details like excruciatingly thin gaps between neighboring stars.
Aside - with my apo’s the challenge I place on myself is not how high in magnification I can go, but rather how low in magnification can I go to discern a distinct separation. And, I enjoy those with a discernible color difference - along with distinctly red individual Carbon stars... like Hind’s Crimson star or T Lyrae.
P.S. The 6mm Baader Classic Ortho is a solid eyepiece... I own one and see BillP’s reviews in this forum.
Edited by jimandlaura26, 25 February 2021 - 12:28 AM.