Jan.28, 2020 Powermate comparison

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Jan.28, 2020 Powermate comparison

Post by Astrophil »

On the 28th I imaged using a 5x powermate as well as a 2.5x to observe the differences. Both used the same camera for capture on the LS80.
Presented here are a full disk overview, AR2757 using the 2.5x powermate, and AR2757 using the 5x powermate, two more images with the 5x, and final colorized prom image using the 2.5x in that order.

The 5x seems to have a slight advantage in details to me.

Phil
20200128_111042_fd.jpg
20200128_111042_fd.jpg (550.28 KiB) Viewed 6609 times
20200128_120945_ar3757_2.5x.jpg
20200128_120945_ar3757_2.5x.jpg (416.03 KiB) Viewed 6609 times
20200128_112703_ar2757.jpg
20200128_112703_ar2757.jpg (431.64 KiB) Viewed 6609 times
20200128_110007_nr.jpg
20200128_110007_nr.jpg (296.01 KiB) Viewed 6609 times
20200128_113208_prom.jpg
20200128_113208_prom.jpg (212.41 KiB) Viewed 6609 times
20200128_121611_promc2.5x.jpg
20200128_121611_promc2.5x.jpg (239.3 KiB) Viewed 6609 times


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Re: Jan.28, 2020 Powermate comparison

Post by rsfoto »

Hi Phil,

Excellent images all. Of course you have better detail sugin a 5X instead of 2.5X due to the fact that you sesolve twice as much ...

If you have e.g. an image scale of 1" arcseconds per pixel with 2.5X then you will ahve 0.5" arcsecond using a 5X ...

Rainer


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Re: Jan.28, 2020 Powermate comparison

Post by JochenM »

Looks good (both the 2.5x and 5x).

As Rainer mentioned, the 5x will always give you an edge (assuming you have the aperture to support it, which the LS80 has) assuming the conditions allow it. So it's more a matter of the local seeing also supporting said resolution, so it comes down to a bit of trial and error to see where the cutoff point is for you. You'll have days where it'll come out great (like in this case), and others where it's just not worth bothering.


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Re: Jan.28, 2020 Powermate comparison

Post by Montana »

All these images are absolutely fabulous Phil, the prominences especially are an exceptional sight :hamster: :bow

Both the AR region images look wonderful but I am not sure I am seeing any more detail in one or the other, what I am seeing is that one is zoomed in twice as much as the other. If you actually count the dark arch filaments in the images I see the same. It depends on what you class as detail?

Alexandra


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Re: Jan.28, 2020 Powermate comparison

Post by salvo lauricella »

Excellent images!!!


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Re: Jan.28, 2020 Powermate comparison

Post by MalVeauX »

Great captures Phil, love the contrast!

The 5x on a short refractor is meaningful, versus the 2.5x with respect to sampling. The critical sampling level is a minimum, not a max. Seeing conditions of course are the grand limiter there. The 2.5x had you at F14 approximately, pretty close to critical sampling (depending on your pixel size, I'm not familiar with your sensor's info but I'm guessing it's in the near 3um +/- 0.5 range or so?). When you used the 5x at F35, you were of course way over-sampling (unless your pixels were 5+ um in size, like an IMX174 sensor), but it's still a finer image scale than before and if seeing is good, you will see better contrast (though maybe not higher resolved information, as the limit is your aperture and pixel size relative to 656nm wavelength). Was good seeing that day!

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Re: Jan.28, 2020 Powermate comparison

Post by Astrophil »

Thank you for the responses and good information.

Magnification and critical sampling play an essential role in image capture as does camera characteristics, exposure time, and atmospheric stability at the time of recording. What struck me after the imaging session was the relatively similar amount of "detail" in the differing image scales. Probably my inexperience and unrealistic expectations played a part.

This was not a scientific test by any means, only a demonstration of increasing the focal length of an 80mm diameter scope using Barlow lenses. Camera pixel pitch remained the same at 4.54 microns for all images. Processing was individual and done to taste. The full disk image utilized a 1.5x Barlow while the others a 2.5x and 5x, respectively.

So, to illustrate further I have attached an image comparing the three different images cropped and resized to a similar scale. Up sampling does effect quality.

If the clouds ever leave here, I will compare images using cameras with different pixel size. I know this has all been done before, but not by me. It might be interesting.

Phil
comparison.jpg
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Re: Jan.28, 2020 Powermate comparison

Post by MalVeauX »

With 4.5um pixels, it absolutely makes sense that your 5x and 2.5x were great, as your pixel size means F17 would have been critical sampling. Anything over that is not really more resolution, but under good seeing conditions will increase image scale that can make things appear nicer. You were ideal as it is around with your 2.5x, the 5x just shows your seeing was great and supported it, but they're about the same resolution in reality.

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Re: Jan.28, 2020 Powermate comparison

Post by Astrophil »

Thanks Marty, much appreciated. I will next use a camera with 3.45 pixels at the lower focal lenghts, further conformation if seeing permits.

Phil


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Re: Jan.28, 2020 Powermate comparison

Post by Merlin66 »

Nice examples to show the impact of Barlows/ PM and longer focal lengths.
I'm severely limited by the local seeing conditions being so close to the Bay and can't honestly use much above f22.5 on the SM60.
I've used both the ASI 174 and ASI 1600.


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Re: Jan.28, 2020 Powermate comparison

Post by marktownley »

Nice images and good comparison Phil.


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Re: Jan.28, 2020 Powermate comparison

Post by eroel »

Phil:
Super shots, specially the prominences.
best wishes,
Eric.


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Re: Jan.28, 2020 Powermate comparison

Post by christian viladrich »

Interesting test and quite good images.
I would say that something between the x2.5 and the x5 would be great. Maybe a x3 Barlow with some additonal tube to get x3.5 ?


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Re: Jan.28, 2020 Powermate comparison

Post by Astrophil »

Thanks for the additional information. The consensus appears to lean towards a 3x+ Barlow for optimal solar imaging detail with the 80 mm scope. That would be close to critical sampling with my camera, close to f22.5 for the scope, and a good compromise based on the test images, given the seeing conditions, as well.
I will give that a try.

Phil


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Re: Jan.28, 2020 Powermate comparison

Post by bart1805 »

Nice images Phil! I would stay with the 2.5 max. When I look at the images with longer focal length I think of your images with the Quantum 6: in my opinion way better when you want more details.


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Re: Jan.28, 2020 Powermate comparison

Post by MAURITS »

Excellent Phil.


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Re: Jan.28, 2020 Powermate comparison

Post by MapleRidge »

A great session Phil and nice to see the comparison between the Powermates!!!

To me the 2.5x version looks the 'best' to my eye, but its a close call.

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Re: Jan.28, 2020 Powermate comparison

Post by viewer »

Nice job! The 5x appears to have slightly more detail.


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