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12-05-2013, 09:28 AM   #16
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Forgot to mention that detail as well. I use an AstroTrac TT320X-AG tracking mount. It has accuracy to 5 arcseconds at 5 minutes unguided which is good enough for what I do. As for whether the Samyang 14mm would be good for wide field astro work, I can't say since I do not have anything that wide. The key to good astro shots is to get a lens with little to no coma if possible. Coma will make stars near the edges appear teardrop shaped. For example, the "plastic fantastic" DA35 is almost coma-free.

Jack

12-05-2013, 09:43 AM   #17
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QuoteOriginally posted by jbinpg Quote
Forgot to mention that detail as well. I use an AstroTrac TT320X-AG tracking mount. It has accuracy to 5 arcseconds at 5 minutes unguided which is good enough for what I do. As for whether the Samyang 14mm would be good for wide field astro work, I can't say since I do not have anything that wide. The key to good astro shots is to get a lens with little to no coma if possible. Coma will make stars near the edges appear teardrop shaped. For example, the "plastic fantastic" DA35 is almost coma-free.

Jack
Jack,

Did you say that you took the picture of M42 with a DA 300? I'm amazed.... (well, since I know nothing about astrophotography yet I'm easily amazed!) I have a 300 on my wish list.

Bob
12-05-2013, 09:51 AM   #18
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The M42 shot is a crop. The K-3 resolution is high enough to allow for generous cropping while still maintaining a modicum of resolution.

Jack
12-05-2013, 10:21 AM   #19
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QuoteOriginally posted by jbinpg Quote
The M42 shot is a crop. The K-3 resolution is high enough to allow for generous cropping while still maintaining a modicum of resolution.

Jack
My wife and I are amazed that you can capture that much with just a 300mm. I can tell you that this sure helps in my campaign for a new DA*300..... ;-)

12-05-2013, 01:50 PM   #20
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Maybe I should post my crappy shots, but I know what you mean. Tokina does have some coma with stars. Not too much, but pixel peeċing stars, it is easy to see.

I like what I get with 20 mm, but I'd like to have more sky in shot...haven't tried stitching.

I'm waiting to see some clear sky in future to try it again with other lenses...it will be looogn time thou. Storm coming in and lot of snow.
Btw, maybe astro tracer is good enough for noobs like me to begin with?

QuoteOriginally posted by jbinpg Quote
Forgot to mention that detail as well. I use an AstroTrac TT320X-AG tracking mount. It has accuracy to 5 arcseconds at 5 minutes unguided which is good enough for what I do. As for whether the Samyang 14mm would be good for wide field astro work, I can't say since I do not have anything that wide. The key to good astro shots is to get a lens with little to no coma if possible. Coma will make stars near the edges appear teardrop shaped. For example, the "plastic fantastic" DA35 is almost coma-free.

Jack
12-05-2013, 01:56 PM   #21
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The O-GPS1 unit in astrotracer mode works well within its limits. However, it cannot compete with a real tracking mount which allows longer exposures and does better counteracting the earth's rotation.

Jack
12-05-2013, 02:05 PM   #22
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Thank you Jack!

I think that I'll try some stacking and then later some O-GPS1 action, when I can afford it.

-Aapo
12-06-2013, 04:11 PM   #23
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Comet Lovejoy revisited

Headed out into the -20degC cold this morning to see if I could do a better job on Comet Lovejoy. I managed to get a 15-frame stack done before my fingers gave out. 8 frames at ISO6400 and 7 frames at ISO3200, all at 8 second exposures through the K-3 + DA*300 at f4.5, stacked in DeepSkyStacker. Unfortunately, the EXIF is stripped when stacking. The Arctic air will be moving out over the next week which means an increase in cloud over the next few days. Looks like the good observing window will be closing soon. - Jack





12-07-2013, 09:18 AM   #24
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QuoteOriginally posted by repaap Quote
I'm thinking of better wide for astro. 'They(web)' say samyang 14 would be good. Any ideas on that?


The Samyang 14mm has virtually no Coma throughout its image coverage on full frame. It has even less on APS-C. I have not had much opportunity to use it since I got it. But the images below are single tracked 30s, f2.8 exposures at 1600 ISO and 1100 ISO taken with the Samyang 14mm on the K-3. Tracking was with an iOptron SkyTracker. There is significant distortion from the lens and I am still trying to adapt a third party light room Lens Profile that fixes it for full frame so that it works for Pentax APS-C. I am certain I can get significantly more interesting and clear images from this lens/camera combination but it's very early days for me as far as astrophotography is concerned. These are the 4th and 5th night sky shots I have ever taken. I think I am becoming very drawn to the dark side.





12-07-2013, 12:33 PM - 1 Like   #25
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Looks good!. Yes, too bad the lens makers don't publish the recommended corrections somewhere for non-chipped lenses, even in paper form in the sale box.
02-01-2014, 12:51 AM   #26
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SN2014J with a K-3

There is an active supernova thread in the K-5 forum but I thought I had better post here to maintain the camera model separation. Finally after more than a month of low cloud and fog, the skies cleared over the past 48 hours. Did not have perfect transparency and seeing since there were multiple thin layers aloft and the cold air was still sucking the scant warmth from the ground leading to a bit of a soupy atmosphere. I elected to begin earlier in the evening than I would have liked since the target was at a better angle. Blacker skies would have been nice but it was a tradeoff I was willing to make. The blacker the skies, the less you need to crush the blacks in post. As it turned out, stars down to about 16th magnitude were captured.

The supernova SN2014J in M82 in the constellation of Ursa Major, The Great Bear (the Plough for you Brits), has brightened since its discovery and is now near 10th magnitude. It is easily visible in my DA*300 shots. The images here are from a stack of the following frames in DeepSkyStacker: 14 @ 30s each @ ISO3200; 5 @ 30s each @ ISO1600; and 1 @ 15s @ ISO4500. One image is a full frame and the other is a 100% crop to show the crop ability of the K-3. Post-processing included setting the black level, increasing the saturation and some sharpening. No noise reduction other than that obtained via the stacking process was done. All taken from my back porch

The K-3 was guided by an AstroTrac TT320X-AG tracking mount. Camera was in manual mode, daylight WB, and pre-shot mirror lockup using the Remote F IR release. DA*300 was set to MF at an aperture of f4.5. All in-camera lens corrections were enabled. Manual infinity focus before beginning was obtained by piping the Live View feed to a 7" Lilliput field monitor and aiming at Dubhe, alpha Ursa Majoris, at apparent magnitude 2.0. Live View was magnified 10X to help with focus since this is the most critical part of the whole pre-shot setup. Power for the tracking mount, K-3 and field monitor was supplied by two jumpstart batteries with appropriate adapters for connectors and voltages. Ambient temperature was -14C at the start of the shoot and -16C at the end. Equipment performed flawlessly. Can't say the same for my fingers. - Jack
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02-01-2014, 01:59 AM   #27
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Looks good, I have purchased 14/2.8. And tried some astro with it. But W/O any other aid. So nothing too much to share, yet.
QuoteOriginally posted by unkipunki Quote
The Samyang 14mm has virtually no Coma throughout its image coverage on full frame. It has even less on APS-C. I have not had much opportunity to use it since I got it. But the images below are single tracked 30s, f2.8 exposures at 1600 ISO and 1100 ISO taken with the Samyang 14mm on the K-3. Tracking was with an iOptron SkyTracker. There is significant distortion from the lens and I am still trying to adapt a third party light room Lens Profile that fixes it for full frame so that it works for Pentax APS-C. I am certain I can get significantly more interesting and clear images from this lens/camera combination but it's very early days for me as far as astrophotography is concerned. These are the 4th and 5th night sky shots I have ever taken. I think I am becoming very drawn to the dark side.




02-01-2014, 02:00 AM   #28
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Nice work!

QuoteOriginally posted by jbinpg Quote
There is an active supernova thread in the K-5 forum but I thought I had better post here to maintain the camera model separation. Finally after more than a month of low cloud and fog, the skies cleared over the past 48 hours. Did not have perfect transparency and seeing since there were multiple thin layers aloft and the cold air was still sucking the scant warmth from the ground leading to a bit of a soupy atmosphere. I elected to begin earlier in the evening than I would have liked since the target was at a better angle. Blacker skies would have been nice but it was a tradeoff I was willing to make. The blacker the skies, the less you need to crush the blacks in post. As it turned out, stars down to about 16th magnitude were captured.

The supernova SN2014J in M82 in the constellation of Ursa Major, The Great Bear (the Plough for you Brits), has brightened since its discovery and is now near 10th magnitude. It is easily visible in my DA*300 shots. The images here are from a stack of the following frames in DeepSkyStacker: 14 @ 30s each @ ISO3200; 5 @ 30s each @ ISO1600; and 1 @ 15s @ ISO4500. One image is a full frame and the other is a 100% crop to show the crop ability of the K-3. Post-processing included setting the black level, increasing the saturation and some sharpening. No noise reduction other than that obtained via the stacking process was done. All taken from my back porch

The K-3 was guided by an AstroTrac TT320X-AG tracking mount. Camera was in manual mode, daylight WB, and pre-shot mirror lockup using the Remote F IR release. DA*300 was set to MF at an aperture of f4.5. All in-camera lens corrections were enabled. Manual infinity focus before beginning was obtained by piping the Live View feed to a 7" Lilliput field monitor and aiming at Dubhe, alpha Ursa Majoris, at apparent magnitude 2.0. Live View was magnified 10X to help with focus since this is the most critical part of the whole pre-shot setup. Power for the tracking mount, K-3 and field monitor was supplied by two jumpstart batteries with appropriate adapters for connectors and voltages. Ambient temperature was -14C at the start of the shoot and -16C at the end. Equipment performed flawlessly. Can't say the same for my fingers. - Jack
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