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03-25-2016, 05:36 AM   #1
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P645Z and 28-45mm lens for landscape astrophotography

As the title suggested, has anyone tried this combination? I just picked up the lens after saving my pennies and wanted to give it a try. I also have a Nikon D750 and was thinking of trying the 14-24mm lens with that, but only if the 645Z setup didn't fare well.

I wanted to know if the 28-45 was wide enough, if what they called coma was present, and if the results of the bigger sensor were acceptable.

03-25-2016, 08:18 AM   #2
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That's my dream setup.
03-25-2016, 02:49 PM - 2 Likes   #3
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QuoteOriginally posted by Femtometer Quote
As the title suggested, has anyone tried this combination? I just picked up the lens after saving my pennies and wanted to give it a try. I also have a Nikon D750 and was thinking of trying the 14-24mm lens with that, but only if the 645Z setup didn't fare well.

I wanted to know if the 28-45 was wide enough, if what they called coma was present, and if the results of the bigger sensor were acceptable.
if you just bought it, why are you asking if it's ok?
03-25-2016, 05:49 PM   #4
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I have tried it but not seriously.
I found it too slow and not wide enough. I am going to have another go with the K1 and 15-30 once I get it which I am hoping will be ideal.

03-26-2016, 12:39 AM   #5
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QuoteOriginally posted by gavincato Quote
if you just bought it, why are you asking if it's ok?
I bought it for all the other things the lens can do, but I've never tried landscape astro before & wanted to see if it's worth using for that. I have to drive 2+ hours away, check the weather, try not to get robbed, etc, and just wanted to see if the lens would make all that worth it.

I'll get plenty of use out of the lens in other areas.
03-26-2016, 09:43 AM   #6
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I am also interested in using 645z for astro-landscape. 28mm is a very good focal length for this, although 24mm may be even better.

For the 28-45/F4.5, I worry that it's aperture is not large enough. On my D800, I almost always use F2.8 for astro-landscape, and I don't feel I can stop the lens down further and still get satisfying results. To shoot at F2.8 on an ultrawide without getting strong coma, the lens has to be very good. (I use Tamron 15-30/F2.8.) On the 645z side, F4.5 on 645z has a light collecting power that's equivalent to F3.5 on a 35mm camera. If there is strong coma, then this will be a disaster, since there is very little room for you to stop it down to improve coma while maintaining enough light gathering power. I found my 645 FA 35mm/F3.5 has to be stopped down to at least F4.5 to reduce coma, preferably F5.0 (https://www.flickr.com/photos/weihaowang/24795271809/). F5.0 is acceptable for deep-sky astrophoto, but probably way too faint for astro-landscape. If the 35mm needs to be stopped down F4.5, then it is not very likely that the 28-45 does not require any stopping down. I might be wrong though, since the requirements for deep-sky and astro-landscape may not be the same.

I think you can try to find some point-like light sources and take test shots when you use this lens for normal purposes. If you do not notice strong coma, then there is a hope that this lens performs well on astro-landscape.

Cheers,
Wei-Hao
03-26-2016, 09:51 AM   #7
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K1 seems like a better choice for this due to wider, faster lenses and built in astrotracer.
I upgraded my K5 to a K3II for astros and have yet to use it...doh, i need to get out there.
03-27-2016, 03:39 AM   #8
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Yes the astrotracer will be interesting in the K1 and I look forward to trying it out. However, I assume that this will only work for images that don't include any landscape in them? If the sensor is moving then any interesting rock formation or tree or whatever you want in the foreground is going to be blurred right? I'm guessing we will have to take two images one with the astrotracer on then the other off and blend in PS?

03-27-2016, 10:43 AM   #9
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QuoteOriginally posted by Gyroscope Quote
Yes the astrotracer will be interesting in the K1 and I look forward to trying it out. However, I assume that this will only work for images that don't include any landscape in them? If the sensor is moving then any interesting rock formation or tree or whatever you want in the foreground is going to be blurred right? I'm guessing we will have to take two images one with the astrotracer on then the other off and blend in PS?
that is the technique (one shot with GPS on and one with it off, and blend).
03-27-2016, 09:07 PM - 1 Like   #10
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What I do on my D800 is to take several (8 to 16) short (6 to 20 sec) exposures on a tripod without any tracking, at ISO 800 to 3200. Then I stack the sky and foreground separately. The foreground can be easily stacked in Photoshop, and the sky needs to be stacked after the stars are aligned (many astro-softwares can do this). Then I blend them together. This can produce an image that's equivalent to a long exposure in term of noise, and both sharp sky and foreground, without any tracking device. Last night I used my 645z the same way. We will see how it works in a few weeks after I process the images.
03-28-2016, 01:32 AM   #11
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For star shots, I do find f4.5 somewhat restrictive and use the 25mm f4 and 35mm f3.5 in preference to the 28-45... Using f4.5 (or smaller) requires higher ISO (for any given exposure length) which, even with the Z's superb high ISO performance, is sub-optimal.

That said, I am sure great star shots can be taken with it. I just prefer other options.
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