What is the definition of, "Hi Resolution"

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What is the definition of, "Hi Resolution"

Post by Starry Jack » Fri Jul 31, 2020 6:44 pm

I'm always hesitant to label any of my images as HIGH or MED or LOW resolution...what are good guidelines?

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Jack


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Re: What is the definition of, "Hi Resolution"

Post by Montana » Fri Jul 31, 2020 7:02 pm

Whatever you like :lol: high res to one person is higher than what they have ever imaged before :)

I guess SDO is hi res :)

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Re: What is the definition of, "Hi Resolution"

Post by Starry Jack » Fri Jul 31, 2020 7:20 pm

Love it!!!


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Re: What is the definition of, "Hi Resolution"

Post by GreatAttractor » Fri Jul 31, 2020 9:03 pm

Montana wrote:
Fri Jul 31, 2020 7:02 pm
high res to one person is higher than what they have ever imaged before :)
Right, something along these lines. A few years ago I considered all those PST and Lunt 35-60 images "low-res", and anything from 80 mm up "hi-res". Since having advanced to a 90 mm Hα setup myself I now consider it "mid-res", and 120-150 mm - "lower-hi-res". Nowadays proper "hi-res" starts for me with 200 mm ;)


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Re: What is the definition of, "Hi Resolution"

Post by EGRAY-OBSERVATORY » Fri Jul 31, 2020 9:08 pm

I depends on people's opinions, but in reality the most number of digital-pixels in a given area could define HD, although the old film-photograph-system can be a better resolution without any pixels at all.

Light and focusing are still all important features of digital, HD and film, so much depends on whichever detail is required to be seen by the viewer...

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Re: What is the definition of, "Hi Resolution"

Post by DeepSolar64 » Fri Jul 31, 2020 9:11 pm

With me my SMII60 is low res and my SMII90 is high res!! 😁


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Re: What is the definition of, "Hi Resolution"

Post by Starry Jack » Fri Jul 31, 2020 9:23 pm

Does magnification have anything to do with our topic? I know "res" means resolution, but what if good seeing allows that Barlow to be used effectively giving greater magnification...food for thought.
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Re: What is the definition of, "Hi Resolution"

Post by EGRAY-OBSERVATORY » Fri Jul 31, 2020 9:54 pm

Well of course Jack, the apparent-closer one can get to the target by any means including telephoto-lens/Barlows/Telescope-aperture and of course the camera's specifications etc., certainly will make for a better and clearer image, subject to lighting-conditions, seeing-conditions etc., plus tracking in some cases too.

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Re: What is the definition of, "Hi Resolution"

Post by Starry Jack » Fri Jul 31, 2020 10:41 pm

Thanks all, interesting commentary. I'll think I'll go with my current 152 to Barlow to Quark to Focal Reducer as Med or "Near High Res" and if I remove my Focal Reducer I'll be definately HIGH Res.

The Quark by nature creates a higher mag so I think Daystar considers anything over f20-to f25 high-ish.

Anyway,
Thanks for the informative, "guidelines".
:)
Jack


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Re: What is the definition of, "Hi Resolution"

Post by JochenM » Sat Aug 01, 2020 10:09 am

As long as you're able to show a specific feature in nice detail; it's high res to me.

The aperture used (or technically the focal length supported by the appropriate aperture) is secondary. If your local conditions allow you to get great detail with lets say 120mm of aperture at f20 (just a random example); then that's what you should do. Even though I'm sure there's someone who would consider this low res imaging. There's no point in forcing yourself to go higher if the results suffer.

Just my opinion :)


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Re: What is the definition of, "Hi Resolution"

Post by Starry Jack » Sat Aug 01, 2020 1:34 pm

As long as you're able to show a specific feature in nice detail; it's high res to me.
Love that definition.

Jack


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Re: What is the definition of, "Hi Resolution"

Post by eroel » Sat Aug 01, 2020 2:40 pm

Jack:
I remember when I was a telescope maker, that resolution was the ability of a telescope to separate details in the observed object.
There was the resolving power of point sources (Stars) and of extended objects (Sun, Moon and Planets).
The bigger the aperture of the scope means more resolution, as for example the ability to separate double Stars, or to observe more planetary, lunar or solar details.
Then comes the "High Resolution" in digital cameras, and that is the way to express the size in pixels of the chip.
Then comes the way for some of us, to use HR to express the amplification of the object observed or imaged.
Have a nice weekend.
Eric.
Last edited by eroel on Sat Aug 01, 2020 4:35 pm, edited 1 time in total.



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Re: What is the definition of, "Hi Resolution"

Post by Starry Jack » Sat Aug 01, 2020 4:12 pm

Nice summary. Thank you!
I just had a FANTASTIC session with the sun and I'll post in a bit Low Med and High images. What a day!!!

I agree it is a mixed bag as you describe and on different objects and equipment.


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Re: What is the definition of, "Hi Resolution"

Post by GreatAttractor » Sat Aug 01, 2020 4:30 pm

In my post by "resolution" I meant: smallest resolvable features assuming optimal sampling rate (i.e., Barlow + pixel size combination) and very good seeing.


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Re: What is the definition of, "Hi Resolution"

Post by rsfoto » Sat Aug 01, 2020 4:57 pm

Hi Jack,

Interesting question as well as interesting answers ...

IMHO it is in the Eye of the Beholder


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Re: What is the definition of, "Hi Resolution"

Post by MalVeauX » Mon Aug 03, 2020 1:48 pm

Heya,

I think the bottom line of high resolution is simply to have excellent seeing conditions that allow whatever aperture & wavelength of light combination you're using to be critically sampled on your pixel size.

Personally I think of our star very much like our moon in terms of what size aperture with associated critical sampling in terms of where the line is in terms of crossing over in to "high res." While all of this is solar system imaging really, the planets are tiny relative to our star & moon, so it takes a lot of aperture to resolve the major features and then there are slightly smaller features that become resolved, nearly invisible to smaller apertures, as the aperture increases (with a relative supporting seeing condition). Seeing is the limit, so it's quite often in planetary imaging that an 11" aperture often never meets its theoretical maximum resolution on Jupiter for example and very often a 14" and 11" aperture results in the same or similar resolution but simply different scale, all because seeing is the great limit. The moon is different in that a smaller aperture can resolve a lot, the major features are resolved with rather small apertures, and the contrast is quite high along the terminator which makes it even more contrasty and obvious to us. So I find 6" to be a real opener for resolution on the moon. For planets, high resolution really starts to happen closer to that 10"~11" I think to resolve tiny things that are barely noticeable in 6~8" apertures (such as on Jupiter, minor storms, etc). The moon opens up nicely however at 6" and there are minor features that become more apparent; however, to resolve features that are not visible in smaller apertures on the moon, things change at 10", 12" and 14" or more on specific minor features that are literally invisible to most apertures smaller and require excellent seeing. So it's relative.

Anyhow, how about our star? Well it depends on what wavelength and what scale you want to see the feature. It's all too easy to see the same resolution from large instruments due to seeing limits. HA for example, a small aperture can resolve all the major features (spicules at the limb, mottling in an AR, prominences, filaments, etc), such as a little 60mm. Our star's apparent size is huge and rather close relative to the planets to us, so a small aperture can do a lot of work. But the photosphere for example is different, the smaller structures (convection cells) can show up as a texture with smaller aperture, but don't really show their structure in detail until you get much larger, somewhere around 102~127mm aperture it begins, assuming seeing is excellent and angular resolution is recorded at critical sampling (and even better at short wavelength for higher angular resolution). Things really start to open up at 6" and 8" in the photosphere in terms of tiny detail having a lot of structure to the convection cell individually if seeing supports it, and after 10" things are just crazy (but rarely does seeing support this).

So, for an "all wavelength" approach to "all structures" in the chromosphere & photosphere, I would say it's somewhere around 150mm give or take a little bit as things transition for me into high resolution for solar (I think it can be lower than this for others, again, its all about the seeing conditions). Assuming the seeing supports it (rarely does it though). Overall I think 102mm aperture is the sweetest spot in general for solar without getting crazy and without needing top seeing conditions to get close to the limits of resolution of the system with lucky imaging at least. Even with sub-arc-second seeing, often I cannot get to the limit of a 6" instrument's resolution with shorter wavelengths (430nm, 393nm, etc).

Anyhow, just my thoughts on it. I think high resolution is different for everyone and it's not their instrument size, but their seeing conditions that define what high resolution is for them. The difference between excellent seeing and poor seeing even with a 60mm aperture is rather apparent! I have lots of data at different resolutions under excellent seeing and poor seeing and it's obvious even with small instruments when seeing is bad, let alone large instruments where seeing rarely ever supports maximum resolution.

Very best,



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