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markclaire50

Highest mag before breakdown?

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I'm interested in hearing stories about how far people have pushed their scopes before loss of image quality? 

For example, loss of pin point stars; bloating of planets ; other examples 

Any scope. 

Thank you 

Mark 

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Wow, thats a complex question Mark :icon_biggrin:

I think I'll wait to see what details others offer up before venturing in myself, other than to say that I've found that excellent optical quality generally seemes to enable scopes to deliver better quality images at higher magnifications than similar specced scopes with more mediocre optics.

Seeing conditions have a very significant influence as well, of course.

 

 

 

 

 

 

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As to what magnification one can use on a given object/day that would vary greatly depending on seeing, for me, i would say this past summer Saturn on a great night held up nicely at 256X before it started degrading.

Theres quite a few variables to consider in order to  answer that question but i gave one example on one day specifically.

Edited by Sunshine
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3 minutes ago, Sunshine said:

As to what magnification one can use on a given object/day that would vary greatly depending on seeing, for me, i would say this past summer Saturn on a great night held up nicely at 256X before it started degrading.

Took the words right out of my mouth.

Seeing is everything really when pushing a scope to its limits.

Edited by Geoff Barnes

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FS128 - some nights x140, some nights x350, most nights x180 to x220

Edited by dweller25
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1 minute ago, dweller25 said:

FS128 - some nights x140, some nights x350

I think that sums it up !

I guess with the higher optical quality, the potential is there, if the conditions allow it.

 

 

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27 minutes ago, Sunshine said:

As to what magnification one can use on a given object/day that would vary greatly depending on seeing, for me, i would say this past summer Saturn on a great night held up nicely at 256X before it started degrading.

Theres quite a few variables to consider in order to  answer that question but i gave one example on one day specifically.

Hi. What scope were you using? 

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I have a case in point tonight as it happens. a few nights ago I had my 12 inch dobsonian out and observed E & F Trapezium and Sirius B quite clearly at 265x and 318x - probably some of the best views of these targets I've had this year. Tonight, same scope, same eyepieces, same location, same targets and things are quite different E & F Trapezium hard to more than glimpse on and off and no chance of Sirius B - the seeing conditons this evening are just not stable enough.

On the other hand the sky transparency is greater tonight and my views of galaxies and nebulae are better than they were a few nights back. These are low to medium magnification targets though.

Swings and roundabouts, as the saying goes.

 

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5 minutes ago, markclaire50 said:

Hi. What scope were you using? 

My 150mm Skywatcher Maksutov.

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25 minutes ago, dweller25 said:

FS128 - some nights x140, some nights x350, most nights x180 to x220

Very interesting, Dweller. A range of 2.5:1 with majority about 50% above aperture. Is the FS an apo? 

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7 minutes ago, John said:

I have a case in point tonight as it happens. a few nights ago I had my 12 inch dobsonian out and observed E & F Trapezium and Sirius B quite clearly at 265x and 318x - probably some of the best views of these targets I've had this year. Tonight, same scope, same eyepieces, same location, same targets and things are quite different E & F Trapezium hard to more than glimpse on and off and no chance of Sirius B - the seeing conditons this evening are just not stable enough.

On the other hand the sky transparency is greater tonight and my views of galaxies and nebulae are better than they were a few nights back. These are low to medium magnification targets though.

Swings and roundabouts, as the saying goes.

 

Thanks John. That is a very interesting report. A useful lesson (to beginners like me) on the importance of looking at the same targets on different nights. 

In a few words, what's the key difference between seeing and transparency? 

Thanks 

Mark

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I recall the highest mag I've pushed my 12 inch Dob to so far is 640x, that was with an ES 4.7mm with 2x Barlow, looking at Saturn on a clear still night. Whilst for most of the time it was a wobbly blur, just occasionally it would settle for a few seconds and snap into focus, it was the only time I've been able to spot the Encke minima so far.

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7 minutes ago, Sunshine said:

My 150mm Skywatcher Maksutov.

That's very interesting to me, because I have its little brother, the 127mak. I noticed that on the first few occasions I have used it since acquiring it in January, it is sharp on stars up to about 150-160x but bloating starts by 180x. The collimation seems OK, as I saw perfect symmetrical concentric circles on Sirius, and the scope was outside for over 2 hours before using it. I wonder if this is seeing or optical threshold? 

Mark

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7 minutes ago, Geoff Barnes said:

I recall the highest mag I've pushed my 12 inch Dob to so far is 640x, that was with an ES 4.7mm with 2x Barlow, looking at Saturn on a clear still night. Whilst for most of the time it was a wobbly blur, just occasionally it would settle for a few seconds and snap into focus, it was the only time I've been able to spot the Encke minima so far.

Impressive! A very good example of seeing vs optical potential. 

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35 minutes ago, markclaire50 said:

That's very interesting to me, because I have its little brother, the 127mak. I noticed that on the first few occasions I have used it since acquiring it in January, it is sharp on stars up to about 150-160x but bloating starts by 180x. The collimation seems OK, as I saw perfect symmetrical concentric circles on Sirius, and the scope was outside for over 2 hours before using it. I wonder if this is seeing or optical threshold? 

Mark

Lets say that if seeing was perfect, your scope was collimated perfectly, your mirror specs were excellent,  dark sky etc, you were able to achieve 50x per inch for max 250. This is a dream only, considering all the variables lets be more realistic and assume 30x per inch, this would leave you at 150x on an average night for your limit. My 256x i was never able to do again, 200x was average this past summer on planets, my collimation is as good as it will get, i guess  my mirror is a good specimen, and seeing was fantastic that night. Even then, the image would fuzz as pockets of hot air crossed the view, occasionally though, Saturn at 250 would snap into sharp view.

Edited by Sunshine
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I think it depends on the target. I have used 533x in my 6" f11 Newtonian on double stars and the moon, occasionally 300x on Mars and Saturn with my 16" dob and perhaps very occasionally 250x on Jupiter. Galaxies more often are best at lower powers and clusters need an appropriate magnification to get them in field. Planetary nebulae sometimes take more, sometimes less.

I suppose it's a reasonable question to ask but (without wishing to sound rude) is slightly meaningless as the answer is always going to be 'it depends'.

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2 minutes ago, Moonshane said:

'it depends'.

Way too many variables in there, good answer.

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52 minutes ago, markclaire50 said:

In a few words, what's the key difference between seeing and transparency? 

These two are often mixed up but are quite distinct.

Seeing is the stability of the atmosphere, and is generally relevant for high power planetary, lunar and doubles observing. It can depend on a number of factors, the jetstream position has a big impact, if it is overhead then objects can often look like they are being viewed under a steam of water! Weather systems can affect it too, aswell as local conditions such as viewing over houses or through central heating flames although that is not technically seeing as such as it can be avoided.

Transparency is literally how transparent the atmosphere is, and is largely relevant for observing faint objects such as nebula and galaxies, and tends to be related to low power observing (although the big dob boys would disagree with this as they observe faint galaxies at relatively high powers). High haze, moisture and pollution cause poor transparency, often the best time  to observe is after a heavy rain storm which clears all the muck out of the atmosphere and leaves lovely transparent skies.

One thing to note is that you don't often get both at once, nights with poor transparency can be very stable and good for planetary observing, whilst nights with great transparency often have poor seeing!

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44 minutes ago, markclaire50 said:

...In a few words, what's the key difference between seeing and transparency? 

Thanks 

Mark

What Stu has just said ! :smiley:

 

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2 minutes ago, John said:

What Stu has just said ! :smiley:

 

I think I missed the bit about 'a few words' ??

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To be honest i never really push my 120ed above 150 x mag . 6mm 

If gives me a a comfortable sharp image at that range.

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Regarding the main question, I think Shane has said it best, it depends.

So many factors can affect the views, and seeing conditions are a great leveller, making excellent kit look very ordinary. A rough guide is a max of around x250 in the UK but that is very rough.

What you see depends on seeing, scope cooling and collimation, object altitude, observer experience (and condition.... tiredness... alcohol....) and probably a few more.

Larger scopes have a higher potential resolution but can be more affected by poor seeing, so can under perform compared with their maximum potential. Also don't forget that at the same power, a larger scope will still have better resolution potential than a smaller scope.

My normal maximums are in line with the others quoted. My best ever view of Saturn was at x400 in a 200mm Mak, lovely conditions and an amazing view. Most of the time it is between x150 and x250 almost regardless of scope. My Tak took x308 with quite acceptable results the other night but I would not want to be observing at those levels that often.

I could go on (he always does I hear you cry! ??) but.... it depends... 

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There is considerable good advice by Al Nagler; 'Choosing an Eyepiece - Step by Step'; which you can easily search for online.  A quote from this article

Remember, that choosing the lowest-high power eyepiece that reveals the detail you're looking for, you'll have a brighter, sharper appearing more contrasty image. Too high a power may reveal telescope limitations, mount shakiness and floaters in your eyes.

 

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54 minutes ago, Moonshane said:

I think it depends on the target. I have used 533x in my 6" f11 Newtonian on double stars and the moon, occasionally 300x on Mars and Saturn with my 16" dob and perhaps very occasionally 250x on Jupiter. Galaxies more often are best at lower powers and clusters need an appropriate magnification to get them in field. Planetary nebulae sometimes take more, sometimes less.

I suppose it's a reasonable question to ask but (without wishing to sound rude) is slightly meaningless as the answer is always going to be 'it depends'.

Thank you Moonshane. I think it has interest from the point of view of showing what can be done when seeing permits, or not, with particular scopes. 

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51 minutes ago, Stu said:

These two are often mixed up but are quite distinct.

Seeing is the stability of the atmosphere, and is generally relevant for high power planetary, lunar and doubles observing. It can depend on a number of factors, the jetstream position has a big impact, if it is overhead then objects can often look like they are being viewed under a steam of water! Weather systems can affect it too, aswell as local conditions such as viewing over houses or through central heating flames although that is not technically seeing as such as it can be avoided.

Transparency is literally how transparent the atmosphere is, and is largely relevant for observing faint objects such as nebula and galaxies, and tends to be related to low power observing (although the big dob boys would disagree with this as they observe faint galaxies at relatively high powers). High haze, moisture and pollution cause poor transparency, often the best time  to observe is after a heavy rain storm which clears all the muck out of the atmosphere and leaves lovely transparent skies.

One thing to note is that you don't often get both at once, nights with poor transparency can be very stable and good for planetary observing, whilst nights with great transparency often have poor seeing!

Thanks Stu for this comprehensive reply. Much appreciated. Do you know if there are 'seeing' maps for parts of the UK? 

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