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01-26-2016, 02:29 PM   #16
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Have you considered the Samyang 14mm F2.8 lens? I have both the DA 15/4 and the Bower copy of the Samyang 14/2.8 lens,. I have not done any astrophotography works, but do find a use for both lens. The DA gets most of my use, but when I need a little wider or faster lens the 14 works great. One of the negative things about my Bower/Samyang is the distance scales were not even close to actual distances. What I did with mine was set it up on a tripod with measured distances to targets and mark my own distance scales on a piece of tape. Now if I want to set the focus, anywhere from infinity to a few feet I just dial in the mark I made. I have marks at two feet, six feet, 30 feet and infinity.
The other thing is what "Conqueror" showed in his post, there is a big size difference in the lens. The DA 15 is very easy to carry around.

01-26-2016, 02:39 PM   #17
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I find if you want to really nail focus and have time to take your time, set your camera to live view with focus peaking turned on. You can "zoom in" and get the focus quite exact. Beats distance markers, and I find it's the only way to really be certain about "infinity" on a lens with SDM.
01-26-2016, 04:23 PM   #18
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QuoteOriginally posted by csa Quote
Is this really fair to the seller? I can see returning a defective lens, but taking one on vacation to use for free, then sticking the seller by returning it because you now have no need for it?
If no damage is done and one finds that the product doesn't suit one's needs, I don't see the problem. The purchase was in good faith, but the lens isn't what the buyer needs.
01-26-2016, 04:28 PM - 6 Likes   #19
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QuoteOriginally posted by fuent104 Quote
If no damage is done and one finds that the product doesn't suit one's needs, I don't see the problem. The purchase was in good faith, but the lens isn't what the buyer needs.
It's dishonest to say the least. I would be most unhappy if I sold a lens and it was taken on a vacation, then returned to me! One can try out a lens in an hour or so right around the house, rather than being shady "buying" one for a vacation, then wanting to return it.

Sorry, but I find this very distasteful for someone to even suggest another member do this, there's no "good faith" involved!

01-26-2016, 06:18 PM   #20
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Reading everybody's responses, and talking through things with my wife, has really helped solidify my thinking. I just pulled the trigger on the DA 15/4 and an O-GPS1! I think this will be a great general purpose setup, and good enough to get me started with astrophotography. If I decide to get more serious about the astro thing, I will budget for a more specialized lens then. My sincere thanks to everyone (I love this community)!

-Robin
01-26-2016, 06:27 PM   #21
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QuoteOriginally posted by csa Quote
It's dishonest to say the least. I would be most unhappy if I sold a lens and it was taken on a vacation, then returned to me! One can try out a lens in an hour or so right around the house, rather than being shady "buying" one for a vacation, then wanting to return it.

Sorry, but I find this very distasteful for someone to even suggest another member do this, there's no "good faith" involved!
I agree and it does not sound like it would be on good faith.
01-26-2016, 07:23 PM   #22
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QuoteOriginally posted by csa Quote
It's dishonest to say the least. I would be most unhappy if I sold a lens and it was taken on a vacation, then returned to me! One can try out a lens in an hour or so right around the house, rather than being shady "buying" one for a vacation, then wanting to return it.

Sorry, but I find this very distasteful for someone to even suggest another member do this, there's no "good faith" involved!
QuoteOriginally posted by redrockcoulee Quote
I agree and it does not sound like it would be on good faith.
Retailers consider it a form of return fraud. It's called "retail renting" (or "free renting" or just "renting", or "wardrobing" in the clothing business). The key thing is the seller's return policy, and their (not the buyer's) interpretation of "new condition". I doubt many sellers would consider an item that was taken out of the country, used for a vacation, and then returned to be "new". However, if you told a seller you were going to do it or had done it, they might accept the return - but it should be their call.
01-27-2016, 05:07 PM   #23
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QuoteOriginally posted by bobbotron Quote
I find if you want to really nail focus and have time to take your time, set your camera to live view with focus peaking turned on. You can "zoom in" and get the focus quite exact. Beats distance markers, and I find it's the only way to really be certain about "infinity" on a lens with SDM.
Using live view & tripod is what I do most of the time. But I use the distance markers at night when I am not able to see much through the VF or LV. Using a small flash light I can see the distance marks and know I'm good to go.

01-27-2016, 06:02 PM   #24
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One thing to consider... since the Samyang 16mm doesn't communicate with the camera, you have to dial in the focal length for the O-GPS1's astrotracer feature to work well. However, the focal length input menu on my k-30 & k-50 only offer 15mm and 18mm as selectable options. I haven't had a chance to try out my Samyang 16mm with astrotracer yet, but I fear that the focal length input limitation might effect the accuracy of the whole process. If anyone has experience with this, please post about it.
01-27-2016, 09:46 PM   #25
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The size comparison posted earlier is a really big deal to me. I find the DA15 to be an excellent performer with a snappy quality to the rendition of color. I do not find curvature to be a problem in practice. It also makes a nice partner for the DA18-135, 18-55 or 17-70, adding ultra wide coverage without much bulk.
01-28-2016, 02:43 AM - 2 Likes   #26
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QuoteOriginally posted by WaxPhotographic Quote
I fear that the focal length input limitation might effect the accuracy of the whole process. If anyone has experience with this, please post about it.

In practise this isn't a problem. Look upon it this way: A star near the celestial equator (where stars move the fastest) will move 0.25 degrees in one minute. Hence, with a 15mm lens, the image of the star on the sensor would move (and Astrotracer will compensate for that) 0.0654mm in one minute. For a 16mm lens the corresponding figure is 0.0698mm. Thus, the difference (the tracking error for a 16mm lens dialed in as 15mm) is only 0.0044mm in a minute - and 0.0044mm is just about one, single K-3 pixel width, which you won't notice at all.


For (very) wide angle lenses, the effects of field rotation (star images are stretched away from the center of the image) and oftentimes coma - also most prominent near the edges of the image - will be much more conspicuous.


I am sure that the OP will have some great results with the 15mm Limited + Astrotracer. F/4 isn't that bad for wide field astro-landscape photography. But I went with the samyang 14mm f/2.8 because Samyang has done a really good job at minimizing coma.
01-28-2016, 03:06 AM - 1 Like   #27
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QuoteOriginally posted by fuent104 Quote
If no damage is done and one finds that the product doesn't suit one's needs, I don't see the problem. The purchase was in good faith, but the lens isn't what the buyer needs.
I too would consider this approach to be quite immoral. Not good faith at all. Returns are for defective lenses - rental is for trials.
01-28-2016, 08:52 AM   #28
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QuoteOriginally posted by Sandy Hancock Quote
I too would consider this approach to be quite immoral. Not good faith at all. Returns are for defective lenses - rental is for trials.
Very well said!
01-28-2016, 09:46 AM   #29
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QuoteOriginally posted by Stone G. Quote
In practise this isn't a problem. Look upon it this way: A star near the celestial equator (where stars move the fastest) will move 0.25 degrees in one minute. Hence, with a 15mm lens, the image of the star on the sensor would move (and Astrotracer will compensate for that) 0.0654mm in one minute. For a 16mm lens the corresponding figure is 0.0698mm. Thus, the difference (the tracking error for a 16mm lens dialed in as 15mm) is only 0.0044mm in a minute - and 0.0044mm is just about one, single K-3 pixel width, which you won't notice at all.


For (very) wide angle lenses, the effects of field rotation (star images are stretched away from the center of the image) and oftentimes coma - also most prominent near the edges of the image - will be much more conspicuous.


I am sure that the OP will have some great results with the 15mm Limited + Astrotracer. F/4 isn't that bad for wide field astro-landscape photography. But I went with the samyang 14mm f/2.8 because Samyang has done a really good job at minimizing coma.

Thanks for doing the math on this. I hadn't thought about the lack of a 16mm option when entering manual lens info, but it's nice to know that it essentially doesn't matter. If I get a dedicated astro lens in the future, I'm not sure it would be the 16/2, since I will have the DA 15/4. I might be tempted to go even wider like the Samyang 14/2.8 or 10/2.8.

-Robin
02-26-2016, 03:52 PM - 1 Like   #30
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So I thought I'd add a Postscript to this thread. I am back from our vacation, and I can officially say I love the DA 15/4! The rendering is everything people say it is, and the size and build are fantastic. Unfortunately, I didn't try any astro shots as it was somewhat cloudy and quite breezy every night (my travel tripod is not very sturdy), and the very bright moon didn't help, either. I do hope to have a clear night sometime when I have the time to stay up half the night and give it a shot! Thanks again for all the help.

-Robin
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