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Equal exit pupil brightness in larger/smaller refractors

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#26 gnowellsct

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Posted 27 June 2020 - 10:35 AM

When I rack-up the power on a refractor, I'm looking for fine details, so I'll sacrifice colors. On my 1950s Edmund 4" F15 @ 300x (75x / inch), that meant whites, grays, & blacks... but, I could not only see a festoon on Jupiter, I could trace its "tail" in a zone until it faded away...

The first time I saw really intense colors on Jupiter, I was testing my Tinsley 6" F20 Cass after Majestic recoated its mirrors. No Lie: At just 60x with a spectros KE 50mm, I was stunned. So many shades of brown, orange, & gray -- and the GRS looked like a bloody wound. More amazing to me, the intensity didn't fade much going up to 100x & 200x in that scope. (Yeah, it's a Keeper!)


You hardly ever hear about Jovian color in the refractor. Whether or notthis constitutes a detail one wants to see I suppose is a very complicated question. in some instances black and white photographs even of landscapes will show things that color photographs do not, but also vice versa.and I suppose that could be true of telescopic observation as well though I have yet to see something in my top mounted refractors that I couldn't see in the big scope next to it.

It is true that colors are distracting. They might lure the attention away from details. When I was active on the Yahoo Alpo group I once gave a detailed description of a split in one of the cloud bands that was not visible in some otherwise very excellent CCD images taken the same night. As the band widened it became more evident to the images in the following days. So the camera does not always win over the eye.

I sort of see what Alan is getting at and it is an important point. When you look at an open cluster in an 80mm telescope the stars you see look look like a bright star field. You don't feel that you're starved for stars. If you simultaneously look through a larger scope you're going to see many more stars. One can do this experiment with the double cluster in Perseus. I think at equivalent exit pupils it probably is true that the brightness is the same. But this does not account for why it is the color is so much easier to see in the FS-128 and then it is in the 81 or 92 mm.

I suspect that at a larger image scale the colors trigger more cones in the eye.

I'm also pretty sure all of this, meaning the relationship between detail, color, exit pupil, and perception, has been figured out by people smarter than me. I could give you my reasons why one type of car corners better than another type of car and some of those reasons might even be true. But when it gets into all the details of cornering performance I'm sure someone who designs cars for racing or even race tracks would have a much more thorough understanding than anything I could offer.

Greg N
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#27 Bomber Bob

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Posted 27 June 2020 - 10:42 AM

You hardly ever hear about Jovian color in the refractor.

 

IME, I see more colors on Jupiter & Saturn with my 6" Reflectors than with my APM 152ED.  Saturn, especially, has so many shades of purple & faint rose in the Tinsley -- gorgeous!

 

But... in terms of resolving fine detail, the 152 ED eats their lunch.  400x is easy on an 8 or higher night, and the amount of detail is more than I can sketch.  In a word:  Overwhelming.

 

MARS is different.  Even in one of my 60mm F15 fracs, Mars is vivid, and I have to zoom up to see fine detail.



#28 Jon Isaacs

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Posted 27 June 2020 - 11:45 AM

I suspect that at a larger image scale the colors trigger more cones in the eye.

 

 

I believe that is what Alan was suggesting. 

 

The eye is an important part of the equation. 

 

As far as color versus detail: Color is a detail.

 

Viewing Jupiter at dusk in the 16 inch at 170x.

 

It's rich in color, super crisp and detailed. Gorgeous.

 

Jon


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#29 TNmike

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Posted 27 June 2020 - 11:48 AM

In terms of magnification per inch Televue on their website recommend a "350x maximum regardless of aperture"...

 

I would think they were referring to only the scopes they offer when they wrote that. Surely they don't think that with BIG scopes, excellent seeing, guided mount, etc.



#30 gwlee

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Posted 27 June 2020 - 11:50 AM

Here’s how I think about one of the critical differences between a large scope and a small scope that’s related to magnification and exit pupil. This is a personal definition based on my observations with scopes between 60mm and 210mm. For me, a “large scope”  usually runs out of the need for more magnification (becomes seeing limited) before it runs out exit pupil (image becomes too dim and cluttered with floaters). A “small scope” usually runs out of exit pupil long before it runs out of the need for more magnification. 

 

Do small scopes “cut through” poor seeing better than large scopes? Yes and no.  If I am using a “large scope” and a “small scope” side-by-side” at the same magnification, to me, seeing appears to effect both scopes more or less equally. However, because a large scope is capable of operating a higher magnification before it runs out of exit pupil, I am usually operating it at higher magnification, so it’s more frequently effected by poor seeing. 
 

In poor seeing conditions, do “small scopes” show as much or detail than “large scopes?” Not that I’ve ever seen in operating these scopes side-by-side at the same magnification. In poor seeing, the large scope always shows shows a bit more detail. In good seeing it usually shows much more detail. 
 

This just my take on the subject from using my relatively small scopes from four homes that were my principal observing sites over the last four decades or so. More critical observers with better eyes, larger “large” scopes, and different observing sites might have a different take on the subject. 



#31 gnowellsct

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Posted 27 June 2020 - 02:30 PM

In terms of magnification per inch Televue on their website recommend a "350x maximum regardless of aperture"...

 

I would think they were referring to only the scopes they offer when they wrote that. Surely they don't think that with BIG scopes, excellent seeing, guided mount, etc.

Well this is something we haven't talked about in this thread.  It is related though it is suggesting a maximum ceiling  due to seeing regardless of optic.  I think it is, for the most part, true, and noobs should certainly be advised that 2x per mm or 50x per inch should be followed "much more often than not."

 

I do think we should start talking in terms of 2x per mm because a lot of other relationships become clear, i.e. that 1x per mm is yielded by an eyepiece equivalent to the focal ratio of the scope, and that 2x per mm is always half that, and that this is the number in and around which we are approaching the organic limit of the eye.  Yeah you can push further but it ain't great.  I pushed the c14 to 3x per mm on the moon once just to say I did.  But I don't recommend it.  

 

But you teach 2x and 1x per mm (and the related ratios) you are also teaching why it is that eyepiece designs tend to max out at around 3mm.  There are some that are shorter but not many, and their existence on the market, I think, reflects the vogue for fast telescopes.  

 

As a practical matter I have also found that using power as a function of mm of aperture is useful in the field for quick estimating the magnification.  If I know that 11 mm gives 391x in my c14, I know that 22mm gives 195x and 5.5 mm puts me just shy of 800x.  I find this is more useful than dividing the scope's fl by the eyepiece fl and it has the benefit of being a technique that ports around to any scope, as it gets to be difficult, if you're a multi-scope owner, remembering that this one is 1080mm and that one is 3916 mm and this other one is 635 mm.  Simple multiples of the magnification as a function of focal ratio of the scope to the focal length of the eyepiece gives you a range of estimation points that are pretty easy to calculate.

 

And I'll repeat it easily ties into exit pupil which gives an idea that the physics of the eye are a part of the usability of the magnifciation.  The interconnectedness of all these things is lost when you teach multiply the objective or primary by the focal ratio than divide the resulting focal length by the focal length of the eyepiece.  That's just a bunch of stuff to do.   It is arithmetic to get one value and basically just a chore.

 

But to close, Looking at the moon at  did give me an opportunity to use the .3x control on my paddle (instead of the usual 16x sidereal speed).  .3x is typically used by imagers needing ultra fine and slow control.  And yeah I could kinda see shadows and edges of a crater and that sort of thing.  But it is not a useful magnification.

 

Greg N


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#32 gwlee

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Posted 27 June 2020 - 03:24 PM

Well this is something we haven't talked about in this thread.  It is related though it is suggesting a maximum ceiling  due to seeing regardless of optic.  I think it is, for the most part, true, and noobs should certainly be advised that 2x per mm or 50x per inch should be followed "much more often than not."

 

I do think we should start talking in terms of 2x per mm because a lot of other relationships become clear, i.e. that 1x per mm is yielded by an eyepiece equivalent to the focal ratio of the scope, and that 2x per mm is always half that, and that this is the number in and around which we are approaching the organic limit of the eye.  Yeah you can push further but it ain't great.  I pushed the c14 to 3x per mm on the moon once just to say I did.  But I don't recommend it.  

 

But you teach 2x and 1x per mm (and the related ratios) you are also teaching why it is that eyepiece designs tend to max out at around 3mm.  There are some that are shorter but not many, and their existence on the market, I think, reflects the vogue for fast telescopes.  

 

As a practical matter I have also found that using power as a function of mm of aperture is useful in the field for quick estimating the magnification.  If I know that 11 mm gives 391x in my c14, I know that 22mm gives 195x and 5.5 mm puts me just shy of 800x.  I find this is more useful than dividing the scope's fl by the eyepiece fl and it has the benefit of being a technique that ports around to any scope, as it gets to be difficult, if you're a multi-scope owner, remembering that this one is 1080mm and that one is 3916 mm and this other one is 635 mm.  Simple multiples of the magnification as a function of focal ratio of the scope to the focal length of the eyepiece gives you a range of estimation points that are pretty easy to calculate.

 

And I'll repeat it easily ties into exit pupil which gives an idea that the physics of the eye are a part of the usability of the magnifciation.  The interconnectedness of all these things is lost when you teach multiply the objective or primary by the focal ratio than divide the resulting focal length by the focal length of the eyepiece.  That's just a bunch of stuff to do.   It is arithmetic to get one value and basically just a chore.

 

But to close, Looking at the moon at  did give me an opportunity to use the .3x control on my paddle (instead of the usual 16x sidereal speed).  .3x is typically used by imagers needing ultra fine and slow control.  And yeah I could kinda see shadows and edges of a crater and that sort of thing.  But it is not a useful magnification.

 

Greg N

A magnification equal to aperture in millimeters gives a 1mm exit pupil. Magnification twice the aperture gives a 0.5mm exit pupil, which is probably the practical limit for the eyes of the majority of people and probably provides the full resolution of most scopes. This magnification might be much less than, equal to, or much more than the seeing supports at any given time and place. 


Edited by gwlee, 27 June 2020 - 03:28 PM.

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#33 Asbytec

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Posted 27 June 2020 - 04:53 PM

We know that size plays a role in the perception of faint objects. A dim DSO may only become visible when it is enlarged and covers a larger area of the retina. 

 

The perception of colors can also depend on size.

https://research.tab...Matters-CGA.pdf

 

Anyone know of any articles on image scale and color perception in planetary viewing?

 

Clear skies, Alan

Its a great question. As Jon said above, it dawned on me years ago that color is detail. Especially on Jove. It's not a coloring book with lines drawn between the features, but a smooth transition between different colors defining detail. It requires we be able to distiguish between soft low contrast hues. That epiphany first hit me when I first noticed white. If that detail was white, then the adjacent zone could not be as white as it might appear at a glance. It had to have a different hue, and if that hue is not white then some other detail nearby was not that hue either. It had to be something else, Jupiter is full of hues that are something else. Colors in a 6" aperture are pretty close to grey scale, they are not pronounced and vivid at the magnification I normally observe with. So, learning to distinguish between softer hues means Jupiter explodes with detail once we learn to discriminate soft differences in hue. 

 

I do not know of any articles on image scale and color perception. However, my experience is Jove appears much more colorful and higher contrast at lower magnifications near the "ideal" magnification of about 25x to 30x per inch. The hue saturations are much stronger, and the image is much smaller and brighter. I believe some observers prefer the higher contrast image and strong color saturation at modest magnification. However, I began noticing more extended detail on Jove at somewhat higher magnification closer to 40x and 50x per inch. It may be that image scale matters for small detail and softer contrast between different hues in much the same way we observe planetary nebula at ludicrous magnification. Soft hue and lower contrast detail covers a larger area on the eye (more receptors) allowing us to better discriminate it. At least as long as Jove remains bright enough on our eye stimulating photopic vision.

 

Much above that apparently optimal magnification, then Jove begins to dim just enough so those finer details are lost as our eye enters mesopic vision and may be losing some photopic sensitivity. At very high magnification, some colors are still visible. Especially in Jove's large high contrast features. But the color saturation appears much more subdued than it is at much lower magnification. That has to apply to the softer contrast detail we saw at lower magnification, too. To my eye, that loss of detail begins around 60x per inch and becomes increasingly worse with higher magnification (around 0.4mm exit pupil and smaller). I believe this is because with larger image scale comes a dimmer image so hues become much less saturated on our eye and harder to discern them as we (might) begin to lose some photopic sensitivity under increasingly lower light conditions. Surely there are acuity differences between observers and differences between scopes, observing conditions, and magnification. So others will vary around the mean acuity. 

 

Jupiter 22 Dec 1600UT.jpg


Edited by Asbytec, 27 June 2020 - 05:05 PM.

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#34 Bomber Bob

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Posted 27 June 2020 - 05:11 PM

When I say Mars is different, here's what I mean...

 

First, in a 1964 Monolux 4380 (optics by Hiyoshi / Japan):

 

M4380 - Mars 20140503U0330S.jpg

 

Second, in a 1964 Sears Model 6336 (optics by Astro Optical / Japan):

 

S6336 - Mars 20140427U0330F.jpg

 

I'n not a great sketch artist, and the colors are exaggerated, but the 76mm could deliver tiny detail at 100x per inch. 


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#35 Asbytec

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Posted 27 June 2020 - 05:17 PM

Yes, Mars is a different animal. It can take (and kind of needs) higher magnification. It /may be/ a little brighter per unit area than Jove. But, I find Mars to be better seen closer to 70x to 80x per inch. Those are some nice sketches, Bob, expecially for a modest aperture. 



#36 Bomber Bob

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Posted 27 June 2020 - 05:51 PM

Thanks!  I've used a ton of 60mm F15 fracs.  That Hiyoshi gave the brightest views of any.  I'm not a lunar observer, but the way it presented all the subtle shades of gray in the Maria was awesome.  

 

I still have my A-O 76mm, because it out-performed a 1950s Unitron 142, and a Meade S5000 ED triplet at 200x & above.

 

Both fracs were very well made systems, starting at the lens, and all the way to the eyepiece.

 

On Topic:  Regarding exit pupils, image brightness, etc.  Gotta mention the quality of the accessories, too.  I put a Baader prism on that A-O 76mm, and a Nagler 7, and it really shows what it can do.


Edited by Bomber Bob, 27 June 2020 - 05:53 PM.


#37 Rutilus

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Posted 28 June 2020 - 08:09 AM

In practice, folks tend to use larger exit pupils with larger apertures because the magnification is already pretty high. The eye likes a bright image, but it also like a large image. In smaller apertures, the eye is starved for image scale so we tend to push magnification a little higher, i.e., working at smaller exit pupils. 

Very true. I also think that working at smaller exit pupils in smaller scopes brings other problems to the table in regard to 

planetary viewing. When I have used small exit pupils in small scopes I see  defects/artifacts in my own eye that are

made to exacerbate due to the small exit pupil.

 

The same applies to larger scope, but as mentioned in this thread you reach higher magnifications before you encounter

the troublesome smaller exit pupils. 


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#38 daquad

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Posted 28 June 2020 - 09:51 AM

You hardly ever hear about Jovian color in the refractor. Whether or notthis constitutes a detail one wants to see I suppose is a very complicated question. in some instances black and white photographs even of landscapes will show things that color photographs do not, but also vice versa.and I suppose that could be true of telescopic observation as well though I have yet to see something in my top mounted refractors that I couldn't see in the big scope next to it.

It is true that colors are distracting. They might lure the attention away from details. When I was active on the Yahoo Alpo group I once gave a detailed description of a split in one of the cloud bands that was not visible in some otherwise very excellent CCD images taken the same night. As the band widened it became more evident to the images in the following days. So the camera does not always win over the eye.

I sort of see what Alan is getting at and it is an important point. When you look at an open cluster in an 80mm telescope the stars you see look look like a bright star field. You don't feel that you're starved for stars. If you simultaneously look through a larger scope you're going to see many more stars. One can do this experiment with the double cluster in Perseus. I think at equivalent exit pupils it probably is true that the brightness is the same. But this does not account for why it is the color is so much easier to see in the FS-128 and then it is in the 81 or 92 mm.

I suspect that at a larger image scale the colors trigger more cones in the eye.

I'm also pretty sure all of this, meaning the relationship between detail, color, exit pupil, and perception, has been figured out by people smarter than me. I could give you my reasons why one type of car corners better than another type of car and some of those reasons might even be true. But when it gets into all the details of cornering performance I'm sure someone who designs cars for racing or even race tracks would have a much more thorough understanding than anything I could offer.

Greg N

Point sources, i.e., the stars, will appear brighter in the larger aperture scope even with the same exit pupils.  I think your comments apply to extended objects, where the surface brightness is the same for equal exit pupils.

 

Dom Q.



#39 Bomber Bob

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Posted 28 June 2020 - 10:00 AM

Very true. I also think that working at smaller exit pupils in smaller scopes brings other problems to the table in regard to 

planetary viewing. When I have used small exit pupils in small scopes I see  defects/artifacts in my own eye that are

made to exacerbate due to the small exit pupil.

 

The same applies to larger scope, but as mentioned in this thread you reach higher magnifications before you encounter

the troublesome smaller exit pupils. 

Before my aggressive A/S treatment, I had lots of floaters in both eyes, though more in my dominant right eye.  So, yes, that made using high-powers / small exit pupils difficult.  Post-treatment, I now have zero floaters, and can push my small fracs up to their limits in the seeing.  But... the treatment altered my color vision, and I have areas on my retina where the cones fire faster / stronger than they should, again mostly in my right eye.  With "new" scopes, I assess colors with my left eye when things don't look right.  Otherwise, eye exams show my visual acuity hasn't declined with age.  Too bad the weather doesn't give me a chance to use this ability!



#40 Asbytec

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Posted 28 June 2020 - 10:05 AM

Yes, floaters are a problem with small exit pupils and bright objects. Especially the moon. But, astigmatism is greatly reduced.
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#41 Bomber Bob

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Posted 28 June 2020 - 10:21 AM

Trying to keep it on topic.  IME, the debate about using extreme magnifications boils down to the Observer, the Scope, and the Seeing.  If you lose detail at 60x per inch, don't use it.  And, please don't assume that your experience applies to every observer.  I won't keep a refractor that goes soft at 75x per inch, or a reflector that goes soft at 50x per inch.  But, I live in an area where there (usually) are lots of clear & still nights where high magnifications work; and, my eyes can deal with the dim views.  Is it easier on my eyes at 25x per inch?  Yes & No.  Moon is way too bright.  I probably won't see fine details on Mars or Jupiter.  In most of my scopes, about 150x is comfortable; most have 1200mm focal lengths, so a quality 7mm or 8mm eyepiece is a good match.

 

If I lived under a jet stream, and/or in a dark rural location, my scope selections & uses would be entirely different.  Long refractors & shortish EDs are my first-line scopes here in town, and dealing with stagnant swamp air is my habit after nearly 30 years here.


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#42 Wildetelescope

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Posted 28 June 2020 - 10:28 AM

You hardly ever hear about Jovian color in the refractor. Whether or notthis constitutes a detail one wants to see I suppose is a very complicated question. in some instances black and white photographs even of landscapes will show things that color photographs do not, but also vice versa.and I suppose that could be true of telescopic observation as well though I have yet to see something in my top mounted refractors that I couldn't see in the big scope next to it.

It is true that colors are distracting. They might lure the attention away from details. When I was active on the Yahoo Alpo group I once gave a detailed description of a split in one of the cloud bands that was not visible in some otherwise very excellent CCD images taken the same night. As the band widened it became more evident to the images in the following days. So the camera does not always win over the eye.

I sort of see what Alan is getting at and it is an important point. When you look at an open cluster in an 80mm telescope the stars you see look look like a bright star field. You don't feel that you're starved for stars. If you simultaneously look through a larger scope you're going to see many more stars. One can do this experiment with the double cluster in Perseus. I think at equivalent exit pupils it probably is true that the brightness is the same. But this does not account for why it is the color is so much easier to see in the FS-128 and then it is in the 81 or 92 mm.

I suspect that at a larger image scale the colors trigger more cones in the eye.

I'm also pretty sure all of this, meaning the relationship between detail, color, exit pupil, and perception, has been figured out by people smarter than me. I could give you my reasons why one type of car corners better than another type of car and some of those reasons might even be true. But when it gets into all the details of cornering performance I'm sure someone who designs cars for racing or even race tracks would have a much more thorough understanding than anything I could offer.

Greg N

I have one vivid memory of seeing the red spot on Jupiter with my tv 102 at 150x or so and it being red.   I was doing a side by side with my 120 mm achromat and saw no color on the planets disk with that scope.  Given the physics involved, I have more or less chalked that up to my mind filling in the color as the overall contrast in the ED doublet was much better.  Regardless, it was a memorable and enjoyable moment.   The brain is a tricky thing.  After a few moments, I can totally tune out the garish flashes of false color in the 5 inch achromat(but not the loss of detail!) like they are not even there.  If I can tune out color, I am guessing i can also put it in where I expect it, lol.  

 

Jmd 


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#43 Asbytec

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Posted 28 June 2020 - 10:56 AM

"I won't keep a refractor that goes soft at 75x per inch, or a reflector that goes soft at 50x per inch."

This always raises the question, does the scope go soft or do we? Up that high, I suspect we go soft at small exit pupils because we're well past the point where we can see aberration and obstruction effects break down the image. The telescope image does not change with magnification, but the afocal image on our eye does. So, successful observation at very high magnification has to depend on differences in our individual acuity. (And probably some design factors, too).

Someone mentioned above splitting stars at 200x. To my mind, the stars are split on the focal plane by the aperture and laws of physics regardless of afocal magnification. It's our acuity that requires 200x to split those stars.

Edited by Asbytec, 28 June 2020 - 11:06 AM.

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#44 Bomber Bob

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Posted 28 June 2020 - 11:27 AM

Forget Planets for a moment.  With stars, I want natural colors, and IME fluorite doublets & some ED triplets deliver (even that cheap used Meade 80mm S5000).  For double stars, I rack up the power until I get a view of the Airy disks that I like, and I really don't care what that good magnification is.  And, it depends on the double star in the eyepiece.  IME, small fracs (3" & under) can really shine with these objects, and you don't have to use a small exit pupil on many of them to get a very fine view.  Again, switching my old AO 76mm F15 to 1.25" accessories, and putting the Baader + Nagler 7 on it makes a huge difference in the views -- and that's only 57x per inch on a frac that can go to 100x / inch when the seeing & object cooperate.

 

With lots of doubles, I'm looking for the lowest magnification required to make a clean split -- another sign for me of a scope's quality.


Edited by Bomber Bob, 28 June 2020 - 11:30 AM.


#45 gwlee

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Posted 28 June 2020 - 02:05 PM

When we feel the need for greater magnification, we can put a shorter fl eyepiece in the same scope, or we can use a larger scope with the same EP. Having three EPs and more than one scope gives me the option to choose the scope/eyepiece combination that works best for me in any situation, so I have no need to use magnifications greater than 50x/inch, and in practice seldom use magnifications greater than 25x/inch.

 

Using this approach, I can usually avoid the problems of floaters that come with small exit pupils and the problems with astigmatism that come with large exit pupils. For me, it only takes two scopes to make this approach work, and the largest scope costs less than my least expensive EP.


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#46 Bomber Bob

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Posted 28 June 2020 - 02:27 PM

When we feel the need for greater magnification, we can put a shorter fl eyepiece in the same scope, or we can use a larger scope with the same EP. Having three EPs and more than one scope gives me the option to choose the scope/eyepiece combination that works best for me in any situation, so I have no need to use magnifications greater than 50x/inch, and in practice seldom use magnifications greater than 25x/inch.

 

Using this approach, I can usually avoid the problems of floaters that come with small exit pupils and the problems with astigmatism that come with large exit pupils. For me, it only takes two scopes to make this approach work, and the largest scope costs less than my least expensive EP.

Besides collecting Classic Scopes, I have the advantage of different types & apertures to select for a given night.  And some, like my RV-6 & Meade 826, were super cheap at $150 or less.  Lots of capability for very little $$$.



#47 gwlee

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Posted 28 June 2020 - 03:28 PM

Besides collecting Classic Scopes, I have the advantage of different types & apertures to select for a given night.  And some, like my RV-6 & Meade 826, were super cheap at $150 or less.  Lots of capability for very little $$$.

Bob,

 

I am not a collector, and I prefer to minimize the amount of astro gear that I own, but I understand what you are saying. For me, I have learned that to get the best possible views, it’s far, far more important to feed my old eyeballs photons through exit pupils that allow them to perform at their best than feeding them through a super scope with exit pupils that give them indigestion. So, much as I like my expensive super scope, I often find that my good quality, $150, Craig’s List Rescue scope gives me far better views.
 

Gary 


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#48 Bomber Bob

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Posted 28 June 2020 - 03:55 PM

At one point, I had almost Three Dozen scopes...  I'm down-sizing, and shooting for 10 or less...

 

My point for this thread:  Choose the scope for the seeing, the object, & your eyeballs (a comfortable / usable exit pupil).  This is the Refractor Forum, so I try not to mention other types, but... I don't hesitate to use them as needed, and I'm glad I have them.


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#49 gnowellsct

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Posted 28 June 2020 - 04:01 PM

The detection of color is not purely a function of the particular instrument aperture, the instrument maker, or the magnification used with the instrument.  It also depends both on genetic sensitivity of the eyes and also the particular condition of the eyes as they have aged, no matter their baseline sensitivity in youth.   The rendition of color in a drawing/painting depends on all of the former factors and then depends on the artist's ability to match what was seen with whatever colors are available in the palette (or chalks, or colored pencils).   The reproduction of color in astrophotography depends on the initial data gathering and then the decisions made while processing.  

 

It's an extremely subtle topic when you get to the gnarly details.  And then there is the experience of the viewer or artist.  It is not easy to separate what one sees today from what one has seen over the years.    Speaking for myself, I find changes in the hue of the GRS fairly easy to follow over the years.  But I have seen "Jupiter blue" festoons enough that I have fairly strong sense of how they look (both bunched up in tight knots against the band, and strewn out as thinning wisps).  

 

I have seen the festoons in 80 mm and 92 mm apertures.   To me they are relatively easy to detect now.  I usually have to coach newcomers.  They say the festoons look gray (in very small apertures).  To me there is still a bluish hue, much less pronounced than in the larger scopes at my disposal.  I don't know if it has to do with my color sensitivity or their lack of color sensitivity or alternatively a tendency on my part to project past views (from experience viewing) into my description of the present.  When we're using the C14 and others tell me the festoons are gray, I think it is an eyeball sensitivity thing.  But I have no proof either way.

 

I've also noticed that color rendition in my friends' Newtonians is not the same as in the C14.    And I have a good friend who doesn't share my happiness with daytime solar h-alpha because he has some R-G color blindness.  The red sun, the whitish red prominences, that doesn't do good things for him.

 

In any case mo' aperture is mo' bettah on planet detail, in my experience.  But the guy who is out accumulating observing hours (and drawing experience) with a 60 mm is going to see a lot more details over time than the guy who is too tired to set up the 15".  

 

Greg N


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#50 Bomber Bob

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Posted 28 June 2020 - 04:20 PM

But the guy who is out accumulating observing hours (and drawing experience) with a 60 mm is going to see a lot more details over time than the guy who is too tired to set up the 15".

 

My 1978 Tasco (Towa) 80mm F15 was my planetary scope for about 10 years, until I bought my 1988 D&G 5" F10.  Conservative estimate of observing hours... at least 3000.  So, I trained my brain to look for very tiny details.  Imagine!  My first views of Mars / Jupiter / Saturn in that D&G.  Eye-popping.  The Towa had a good lens (the Model 339 was their flagship refractor back then), and I upgraded it to 1.25" accessories, and bought Meade Research Grade Orthos for it (still have that set 40 yrs later).

 

Anywho, I didn't want to go too far off-topic, but I did want to share what I've found at the eyepiece for 50+ years now.  

 

In observing, you can only go as high as the object, your scope, your seeing, and your eyes allow.  If your view is too dim, too fuzzy, too susceptible to floaters, then you have to back off the magnification.  If you're new to the hobby, keep in mind that posts by experienced observers at different locations may see more than you do.  Don't junk the scope, and/or drop out of the hobby, just spend more time at the eyepiece.  And, ask the folks on CN when you're not seeing what you think you should.


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