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Orion and Milky Way
Jan 13, 2019 21:33:41   #
guardineer
 
I am finding it very difficult to focus Nikkor 10-20 DX. I am trying to make stars as small as possible as it seems larger equals out of fucus, Even in daylight focusing on infinity at 10 mm is difficult. Any suggestions?

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Jan 13, 2019 21:42:18   #
guardineer
 
guardineer wrote:
I am finding it very difficult to focus Nikkor 10-20 DX. I am trying to make stars as small as possible as it seems larger equals out of fucus, Even in daylight focusing on infinity at 10 mm is difficult. Any suggestions?


Here's a sample


(Download)

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Jan 14, 2019 09:55:39   #
Europa Loc: West Hills, CA
 
I’m not familiar with your equipment, so can’t help you with that. The image you posted looks to have pretty good focus tho.

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Jan 14, 2019 11:29:04   #
BassmanBruce Loc: Middle of the Mitten
 
I’ve had my best luck focusing on stars using live view 10x and manual focus.
I found out the hard way the infinity stop on my Minolta 50mm f1.4 stopped just short of infinity. It’s fixed now but cost me an under the stars pick of Yosemite falls.

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Jan 14, 2019 22:19:07   #
nikonshooter Loc: Spartanburg, South Carolina
 
I assume that you shot this on a fixed tripod - 30 second exposure at about 1600 ISO. Your stars are not out of focus in this image....what has happened is you have motion blur. The stars moved enough in your 30 second exposure to look oblong.


That's my two cents!

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Jan 15, 2019 09:55:52   #
guardineer
 
I shot another batch last night with same result. I did live view focus at 10x but at 10mm there's nothing to see but the size of the star. (I then go back to viewer before shutter release.) I think I eliminated motion blur by reducing time to 20 and 10 seconds. My plan is to make semi permanent marks on focus ring after daytime focus.

Thanks to each of you.

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Jan 15, 2019 11:10:44   #
Europa Loc: West Hills, CA
 
guardineer wrote:
I shot another batch last night with same result. I did live view focus at 10x but at 10mm there's nothing to see but the size of the star. (I then go back to viewer before shutter release.) I think I eliminated motion blur by reducing time to 20 and 10 seconds. My plan is to make semi permanent marks on focus ring after daytime focus.

Thanks to each of you.


Use painters tape to tape the focus control and turn off the autofocus once you have it in focus.

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Jan 15, 2019 11:15:24   #
nikonshooter Loc: Spartanburg, South Carolina
 
guardineer wrote:
I shot another batch last night with same result. I did live view focus at 10x but at 10mm there's nothing to see but the size of the star. (I then go back to viewer before shutter release.) I think I eliminated motion blur by reducing time to 20 and 10 seconds. My plan is to make semi permanent marks on focus ring after daytime focus.

Thanks to each of you.


I think you are headed in the right direction by dialing up the ISO and exposure time down. The difference in the glass BTW, besides 1600 dollars in price spread - is the 70x200 F/2.8 is so superior in every way!

Now, my guess is there is something wrong with your other lens....at 10mm and F/4.5 everything from 2 ft to infinity should be in focus. One thing you can try, trip pod your camera outside and 10 ft away take a yard stick and lean it against something so that it is on a 45 degree angle with the one inch mark closest to you and the 36 furtherest away. Take a red marker and mark the 18 inch mark to make it easier to see and focus on it. Take a picture while focusing on the red 18 inch mark. Then load the picture in LR or PS and see if the 18 inch mark is in focus....if not, scroll up and down the ruler to see where focus it obtained if at all.....if the focus is achieved in the 19 or up area you have back focus problems......or 17 inch and back to you front focus. Nikon and all companies calibrate their lens to work with all camera bodies....but it is not a perfect world. I have had to calibrate all of my bodies to the lens I use most. You have settings in your camera that will allow you to do this.

If you cannot focus achieve anywhere up and down the ruler, take a pencil eraser and clean the contacts on both your camera and lens - this is where the camera and lens connect. Just lightly run each of the metal contacts and be sure to blow off the area . I routinely do this to eliminate "on site" focus issues. If you still cannot achieve focus anywhere up and down the ruler. The lens is not communicating with the camera and needs to be serviced and if new, returned.

I have posted a pic of the calibration tool I use for calibrating my lens/cameras.


(Download)

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Jan 24, 2019 12:08:50   #
DickC Loc: NE Washington state
 
A great capture, I can see Orion!

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Jan 24, 2019 13:42:02   #
guardineer
 
Thank you. I have captured a few more constellations and edited out the peripheral stars.

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Jan 25, 2019 02:35:19   #
JimH123 Loc: Morgan Hill, CA
 
nikonshooter wrote:
Now, my guess is there is something wrong with your other lens....at 10mm and F/4.5 everything from 2 ft to infinity should be in focus.


Actually, this is not true for stars. They have to be in perfect focus, or they grow bigger and dimmer. They are point sources of light.

With terrestrial objects, we can focus for the hyper-focal distance and have everything from somewhere close to use to somewhere far away be in focus. Or at least appear to be in focus at normal viewing distances.

Stars will just not cooperate. As soon as a star is the slightest out of focus, in either direction, it grows in size and grows very dim. What I end up doing is to watch with focus magnifier on. If you have a choice on the amount of magnification, try different amounts. If there is too much shake and fuzziness at the max magnification, dial it back a bit. What I do is to focus the best I can on a brighter star. And then I turn my attention onto a faint star and adjust it to max brightness. The final adjust is ridiculously tiny. Basically just barely touching the focus ring with the tiniest nudge in one direction or the other.

And by the way, focus-by-wire lenses drive me absolutely crazy in doing this.

Also, if the temperature changes very much from when you focus to when you use it, it may be off again.

I am attaching a test shot using my full frame Sony A99 with a Tamron 15-30mm at 15mm f2.8 and ISO 1600. The shutter time was 15 sec. Wasn't a great night as you can see with the cloud, but I wanted to test the lens. I was able to use the focus magnifier and to start by using a bright star and then looking for a dim star to achieve its brightest focal position. It can be done.


(Download)

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Jan 25, 2019 09:17:57   #
guardineer
 
Thank you for sharing your technique, JimH123. Your shot is very sharp focus. I will try it.

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