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10-11-2019, 05:35 AM - 1 Like   #16
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QuoteOriginally posted by mctaveck Quote
This shot has been taken using the astrotracer O-GPS1, with 150 seconds of exposure, wide open at 16mm. The boat is slightly cloned because of the sensor movements. Any critique is more then welcome of course; feel free to ask any detail may be required.
Thanks
Danilo
This picture is stunning. I tried many times to do similar ones, but I never like the results (it was never sharp enough). I wonder if it has to do with my lenses or with my exposure time since I don't have an astrotracer. Seeing this picture makes me want to try it out again.

10-11-2019, 06:15 AM - 1 Like   #17
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QuoteOriginally posted by mctaveck Quote
lens: depending on the focal you like and the result you want to achieve, the more is fast the best result you will have
Another step you could perform in non post processing step is to collect pano images to stack them. You will obtain a very high quality image, with a little bit of extra effort in shooting. This is a DA 50mm f1.8 (f1.8 ISO500 80seconds) pano of 4 or 5 images

---------- Post added 10-11-19 at 06:43 AM ----------

QuoteOriginally posted by felipeamaciel Quote
This picture is stunning. I tried many times to do similar ones, but I never like the results (it was never sharp enough). I wonder if it has to do with my lenses or with my exposure time since I don't have an astrotracer. Seeing this picture makes me want to try it out again.
Hi Felipe,
good lenses (no coma or aberrations) and astrotracer helps for sure. But you can achieve very good results with an old and good prime lens (i bought the M28 f3.5 for that reason) or a DA prime, indeed not expensive (see the 50mm I posted above) and using the stacking technique. Of course raw file, pretty much mandatory.

the only cons is the sky: if you live in a very light polluted area, like me, you can save time and sleep. But if you can go for a place bortle 3 or below.... have fun !

Danilo

---------- Post added 10-11-19 at 06:47 AM ----------

QuoteOriginally posted by bdery Quote
It's probably a matter of dodge and burn, mostly, then. I do this kind of editing in Lightroom usually (I have GIMP but not Photoshop). Steps 2-3-4 (mostly the last two) are probably key.

Thanks.
Yes, that's important as well as blending layers (you cannot do it with LR) and noise reduction with mask: i use the PS channels to create luminosity mask, but I guess there's a bunch of ways to generate those masks

Thanks
Ciao
Danilo
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10-11-2019, 10:15 AM - 1 Like   #18
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QuoteOriginally posted by mctaveck Quote
Yes, that's important as well as blending layers (you cannot do it with LR) and noise reduction with mask: i use the PS channels to create luminosity mask, but I guess there's a bunch of ways to generate those masks
That's something I have yet to learn.
10-15-2019, 01:53 PM - 1 Like   #19
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Nice Milky Way!! Honestly the boat is so small, I would have just cropped it out and gone with a sky only shot. If you have to explain to someone its a boat then its kinda already not ideal, as I think a photo should explain itself easily.

10-15-2019, 01:55 PM - 1 Like   #20
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Love the soft subtle colors.
10-15-2019, 02:12 PM - 1 Like   #21
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I really need to try astrotracer.
Nice shot !
10-15-2019, 06:20 PM - 1 Like   #22
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The stars in the corners haven't started to streak due to movement but because of the physical limitations the alt-az tracking of the sensor imposes on the craft. If you were to use an alt-az mount, you'd get the same result in the corners and it gets worse as you add time, either by stacking or just longer exposure. To compensate, you can just shoot a bit of a panorama and then crop the corners in. That is what I have started doing.
Come spring, I hope to actually get out with my Skywatcher HEQ5 Pro equatorial mount and do some real long Milky Way photography.
As others said, the boat doesn't add much, and cropping it out would make its light less distracting.
Nice job on the processing.
10-16-2019, 12:08 AM   #23
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QuoteOriginally posted by aitrus3 Quote
The stars in the corners haven't started to streak due to movement but because of the physical limitations the alt-az tracking of the sensor imposes on the craft. If you were to use an alt-az mount, you'd get the same result in the corners and it gets worse as you add time, either by stacking or just longer exposure. To compensate, you can just shoot a bit of a panorama and then crop the corners in. That is what I have started doing.
Come spring, I hope to actually get out with my Skywatcher HEQ5 Pro equatorial mount and do some real long Milky Way photography.
As others said, the boat doesn't add much, and cropping it out would make its light less distracting.
Nice job on the processing.
That is very very interesting! So you think astrotracer or a "professional" mount does not make any difference for that trails in the corner? And it is NOT a matter of precision of position, GPS, hours/time etc.? That's calm me down: I do not have the ambition to shoot professional astrophotographs but to take the maximum from my gears. So, if I have to end up with panoramas (like I did), it's perfectly fine with me. If this is the best result I can have with a single shoot (technically speaking) it's fine , I'm happy.

The boat. I'm very surprised many of you doesn't accept it or consider it distracting. To me seem a star fallen down and, although it's not clear what it is, at least can rise curiosity. Well ....at least this was my intention.
Maybe, like you are suggesting, the intention doesn't reach the goal. I got it, that's why I'm asking for critique!

So at the very end, really thanks to you for this technical explanation and to everybody for the critique (and also for the positive comments)

Danilo

10-16-2019, 06:35 AM - 1 Like   #24
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QuoteOriginally posted by mctaveck Quote
That is very very interesting! So you think astrotracer or a "professional" mount does not make any difference for that trails in the corner? And it is NOT a matter of precision of position, GPS, hours/time etc.? That's calm me down: I do not have the ambition to shoot professional astrophotographs but to take the maximum from my gears. So, if I have to end up with panoramas (like I did), it's perfectly fine with me. If this is the best result I can have with a single shoot (technically speaking) it's fine , I'm happy.

The boat. I'm very surprised many of you doesn't accept it or consider it distracting. To me seem a star fallen down and, although it's not clear what it is, at least can rise curiosity. Well ....at least this was my intention.
Maybe, like you are suggesting, the intention doesn't reach the goal. I got it, that's why I'm asking for critique!

So at the very end, really thanks to you for this technical explanation and to everybody for the critique (and also for the positive comments)

Danilo
Careful! A professional EQ mount will make a huge difference. If you were to really get into this, i'd suggest the Skywatcher Star Adventurer.

What I was referring to was a professional Alt-AZ mount. Alt-AZ mounts are the quintessential mount that people think of when you tell them to picture an old telescope in their minds. They track the sky on the X-Y axis, so as the star arcs across the sky, they move up one step, over one step, like a set of stairs. The elongated stars in the corners comes from the field rotation of the stars (they don't just move linearly but as an arc). The Alt-AZ mount is great for visual because it is so simple to use and set up but because it doesn't compensate for the field rotation, the longer you image with one the less of the frame you can use due to the rotation. You get the same result if you were to stack a whole bunch of untracked shots and anyone who tries to say otherwise is selling you a unicorn. You can get away with stacking 20 or so 10-15s shots, and the wider the lens, the longer it takes to notice, but if you were to try stacking say 30x 30s shots, you'd end up with stars in the corners elongating.
An EQ mount tracks the sky properly, following that arc in a smooth motion on one axis so you don't get the field rotation and you can stack as many images as you want with no issues.
I went out the other day to make a test, to see how much of Orion I could fit in 50-55mm for a shot I want to try but not sure if it's possible. This was taken with my camera attached to my Skywatcher HEQ5 Pro equatorial mount. It's a stack of 9x 5minute exposures, no star elongation.



This next one was taken Sept 2018 with my ZS 71ED Telescope with Field Flattener/Focal reducer so my focal length was 330mm (ish) also taken on my Pro EQ tracking mount.



As you can see, with a proper EQ mount, you don't get those issues in the corner.


However don't confuse comatic aberration, which is a lens defect that elongates the stars in the corners, with field rotation. They are different! But, the former (Comatic Aberration) will make the latter (field rotation) far worse. This is why in the shot with my telescope I used a field flattener: it corrects my telescopes comatic aberration and turns the stars in the corners round again, but even with that, if I were to use my K3II's built in astrotracing, I'd end up with elongated stars.
Hope this isn't too confusing, just want to arm you with more knowledge.

---------- Post added 10-16-2019 at 06:48 AM ----------

Here is an example I found of one of my full milkyway images. It was taken with Astrotracer and that night I took a bunch with the astrotracer. The top is a single astrotraced shot, with some elongation. The bottom is a bunch of those stacked. As you can tell, stacking astro shots without the use of a proper EQ mount is what causes the worst of the elongation. I always shoot more of the sky than I will use int he final photograph. In this case I shot the sky in landscape but knew my final image would be portrait, so I cut off a huge amount from the sides and top.

10-16-2019, 07:42 AM - 1 Like   #25
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QuoteOriginally posted by mctaveck Quote
According Lightpollitionmap.com
Zenith sky brightness information
Coordinates
SQM 21.75 mag./arc sec2
Brightness 0.216 mcd/m2
Artif. bright. 45.0 μcd/m2
Ratio 0.263
Bortle class 3
Elevation 12 meters
In Italy unfortunately is not so easy... well , it's almost impossible find darker areas
Thanks
Danilo
Considering it was in Italy, itís a great shot.
10-16-2019, 03:44 PM   #26
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Bunch of info!! I Will have to ready then many times! Thanks!!!
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