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09-16-2020, 09:01 AM - 1 Like   #1
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Astro - sell the Sigma 10-20 f3.5 for a prime?

I find myself always trying to get milkyway shots but always being dissapointed. I know I want foreground so that always leaves me using a wide angle. I have a Tamron 17-50 F2.8, a Sigma 10-20mm F3.5, Samyang 35mm F1.4, Pentax 50mm F1.4. I just got in a 0-GPS1 and a remote trigger I haven't tried yet. But I keep wanting a Samyang/rokinon 10mm F2.8 or even the 14mm but haven't pulled the trigger since I have already have the lenses above. I just keep think I could do better with a faster prime. But so far I've also been limited to the 30 second in body timer and no tracking. Latest sample pic. I live near Pittsburgh so low light is only up at my cottage (below) or at the beach in a few weeks.



09-16-2020, 09:31 AM   #2
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Looks good to me, If you are going to do this more often I'd invest in a light pollution filter to cut the yellow/pinkish cast that city lights make
09-16-2020, 09:42 AM   #3
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I have one of the Sigma lenses in question that I like but I haven't used it for astro. It looks like you are doing very well with yours. Here is one I made aerlier.



There have been reports of Samyang/Rokinon ultra wides with de-centering issues. If do pull the trigger on one, be sure to get it from a seller that accepts returns. The sort-of good news is that it will be bad straight out of the box. They come like from the factory because of poor quality control. It's not something that breaks when you use the lens. AFAIK the issue manifests itself as one corner/half of the image being out of focus while the rest is sharp. If you get a good one, it will serve you well.
09-16-2020, 09:51 AM   #4
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QuoteOriginally posted by no694terry Quote
I find myself always trying to get milkyway shots but always being dissapointed. I know I want foreground so that always leaves me using a wide angle. I have a Tamron 17-50 F2.8, a Sigma 10-20mm F3.5, Samyang 35mm F1.4, Pentax 50mm F1.4. I just got in a 0-GPS1 and a remote trigger I haven't tried yet. But I keep wanting a Samyang/rokinon 10mm F2.8 or even the 14mm but haven't pulled the trigger since I have already have the lenses above. I just keep think I could do better with a faster prime. But so far I've also been limited to the 30 second in body timer and no tracking. Latest sample pic. I live near Pittsburgh so low light is only up at my cottage (below) or at the beach in a few weeks.

Which camera body are you using?
My Sigma 10-20m f/4-5.6 works quite happily on my K-70 with O-GPS1, within the limits imposed by light pollution in my locality.
A wider aperture will allow more faint detail to be recorded if you're in a dark-sky location.
You should be able to make some comparison shots between your existing Sigma 10-20mm and your Tamron or Samyang to confirm the benefit of a wider aperture ... if it's significant then you've got some valid data to support the purchase of (yet) another lens

Good luck

09-16-2020, 10:22 AM - 1 Like   #5
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Concluding from the sample image (I can't find the exif data, but I am guessing it's the Sigma 10-20mm @10mm wide open?) corner sharpness is not that great, but with the newly acquired GPS unit you probably will be able to stop down the lens a little further and this might improve the results you get. As for selling the Sigma 10-20mm lens for the Samyang 10mm prime, it depends on your photographic interests if you benefit from this trade.
If you plan to focus on astro-work a fast prime lens is more important than the versatility of a zoom in my opinion, but for landscapes or architecture the Sigma 10-20mm lens is probably more handy.

Observing your sample image I think there is some room for improvement even with the Sigma 10-20mm. When combining night sky with a foreground I usually don't do it with a single shot. I use low ISO, a slow aperture and a long shutter speed for the foreground and high ISO, fast aperture and shortish shutter speed for the night sky (as short a shutter speed as possible before the stars become lines in the image - when this is the case depends on the focal length and if you are using astrotracer or not). To get a clean night sky I usually stack around 10 pictures together to reduce the sensor noise because of the high ISO.

With the astrotracer you will have to combine at least 2 shots too, because you get motion blur in the foreground when tracking stars.


I haven't done much astrophotography myself (therefore I don't own a GPS unit) but depending on your subject even your Samyang 35mm lens can be wide enough to include foreground

K-3 + Samyang 35mm:
09-16-2020, 10:48 AM   #6
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QuoteOriginally posted by othar Quote
Concluding from the sample image (I can't find the exif data, but I am guessing it's the Sigma 10-20mm @10mm wide open?) corner sharpness is not that great, but with the newly acquired GPS unit you probably will be able to stop down the lens a little further and this might improve the results you get. As for selling the Sigma 10-20mm lens for the Samyang 10mm prime, it depends on your photographic interests if you benefit from this trade.
If you plan to focus on astro-work a fast prime lens is more important than the versatility of a zoom in my opinion, but for landscapes or architecture the Sigma 10-20mm lens is probably more handy.

Observing your sample image I think there is some room for improvement even with the Sigma 10-20mm. When combining night sky with a foreground I usually don't do it with a single shot. I use low ISO, a slow aperture and a long shutter speed for the foreground and high ISO, fast aperture and shortish shutter speed for the night sky (as short a shutter speed as possible before the stars become lines in the image - when this is the case depends on the focal length and if you are using astrotracer or not). To get a clean night sky I usually stack around 10 pictures together to reduce the sensor noise because of the high ISO.

With the astrotracer you will have to combine at least 2 shots too, because you get motion blur in the foreground when tracking stars.


I haven't done much astrophotography myself (therefore I don't own a GPS unit) but depending on your subject even your Samyang 35mm lens can be wide enough to include foreground

K-3 + Samyang 35mm:
Your blacks are nice. Also using a K-3. My initial hopes are to get the GPS1 to allow lower ISO and bump the Fstop up to sharpen the image and keep the Sigma. I'd probably keep it anyway.

The foreground in my sample was lit up a bit with an LED spotlight I have.

Sigma 10-20 at 10mm F3.5 30s ISO3200

09-16-2020, 10:52 AM - 2 Likes   #7
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I assume the picture was shot with the Sigma 10-20 and was wide open. With those assumptions that lens looks like it has some really bad coma. Stopping it down from 3.5 would result in having to use a higher ISO. So based off of those 2 things I would consider a different lens for ultra wide astro. In general there are other benefits to using a prime for astro shooting but given what I have seen from the lens you used I don't need more to convince me. You also mentioned that you now have the O-GPS1 to enable astrotracer but astrotracer with wides and ultra wides can become a hot mess when pointed in some directions. This is just a function of how the sensor can move, the movement of the night sky, and the wideness of the lens fighting each other.

Since you state you want an ultrawide like an 8 or 10mm Samyang/Rokinon if you get a good one using 25-30 seconds shots will provide good results with little to no trailing. Using a stacking program like Sequator to drive the noise down and align the images with 10 or so will give good results and you can further edit from there.

For ultrawide astro shots I use the Laowa 12mm f/2.8 Zero-D which I can run wide open without issue but it has some very slight coma in the corners until you get to f/4. When I say very slight I mean you can only notice it if you are at 50% or greater zoom so you are pixel peeping. My entry for the nigh sky contest was shot wide open using that lens and using 13 second shots that were stacked. The Laowa is substantially more than the similar Samyang/Rokinon ones but the lower distortion, excellent build quality, and much better quality control to me made it worth it.

If you really want to get a light pollution filter I suggest getting something like the Hoya Red Intensifier as they do a good job of pretending to be one but as your ability improves in editing astro images you will find that you no longer need it. by going with the Hoya Red Intensifier you also aren't out nearly as much money as you would be if you went with other options that perform slightly better.
09-16-2020, 11:33 AM   #8
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QuoteOriginally posted by MossyRocks Quote
I assume the picture was shot with the Sigma 10-20 and was wide open. With those assumptions that lens looks like it has some really bad coma. Stopping it down from 3.5 would result in having to use a higher ISO. So based off of those 2 things I would consider a different lens for ultra wide astro. In general there are other benefits to using a prime for astro shooting but given what I have seen from the lens you used I don't need more to convince me. You also mentioned that you now have the O-GPS1 to enable astrotracer but astrotracer with wides and ultra wides can become a hot mess when pointed in some directions. This is just a function of how the sensor can move, the movement of the night sky, and the wideness of the lens fighting each other.

Since you state you want an ultrawide like an 8 or 10mm Samyang/Rokinon if you get a good one using 25-30 seconds shots will provide good results with little to no trailing. Using a stacking program like Sequator to drive the noise down and align the images with 10 or so will give good results and you can further edit from there.

For ultrawide astro shots I use the Laowa 12mm f/2.8 Zero-D which I can run wide open without issue but it has some very slight coma in the corners until you get to f/4. When I say very slight I mean you can only notice it if you are at 50% or greater zoom so you are pixel peeping. My entry for the nigh sky contest was shot wide open using that lens and using 13 second shots that were stacked. The Laowa is substantially more than the similar Samyang/Rokinon ones but the lower distortion, excellent build quality, and much better quality control to me made it worth it.

If you really want to get a light pollution filter I suggest getting something like the Hoya Red Intensifier as they do a good job of pretending to be one but as your ability improves in editing astro images you will find that you no longer need it. by going with the Hoya Red Intensifier you also aren't out nearly as much money as you would be if you went with other options that perform slightly better.
Downloaded Sequator. Will give that a go. Thank you

09-16-2020, 02:38 PM   #9
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QuoteOriginally posted by titrisol Quote
Looks good to me, If you are going to do this more often I'd invest in a light pollution filter to cut the yellow/pinkish cast that city lights make
Sadly, those filters work wonders with sodium lights since the light they emmit is narrow band, but not with the modern LED replacements, which have a wider spectrum.

09-16-2020, 02:54 PM - 1 Like   #10
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QuoteOriginally posted by torashi Quote
Sadly, those filters work wonders with sodium lights since the light they emmit is narrow band, but not with the modern LED replacements, which have a wider spectrum.
There is still a lot of sodium vapor lamps in use. Jumping up to a better filter there are ones that also will get rid of a fair amount of the pollution for mercury vapor lamps too. However neither one does a perfect job and you do lose some signal from the night sky. A light pollution filter can offer a good jump in quality for someone starting out but eventually one will likely get good enough at editing that they would be better served by not using one and dealing with things in post processing.

You are correct that LEDs are more broad band and are harder to deal with light pollution filters but like I said there are still a lot of sodium and mercury vapor lamps in use so you will still get a benefit from using a filter for them. My town loves really crappy sodium vapor lamps with big glass globes where there are 2 globes on a bunch of posts and they are about 50 feet apart on both sides of the streets. They send as much light up as they do down and there are tons of them. I get orange glow all the way to the zenith.
09-17-2020, 01:10 AM - 1 Like   #11
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Be advised that the Sigma 10-30mm f/3.5 EX DC HSM has been discontinued in the Pentax mount. Too bad, as it is an excellent WA zoom lens for APS-C. That extraordinarily fine shot by Wasp posted here is a great example of what it is capable of. The older but still good Pentax DA 12-24mm f/4 has also been discontinued. So if having such a capable WA zoom lens in your lens arsenal, good for many uses and applications, is of importance to you or perhaps will be, keep this in mind before letting it go. Pentax APS-C shooters are now left with only the very expensive DA* 11-18mm f/2.8 as the sole choice remaining for an ultra-wide quality zoom lens.

Personally, I doubt that the difference between f/3.5 and f/2.8 will make a huge difference. You might consider putting money towards a KP, which can allow a higher ISO enough to compensate for such a difference and more.

I really like the post-sunset afterglow in your first image along with the starry scene above and reflected light on the trees- I think it is a fine composition with terrific effects. Any shortcoming of the lens becomes very minor compared to the eye-catching effects of the overall scene. The OGPS-1 should be of value for you. I think there is a built in tracking program in the latest camera models. I have the KP but have not yet got myself into this kind of fun, so I have not even sought out the info in the users manual.

Last edited by mikesbike; 09-17-2020 at 01:23 AM.
09-17-2020, 05:11 AM   #12
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unedited pic to test the gps function, stars still seem sharp after 2 minutes. I wanted to compare this to a stacked sample but the lighting wasnt quite right. #citylife

k3 - Samyang 35mm @F4, 120s ISO 100
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09-17-2020, 06:21 AM - 1 Like   #13
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QuoteOriginally posted by MossyRocks Quote
There is still a lot of sodium vapor lamps in use. Jumping up to a better filter there are ones that also will get rid of a fair amount of the pollution for mercury vapor lamps too. However neither one does a perfect job and you do lose some signal from the night sky. A light pollution filter can offer a good jump in quality for someone starting out but eventually one will likely get good enough at editing that they would be better served by not using one and dealing with things in post processing.

You are correct that LEDs are more broad band and are harder to deal with light pollution filters but like I said there are still a lot of sodium and mercury vapor lamps in use so you will still get a benefit from using a filter for them. My town loves really crappy sodium vapor lamps with big glass globes where there are 2 globes on a bunch of posts and they are about 50 feet apart on both sides of the streets. They send as much light up as they do down and there are tons of them. I get orange glow all the way to the zenith.
My experience is a bit different. I live in the outskirts of a big city, and most street lights are sodium vapor, but in the last eight years, the lights everywhere else (houses, yards, fields, buildings, access roads and gates, etc.) have become brighter and whiter. Even though it lies in a valley, you can see the dome of light shining out of it from miles away. It's a bummer, but it's also very difficult to do astrophotography here because of the climate conditions.
I do fear the day when all these lights will outshine even the full moon since there are no regulations about spill.

09-17-2020, 09:29 AM   #14
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QuoteOriginally posted by no694terry Quote
I just keep think I could do better with a faster prime. But so far I've also been limited to the 30 second in body timer and no tracking. Latest sample pic. I live near Pittsburgh so low light is only up at my cottage (below) or at the beach in a few weeks.
So, which focal length prime would you get??

The 'problem' with prime lenses is that each - by definition - comes in only one focal length. Has your use of the Sigma lens allowed you to concentrate on just one length??
09-19-2020, 11:34 AM   #15
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You are right, LED have introduced another variable to the mix
I did some reading and there are a few "wide range" filters that also take care of LED pollution
Sich as the optolong L-pro or the SkyTech LPro
They supposedly block a wide range of frequencies, nlducing the bluis/green from LEDs



Articel here: 10 Light Pollution Filters for Astrophotography in the City


QuoteOriginally posted by torashi Quote
My experience is a bit different. I live in the outskirts of a big city, and most street lights are sodium vapor, but in the last eight years, the lights everywhere else (houses, yards, fields, buildings, access roads and gates, etc.) have become brighter and whiter. Even though it lies in a valley, you can see the dome of light shining out of it from miles away. It's a bummer, but it's also very difficult to do astrophotography here because of the climate conditions.
I do fear the day when all these lights will outshine even the full moon since there are no regulations about spill.
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