140 replies to this topic

[clamchip]

The best seeing I have here in my front yard is during the day.

When the ground and air are the same temp I can use power that would

curl Einstein's mooseashe.

Daytime gives me serious instrument information and really helps me at night.

 

Robert

[Terra Nova]

you need to talk to Terra. She is using her Questar at powers you only have dreamed about.  She has reported powers I will not even try.    I would be scared to try that high a power.  If I would accidently swing past the moon at 3500 power or more my Questar would blow up. 

Absolutely, on nights of average seeing, with the Q’s focal length of 1300mm, my 3mm TV delite gives me 433X, enabling the Q’s internal barlow brings it up to 866X. My Ultima 2X barlow brings that up to 1733X. For the coup de grâce, we now drop the TV 2X barlow in and that brings us up to 3467X. Of course, given the Q’s aperture of 89mm, the exit pupil thus produced is now only 25.67μm. However, on nights of perfect seeing, I’ve been temped to top that barlow stack off with my excellent old SV 3X to bring things up to ethereal heights of 10,401X magnification. Of course this will diminish my exit pupil to 8.67μm. Seeing that (no pun intended) the diameter of cone cells in the average adult human eye varies from 0.5 to 4.0 µm, being smallest and most tightly packed at the center of the eye at the fovea, and given my excellent visual acuity since my cataract removal and toric lens replacement, the light will be falling on a sensor matrix containing somewhere on the order of between 4 to 64 visual receptors*, I really don’t see (again, no pun intended) that as a problem. These are all within theoretical limits of course. Please check my math.

*https://arxiv.org/pdf/1904.04175v1.pdf

Edited by Terra Nova, 21 February 2024 - 11:11 AM.

[Bomber Bob]

Well, if you judged that 76mm objective by views with the bundled 6mm & 4mm bundled junk eyepieces...

 

OTOH, there are exceptions.  That SR12.5mm bundled with my Monolux 4380 was a very good example -- I used it often in my early nights of digital imaging - for old-fashioned Eyepiece Projection.

Edited by Bomber Bob, 21 February 2024 - 11:11 AM.

[deSitter]

Well, if you judged that 76mm objective by views with the bundled 6mm & 4mm bundled junk eyepieces...

 

OTOH, there are exceptions.  That SR12.5mm bundled with my Monolux 4380 was a very good example -- I used it often in my early nights of digital imaging - for old-fashioned Eyepiece Projection.

No, those 6mm and 4mm HM eyepieces are really very good. They just produce 67x and 100x and per inch I tested them in my f/9 ED refractor and they are really very good.

 

-drl

[Terra Nova]

For an identical thread running concurrently, and started by the same OP please see:

 

https://www.cloudyni...wers-for-kicks/

[starman876]

This is Charles opening post and is where the thread should stay.Though spoken in jest, mocking is seldom useful and more often a thread derailer. This is why some will notice their posts removed. Back on track please!

Charles opening post said

 

"What is the most pow wow you ever used in your classic on a dead still nite?  I have had no trouble at 100x+ per inch on SOME OBJECTS.  This is just for kicks as it seems many take it the wrong way."

It is even mentioned in the opening post "This is just for kicks" 

we were responding with light hearted fun about using crazy high powers.  I do not see anyone mocking the poster. I do see others mocking each other about what they posted about crazy high powers.   This has been a fun post about a subject that all of us have experienced.  

[Terra Nova]

For my to-the-point, correct, accurate, non-tongue-in-cheek, unexpurgated, and uncensored, answer to the identical question, posed this time as a proposition, posed by the same person as the OP herein, please note my comments on yet another concurrent thread at:

 

https://www.cloudyni...5#entry13269757

 

Pay particular attention to my penultimate sentence!

[Bomber Bob]

No, those 6mm and 4mm HM eyepieces are really very good. They just produce 67x and 100x and per inch I tested them in my f/9 ED refractor and they are really very good.

 

-drl

Okay... so, either your Seeing doesn't support the mag, or your scope doesn't, or your eyes don't.

 

My DX8 maxed out at about 35x / inch for planetary.  It was definitely the Scope...

Edited by Bomber Bob, 21 February 2024 - 11:58 AM.

[CBM1970]

50 years ago, I had 2 Sears branded 60mm refractors, 700mm & 900mm FLs.  I never tried 600x in either.  I did try about 300x with the F15 model, on Saturn, IIRC, and had to back-off because those lousy .965" bundled eyepieces wouldn't provide any kind of decent views that high -- even using the higher FL eyepieces with the 2x Barlow.

 

When I won my Tasco 15K (Towa 339) in 1978, that opened up my universe.  That 80mm refractor had an excellent lens -- got me buying quality 1.25" accessories, like my Research Grade eyepieces... 

Now you're speaking my language.

 

The 0.965" 5mm huygens eyepiece that came with my 60/700 Selsi refractor gave me 140x (about 60x per inch). I used it on the moon from time to time and it was very dim, and never truly sharp.

 

What's crazy is that I used that same eyepiece on the moon with my C8 and a 1.25/0.965" adapter, and it was honestly better. It wasn't great of course, and it produced some wild false color - even on crater rims, but it was brighter and sharper.

In fairness, I wasn't exactly experienced enough to know what i should be looking for in terms of quality at the time. Still, I knew enough to know that the image looked better than it did in the 60/700 refractor on nights when the air was still enough.

 

Maybe it was an unfair fight. It was only 50x per inch in the C8, but still...

 

A simple 8 or 9mm Kellner would probably have been vastly better in both scopes, but I didn't know what I didn't have at the time.

[Bomber Bob]

Great points.  It takes time in this hobby to figure out:  Is it my Seeing, or is it my Scope, or is it Me??

 

Anyhoo, I thought this was a fairly simple Thread:  IF you can use higher powers, count yourself Lucky.  IF you can't, move to The Swamp.  (Depending on where you are now, I might just swap houses with ya!)

[Garyth64]

For an identical thread running concurrently, and started by the same OP please see:

 

https://www.cloudyni...wers-for-kicks/

That's what I said,  the  two threads could be combined and no one would know the difference.  The other post is in refractors, and the first reply was from a guy with C14.    Later, there are posts about C8's and Zambuto mirrors.   Posts about reflectors in the refractor forum?

[Ian King]

Even with my FC100DZ I max out at 180x to 200x on most nights, the seeing won't support more.

 

I have used silly magnifications with my classics on occasion, 185x on the Moon with some of my best 60mm refractors gives a sharp image but of late I have gone full circle and have started enjoying the benefits of wider exit pupils at lower powers. I have found an exit pupil size of 0.6mm to 0.7mm seems to give the most pleasing planetary views, that equates to about 100x with my 60mm and 68mm scopes - even the fab FOA60Q looks best at these mags.

 

I would love to routinely have skies that support the use of much higher magnifications, I have read loads of reports over the years of observers using what to me sound like ridiculous magnifications with small refractors, but under South East England skies those conditions never happen or are so rare I never manage to be out to take advantage.

[deSitter]

Okay... so, either your Seeing doesn't support the mag, or your scope doesn't, or your eyes don't.

 

My DX8 maxed out at about 35x / inch for planetary.  It was definitely the Scope...

That SYW scope had a perfect star test. That part I understood even very young. But I did not understand the idea that you were just limited by physics, because I didn't yet know any

 

-drl

[Bomber Bob]

I know just enough physics to be dangerous.  Even if I had a PhD, it wouldn't change seeing conditions, or the structure of my eyeball, or all the highly complex neurobiology for the eye - brain connection & (data) processing.

 

No control over those factors.  But I do control the Telescope System.  Quality objective + quality accessories makes the most of what ya got.

[Terra Nova]

Charles opening post said

 

"What is the most pow wow you ever used in your classic on a dead still nite?  I have had no trouble at 100x+ per inch on SOME OBJECTS.  This is just for kicks as it seems many take it the wrong way."

It is even mentioned in the opening post "This is just for kicks" 

we were responding with light hearted fun about using crazy high powers.  I do not see anyone mocking the poster. I do see others mocking each other about what they posted about crazy high powers.   This has been a fun post about a subject that all of us have experienced.  

Yes, my feelings exactly. And in his opening remarks (original post), he did begin by saying: “What is the most pow wow…”

 

Knowing full well that the originator of this topic would most certainly eschew the use of baby-talk, we can only take him at his word in his use of this particular term which would translate to:

 

“What is the most one can say…” (sic.)

 

Now despite the insulting co-opting of this Native American euphemism which Merriam-Webster defines as:

a: a social get-together
b: a meeting for discussion

 

I submit that in his use of such parlance, how can we do anything but take Charles at his word, and interpret his meaning as being nothing more (or less) than an invitation for a full informal discussion of his question, in a social and amiable way, both with serious and jocular locution. My motivations were certainly in line with this, while just trying my utmost to ‘keep it light and fun’.

Edited by Terra Nova, 21 February 2024 - 02:23 PM.

[starman876]

wish I could control the jet stream so I could move it somewhere else when I view.  

[Joe Cepleur]

I know just enough physics to be dangerous. Even if I had a PhD, it wouldn't change seeing conditions, or the structure of my eyeball, or all the highly complex neurobiology for the eye - brain connection & (data) processing.

No control over those factors. But I do control the Telescope System. Quality objective + quality accessories makes the most of what ya got.

Exactly. That's what I meant when I said that the quality of an image is not based on adding together everything that goes into making it, but on not subtracting from what is available by introducing bad seeing, bad optics, or bad technique.

Edited by Joe Cepleur, 21 February 2024 - 04:43 PM.

[Joe Cepleur]

What is the cutoff set by the laws of physics for the most power possible, per inch of aperture, after which no further resolution occurs when viewing objects with extent? Is that 50x/inch?

There is a limit to what a perfect lens could see, if a perfect lens were possible.

This is an awkward thread because I have not wanted to doubt those who have used higher powers, although I do find it interesting that there are legitimate reasons for using them. But, I confess to having wondered the extent to which averted imagination may accept overly high powers at times when they would appear to be bending the laws of physics.

Edited by Joe Cepleur, 21 February 2024 - 05:11 PM.

[deSitter]

What is the cutoff set by the laws of physics for the most power possible, per inch of aperture, after which no further resolution occurs when viewing objects with extent? Is that 50x/inch?

There is a limit to what a perfect lens could see, if a perfect lens were possible.

This is an awkward thread because I have not wanted to doubt those who have used higher powers, although I do find it interesting that there are legitimate reasons for using them. But, I confess to having wondered the extent to which averted imagination may accept overly high powers at times when they would appear to be bending the laws of physics.

It's the size of the Airy disk, which is a number you can give for the minimum size of a point light source, which is essentially any star. That's determined by the spatial extent of the entrance pupil (a ten dollar way of saying the aperture, which need not be circular) and the frequency of light. Linear features far narrower than the Airy disk can be perceived with the best optics, but there is no easy way to characterize it, and it depends on the particular object. Once the Airy disk is clearly visible, any more magnification only steals surface brightness in favor of size. Terrestrial targets are deceptive - we fill in details with our minds based on optical suggestions because we are familiar with them, so we "see" what is objectively not visible.

 

Look at the terminator of the Moon, and look for isolated mountain peaks in the dark area that are just catching the light. Those are essentially point sources and will produce an Airy pattern just like a star. Compare that Airy pattern to linear features seen on the terminator proper. You will see how the Rayleigh (Dawes etc.) criterion is not the entire story, but it is most of the story.

 

-drl

[Kasmos]

I've heard it said something like this:

Not a star but an image is built up by a bunch of airy disks (I can't recall if they said they are overlapping or not)

In anycase the details of any image is limited to an objective's resolution and are also affected by the diffraction rings which would overlap.

 

Edited by Kasmos, 21 February 2024 - 06:07 PM.

[Bomber Bob]

What is the cutoff set by the laws of physics for the most power possible, per inch of aperture, after which no further resolution occurs when viewing objects with extent? Is that 50x/inch?

There is a limit to what a perfect lens could see, if a perfect lens were possible.

This is an awkward thread because I have not wanted to doubt those who have used higher powers, although I do find it interesting that there are legitimate reasons for using them. But, I confess to having wondered the extent to which averted imagination may accept overly high powers at times when they would appear to be bending the laws of physics.

That's why I posted the Mars photo.  No imagination there.  I did find out later that the white feature at about 4 o'clock was indeed a patch of haze / thin cloud -- captured by others with larger scopes and / or better cameras.

[deSitter]

I've heard it said something like this:

Not a star but an image is built up by a bunch of airy disks (I can't recall if they said they are overlapping or not)

In anycase the details of any image is limited to an objective's resolution and are also affected by the diffraction rings which would overlap.

Yes they are overlapping. It's a limiting process by which the object is divided up into tiny point sources in such a way that the light intensity taken as a whole is preserved.

 

The diffraction fringes seen near the edge of an extended object, are the superposed diffraction rings of the constituent Airy disks.

 

-drl

[deSitter]

This is an awkward thread because I have not wanted to doubt those who have used higher powers, although I do find it interesting that there are legitimate reasons for using them. But, I confess to having wondered the extent to which averted imagination may accept overly high powers at times when they would appear to be bending the laws of physics.

As I speculated above, there is more to vision than resolution. The visual system is finely tuned to motion, particularly in the periphery where resolution is terrible! We in the South are plagued by palmetto bugs, which are roaches the size of Buicks. These things are not only gross, they are phenomenally stupid, and blunder around at random, begging for a dose of Raid. I can ALWAYS see these nasty things long before they are allowed to surprise me. It always amazes me how in a dim room where I am reading a computer screen, I can STILL see the faint hints of motion in the far corner of my vision. That is not a matter of resolution. However I am seeing this, it is not because I can resolve a roach across the room 40 or more degrees off axis.

 

High magnification will absolutely be a benefit to that way of seeing. A roach the size of a sneaker would occasion more than annoyance. (So far, we are just short of sneakers. Global warming has been kind to the roaches, and they are getting up there is size.)

 

-drl

[CHASLX200]

Best Planetary Seeing at The Swamp is usually from mid-FEB to mid-MARCH:  Daytime highs in the 60s, and nighttime lows in the 30s.  About a half-hour after sunset, the air can get very still, and that's when extreme magnifications are most useful.  (By Extreme, I mean 100x / inch or higher.)  IMO, one of my Very Best Jupiter photos with my RV-6 was at Sundown, in a large gap between Powder-Puff clouds - perfect focus, great resolution, and such natural belt colors -- EXACTLY the same as I saw in the eyepiece.  I still remember:  I was sweatin' it while recording, as a cloud's edge approached, and I wanted to hit 5000 frames... I beat the clock, but just barely!

 

About Photos:  As I've posted before, these pix are proof that my scopes can do what I claim.  Yes, they can be improved in post-processing, BUT only so much.  If the RAW data is blurry, then short of owning my own AI, they're not going to turn out sharp as a TAK [pun intended].  After I posted my famous Monolux 4380 Mars photo, a CNer PM'ed me, wanted to verify that the pix really was made with a rinky-dink Dept Store scope.  I assured him that this 4380 had a Hiyoshi objective, gave near-perfect star tests (no DPAC Rig back then), and made that image.

Feb is all my all time best seeing but only if it is super warm and no temp drops and sea fog coming onshore.  Not been that way this month with colder than normal weather

[CHASLX200]

yes, you could go to 600X but you had no idea what you were looking at.  And 600X could only be used on the moon.  However, focusing was really hard.  Every time you touched the focusing knob the object would go out of view

You can go to 6 millions i guess. But for a 60mm i find 300x about it for the moon. 400x for a 80mm and 600x for a 4".  That is for my eyes and my scopes and my seeing.  Not everyone will want to do the same or has my optics or my seeing.