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11-06-2013, 04:31 AM   #1
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Pentax K30 Astro lens help

Hi everyone

I have been using a pentax 50mm A lens and the kit 18-55 lens for some night sky photography and am really wanting an new lens. I have been looking at the samyang 14mm as a potential but would just like some conformation. My max is 275 to spend on the lens and i can get the samyang for 275. i have also included a sample picture of what i am getting just now.

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11-06-2013, 04:50 AM   #2
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Hey there. I have the Samyang 14mm. Here are some astro photos I took with it (Press M on the keyboard, and that should make the photos larger):
500px / Stars and satellite above city by Stolpulus II
500px / Stars above city by Stolpulus II
I took these as test for the recent astrophotography challenge and they were taken in the city, so the conditions were far from perfect. These photos are quite processed. Shot in raw and overexposed, then brought the brightness down and maximized contrast and clarity, sharpened, use NR.. You can also google for sample photos of astrophotography with the Samyang 14mm, some are really breathtaking.

The Samyang is a good choice for astrophotography, but it is very wide, so the stars are tiny and you get lots of surroundings. And make sure you get it with warranty and test that it doesnt have decentered elements, as that can make part of the photo look soft.
How fast is your A 50mm? It is not a bad choice for astrophotography if it has a large aperture, but the problem is that you get star trails if you expose for more than around 6 seconds. If you really like astrophotography, maybe the O-GPS1, with its start tracking feature, might be the best investment, as it makes all lenses much more useable. Just make sure its compatible with the cameras you want to use (I think it doesnt work with K-01 yet?).

With the photo you attached you are already on the right track. Don't be afraid to process it some more.
11-06-2013, 05:42 AM   #3
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Thank you for the quick reply! I have had a look on google and found some amazing shots but none with the K30. Those pics look great btw! i stay in a rural area so light pollution ins't too bad. I am more into wide field photos too so i would really like to get the surroundings in the picture too. I still have loads to learn yet and am just teaching myself right now and trying different settings. The samyang is the only lens i can find in my pric range and the pics i have seen with it are of great quality so i think i will go ahead and purchase it and may buy the O-GPS1 later on.

Would you recommend using multi-exposure or stacking pictures? i haven't tried those yet but will have a o next time i am out. I have also heard of using Bulb mode for night sky photography but not sure how it works.
11-06-2013, 06:39 AM   #4
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QuoteOriginally posted by R_McKillop Quote
i have also included a sample picture of what i am getting just now.
QuoteOriginally posted by R_McKillop Quote
I am more into wide field photos too so i would really like to get the surroundings in the picture too. I
You may already be aware of it(?) but, anyway, your K-30 sensor and lens have actually captured much more and more differentiated light than one can see off-hand from your uploaded image. So, hopefylly with your permission, I have played a bit with your image in curves and levels.

The massage is: Camera and lens are only parts of the means to success. In astrophotography som post-processing is usually a must to get the full benefits out of your gear. And yes, stacking does make post-processing easier and more rewarding, because stacking enhances the signal-to-noise ratio in your long exposures.

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11-06-2013, 08:43 AM   #5
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But stacking is far from an easy task. Astrophotography has a lot of tricks, like dark frame, stacking, using tripod mounts that rotate with the stars, and heavy digital processing. The photos I posted were a single shot (raw dng, possibly with in-camera slow shutter/long exposure NR, then processed in Lightroom)
Only other lens that you might find interesting is the Samyang 16mm 2.0. It is a newer lens and might be easier to handle than the 14mm f2.8 (not as awkwardly wide, slightly faster aperture). Not sure how much it costs or how it handles on tests.
Oh, and one more tip, apparently the 14mm in Pentax mount has miscalibrated focus ring. Not sure if its all copies, but definitely many. This means that 2m isn't at the 2m mark, infinity isn't at the infinity mark.. There are online tutorials on how to fix it yourself. Unfortunately this lens is manual focus only. Catch-in-focus and focus peaking dont really help much with this lens.

Last edited by Na Horuk; 11-06-2013 at 08:52 AM.
11-06-2013, 11:43 AM   #6
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Thanks for all the advice guys!! some great info and tips! i knew i had picked up more detail just wasn't sure how to bring out. I don't edit my pictures much so i will look into some tutorials on editing astro pictures. Thanks for the lens suggestion too but its just out of my price range unfortunately. All of the pictures i have seem to have a lot noise even at ISO800. Has anyone got any explanations for this? is it the lens? or i it just the K30? The other photos i have seen from a K30 have no where near as much noise.

I am going to research some more techniques and look into stacking and Bulb mode. Will have to wait till the next clear night, which could be a while knowing the weather in Scotland!

P.s. sorry for all the questions, i'm new to all this astro stuff
11-06-2013, 11:58 AM   #7
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In long exposures noise will show up. It will be especially noticeable because the photo has lots of empty space (sky) and tiny subjects (stars, sometimes as small as noise grain). In a short-exposure photo of a forest with many branches and leaves and fine detail, the noise would be much harder to notice.
If you shoot raw and use a raw editor software (Lightroom, Silkypix, AfterShot Pro, FastStone, Gimp, Aperture, Raw Therapee, etc., there are many options, some free) you have noise reduction options, even plugins (like Topaz denoise, NoiseNinja,..). some processing can cause noise to show up more (for example, if you make a dark photo much brighter). Raw files (.dng) contain much more data than jpeg files, so you have more leeway to process them. And when you edit and save a jpeg, you lose more data, because the compression is lossy. Raw editors generally leave the raw data alone and only add transformations, so you can experiment and always just hit "reset" to go back.
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