setting up the infinity point on a camera lens for dso work

[Wirral man]

Hi all I'm still new to imaging and just wondered what different methods people use for setting the dslr camera lens for a tack sharp image in manual focus?

my current method is I set to auto and let the camera focus on the moon in live mode and simply place to bits of tape on the lens barrel and mark both points and then switch back to manual so I'm putting my faith in the auto focus, but I have took some shots of the orion nebula and I feel the image could be sharper.

my setup is a nikon d5300 with a tamron 16-300mm and 18-55mm af-p vr on a skywatcher star adventurer thanks 

[SteveNickolls]

Hi, Thanks for posting. A lot will depend on your lenses, some can move by themselves during an evening and wider lenses make it harder to focus as the stars are smaller :-( However when first setting up I use my Canon's Live View at x5 or x10 magnification and manually focus on a bright star, going in and out of focus until I judge the best position. Take your time. At a pinch a street light way off in the distance will also do. I also have BYEOS in which I could try to focus with certain lenses but much prefer the manual method. Obviously after focusing be careful not to touch the focus ring.

Good luck with your imaging and do remember to post.

Cheers,
Steve

[Demonperformer]

You might consider knocking-up a simple Lord mask - these work very well when using a scope and are probably not quite as effective using a camera lens, but I have used them with great effect although I tend to view my camera on the laptop magnified as much as possible. One upside is that they take very little in the way of manual dexterity to make - Blue Peter skills, really.

[Macavity]

I do some variant on (most of) the above! Auto-Focus with a *bright* object...
Use 10x magnified image to focus on stars. Easier with lenses that don't rely on
electrical power (non-STM?) for so-called manual focus as well (if I remember)! 

For long focus lenses, I remain somewhat intrigued by devices like:
https://www.teleskop-express.de/shop/product_info.php/info/p3284_Microfocuser-and-focus-lock-fuer-camera-lenses-up-to-D-105mm.html

For what it's worth I did make a "mounting cage" for my one an only "decent" lens
(Canon 70-200 f/4) using guide scope rings... Not to use them to focus, but rather
to CLAMP the various rotating components once I had manually focused the lens!
It is rather easy to "knock things off" either with stray hands or "other vibrations". 

[michael.h.f.wilkinson]

I focus on stars using 10x magnification in live view. I have put a micro-focuser and focus-lock device on my birthday wish list. That prevents accidental nudging and consequent need to refocus.