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DSLR Focusing

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#1 dsallette

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Posted 11 July 2020 - 09:09 AM

So this past evening, I was attempting to shoot the crescent nebula.  In order to achieve focus, I used Deneb as a guide with my Bahtinov mask.  I got Deneb sharp as a tack, took the mask off and turned to the nebula.  I shot a couple of tests. Everything looked ok.  Then i ran a series of exp. for over an hour.  None of the images will stack because DSS is not reading any stars.  Upon closer inspection, I do not have stars in my images; I have tiny illuminated nipples. What am i doing wrong? 



#2 Tapio

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Posted 11 July 2020 - 09:26 AM

What kind optics did you use?
Some zoom lenses have bad habit of focus crawling.
So best to use tape or rubber band to fix focus (and zoom) when you have focused.
Also temperature change affect focus but I don't think this is your problem here.

#3 Gipht

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Posted 11 July 2020 - 09:44 AM

This could also be a tracking issue.   Elongated stars with the elongations in the same direction would indicate a tracking problem.

 

The Crescent is a tough target for a DSLR.



#4 kathyastro

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Posted 11 July 2020 - 10:03 AM

It could also be a temperature change.  I find a significant change in focus with as little as a 0.5 C change in temperature.



#5 spereira

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Posted 11 July 2020 - 10:06 AM

Moving to DSLR, for a better fit.

 

smp



#6 the Elf

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Posted 11 July 2020 - 12:12 PM

Please let us know what equipment you used. I suggest you put it in the signature in your profile as most of us do. This saves you from listing it every time. Could you also attach an image or upload it to dropbox or Google drive, etc?




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