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05-16-2016, 09:11 PM   #1
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Pixel Shift and Astrophotography

Hello all,


New lurker to the Pentax forum and longtime Canon user. I've started switching to the Pentax system after getting tired of Canon's lousy dynamic range. I've spent the last 5 years living in Germany with extensive travels in Europe and 7 years before that in Arizona. I do mostly landscape and architecture work. So lots of wide angle and telephoto shots.


Now on to my question, regarding pixel shift and astrophotography. I will be putting the camera onto a tracking mount that will track the stars(I won't be using the astro tracer), the exposures will range in the minutes. Will pixel shift work with this type of work?
I've read some blips of info that it works from an older Pentax camera with astrotracer but I can't find specific info from Pentax themselves or any other user for the K-1. I currently have the Pentax 15-30mm and will be driving tomorrow to pickup my K-1!


Any info, related threads I might have missed or good websites would be appreciated!


Curt

05-16-2016, 09:52 PM   #2
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QuoteOriginally posted by NachtSchicht Quote
Will pixel shift work with this type of work?
No, because pixel shift is not appropriate for moving subjects, or if the camera is moving. I doubt any sort of tracker will be able to maintain pixel-level accuracy for exposures that long. Plus, remember that pixel shift quadruples the exposure time.

It will yield an increase in resolution when shooting perfectly stationary subjects from a tripod (i.e. product photography, landscapes when it's not windy, and cityscapes).

Adam
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05-16-2016, 10:20 PM   #3
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It works a treat. There is someone on dpreview (pentax forum) who photographed the moon with k1 and scope on tracking mount with pixel shift. He said results were better than some 20plus stacked images that he had done. The 4 stack helps with atmospheric turbulence a lot it seems.
05-16-2016, 10:32 PM   #4
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QuoteOriginally posted by NachtSchicht Quote
Any info, related threads I might have missed or good websites would be appreciated!
There is an ongoing astrophotography group: Astrophotography - PentaxForums.com

and a six-part series of articles (all six are hard to find, but here is the first): Astrophotography Part 1 of 6: Planning the Shoot - Articles and Tips | PentaxForums.com

and various threads here and there discussing stacking software and techniques.


Steve

05-16-2016, 10:37 PM   #5
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Is there a limit on exposure time when Pixel Shift is enabled? For Moon shot you can get away with 1/500s but for stars clusters and nebula 30s - 60s is more common. Great if Pixel Shift works with such long exposures but can your tracking mount provide 1-pixel accuracy?
05-16-2016, 10:44 PM   #6
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QuoteOriginally posted by stevebrot Quote
and a six-part series of articles (all six are hard to find, but here is the first): Astrophotography Part 1 of 6: Planning the Shoot - Articles and Tips | PentaxForums.com
Found the page with links to all the articles:

astrophotography series - Tagged Articles | PentaxForums.com


Steve
05-16-2016, 11:02 PM   #7
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QuoteOriginally posted by dainiushst Quote
Is there a limit on exposure time when Pixel Shift is enabled? For Moon shot you can get away with 1/500s but for stars clusters and nebula 30s - 60s is more common. Great if Pixel Shift works with such long exposures but can your tracking mount provide 1-pixel accuracy?
There isn't a limit, but if you have a 5s shutter speed selected, the image will be exposed for 20s (5s x 4). Pixel-level accuracy for that long is highly improbable (except when you're indoors and on a tripod, in which case it works surprising well!).

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05-16-2016, 11:12 PM   #8
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QuoteOriginally posted by Adam Quote
No, because pixel shift is not appropriate for moving subjects, or if the camera is moving. I doubt any sort of tracker will be able to maintain pixel-level accuracy for exposures that long. Plus, remember that pixel shift quadruples the exposure time.

It will yield an increase in resolution when shooting perfectly stationary subjects from a tripod (i.e. product photography, landscapes when it's not windy, and cityscapes).
I respectfully disagree. I have a tracking mount I use with my 645Z for astro work and when I get it really well tweaked (leveled, dead on elevation and aligned with true N) using digital alignment tools, even after exposing five minutes there are no star trails whatsoever. I think the alignment error with pixel shift will be so small as to be irrelevant.

The real problem with long exposures of the night sky is that the images start revealing far more stars than you anticipate and the image becomes awash with thousands of points of light, making it very 'busy'. Other astro photographers have discovered the trick is to use high ISO and short exposures, eliminating the unwanted points of light, especially when shooting the Milky Way. Then stack the images. I imagine a series of a dozen or more images shot with pixel shift and then stacked, could be very effective.

05-16-2016, 11:59 PM   #9
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QuoteOriginally posted by CDW Quote
I respectfully disagree. I have a tracking mount I use with my 645Z for astro work and when I get it really well tweaked (leveled, dead on elevation and aligned with true N) using digital alignment tools, even after exposing five minutes there are no star trails whatsoever. I think the alignment error with pixel shift will be so small as to be irrelevant.

The real problem with long exposures of the night sky is that the images start revealing far more stars than you anticipate and the image becomes awash with thousands of points of light, making it very 'busy'. Other astro photographers have discovered the trick is to use high ISO and short exposures, eliminating the unwanted points of light, especially when shooting the Milky Way. Then stack the images. I imagine a series of a dozen or more images shot with pixel shift and then stacked, could be very effective.
No doubt- but pixel shift is somewhat of a different beast. It's extremely sensitive to even the smallest displacement. The longer you expose, the higher the risk of artifacts. Not to mention the fact that the duration of the exposure is quadrupled.

Effective PSR would only exacerbate the busy details in the image, hence even with perfect technique and luck I wouldn't recommend it.

If you search the forum, there are lots of users who have effectively used the stacking technique. It takes patience by can be super-rewarding!

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05-17-2016, 12:21 AM - 1 Like   #10
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Perhaps I can answer this one, as I've attempted to PS the night sky several times. In short, when doing traditional astro from a stationary tripod, you have to use higher iso with a 3s shutter time on a 10mm lens to not get trails using pixelshift on a K-3II. You CAN get some usable shots. HOWEVER, and a biiig however it is, adam is also correct in that movement will cause issues. I don't think the tracking mount will have fine enough movements to not cause errors (artifacts). Yes, the K-1 will have an extra stop available to it so you can use shorter exposures than the K-3II, but you're still dealing with the quadruple exposure time that adam mentioned. It is more likely you'll get trailing. Using pixelshift for a short time might be good for getting the milky way though. I would honestly just use the astrotracer function in conjunction with the tracker mount for better results.
05-17-2016, 12:38 AM   #11
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Remember that PS does not work in bulb mode. So you are tied to 30 second exposures at the most anyway. This will mean higher than base ISO for sure for starfields and deep sky objects. I did a pixel shift test of the moon at 1/90s, ISO100 the other night and it came out fine but that is a bright object. The stumbling block for PS files in astro may be the large file sizes if stacking. Everything is going to take a lot longer to process and smoke may come out of your computer. - Jack


05-17-2016, 02:06 AM   #12
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If the tracking is good enough and the atmospheric turbulence is low enough it might work. I wonder though if the result will give you any new details. But it would be fun to try.

As for large magnifications of the moon, you would still need tracking and turbulence free air. I have tried stacking the moon but due to turbulence the images where all slightly warped and didn’t line up properly so in the end it turned out that a single shot looked better than a stack of warped images.
05-17-2016, 03:01 AM - 1 Like   #13
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The thread I was talking about.
k1...when too many megapixel,s is barely enough for the moon: Pentax SLR Talk Forum: Digital Photography Review
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