Scopes, filters and magnification
Given the faintness and small size of these targets, imaging details in IR only really becomes a realistic proposition with 8-inch scopes and above. Even then it is important that you choose a night of good seeing, collimate accurately, allow the scope to properly cool prior to imaging and choose your telescope magnification appropriately.
Too high a magnification and the planet becomes overly faint with no benefit in resolution; too low and although the planet’s brightness might be improved, you lose resolution because there aren’t enough pixels to render all the detail the scope can provide. There’s a rule of thumb in planetary imaging that will help you optimise magnification: pick a power which gives an effective focal ratio of 3x to 5x the pixel size in microns. For instance, with an IMX290 chip that has 2.9+m pixels, pick a magnification that gives you f/9 to f/14.5, while for the IMX224 chip and its 3.5+m pixels, you want a focal ratio of f/10.5 to f/17.5. Selecting your Barlow lens’s power to stay within these bands gives you the best chance of imaging success.
When imaging the ice giants you need to choose a filter that lets IR light through but blocks visible wavelengths, which would otherwise decrease the contrast of subtle surface features. Look for IR filters with a wide acceptance band to maintain image brightness, such as the Baader red 610nm longpass filter, the Baader IR pass 685nm filter and the Astronomik Planet Pro 642 filter.
"Too high a magnification and the planet becomes faint with no benefit in resolution; too low and you lose resolution"