What have you seen in a 5" Refractor, that you've not seen in an 8" newt?

[Flame Nebula]

3 minutes ago, mikeDnight said:

Doesn't this go to show there's nothing written in stone when it comes to one aperture or scope design vs another!  A number of years ago I'd been loaned a very nice SW 8" Dob which I'd set up in my garden at around 3pm on a clear afternoon. Alongside the Dob was my Equinox 120ED and both spent a good six hours standing in the cool air before being aimed at the Moon. My friend Derek witnessed this event as we looked at the Moon using the 8" and both genuinely felt the view was quite literally as good as it could ever possibly be. I knew in my heart that the 120ED would be hard pushed to get anywhere close to the 8", but when we looked at the Moon through the 120ED standing alongside, we were both in awe at the improved sharpness. The night had excellent seeing and both scopes were giving their best.  It would have been very easy to assume the 8" would be unbeatable by a smaller scope had the smaller scope not been standing right alongside, and anyone with that 8" would have had a seriously great scope.  

 It didn't stop there however, as we next aimed the 8" at Saturn which was high in the south east, and again the 8" gave what appeared to be another unbeatable view of the planet and its rings. Again I felt that the 120ED would struggle to get close to the view given by the 8" as it was perfection. Anyone seeing that 8" perform as it did on Saturn would be convinced it wouldn't be possible to get a better view through a smaller scope, as the A ring, Enke minima, Cassini's division, variations in the brilliance of the B ring, and the Crepe ring were all visible with ease, as well as globe detail. Nervously I aimed the 120ED at Saturn and Derek took the first look. His response to what he saw was littered with expletives which made me want to push him out of the way and look for myself. Instead I patiently waited for my turn to look, and when it came I was gobsmacked at the improved definition. The rings in the 120ED were as in the 8", but unlike the 8" were littered with the finest grooves similar in appearance to the grooves on a vynil record.  Derek likened the view to a Voyager image! 

Mike, 

This is fantastic stuff! Exactly what I was after! And certainly justification for both. 😉

Thanks 

Mark

[Earl]

A bigger bank balance just buying the newt 😜 

[mikeDnight]

13 minutes ago, Flame Nebula said:

Mike, 

This is fantastic stuff! Exactly what I was after! And certainly justification for both. 😉

Thanks 

Mark

 That was only one night of course, and afterwards the 8" went back to its owner, and I continued using the 120ED for many more years. Had I have continued observing with the 120ED and 8" Dob, there may very well have been times when the opposite occurred. Either scope could have been the scope of a lifetime, but I suppose my love of refractors has given me more hours using them and seeing great sights along the way. 

[Alan White]

Let's be honest on this, to an extent we all have bias on scope type, aperture etc.
It may be a unconscious bias, but we will all have it and that will navigate our response to the OP question.

I did laugh at @Earl and his Bank Balance answer, which is patently correct.

I have always flip flopped about Newtonian and Refractor scopes, I have a deep love for both.
My last direction was all refractor and I quickly added back a reflector to the mix, as horses for courses applies.

This year due to a back issue, that is long term, I find I cannot sit and use a refractor of the aperture and focal length that I like without making my back far worse for days on end. 
I am presently only using Newtonians from 6 to 10 inch aperture and thoroughly enjoy my lot.

One thing to bear in mind is the question posed needs to take into account funds available and mounts available,
A badly mounted 5" or 8" or even 10" is a scope that will be a drain on the pleasure it could bring to its user.

 

[wookie1965]

20 hours ago, IB20 said:

Just to qualify my statement, I’ll try and get round to observing some targets with the 5” that, from memory, really impressed me in the 8”.

Blue snowball nebula

M5

M51

Sombrero Galaxy (M104)

Hopefully in less moon affected skies than last night. Although I was quite chuffed making out two very faint smears of m65 and m66 in the 5”. I’ve struggled to see those with the 8” in bright moonlit skies.

 

M51 is my nemesis I have seen it once in Damians (Mapstar) 22", I have had 6" 8" 10" reflectors  4" and 5" Refractors and never seen it from home. Just got a 120mm refractor as I sold my 5" so I will try this one. 

Blue snowball I have found looks much better in a refractor the colour is unmistakable. 

Edited April 19 by wookie1965

[DirkSteele]

It is an interesting question.  I am not sure your thought experiment of a 5inch vs 8inch would see the smaller scope beat on any object (caveat shortly), but having been doing this for a very long time and used more scopes than I can count, I have found high quality refractors typically make up for 2-3 inch deficiency in aperture by the improved contrast against obstructed scopes where the same extent of detail can be seen even if the image itself is dimmer.  The obvious exception is something like M33.  That is very low surface brightness and I have had scopes quite a bit bigger than 8" fail to show it where as a 4-5" scope shows it pretty easily.  Something like the E and F stars in the trapezium mentioned above also does not surprise me.  If seeing is decent, those two stars are a good test for spherical abberation in smaller scopes as the dim stars against bright glowing nebula means they are smeared out by SA and rendered invisible.  The impact of extra diffraction from spider vanes and secondary could have a similar impact.

[Mr Spock]

I think there are many swings an roundabouts between a good apo and a Newtonian.

On a day of good seeing my 12" Newt can reveal the finest detail on the moon. A few nights ago it was cruising at x380. It's not the highest it can go as the seeing wasn't perfect, but high enough to see 1km craters. However, the same night, double stars were fuzzy. When seeing is excellent it shows pinpoint airy discs, and I have split 0.4" doubles, but it does require excellent seeing. Very good isn't good enough and most of the time stars can look fuzzy.

With something like Jupiter you have to use a variable polariser with the 12" to cut down brightness. When you do you can't see diffraction spikes.

The 4" apo on the other hand shows airy discs at the drop of a hat. Seeing can be just acceptable and it is good. It can never approach the 12" for detail, but its performance belies its size, especially when seeing isn't so good.

If I was going purely for double stars I'd want a large apo. 150mm+ if funds were unlimited.

There's the other issue, cost. If you include the mount, the 4" in total cost four times what the 12" cost... I'm sure you could create an offset sub aperture mask for the 12" to avoid the central obstruction and get the same mm for mm performance - without the size convenience of course.

[Flame Nebula]

1 hour ago, mikeDnight said:

 That was only one night of course, and afterwards the 8" went back to its owner, and I continued using the 120ED for many more years. Had I have continued observing with the 120ED and 8" Dob, there may very well have been times when the opposite occurred. Either scope could have been the scope of a lifetime, but I suppose my love of refractors has given me more hours using them and seeing great sights along the way. 

Indeed the beauty of the Az-eq6, is it can hand both simultaneously, so I could build up a record of differences. Obviously there will be times when I only want to have one set up, but the options there. 

[Flame Nebula]

1 hour ago, Alan White said:

Let's be honest on this, to an extent we all have bias on scope type, aperture etc.
It may be a unconscious bias, but we will all have it and that will navigate our response to the OP question.

I did laugh at @Earl and his Bank Balance answer, which is patently correct.

I have always flip flopped about Newtonian and Refractor scopes, I have a deep love for both.
My last direction was all refractor and I quickly added back a reflector to the mix, as horses for courses applies.

This year due to a back issue, that is long term, I find I cannot sit and use a refractor of the aperture and focal length that I like without making my back far worse for days on end. 
I am presently only using Newtonians from 6 to 10 inch aperture and thoroughly enjoy my lot.

One thing to bear in mind is the question posed needs to take into account funds available and mounts available,
A badly mounted 5" or 8" or even 10" is a scope that will be a drain on the pleasure it could bring to its user.

 

Thanks Alan, 

Thanks to many people in the forum, plus other research, I decided early on that the az-eq6 was to be the foundation stone, and building from that. So, a 200pds and 120ed will be OK. But, it could handle bigger. Problem is, my ability to handle the larger scopes is inversely proportional to my age now. But, I may decide, 8" is all I need. 😊

[Flame Nebula]

1 hour ago, DirkSteele said:

It is an interesting question.  I am not sure your thought experiment of a 5inch vs 8inch would see the smaller scope beat on any object (caveat shortly), but having been doing this for a very long time and used more scopes than I can count, I have found high quality refractors typically make up for 2-3 inch deficiency in aperture by the improved contrast against obstructed scopes where the same extent of detail can be seen even if the image itself is dimmer.  The obvious exception is something like M33.  That is very low surface brightness and I have had scopes quite a bit bigger than 8" fail to show it where as a 4-5" scope shows it pretty easily.  Something like the E and F stars in the trapezium mentioned above also does not surprise me.  If seeing is decent, those two stars are a good test for spherical abberation in smaller scopes as the dim stars against bright glowing nebula means they are smeared out by SA and rendered invisible.  The impact of extra diffraction from spider vanes and secondary could have a similar impact.

Thanks Dirk. Interesting comments! 

[Flame Nebula]

40 minutes ago, Mr Spock said:

I think there are many swings an roundabouts between a good apo and a Newtonian.

On a day of good seeing my 12" Newt can reveal the finest detail on the moon. A few nights ago it was cruising at x380. It's not the highest it can go as the seeing wasn't perfect, but high enough to see 1km craters. However, the same night, double stars were fuzzy. When seeing is excellent it shows pinpoint airy discs, and I have split 0.4" doubles, but it does require excellent seeing. Very good isn't good enough and most of the time stars can look fuzzy.

With something like Jupiter you have to use a variable polariser with the 12" to cut down brightness. When you do you can't see diffraction spikes.

The 4" apo on the other hand shows airy discs at the drop of a hat. Seeing can be just acceptable and it is good. It can never approach the 12" for detail, but its performance belies its size, especially when seeing isn't so good.

If I was going purely for double stars I'd want a large apo. 150mm+ if funds were unlimited.

There's the other issue, cost. If you include the mount, the 4" in total cost four times what the 12" cost... I'm sure you could create an offset sub aperture mask for the 12" to avoid the central obstruction and get the same mm for mm performance - without the size convenience of course.

Thanks Mr Spock, 

Pulling out one particular comment, I was interested in the variable polariser. How does it affect the appearance of jupiter, wrt bands, GRS, etc? 

Edited April 19 by Flame Nebula

[dweller25]

Here is one of my old posts from 2010 where my wife and I visually compared a 5” refractor to a Skywatcher 8” F/6 Newtonian…

 

“I was really enthusing about how good the seeing was so Mrs Dweller25 decided to come out and have a look.

Now this is a rare event as Mrs D and the cold night air don't mix so to spice things up a little I suggested a shootout between the 5" Takahashi FS128 and the Skywatcher 8" F/6 Newtonian. Each of us would take a turn observing and drawing Mars in each scope so we could compare and contrast.

Seeing was very good - AII, temp was -4'C.

We concluded :-

1. Mrs D25 has better eyesight than me - I have astigmatism 😕

2. The humble Skywatcher slightly outperforms the Tak 😱 🙂

 

 

[paulastro]

17 hours ago, Captain Scarlet said:

Planetary detail, especially Jupiter. I think that 8” Newt vs 5” refractor might be close to an equilibrium between the two. The refractor of course has a purity of view and a minimum level of diffraction “light-spreading”.

Whereas a Newt has its diffraction spikes. Mostly, those spikes are diffraction “thrown away” from the star you’re looking at, so don’t affect the view of the star itself too much. But Jupiter can be imagined as a multitude of bright stars all clumped together, each “star” throwing its spikes directly into the neighbouring “stars”, dramatically smearing out contrast on the disc and negating the effects of the extra aperture.

As it happens my own best views of Jupiter are equally split between my top-notch 5.5” refractor, and my 8” Newt. But of course they were on different nights with different seeing.

Magnus.

I agree re seeing is so important of course.  If a persons best view ever of, say Jupiter, was with a certain scope it doesn't mean its better than any other scope that wasn't available to compare it with at the time of the observation. 

Even having a quality 5 inch refractor along with a quality 8 inch Newtonian and comparing them directly is flawed. The comparison would have to be on a night when the seeing is good enough that the larger telescope, can be used to perform to its best resolution as well as the smaller one.  If not then its not a fair comparison. Any differences would be more of a test of the observing conditions rather than the telescopes ability.

So when I say that a such and such telescope gave me my best view ever of Mars, it may be interesting, but it doesn't meant it was the best planetary scope I've ever used.  It happened to be a 16 inch SC one early morning just before dawn, when the seeing was exceptional.

The best person to answer the original question would be one who has owned both a 5inch refractor and 8inch Newtonion simultaneously over quite a few years.  Not only that, but they would have had to frequently used them side by side on numerous occassions when the seeing was good enough for both to perform to their respective maximum possible resolutions.  Oh yes, and on a good variety of targets.

Any takers?

 

 

Edited April 19 by paulastro

[Mr Spock]

36 minutes ago, Flame Nebula said:

Pulling out one particular comment, I was interested in the variable polariser. How does it affect the appearance of jupiter, wrt bands, GRS, etc?

Approximate view of Jupiter without and with a polariser in a large aperture. Not entirely accurate but you get the idea.

It's especially important for Venus with almost any aperture.

[Flame Nebula]

20 minutes ago, dweller25 said:

 

Here is one of my old posts from 2010 where my wife and I visually compared a 5” refractor to a Skywatcher 8” F/6 Newtonian…

 

“I was really enthusing about how good the seeing was so Mrs Dweller25 decided to come out and have a look.

Now this is a rare event as Mrs D and the cold night air don't mix so to spice things up a little I suggested a shootout between the 5" Takahashi FS128 and the Skywatcher 8" F/6 Newtonian. Each of us would take a turn observing and drawing Mars in each scope so we could compare and contrast.

Seeing was very good - AII, temp was -4'C.

We concluded :-

1. Mrs D25 has better eyesight than me - I have astigmatism 😕

2. The humble Skywatcher slightly outperforms the Tak 😱 🙂

 

 

Hi Dweller, 

Very interesting comparison. As you say, not much in it! But, considering it was a Tak, that's very encouraging. 

I think if I remember, we both have early signs of cataracts too (I have astigmatism in one eye as well). So, sooner I get the scopes the better. At the moment though, job security is not what I'd like it to be, but I wasn't planning to make major purchases until first half September anyway, as the nights draw in. Hopefully by then things will be clearer (skies and job! 😉) 

At the moment, the plan is for me to get the 200pds first, then if a good deal appears on a SW120, consider that. I have heard some stories that earlier Sw120 fracs may have a different coating to newer ones, but not sure if that matters 

[Flame Nebula]

5 minutes ago, Mr Spock said:

Approximate view of Jupiter without and with a polariser in a large aperture. Not entirely accurate but you get the idea.

It's especially important for Venus with almost any aperture.

Wow, I wasn't expecting such  a difference! 

So, would a smaller newt also benefit, do you think? 

[Mr Spock]

3 minutes ago, Flame Nebula said:

So, would a smaller newt also benefit, do you think? 

Likely, but obviously not at the same setting. That's the advantage of the variable polariser. You can set it to whatever feels comfortable.

[Flame Nebula]

5 minutes ago, Mr Spock said:

Likely, but obviously not at the same setting. That's the advantage of the variable polariser. You can set it to whatever feels comfortable.

I'll be investing in one! 

[mikeDnight]

3 hours ago, Alan White said:

Let's be honest on this, to an extent we all have bias on scope type, aperture etc.
It may be a unconscious bias, but we will all have it and that will navigate our response to the OP question.

I did laugh at @Earl and his Bank Balance answer, which is patently correct.

I have always flip flopped about Newtonian and Refractor scopes, I have a deep love for both.
My last direction was all refractor and I quickly added back a reflector to the mix, as horses for courses applies.

This year due to a back issue, that is long term, I find I cannot sit and use a refractor of the aperture and focal length that I like without making my back far worse for days on end. 
I am presently only using Newtonians from 6 to 10 inch aperture and thoroughly enjoy my lot.

One thing to bear in mind is the question posed needs to take into account funds available and mounts available,
A badly mounted 5" or 8" or even 10" is a scope that will be a drain on the pleasure it could bring to its user.

 

If someone were to give me a Vintage Parks 10 or 12 inch Equatorial Newtonian I would be in astro heaven. No modern manufacturer I know of comes close to reproducing their beauty.

[Alan White]

16 minutes ago, mikeDnight said:

If someone were to give me a Vintage Parks 10 or 12 inch Equatorial Newtonian I would be in astro heaven. No modern manufacturer I know of comes close to reproducing their beauty.

You would be building a larger observatory first Mike.

[paulastro]

20 minutes ago, mikeDnight said:

If someone were to give me a Vintage Parks 10 or 12 inch Equatorial Newtonian I would be in astro heaven. No modern manufacturer I know of comes close to reproducing their beauty.

I think at the first Astrofest, there were 6 and 8 inch Parks equatorially mounted Newtonians.  Lovely quality and engineering with rotating tube ends to rotate the eyepiece position.  Alas, I've never had the chance to use one.

[John]

Something else that has occurred to me is that we are reaching the end of a period of several years when the planets that we love to observe most (ie: Mars, Saturn and Jupiter) have not been well placed for observing from the UK - generally low in the sky. 

Jupiter is looking better now and Saturn and Mars will slowly get better placed as well. 

I found that observing the planets when they were low in the sky was quite a different proposition, scope choice-wise, than when they were high in the sky, as they were when I was observing them 20 years or so back. My refractors took over from my 10 and 12 inch dobsonians because they were able to provide better views and cut through the shaky seeing and the additional atmosphere thickness. There was a period of a couple of years when I gave up using my 12 inch dob for observing these planets altogether.

I guess what I'm suggesting is that what has delivered the best planetary observing for the past 5-6 years or so may not be the optimum instruments for the future, or at least might have any edge that they had in the past few years removed by more favourable planet positions allowing newtonians, SCT's and maks to deliver more of the benefits that their additional aperture suggests they have the potential to do.

Just a thought 🙂

 

Edited April 19 by John

[Flame Nebula]

6 minutes ago, John said:

Something else that has occurred to me is that we are reaching the end of a period of several years when the planets that we love to observe most (ie: Mars, Saturn and Jupiter) have not been well placed for observing from the UK - generally low in the sky. 

Jupiter is looking better now and Saturn and Mars will slowly get better placed as well. 

I found that observing the planets when they were low in the sky was quite a different proposition, scope choice-wise, than when they were high in the sky, as they were when I was observing them 20 years or so back. My refractors took over from my 10 and 12 inch dobsonians because they were able to provide better views and cut through the shaky seeing and the additional atmosphere thickness. There was a period of a couple of years when I gave up using my 12 inch dob for observing these planets altogether.

I guess what I'm suggesting is that what has delivered the best planetary observing for the past 5-6 years or so may not be the optimum instruments for the future, or at least might have an edge that they had in the past few years removed by more favourable planet positions allowing newtonians, SCT's and maks to deliver more of the benefits that their additional aperture suggests they have the potential to do.

Just a thought 🙂

 

Thanks John 

Indeed, I started saving up, on a slow trajectory from early 2021 towards planned purchase, late 2024, as I am essentially a planet person, and checked when jupiter would be high in the sky again , back in early 2021. I even have my wife's permission to buy a 'special' scope. Not exactly mentioned the mount, plus AP accessories, but given I originally intended to get a C9.25 evolution, you're already talking around 2.5K anyway. So, what's a K (ish) more, between friends. 🤔😉. Initially the cost of the mount and vanilla 200pds would be < 2.5K anyway. It's adding AP stuff that increases cost. If all goes well, I'll have saved 4k by September. So, the budget will cover most of the things I'd like. Do you think a used SW120ED will be as good as newest version? I've heard some things about different coatings? 

But, what will stop me, is if things go sideways on job front, as I can't really justify that sort of expenditure then, even though I've tried to ring fence it and keep it separate from other expenses. Fingers crossed. 🤞

[Zermelo]

28 minutes ago, John said:

Something else that has occurred to me is that we are reaching the end of a period of several years when the planets that we love to observe most (ie: Mars, Saturn and Jupiter) have not been well placed for observing from the UK - generally low in the sky. 

Jupiter is looking better now and Saturn and Mars will slowly get better placed as well. 

I found that observing the planets when they were low in the sky was quite a different proposition, scope choice-wise, than when they were high in the sky, as they were when I was observing them 20 years or so back. My refractors took over from my 10 and 12 inch dobsonians because they were able to provide better views and cut through the shaky seeing and the additional atmosphere thickness. There was a period of a couple of years when I gave up using my 12 inch dob for observing these planets altogether.

I guess what I'm suggesting is that what has delivered the best planetary observing for the past 5-6 years or so may not be the optimum instruments for the future, or at least might have any edge that they had in the past few years removed by more favourable planet positions allowing newtonians, SCT's and maks to deliver more of the benefits that their additional aperture suggests they have the potential to do.

Just a thought 🙂

 

That's a very interesting observation, John.
So, the seasoned planetary observer might be "cycling" their kit between larger mirrors and smaller lenses, on a scale of several years.
Or, perhaps more likely, they buy the new kit to suit the current planetary placements, but somehow "forget" to sell what they already have 😊

[dweller25]

38 minutes ago, John said:

Something else that has occurred to me is that we are reaching the end of a period of several years when the planets that we love to observe most (ie: Mars, Saturn and Jupiter) have not been well placed for observing from the UK - generally low in the sky. 

Jupiter is looking better now and Saturn and Mars will slowly get better placed as well. 

I found that observing the planets when they were low in the sky was quite a different proposition, scope choice-wise, than when they were high in the sky, as they were when I was observing them 20 years or so back. My refractors took over from my 10 and 12 inch dobsonians because they were able to provide better views and cut through the shaky seeing and the additional atmosphere thickness. There was a period of a couple of years when I gave up using my 12 inch dob for observing these planets altogether.

I guess what I'm suggesting is that what has delivered the best planetary observing for the past 5-6 years or so may not be the optimum instruments for the future, or at least might have any edge that they had in the past few years removed by more favourable planet positions allowing newtonians, SCT's and maks to deliver more of the benefits that their additional aperture suggests they have the potential to do.

Just a thought 🙂

 

At least Mars and Jupiter will be high in the sky until 2027, see this from @Stu

Edited April 19 by dweller25