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Hi all,

So I've finally ordered a mount, the HEQ-5 Pro which will be here in a few days, but as a total newb, I'm still having issues with focusing.  I've been using a canon 100-400mm lens and max digi zoom is 10x in the live view, using the focus ring, I still can't seem to get sharp stars.  I've tried putting a Bahtinov mask on, but this seems to make the star too dim to even see the diffraction pattern.

My last time out, I actually just tried to focus on mars as it was the brightest in the sky, and even with that I was still having issues.

Is there any suggestions to help here?  Is there something in the camera settings that might make things "Brighter" in the live view? (I can't imagine the ISO or any other settings affect the live mode correct?)

Thanks for everyone's help in getting started to this hobby, I'm so inspired by the community!

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Mistakes I have made in DSLR focusing ;

- display was set to lowest brightness in camera settings (from the previous session). Yes, really 😉 

-exposure wasn't set to bulb. My old Nikon wouldn't change the live view dependent on exposure, but the Canon does - and so the star in live view is as bright as the exposure time will give you. I had too short an exposure, as I was going to set that after focusing. D'oh. 

Hope this helps, 

Ady

Edited by adyj1
Tyoo
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oh that may very well be the ticket!  I've been using an intervalometer, but just for the delay and number, I've been using the internal exposure setting on the canon... so I'll be curious if I set it to bulb if it will make it brighter!  huge gold stars if this works haha, thanks!

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Canon live view should have exposure simulation . So yes whatever parameter you alter shutter speed or iso should be obvious on screen. Certainly on my 5d mk2 I will deliberately set it to over expose  for low light focus or composition then reset to to my desired exposure.

Note also you may be getting zoom movement on the 100 to 400 if it's the older version of the lens with the push pull zoom action. If tripod mounted turn all lens stabilisation off.

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Interestingly.. I just went outside and while I'm in heavy light pollution here, the sky opened up for a bit, and I was looking at Cassiopeia, pretty bright, and couldn't get any of the stars in the live view.. Mars did seem to be a little 'brighter'... maybe?  I set the ISO high, had the lens at 100mm infinity, and set the exp to bulb.   Also turned the 'brightness' on the live view all the way up.  I focused fairly well on Mars, and when I pointed back to the constellation, I still couldn't see any stars in the live view, though I could just make them out in the viewfinder.

Edited by Osiris777
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I've often found the marked infinity point on a lens isn't always the sweet spot. My advice would be to work around that point. 

It's time consuming but what you can do is take test shots review magnified on camera lcd and fine tune focussing.  Once happy tape the focus ring . You can afford to do do that at high iso.

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I find that with my Canon camera that its best to set exposure to 20s and NOT bulb when focusing, this with the ISO set high gives me lots of stars visible on the live view screen but they are only visible if the focus is close to optimum. The abundance of visible stars makes it easy to concentrate on the very faintest in the FOV as these will blink on/off with the slightest adjustment.

Alan

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18 minutes ago, Alien 13 said:

I find that with my Canon camera that its best to set exposure to 20s and NOT bulb when focusing, this with the ISO set high gives me lots of stars visible on the live view screen but they are only visible if the focus is close to optimum. The abundance of visible stars makes it easy to concentrate on the very faintest in the FOV as these will blink on/off with the slightest adjustment.

Alan

That’s pretty much my experience with a Canon 450D. I put a bright star in the x10 window and reduce exposure time until it’s easy to see when the star is both smallest and brightest at focus. If the star is too bright (saturated) on the screen  it’s more difficult to focus accurately.  
     Using a computer helps too because programs like BackyardEOS have focusing routines allowing you to adjust focus from the computer whilst looking at an image of the star, its cross section and fwhm. 

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14 hours ago, Osiris777 said:

Thanks for the info, I'l give the try at 20sec exp and highest ISO setting.  I'm hoping the act of taping down the focuser won't accidentally knock it out of focus haha 😉

Yes that's a problem isn't it. That's another plus for remote control of the focus from a computer in that it holds the focus position. 

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