[Startrek (Martin)]

This open cluster called “The Gem” cluster is adjacent to Gabriela Mistral Nebula ( a huge arm of the Carina Nebula ) and has dense nebulosity clouds surrounding it.
If using OSC camera you need your Gain set for a higher dynamic range with lowest read noise ( ZWO 2600MC is Gain 100 ) at least 13 stops

You definitely need a OSC Dualband filter like L Enhance , L Extreme , L ultimate or Antlia ALPT to adequately expose the Ha. (L Ultimate and Antlia ALPT are the best )

If using a f5 scope 3 minute subs are satisfactory and require just an hour or 2 to expose the nebulosity ( see my image attached with 2 hours or so of data with the L Extreme captured in 2021 )
Sorry for the crappy resolution I use my iPhone to downsize it but you can see the nebulosity, also my Star colours are crap as I used a Star mask to try and fix the colour but didn’t work ( no orange Star ) should have imaged RGB for stars only.

If using an f10 scope I’d reckon you need 4 to 6 hours with 3 to 5 min subs using the OSC Dualband filter

Also my image was under Bortle 7/8 Sydney skies ( heavy LP ) so yes you have to remove the gradient as best you can which doesn’t restrict your image Stretch but more signal or more hours on the target will greatly improve the result.

I looked at the specs and performance charts on the 268C and for narrowband imaging ( using Filter ) and Mode #1 is most suited ( Gain 55 and above ) however I’ve never used this camera , only going by recommendation
Cooling the camera down to -5C to -10C should be more than satisfactory for mitigating dark current

Hope the above helps

Martin