[pyman]

Making the jump to a K-1 since I mainly shoot landscape and would like to shoot more astro/nightscapes. After doing some research on the astrotracer function on the K-1's full frame sensor with wide lenses, it seems like the astrotracer work well in the center of the frame but the edges and corners will be smeared due to the physics of wide/ultrawide lenses. I'm wondering if anyone has any advice on whether it would be better to use astrotracer when shooting in the ultrawide range (i.e. 10-20mm) or just leave astrotracer off and stack multiple exposures to increase details and reduce noise? Right now my only FF astro lens for the K-1 is a Rokinon 14mm f/2.8.


Another option would be to shoot at a longer focal length (50mm?) which would allow the use of astrotracer without much distortion and stitch together multiple frames for a wider view. A lot more work in post processing, but could yield some great detail. I was thinking of the Rokinon 50mm f/1.4, but I'm wondering if there are any native, Pentax 50mm lenses that have low coma (looking at a Pentax A 50mm 1.4)? Between the legacy lenses and the current lenses, it seems like there are so many variants in the Pentax 50mm group.


Any thoughts?

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Last edited by pyman; 02-17-2019 at 08:40 AM.

[photoptimist]

How large are you printing? That will determine how much detail you want and whether tiling is worth the effort.

Although it is true that astrotracer cannot accurately correct the motion of the star field of a UWA lens, it is better than nothing. Turning astrotracer off will only make the smearing worse and force stacking of an even larger number of short-shutter-time images. Thus, it's better to use astrotracer with stacking but limit the shutter time to avoid smearing in the corners. (Note: the longest acceptable shutter time with astrotracer and UWA is a very complex function the camera pointing direction and lens orientation as well as your subjective opinion about the "acceptable" amount of smearing -- experimentation may be the fastest solution.)

[interested_observer]

Making the jump to a K-1 since I mainly shoot landscape and would like to shoot more astro/nightscapes. After doing some research on the astrotracer function on the K-1's full frame sensor with wide lenses, it seems like the astrotracer work well in the center of the frame but the edges and corners will be smeared due to the physics of wide/ultrawide lenses. I'm wondering if anyone has any advice on whether it would be better to use astrotracer when shooting in the ultrawide range (i.e. 10-20mm) or just leave astrotracer off and stack multiple exposures to increase details and reduce noise? Right now my only FF astro lens for the K-1 is a Rokinon 14mm f/2.8.

Good Morning, Most of what I have shot has been the Milky Way with the DFA 15-30/2.8 (and the Sigma 18-35/1.8 on the K5). What I have found is that the star trailing (smearing) on the edges and corners is a function of exposure time. This can be controlled up through 70 seconds of astrotracking, where I have found none. At 90 second exposures astro tracked, I start to get some star trailing, which is more than what I want. This holds true across the focal lengths of the 15-30.

I went with the 15-30, because of the clear physical aperture, where the aperture area from 15mm to 30mm increases by 4x. The same analysis holds true for the Sigma 18-35 on a crop body (K5/K5IIs). So, the lens provides me with some additional options of still being pretty wide (at 30mm) but I can pretty dramatically increase the amount of light I capture.

In terms of exposure time using astro tracking I have found that

• Up to 30mm, I expose no longer than 70 seconds.

• Up to 200mm, it has been noted here on the forum that you can go up to 60 seconds - My adventures in astrophotography - Astrophotography - PentaxForums.com

Another option would be to shoot at a longer focal length (50mm?) which would allow the use of astrotracer without much distortion and stitch together multiple frames for a wider view. A lot more work in post processing, but could yield some great detail. I was thinking of the Rokinon 50mm f/1.4, but I'm wondering if there are any native, Pentax 50mm lenses that have low coma? Between the legacy lenses and the current lenses, it seems like there are so many variants in the Pentax 50mm group.

Any thoughts?

Since most (essentially all) of what I have done (with the astrotracker) was 35mm or wider, I asked the same question over in the Astronomy area. Rather than repeat, here is the link....

• Question - AstroTracer with 50mm - Astrophotography - PentaxForums.com

In terms of Pentax lenses, the M50/f1.7 has some very good reviews for astro - just scroll down a couple of posts...

• SMC Pentax-M 50mm F1.7 Reviews - M Prime Lenses - Pentax Lens Reviews & Lens Database

As an experiment, I set up my old K5 and a AutoTak 85/f1.8 to try some starfields, and can say that the Tak 85/1.8 has no coma and is excellent.

• Star Field - 1+ hour exposure stacked - Astrophotography - PentaxForums.com

[pyman]

How large are you printing? That will determine how much detail you want and whether tiling is worth the effort.

Although it is true that astrotracer cannot accurately correct the motion of the star field of a UWA lens, it is better than nothing. Turning astrotracer off will only make the smearing worse and force stacking of an even larger number of short-shutter-time images. Thus, it's better to use astrotracer with stacking but limit the shutter time to avoid smearing in the corners. (Note: the longest acceptable shutter time with astrotracer and UWA is a very complex function the camera pointing direction and lens orientation as well as your subjective opinion about the "acceptable" amount of smearing -- experimentation may be the fastest solution.)

That's good to know. I was thinking the smearing on the edges/corners (as opposed to trailing) was a function of the sensor shifting with the astrotracer function on. I generally don't print larger than 16X20, but it looks like I'll need to experiment and see how much smearing there is and how far it extends into the frame. I previously used Ian Norman's shutter speed calculator to get a ballpark range for untracked images on my Canon 80D, but the astrotracer function on the K-1 adds a whole, new variable. Not to mention the ISO invariance on the K-1 sensor.
Advanced Astrophotography Shutter Time Calculator – Lonely Speck
Thanks!

---------- Post added 02-17-19 at 10:57 AM ----------

Good Morning, Most of what I have shot has been the Milky Way with the DFA 15-30/2.8 (and the Sigma 18-35/1.8 on the K5). What I have found is that the star trailing (smearing) on the edges and corners is a function of exposure time. This can be controlled up through 70 seconds of astrotracking, where I have found none. At 90 second exposures astro tracked, I start to get some star trailing, which is more than what I want. This holds true across the focal lengths of the 15-30.

I went with the 15-30, because of the clear physical aperture, where the aperture area from 15mm to 30mm increases by 4x. The same analysis holds true for the Sigma 18-35 on a crop body (K5/K5IIs). So, the lens provides me with some additional options of still being pretty wide (at 30mm) but I can pretty dramatically increase the amount of light I capture.

In terms of exposure time using astro tracking I have found that

• Up to 30mm, I expose no longer than 70 seconds.

• Up to 200mm, it has been noted here on the forum that you can go up to 60 seconds - My adventures in astrophotography - Astrophotography - PentaxForums.com

Since most (essentially all) of what I have done (with the astrotracker) was 35mm or wider, I asked the same question over in the Astronomy area. Rather than repeat, here is the link....

• Question - AstroTracer with 50mm - Astrophotography - PentaxForums.com

In terms of Pentax lenses, the M50/f1.7 has some very good reviews for astro - just scroll down a couple of posts...

• SMC Pentax-M 50mm F1.7 Reviews - M Prime Lenses - Pentax Lens Reviews & Lens Database

As an experiment, I set up my old K5 and a AutoTak 85/f1.8 to try some starfields, and can say that the Tak 85/1.8 has no coma and is excellent.

• Star Field - 1+ hour exposure stacked - Astrophotography - PentaxForums.com

Wow! Had no idea you could go that long with a lens that wide! Looks like one MORE reason to start saving $$ for that 15-30. Here in NJ I'll probably be more limited by light pollution than the time/exposure limits on a wide focal length, but it's good to keep in mind for those times when I can go on on a road trip somewhere dark.

That windmill/desert shot is VERY cool! I'm curious if you've finished the 21 frame stitch @ 30mm and whether you thought the effort was worth it compared to the 3 frame vertical shot you posted. I will definitely take a look at that M50mm 1.7 - looks promising.

Thanks!

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Last edited by pyman; 02-17-2019 at 10:59 AM.

[interested_observer]

Wow! Had no idea you could go that long with a lens that wide! Looks like one MORE reason to start saving $$ for that 15-30. Here in NJ I'll probably be more limited by light pollution than the time/exposure limits on a wide focal length, but it's good to keep in mind for those times when I can go on on a road trip somewhere dark.

The K1 and 15-30 combination is excellent for this type of photography. The 70 second limitation is something that is very easy to live with for the Milky Way. Even out to 200mm you can do a lot, and you can also stack. For the deep space objects (DSO) images that you find in the astrophotography area, you really do need a dedicated equatorial tracking mount, especially with the targets moving out of the field of view of the astrotracing (since the camera itself does not change its pointing position). With a tracking mount, the camera/lens does physically track and resolves the pointing issue (however you still may need to guide).

The K1 (along with the K5/K5IIs) images are very stitchable. I shoot with a 50% overlap, just to be safe. Even if you capture some star trailing, the stitch overlap fixes that. Essentially you wind up with center cuts all the way across the image. Just shoot an extra frame on either end, and trim off the external edge and you are fine.

I also find that the images of the MW are pleasing to the eye (not over done), have excellent color (especially up to ISO800) and excellent definition (even at 15mm), plus at the lower ISO values, you retain the dynamic range that tremendously helps with the detail in the landscape segment. The Pentax lens also renders excellent colors - even at night. I was extraordinary surprised with the colors that I was able to capture/retain in the windmill/desert shot.

That windmill/desert shot is VERY cool! I'm curious if you've finished the 21 frame stitch @ 30mm and whether you thought the effort was worth it compared to the 3 frame vertical shot you posted. I will definitely take a look at that M50mm 1.7 - looks promising.

Thanks!

The acquisition of the K1 and 15-30 emptied my camera fund. I need to re-tool my post processing. The Chancellor of the Exchequer, is telling me that I need to save my nickels, dimes and quarters. Actually, I need to cull some of my lenses.

• LightRoom has problems with the white dot noise, Capture One (C1) fixes that (or in camera LENR - Long Exposure Noise Reduction). RawTharapee also can address the white dot noise issue.
• Microsoft ICE has problems with oversampling when stitching, both PTGui and PhotoShop resolves that problem.
• Affinity Photo does a poor job in masking and compositing. PhotoShop again resolves that issue. If PS has masking problems, I have found that Fluid Mask performs better than PS.

I think I'll just go with PS and I see that C1 has a new version out that I can trial again. So, perhaps I can stitch everything together (the bush on the left hand side is the problem) and composite the parts together in the next couple of weeks. I'm eager to finish it and see what it all looks like. The 3 panel stitch at 15mm was a test to show the potential and help with the colors (and brightness) across the entire image. The problem is making it too bright so that it becomes a very unnatural night image. The details in the landscape are exceptional in the individual frames. It's amazing what the K1 captures - in terms of details in the dead of night. Stitched together, it should be on the order of 19,000 x 11,000 or 215MB large. The local Costco will do large prints up to 20" x 60" for $20. I figure to use the entire 20" on the tall side, the long side would then be ~35", with a resolution of 550ppi, which is way more that what I would ever need.

[Aaron28]

I use a variety of lenses......bower 14/f2.8 (same as your rokinon), promaster 19-35 spectrum7, cosina 24/f2.8, sears 28/f2.8, jc penny 28/f2.8, fa 35/f2, fa 50/1.4.....all lenses but the sears are of the 'a' variety.....the longer the FL the less pronounced the dark edges/coma from astrotracer use on the K-1…...but I have had a lousy year weather wise to really use the K-1 and get familiar with it like the experience I have using the K-3ii or K-50....I stack several astrotracer shots, mask with the landscape shots and stitch it with ICE but my post skills suck but have improved over a few seasons of milky way/astro shooting...….I have only printed one 16x20 which basically cropped out most of the coma and that was only a 2 frame composite with the bower 14/f2.8 & K-3ii
if I were still living in south jersey I would love to hit up Batsto, chatsworth, reckon anything bass river, pine barrens in the spring and hit up the south coast later in the summer

good luck and clear skies!

[pyman]

The K1 and 15-30 combination is excellent for this type of photography. The 70 second limitation is something that is very easy to live with for the Milky Way. Even out to 200mm you can do a lot, and you can also stack. For the deep space objects (DSO) images that you find in the astrophotography area, you really do need a dedicated equatorial tracking mount, especially with the targets moving out of the field of view of the astrotracing (since the camera itself does not change its pointing position). With a tracking mount, the camera/lens does physically track and resolves the pointing issue (however you still may need to guide).

The K1 (along with the K5/K5IIs) images are very stitchable. I shoot with a 50% overlap, just to be safe. Even if you capture some star trailing, the stitch overlap fixes that. Essentially you wind up with center cuts all the way across the image. Just shoot an extra frame on either end, and trim off the external edge and you are fine.

I also find that the images of the MW are pleasing to the eye (not over done), have excellent color (especially up to ISO800) and excellent definition (even at 15mm), plus at the lower ISO values, you retain the dynamic range that tremendously helps with the detail in the landscape segment. The Pentax lens also renders excellent colors - even at night. I was extraordinary surprised with the colors that I was able to capture/retain in the windmill/desert shot.



The acquisition of the K1 and 15-30 emptied my camera fund. I need to re-tool my post processing. The Chancellor of the Exchequer, is telling me that I need to save my nickels, dimes and quarters. Actually, I need to cull some of my lenses.

• LightRoom has problems with the white dot noise, Capture One (C1) fixes that (or in camera LENR - Long Exposure Noise Reduction). RawTharapee also can address the white dot noise issue.
• Microsoft ICE has problems with oversampling when stitching, both PTGui and PhotoShop resolves that problem.
• Affinity Photo does a poor job in masking and compositing. PhotoShop again resolves that issue. If PS has masking problems, I have found that Fluid Mask performs better than PS.

I think I'll just go with PS and I see that C1 has a new version out that I can trial again. So, perhaps I can stitch everything together (the bush on the left hand side is the problem) and composite the parts together in the next couple of weeks. I'm eager to finish it and see what it all looks like. The 3 panel stitch at 15mm was a test to show the potential and help with the colors (and brightness) across the entire image. The problem is making it too bright so that it becomes a very unnatural night image. The details in the landscape are exceptional in the individual frames. It's amazing what the K1 captures - in terms of details in the dead of night. Stitched together, it should be on the order of 19,000 x 11,000 or 215MB large. The local Costco will do large prints up to 20" x 60" for $20. I figure to use the entire 20" on the tall side, the long side would then be ~35", with a resolution of 550ppi, which is way more that what I would ever need.

Great info. I subscribed to your other thread for all the information (and to see how the pano turns out). Might give Capture One a try - or stick with LENR for my foreground shots. The latter would likely be fine unless I'm stitching a long row that requires many exposures. I have LR, PS and Autopano Giga, but I've heard good things about PTGui.

Amazing how much color and detail you're able to pull from the foreground. I'm right with you on the risks of making the foreground too bright - to my mind, a night image should look like it was shot at night, even if that means some detail gets sacrificed to shadows. Also with you on the " Chancellor of the Exchequer", but for @ $50 I can't turn down that 50mm 1.7 as a pano lens. My bigger $ issue is that 15-30 and the fact that I will need a whole, new filter system to go with it. I generally don't use a lot of filters, but need my ND filters for long exposures, waterfalls, etc.

Thanks for all the great tips - look forward to seeing that pano when it's done!

---------- Post added 02-18-19 at 05:56 AM ----------

I use a variety of lenses......bower 14/f2.8 (same as your rokinon), promaster 19-35 spectrum7, cosina 24/f2.8, sears 28/f2.8, jc penny 28/f2.8, fa 35/f2, fa 50/1.4.....all lenses but the sears are of the 'a' variety.....the longer the FL the less pronounced the dark edges/coma from astrotracer use on the K-1…...but I have had a lousy year weather wise to really use the K-1 and get familiar with it like the experience I have using the K-3ii or K-50....I stack several astrotracer shots, mask with the landscape shots and stitch it with ICE but my post skills suck but have improved over a few seasons of milky way/astro shooting...….I have only printed one 16x20 which basically cropped out most of the coma and that was only a frame composite with the bower 14/f2.8 & K-3ii
if I were still living in south jersey I would love to hit up Batsto, chatsworth, reckon anything bass river, pine barrens in the spring and hit up the south coast later in the summer

good luck and clear skies!

Thanks - I actually have the same Bower version of the lens, but always call it a Rokinon/Samyang b/c a lot of people have no idea what I'm talking about if I say "Bower". That Promaster was on my list to look for (along with the Sigma or Tamron versions) - I need something in that range to tide me over until I can buy the 15-30. I also like the fact that it's a lot lighter and can take screw-in filters.

My post-processing skills are also on the lower range - thank Dog for the internet. Depending on where I end up and the foreground, I think I'll try something similar with stacking several astrotacer exposures for each sky frame, separate exposures for the foreground and stitching in PS. I hit Batsto a couple years ago but need to head back there - also Lake Nummy, East Point Lighthouse and Turkey Point Bridge. Those are @ 1 1/ to 2 hours away. Otherwise, to get somewhere fairly dark I'm looking at 3-5 hours (Catskills, Montauk, Assateague, Block Island). Not sure what it's like near Huntsville, but I'm very jealous of anyone who lives in the southwest or Maine coast.

Clear skies!

[riseform]

I'm only a few years into the astro learning curve, but I'll throw in my two cents. I mostly shoot landscape milky way shots.

I really enjoy the astrotracer for shots with a boring (easily merged) flat landscape or "star only" shots. That being said, those kind of shots are not as satisfying to look at when compared to a complex foreground with or without some light painting. If I'm going to be out at 3 am taking photos, I want to make the end product worth my efforts.

My real deficiency is blending astrotracer shots with the foreground. If I were better at refining the edges of an intricate foreground (ie knew what the heck I was doing in photoshop) I'd probably combine the astrotracer and landscape shots more often, but I have a very difficult time with two scenarios:

1) Thin trees or hoodoos are widened by the sensor movement, making it tough to paste and blend the landscape and the astrotraced image. One solution for this is to shift the milky way down on the screen (the height of the hoodoos) but I don't like to sacrifice any of the galactic center. Another solution I learned from this forum is to use the clone stamp at the horizon on the astrotracer shot to remove the widened structures before blending. This would probably work best.

2) The second and most difficult scenario involves thin branches and voids with visible stars within a deciduous tree. If I could select each branch with better detail using the refined edge tools, this wouldn't be such a problem and the above fixes would work. Since I am unable to do this well, the color within the longer, lower ISO landscape tree is never the same as the astrotracer image making it difficult to overlap the two. I suppose I should only shoot trees that are fully leafed out.

So personally, I've come to prefer stacking with free software (Sequator in my case) when I have an interesting and complex foreground. I'll admit, however, that each time out I still shoot quick frames for stacking and also use the astrotracer (and often stack) hoping my post processing skills will improve. I'm always looking for better instructional videos on how to master the refine edge tool in photoshop.

I've used every wide angle lens I own and have even stacked Theta V 360 milky way shots, but my current favorite is the Irix 15 thanks to a time saving and accurate infinity notch. Next favorite is the Rokinon 24 which I focus with a SharpStar (Bahtlnov mask). I have stitched stacked photos with and without astrotracer for panoramas (especially early in the milky way season) and it does make a better picture. If I were a professional, I'd probably use a 50 mm lens and spend the time tracking, stacking and merging.

If you're bored some night, it's also interesting to take an astrotracer shot and light paint the last few seconds, trying to get less of a blur of the foreground. Results aren't too bad, but stacking shots turns out better.

Here's a link to my attempts and evolution over the years, if any desire to peruse. Astro | Flickr

[interested_observer]

Great info. I subscribed to your other thread for all the information (and to see how the pano turns out). Might give Capture One a try - or stick with LENR for my foreground shots. The latter would likely be fine unless I'm stitching a long row that requires many exposures. I have LR, PS and Autopano Giga, but I've heard good things about PTGui.

Amazing how much color and detail you're able to pull from the foreground. I'm right with you on the risks of making the foreground too bright - to my mind, a night image should look like it was shot at night, even if that means some detail gets sacrificed to shadows. Also with you on the " Chancellor of the Exchequer", but for @ $50 I can't turn down that 50mm 1.7 as a pano lens. My bigger $ issue is that 15-30 and the fact that I will need a whole, new filter system to go with it. I generally don't use a lot of filters, but need my ND filters for long exposures, waterfalls, etc.

Thanks for all the great tips - look forward to seeing that pano when it's done![COLOR="Silver"]

With the rain storms last night and today - actually its snowing in the most northern extents of the City of Phoenix, and Flagstaff picked up 31 inches of snow in less than 24 hours - so, today is a good day to start testing out the retooling. Capture One has a new version and with some improvements that I can take advantage of. Turned on that 30 day trial. Working my way through the new updated learning videos. So will start applying them and see how things actually turn out.

Then I need to do the PS trial for masking and compositing the sky and landscape back together again.

I have exceeded Microsoft ICE's capabilities - so hopefully PS works out well for stitching. I've been sitting on the fence for years trying to decide between Autopano Giga and PTGui. Since Kolor went out of business - my choice has been made if PS doesn't work out. At least I have a backup plan - PTGui.

Overall, we'll see how all of this actually works out. The bush and windmill will present the largest challenges. Riseform - outlined these challenges very well below. Hopefully in a week or two, I might have an acceptable final image (or not). I still have about 120 images from Acorn Street in Boston (Bunker Hill) that I have wanted to stitch together in a very long linear pano, that with some geometric projection problems that accumulated over several hundred feet, that I don't have either the skill or the tools to get any type of stitched result.

1) Thin trees or hoodoos are widened by the sensor movement, making it tough to paste and blend the landscape and the astrotraced image. One solution for this is to shift the milky way down on the screen (the height of the hoodoos) but I don't like to sacrifice any of the galactic center. Another solution I learned from this forum is to use the clone stamp at the horizon on the astrotracer shot to remove the widened structures before blending. This would probably work best.

2) The second and most difficult scenario involves thin branches and voids with visible stars within a deciduous tree. If I could select each branch with better detail using the refined edge tools, this wouldn't be such a problem and the above fixes would work. Since I am unable to do this well, the color within the longer, lower ISO landscape tree is never the same as the astrotracer image making it difficult to overlap the two. I suppose I should only shoot trees that are fully leafed out.

You really have outlined very well the challenges I have on my Milky Way shots with the astrotracker. The widening of the tree branches is just enough to cause problems (your item 1), which leads into your item 2. With today's weather, I trying out a new set of tools. Capture One (C1) has some additional masking capabiliteis that I want to try to export with to PS. Or just use the PS tools to mask and then composite. If that doesn't work then I fond another masking tool - Fluid Mask that should (in theory) work possibly better than either C1or PS. Who knows - but I have a challenging set of images to test everything out on.