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07-16-2018, 04:29 PM   #1
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Looking for full res sample astro photos taken with K-1 & 15-30 2.8

As the title says, would be curious to compare with my lens results. Need shots taken at 15mm, 2.8 aperture. ISO doesn't matter Thanks in advance!

07-16-2018, 07:28 PM - 1 Like   #2
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I have 150 frames of this scene - K1 with the DFA 15-30/f2.8 all taken at f2.8, taken at ISO 800, 1600 and 3200, mainly taken at 30mm. All of the sky segments were taken with the astrotracer enabled at 50 second exposures. I'm in the process of stitching these as a 2 row, 7 frame stitch, with 4 of the frames overlaid on the top row for better resolution. I was also shooting the MW as it was rising over the mountain. So, about 18 frames per final stitched, masked and composited together result into a single final image. Trying to decide on some new post processing utilities and work flow - it's going slow....

Right at the last minute before packing up and heading home at midnight, I took these three panels for a quick stitch as a test - essentially a throwaway (I wish all my throwaways were this good). These three are at 15mm, vertical frames stitched together - all tracked (sky and ground) at 50 seconds. Note, I should have taken a dark frame - but alas, I didn't.



So, tell me what you want most - 15mm or 30mm (the 30mm images are 3/4 sky). You say any ISO, but what do you prefer (800 I found to be the best). Do you want a slice of the core or some other part of the sky? PM me an email address....

07-16-2018, 08:09 PM   #3
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Thanks for your input! Curious, do you have non-AT exposures? I've found it adds trailing with UWA lenses (at least it did with my rokinon in past) in corners and edges, and I'm basically looking for a 100% crop of a corner or an edge of such photo. Trying to compare to other 15-30 copies, see if the amount of coma I see is normal and comparable to others.

PS: Any iso works for me, so whatever you have in your disposal basically
07-16-2018, 09:02 PM   #4
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I was out just the other night, All pics K-1 with the 15-30.

OUt Here - PentaxForums.com

I'll have to wait till I get home, I can do a crop out of a corner and upload it.


Last edited by cmohr; 07-16-2018 at 09:12 PM.
07-16-2018, 09:36 PM   #5
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QuoteOriginally posted by cmohr Quote
I was out just the other night, All pics K-1 with the 15-30.

OUt Here - PentaxForums.com

I'll have to wait till I get home, I can do a crop out of a corner and upload it.
Awesome! Images look good, will wait for crops thank you!
07-16-2018, 10:08 PM   #6
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It took me a while to cull through my archives looking for something that would fit your needs.
QuoteOriginally posted by awscreo Quote
....do you have non-AT exposures?
Ok, you are in luck, in that I forgot I actually took these and I normally just save everything, deleting very little. I have 2 that would probably interest you... I can email these if you wish?
  • #2568 - 2.5 sec, f2.8, ISO25600, 15mm - no AT - landscape orientation
  • #2569 - 13 sec, f2.8, ISO1600, 15mm - no AT - landscape orientation
I remember wanting to try 13 seconds without tracking because at that exposure time, the stars should be bounded within a 4 pixel box based on inputs of - crop factor 1, 36.4MP, 15mm and Pixel Tolerance of 4
QuoteOriginally posted by awscreo Quote
I've found it adds trailing with UWA lenses (at least it did with my rokinon in past) in corners and edges, and I'm basically looking for a 100% crop of a corner or an edge of such photo. Trying to compare to other 15-30 copies, see if the amount of coma I see is normal and comparable to others.

PS: Any iso works for me, so whatever you have in your disposal basically
From what I have read, the trailing in the corners is due to the wide field of view at UWA - 15mm, in that the star's apparent rate of motion is greater at the lens' edge and corners than it is at the center. That has come from a couple of sources (one being Ian Norman @ Lonely Speck - How to Photograph the Milky Way – Astrophotography Tutorials, Tools, Gear + Inspiration), however I have not found any specific astronomy/optics reference literature to validate this.

The only logical analysis I can come up with is that with a UWA lens, the light at the lens' edge travels in a slightly longer path through the lens than it travels at the center (and there is a difference in direction of entry into the lens). Thus, when you are taking a long exposure of moving objects (stars) this slight difference will actually be noticeable and appears as trails.

On this particular aspect, I have lots of tracked examples at 15mm, f2.8. I find no real trailing on the left side, and a slight amount on the right side. I have concluded that I may have a slightly off center element, but will having Pentax only make it worse? I have been stitching, in that when combined you only wind up using the center section - thus it winds up being a moot point.


Last edited by interested_observer; 07-16-2018 at 10:42 PM. Reason: grammer
07-16-2018, 10:34 PM   #7
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Here are some corner chip outs from #2569 - left corner and right corner.



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07-16-2018, 11:01 PM   #8
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QuoteOriginally posted by interested_observer Quote
Here are some corner chip outs from #2569 - left corner and right corner.

Thanks for those! I'll check them on my laptop tomorrow. Much appreciated!
07-17-2018, 03:02 AM   #9
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Here is a few crops from one of those pic

Taken from the Full Size of the original. (Reduces preview)
1 - Bottom Left Hand Corner
2 - Bottom right hand Corner
3 - Top Left Hand Corner
4 - Top Right Hand Corner
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07-17-2018, 01:31 PM   #10
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Pure Milky Way:



K-1, DFA 15-30 @ 15mm, F2.8, 10 seconds, 800 ISO.

Southern celestial pole is just below and to the right of the centre of the image.

Same view with more processing and 30 seconds (so shows some trailing in the corners).
07-17-2018, 01:45 PM   #11
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Interesting. I see less coma in your guys photos. In my images the right edge/corner show quite a bit of coma, while left side is fine. Which does correspond with right edge softness in day time. And this is my 3rd copy of the lens, plus this copy has been repaired twice. I'm guessing the issue could be my mount, maybe it's slightly misaligned. I think at this point I'll just have to live with it, I won't send the lens for a third round of repairs, missing another month of summer. Same with the camera. I guess just my luck.

---------- Post added 07-17-18 at 02:01 PM ----------

QuoteOriginally posted by GodsPetMonkey Quote
Pure Milky Way:



K-1, DFA 15-30 @ 15mm, F2.8, 10 seconds, 800 ISO.

Southern celestial pole is just below and to the right of the centre of the image.

Same view with more processing and 30 seconds (so shows some trailing in the corners).
I can't access the first photo (says I have no permissions), could you post it on a public account please?
07-17-2018, 02:11 PM   #12
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QuoteOriginally posted by interested_observer Quote
Here are some corner chip outs from #2569 - left corner and right corner.

Thanks again for providing the photo! Here's what I found.
My image is on the right hand side, 1st frame is center crop, 2nd image is top right corner, 3rd image is top left corner.

I do see more coma in my corners. Exposure time is pretty close (you've used 13s, I used 10s), my image is noisier due to using a higher iso (1600 vs 6400), I think in general,
star shapes should be pretty similar all things considered, but it's pretty clear my top right hand corner stars look different in shape, much more triangular, and larger.
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07-17-2018, 03:03 PM   #13
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QuoteOriginally posted by awscreo Quote
Thanks again for providing the photo! Here's what I found.
My image is on the right hand side, 1st frame is center crop, 2nd image is top right corner, 3rd image is top left corner.

I do see more coma in my corners. Exposure time is pretty close (you've used 13s, I used 10s), my image is noisier due to using a higher iso (1600 vs 6400), I think in general,
star shapes should be pretty similar all things considered, but it's pretty clear my top right hand corner stars look different in shape, much more triangular, and larger.
Wow! That was quick! Thanks for the analysis and comparison. I've been very happy with my copy of the lens - and you have just confirmed that.

07-18-2018, 02:17 AM   #14
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QuoteOriginally posted by awscreo Quote
I can't access the first photo (says I have no permissions), could you post it on a public account please?
Whoops, fixed! Sorry, I only just uploaded it, and forgot to set it to public!
07-18-2018, 10:07 AM   #15
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Here's a stacked series, with astrotracer on, roughly 45 secs at ISO 6400.
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