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Refractor for visual


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Hi just some advice please,

I hear how refractors are not only superb for AP but also for visual use due to their wide FOV and sharp contrast etc but just wondering in terms of their rather small aperture how good they really are against a Good size alternative OTA.

 

Edited by Beardy30
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 A larger aperture reflector will have greater resolution, greater light grasp, and generally cost a lot less than a good refractor of reasonable aperture. Where the refractor scores for me at least, is in its laser etched sharpness, high definition and clarity of image at the eyepiece. Refractors of 4" to 5" aperture are easy to transport to dark sites, are less effected by internal heat, hardly ever lose collimation, never need recoating, have no central obstruction and suffer from no spider diffraction. Also, they cool rapidly and even on a sub zero night can be thermally stable within 15min's if its a doublet. Another beautiful quality that a good refractor of say 4" aperture has, is its ability to magnify while retaining a sharp image. A 4" refractor is often said to magnify upto 200X, which is the telescopes resolution limit. This means that all the detail the 4" is capable of showing is contained in that 200X image, and you can't exceed that. However, because of the high definition of the image formed at the eyepiece,  you can magnify that image well beyond the 200X so as to get a better image scale. A 4" refractor will show albedo markings on Mars even when the planets disc is less than 5 arc seconds in diameter, but it will likely mean you'll have to use higher powers than 200X to obtain an acceptable image scale.   At the same time, a good 4" to 5" refractor will give unmatched wide field views of star fields, exhibiting stars that are so piercingly sharp they almost hurt your retina. And because of the Crystal clarity and high definition of the view, these scopes can pack a punch even on deep sky objects providing you observe from a reasonably dark sky. And one more big plus for the refractor, is that they are beautiful to look at as well as look through, so when its raining for weeks on end you'll at least have a pretty telescope to admire.

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1 hour ago, Beardy30 said:

Wow 😮 well that is certainly an endorsement for a refractor over a Mak, SCT or Dob for visual 

thanks 😊 

 

 

It would certainly seem so, but it's important to remember that each scope design brings something different to the table. Much depends on what you want to observe, or what interests you. If for example you want to look at galaxies, a large Dobsonian or Newtonian will leave even the best Apochromatic refractor in the dust. But if you want to admire double stars, wide, rich star fields, festoons on Jupiter and subtle albedo features on Mars and Venus cloud tops, then a refractor may be ideal.

Prices can be terrifying depending on brand or manufacturer, but Starfield 102ED and Skywatcher 120ED are very worthy contenders to consider. When it comes to high end refractors such as Astrophysics, Takahashi, TEC, Vixen, and TMB, I think only Vixen and Takahashi can be bought off the shelf.

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3 hours ago, mikeDnight said:

Where the refractor scores for me at least, is in its laser etched sharpness, high definition and clarity of image at the eyepiece.

What specification of refractor are you talking about here? I have a 102mm f5 achromatic, and have not been bowled over by its visual performance.

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A good 100mm apo is something everyone should have.

However, there is too much over emotive eulogising about them. 100mm is still 100mm - you cannae change the laws of physics as a colleague once said.
I don't care how good, or expensive, your 100+mm apo is, my 300mm Newt will spank it every time :wink2:

Incidentally, I could draw your attention to one of these beauts...
DSC_0419_DxO.jpg.884406fed7e85c1eddf234340a6b174f.jpg

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3 hours ago, Beardy30 said:

How would the 80ED for example match up against the 127 Mak ? 

Hmmm they are so different , if you had one of each then I would say you have the perfect lightweight set up . Mak for Luna and planetary and 80ed for widefield I have the 80ed and I think it's a great scope for a quick set up and go bit the Mak doesn't take too long to cool and gives very pleasing views . 

Horses for courses ,. No one scope does it all , as the saying goes 

Edited by Stu1smartcookie
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2 hours ago, Cosmic Geoff said:

What specification of refractor are you talking about here? I have a 102mm f5 achromatic, and have not been bowled over by its visual performance.

Hi Geoff,

 I'm talking about an apochromatic refractor such as Michael's lovely Starfield ED above. I've used many ED and Apochromatic refractors and they are in a different league to the SW achromats. I learned that the hard was back in January 2003, when my Helios 150mm F8 achromat was utterly annihilated by a Vixen 102mm fluorite apochromat. The difference was so stark that I never looked through the 150mm achromat again. A couple of years later at an Easter star party at my local astro club, an elderly man who'd looked through every other scope on the field, some very big scopes of every major design, came finally to the Vixen. He took a long look at Saturn, then asked "Why is this one so much better than all the rest"? So even a complete novice with no axe to grind could see the difference.   Back then there were only Vixen, Takahashi, Astrophysics and a new kid TMB. Skywatcher ED's were just about to take the astro community by surprise.

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7 hours ago, Beardy30 said:

Hi just some advice please,

I hear how refractors are not only superb for AP but also for visual use due to their wide FOV and sharp contrast etc but just wondering in terms of their rather small aperture how good they really are against a Good size alternative OTA.

 

My Skywatcher 200P Newtonian beat my Takahashi FS128 on the planets and deep sky for a fraction of the price.

Later I bought a Skywatcher 10” Newtonian that was even better.

BUT - I really like refractors 🤷🏻🤪👍

Edited by dweller25
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6 hours ago, Beardy30 said:

Wow 😮 well that is certainly an endorsement for a refractor over a Mak, SCT or Dob for visual 

thanks 😊 

 

 

A large dobsonian will beat a 4-5” refractor every time. And you will see a great many more details on DSO’s

Edited by bosun21
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42 minutes ago, Beardy30 said:

Yea I guess so but have no room for a Dob

It's all been said above, however... A nice 4" refractor is relatively easy to handle, mount and is incredibly pleasant to use. I've had 130, 150mm and 200mm newtonians, 102 and 127 Maks plus a 120mm fast achromatic refractor. Without a doubt the 4" f7 ED refractor has provided the most pleasure and the two years of ownership next week has left me with no regrets.

I just wish I lived somewhere darker because at dark sites the tiddler really opens up the heavens. Of course the 4" will never go as deep as a larger aperture dob for instance but it can keep you busy for a lifetime nonetheless and also compliments a big Dob or SCT.

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This is the age old argument about which scope is better for what, without these comparisons all forums would collapse. But I will say that aperture aside, there's something special about a good refractor and the way they show

stars, with a purity and cleanliness which mirrors just cant seem to match.  Maybe its my mirror that lacks a more precise finish but, I could collimate till I'm blue in the face, it just doesn't do stars like my frac can.

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15 minutes ago, Beardy30 said:

The main thing I’m hearing hear is nothing beats a big Dob for visual but that fracs do a decent job for their size.

 

thanks all 

Basically thats it.  

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1 hour ago, Beardy30 said:

The main thing I’m hearing hear is nothing beats a big Dob for visual but that fracs do a decent job for their size.

 

thanks all 

I think it would pay for you to look through a few different scopes before making a final decision. I'm sure that Preston has an astro association where you can chat to fellow astronomers and observe through their scopes.  You may find that a 4" ED will keep pace with an 8" reflector on the moon and planets, and an awful lot more pleasurable to use.  

Here's a pic of my 8" F6 Newtonian, 10" Dobsonian, and my two 4" refractors as a size comparison.  The planetary resolution on the 8" was barely discernible over the 4" Takahashi. The 10" was noticeably better at resolving finer detail, but the image was less pleasing, less sharp, and smeared with spider diffraction spikes. The 10" and the 8" we're cumbersome scopes to use, and for the majority of the time I found I prefered the refractor.

8"

20200921_130640.thumb.jpg.649f6576250255db43e64cf9488070bd.jpg

10"

IMG_5847.JPG.656a2130a314bc7cdcac1a7e11655dea.thumb.jpeg.5c57d1d1a437a8be1f1c331089c1e05c.jpeg

100mm Takahashi fluorite apochromat.

image0.jpeg.58597831a4525576a0692877fc127dde.jpeg

101mm Genesis SDF rich field refractor.

1652308428892_image0.jpeg.a63203a23d06341f3c9c80062b057e11.jpeg

Here are a couple of sketches of Mars from the 2020 apparition, the first made using the 8" Newtonian and the second using the 100mm Takahashi. Apart from the images being mirrored, the 8" shows little gain over the 100mm refractor.

IMG_7734.thumb.jpg.c59fa45ca76eb88311741c500269b535.jpg

Edited by mikeDnight
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13 minutes ago, mikeDnight said:

I think it would pay for you to look through a few different scopes before making a final decision. I'm sure that Preston has an astro association where you can chat to fellow astronomers and observe through their scopes.  You may find that a 4" ED will keep pace with an 8" reflector on the moon and planets, and an awful lot more pleasurable to use.  

Here's a pic of my 8" F6 Newtonian, 10" Dobsonian, and my two 4" refractors as a size comparison.  The planetary resolution on the 8" was barely discernible over the 4" Takahashi. The 10" was noticeably better at resolving finer detail, but the image was less pleasing, less sharp, and smeared with spider diffraction spikes. The 10" and the 8" we're cumbersome scopes to use, and for the majority of the time I found I prefered the refractor.

8"

20200921_130640.thumb.jpg.649f6576250255db43e64cf9488070bd.jpg

10"

IMG_5847.JPG.656a2130a314bc7cdcac1a7e11655dea.thumb.jpeg.5c57d1d1a437a8be1f1c331089c1e05c.jpeg

100mm Takahashi fluorite apochromat.

image0.jpeg.58597831a4525576a0692877fc127dde.jpeg

101mm Genesis SDF rich field refractor.

1652308428892_image0.jpeg.a63203a23d06341f3c9c80062b057e11.jpeg

Here are a couple of sketches of Mars from the 2020 apparition, the first made using the 8" Newtonian and the second using the 100mm Takahashi. Apart from the images being mirrored, the 8" shows little gain over the 100mm refractor.

IMG_7734.thumb.jpg.c59fa45ca76eb88311741c500269b535.jpg

So in other words, a 4” refractor is THE! quintessential telescope, yes it is!.

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2 hours ago, Beardy30 said:

The main thing I’m hearing hear is nothing beats a big Dob for visual but that fracs do a decent job for their size.

 

thanks all 

Not really a "decent job"  They do a different job, I like to think, I dunno. 😆

Edited by Sunshine
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