Focus help on DLSR Prime focus

[Rudeviewer]

Hi

I was wondering when I view images on here there are stars that have the 4 lines horizontal and vertical which prob means perfect focus.  I have not been able to achieve this in any of my images yet and was wondering what I can do to cure this.  When I focus I usually zoom on the 4 stars in the middle of the nebula and then focus from there.  I put a homemade focus mask on and I could not get anything to appear that I knew what to do with.  It made the image of the star very dim and blurry.  I did not see the spikes to align with the focuser.  Any help would be greatly appreciated.  Thanks!

[Leveye]

What scope are you using?

[Rudeviewer]

I have the 6SE OTA with 6.3 focal reducer on advanced vx mount.

[reddoss]

I think the lines you are referring to are the diffraction spikes which  are caused by the struts (sometimes called the spider veins)  which hold the secondary mirror in place on Newtonian reflectors. Your SCT does not have theses  (therefore you will not see these spikes in your images) as the secondary mirror is held in place by the corrector plate.

[Rudeviewer]

Ok I was wondering about that.  Thank you for the insight.  I wasn't sure if it was a focus issue or not.  So can someone explain how to properly use the focus mask.  I created one using a generator with my specs and put in on the front of the scope.  Do I leave it attached while imaging or just to obtain focus.  What do I look for when trying to obtain focus? 

[Tinker1947]

You remove it while your imagine, you could find a bright star and focus on that then attach your focus mask and move the focuser in and out to see what changes you may then be able to sort out when its focused properly, do you  have "Liveview" 

[Rudeviewer]

Yea have live view on the camera, but on the camera I am not able to see the lines to line up properly like I do from an eyepiece.  Even checked collimation, and it is good, the circle in the middle is right directly in the middle.  Ill give it another try tonight and see if it makes a difference.  Thanks for the advice.

[reddoss]

Here is a video of how to use a focus mask 

[Astrosurf]

I can only see the mask's diffraction pattern if I zoom in on live view, otherwise it's too small. What type of mask have you made?

Oops! We posted together reddos!

Alexxx

[Rudeviewer]

Basically I went online and found a mask generator that asked me for my specs.  I printed it out and cut it out with exacto knife and attached it to front of scope.  I have not tried to zoom in while using the mask I will do this.  I think I was so excited that I was gunna get better pics I didn't take the time necessary to set it up properly. 

[Rudeviewer]

The video was very helpful!  Thank you for posting that. 

[Leveye]

It's vanes btw. just a note. Use liveview zoomed in to focus properly. If you can do this using a computer or laptop with the screen up all the better as most of these programs have focus assist features. APT is one of the better ones.

[Leveye]

If you use a focal reducer is that still considered "Prime" focus? My assumption is that the term is just camera to open focuser tube with nothing in between. Cept maybe a Coma Corrector like i need to use.

[Rudeviewer]

I was not aware of that.  Thank you for updating a newb.  Still getting used to all the terminology.  All I knew is it wasn't eyepiece projection lol.