dcweather
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Posts posted by dcweather
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On 31/07/2018 at 10:55, Dragon_Astro said:
Ha that's a cool railway
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Ha that's a cool wife 😀
On 31/07/2018 at 10:55, Dragon_Astro said:Ha that's a cool railway
Does your wife use it to drop off drinks/snacks while you're out with the scope? Lol
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I agree with Bright Giant. I am fairly new to astrophotography and have also been looking into this. I see from various maps that the same Bortle zone can cover a large range of radiant light indices. As the Bortle scale seems to be defined by light at the zenith I am assuming that a low radiance value is important because this I presume is affecting viewing at lower angles, say 45 degrees , which will be important when viewing ,say, the Milky Way. I am thinking you would want a lowish Bortle Zone, say 3, but in the UK 4 is more realistically accessible and a low radiance value. The map I am looking at www.lightpollutionmap.info quotes these and whilst I don't fully understand the units it would appear that 0.18-0.3 is very dark, 0.4-1.0 is achievable in more accessible rural areas. I hope this helps but if I am talking rubbish feel free to tell me because it would help me as well !
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I think if you just had lots of the same image the noise will be fixed in each image and so you will always subtract the same amount from the same signal so end up with the same. With a number of images, because of the random nature of the noise, more of it will be removed from the background. Also with lots of images the dynamic range may be increased allowing e.g some of the faint pixels to be occasionally brighter and accumulated. I expect their other reasons.
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On 20/11/2017 at 10:52, Icesheet said:
Here's two of my better efforts so far. Was delighted that I was able to pull out the Horsehead from the Orion widefield. I have a lot to learn but I would not have caught the bug without the Star Adventurer!
All these done with a Nikon D3200 and Sigma 70-200mm F2.8. Exposures range from 60-120sec. Typically ISO800-1600 at f4-6.3. The lens really isn't the best but good enough just now.
I would not hestitate to recommend it to you!
70-200mm f2.8 are among the most highly rated zoom lenses for general photography across several makes so it may be better than you think although what is good for one may not be the case for Astro I guess.
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1 hour ago, Stub Mandrel said:
Most images on this thread are with Alt-Az tracking mounts. They can go up to about 30 seconds before field rotation becomes an issue.
Thank you. I'd wrongly interpreted the thread as no tracking and static stacking only.
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1 hour ago, The Admiral said:
I think that the Pentax has sensor shift image stabilisation which is able to be used to correct for star movement, within limits. May be that's how it was done, though I'm not familiar with that post.
Ian
The K3ii and K1 have a built in GPS astrotracer and some have an optional add on. This was "Pentax K-30, 55-300DAL zoom (@300mm) 30x10sec ISO6400, 5x10sec dark frames. Shot last night after 2 weeks of clouds ." so probably was tracked non-EQ. I had mis-read the thread and thought there was no tracking at all.
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I've just started out so a bit of a learning curve but thought I had a reasonable grasp. Then near the beginning of this thread someone posted an image from a Pentax DSLR with a 55-300mm lens at 300mm. It was a number of long exposure subs (~10 secs). Quite a good image with no star trails. Even with stacking how could you achieve that? Alignment must be impossible? I thought you would have had to have had a tracking mount for long exposures at 300mm?
UWA lenses for Milky Way photography - Canon R-mount
in Discussions - Cameras
Posted
There are limited choices as far as I can make out including older EF lenses, for MW photography. If you take away much in built prejudice it seems that some of the Chinese makers are filling this gap with good build and optical quality manual lenses, which in theory (and in practice according to many reviews) can match the previous Rokinon/Samyang favourites. Plus these are only available as 14mm and the best one, the 12mm f2.0 only available in R-M mount for Canon.
So after much research I have narrowed it down to the similarly priced Nisi 9mm f2.8 sunstar lens and the Meike 10mm f2.0. There are differences but I suspect the performance to be similar enough in the critical areas to be ok for my current opportunities. I welcome any thoughts and specifically I wondered if the Nisi (which produces excellent sun stars even wide open) might put too many in a Milky Way image. I would imagine easier to add than remove pp.