How to focus on a very dim star .... Wind the focus knob inwards or outwards until you just see it disappear off the image using 1sec or 2 sec frames at whatever gain you are at. When you see it just disappear note the focuser knob position and put your index finger at the 12 o'clock position. Wind it so the dim star once again appears, and keep winding through that until it once again just disappears. Correct focus is half way from when it first appeared to when it disappeared. With a dim star you will often find the distance you wind the focus knob through that appear to disappear point is only half a turn of the fine focus knob of a two speed focuser. So wind the focus knob back quarter turn and you will be in focus
If using an e-focuser some come with software which shows some scale representing amount of mm in/out travel. So use the scale to figure out where it 'appeared' and 'disappeared' then half way between those two scaled numbers is focus.
If your e-focuser does not have that software, but maybe just uses a button press in/out travel, then you have to just guess by length of time you press the button. It's the least accurate way of doing this.
Or .... every goto mount I've owned, be it hand control or 'proper' ASCOM control, will show you the current RA and DEC (or ALT AZ) plus also allow you to define USER DEFINED OBJECTS. Note the current position of your target object as displayed by the mount control system (HC or ASCOM software). Put that position into the mounts USER OBJECTS list. Every mount I've had allows you to do this either by manually entering the RA/DEC or ALT/AZ or automatically! By automatic I mean there's no need to note down the mounts current on-target coords! As soon as you get into the User Defined Objects menu and tell it to create a new user defined object the current RA/DEC or ALT/AZ is automatically displayed! Simply press the SAVE button to save the position displayed as your new User Defined object. Anyhow ... once that nicely framed objects current mount coords is saved, slew to any bright star nearby and use the mask or whatever to focus. Then get back into the USER OBJECTS menu and tell it to slew to that user defined position. It will be almost perfectly on-target from where you left it.
For what its worth, here's why the above posts on color balance are bang on when they say if you use filters or a modded or astro cam then use the main camera control histogram to correctly balance with that filter on. Classic mistake by down-under Aussie noobs is Tarantula Neb which is actually greenish-blue. They get themselves a modded camera and filters and blast off to the tarantula and see truly weird colors based on what they've seen on the web where nebulas have masses of red hydrogen. So they process it like that using the stacked histogram sliders to get the sky background looking kinda of black/grey and in the process end up with a red Tarantula and even stars look weird colors. Totally wrong colours.
But, sticking the filters onto your camera and then using the main camera controls to find the correct color balance using a daytime view of your neighbourhood means you can note down the RGB settings for what is 'correct color balance'. At night, you set those in the camera controls. So then when you go to an object and start to stack, at least you know that the color of the light reaching the sensor from that position in the sky including the colors from the object are going to be correct color balance and a true representation of the 'glows' coming from that area and object. So when you start to stack, and thus increase the SNR, you'll see the noise decrease, and more details start to who up, and if you use darks and flats you'll see all this change the overall histogram with each and every frame stacked. So the stacking histogram is used to refine that stacked image with respect to getting rid of the LP but still retain as much dim nebulosity etc. As the image darkens the sky and adds detail with each new stacked image, through better SNR, or you getting rid of LP, you may see the colors dim somewhat or change with respect to the darker sky background ... so you'll increase gamma / midpoint curve to make them 'pop' a bit more. But brightening and adjusting the image may alter the colors somewhat .... and that's when you'll fine tune the color sliders to compensate for those slightly altered colors.
When you use this technique then you end up with correct color balance images of the blue-green Tarantula and still with red and blue stars showing and a nice dark grey/black sky background rather than the whole thing being red'ish. Tada ... isn't that what EAA is all about? Observing with a camera using short exposures. 'Seeing' the true colors in your short exposures EAA you will say "WTH !? How come this neb is blue-green?" So you'll look up and research online why they are those colors and discover far more about the wonders of the Universe which you would never have discovered, nor even seen, if you'd only color balanced using the stacking histogram.
So color balance with camera control on single images (preferably in the daytime on green grass, blue sky, white cloud, brown tree trunk scenery in the distance and using various filters and note the rgb settings down with each). Use the stacking histogram to just fine tune to get rid of LP/Skyglow, brighten/pop the colours, then adjust them to suit your taste whether you like brilliant colors or just lighter shades of color.