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Are refractors really mainly solar system & imaging instruments

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#26 mikeDnight

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Posted 22 November 2019 - 01:10 PM

And more:

5a62637bb8144_2018-01-1808_42_05.jpg.3cd6ed650f4302971f4ad19f3076b1fa.jpg 299580795_2019-03-2808_25_53.jpg.8bc7aa49c72dc8d6cd7e2898bd54f431.jpg


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#27 mikeDnight

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Posted 22 November 2019 - 01:13 PM

My big little refractor. 

 

 

Attached Thumbnails

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#28 Jeff Morgan

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Posted 22 November 2019 - 01:14 PM

So refractors seem more specialised than average sized Newtonians & SCTs, and less good for general viewing of deep sky.

 

Refractors are great for the deep sky too.

 

If you have a night vision eyepiece, they can go surprisingly deep. Check out the sketch through an 18" scope in this article:

 

https://www.cloudyni...simeis-57-r3201

 

Now this is how it looks in a 130mm refractor with a NV eyepiece:

 

IMG_2547.jpg
 
A iPhone X photo through the eyepiece, 1/3 second exposure. Quite close to the visual appearance, and no averted vision required.

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#29 The Ardent

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Posted 22 November 2019 - 01:15 PM

For Takahashi multiply by 1.3 to 1.4 to get the effective comparable aperture. For instance an FS78mm x 1.3 = 101mm. So what you have is the visual impression of a comparable 4” aperture.

The actual multiplication factor will depend on a number of variables, like location, sky conditions, visual acuity, magnification and if the user has experience with multiple telescopes.

#30 RAKing

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Posted 22 November 2019 - 01:25 PM

Most posts here are about the Moon, planets and imaging. 

 

Are refractors with their small apertures but excellent optics really only good for detailed views of solar systen objects, and for imaging?

 

I suppose as higher magnification monoculars, taking over from binoculars, the grab & go hassle free side ipof smaller sizes is good. But beyond that, refractors' apertures are limiting.

 

So refractors seem more specialised than average sized Newtonians & SCTs, and less good for general viewing of deep sky.

Sorry, but I think this is total nonsense.  Refractors are good on everything they can see and are only limited in their versatility by aperture.

 

I rarely look at the moon and planets.  I use my refractors for double stars and variable stars as well as the hundreds of bright DSO.  There are more than a lifetime's worth of great objects to view with a small refractor.

 

Cheers,

 

Ron


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#31 Jeff B

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Posted 22 November 2019 - 01:46 PM

 

Refractors are great for the deep sky too.

 

If you have a night vision eyepiece, they can go surprisingly deep. Check out the sketch through an 18" scope in this article:

 

https://www.cloudyni...simeis-57-r3201

 

Now this is how it looks in a 130mm refractor with a NV eyepiece:

 

 
 
A iPhone X photo through the eyepiece, 1/3 second exposure. Quite close to the visual appearance, and no averted vision required.

 

I've been meaning to check this stuff out.  Would they work well with achromat?

 

Jeff



#32 gwlee

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Posted 22 November 2019 - 02:03 PM

Most posts here are about the Moon, planets and imaging. 

 

Are refractors with their small apertures but excellent optics really only good for detailed views of solar systen objects, and for imaging?

 

For me, small refractors don’t offer enough magnification before they run out of exit pupil to be entirely satisfactory as a visual planetary scope, which starts around 6-8 inches in my typical seeing conditions.

 

I consider small refractors more of a third type of instrument that splits the difference between the capabilities of a handheld binocular that offers great portability and very wide fields, and a larger general purpose telescope that can go deeper for DSOs and can provide brighter high magnification views of planets. 

 

 

 

 

 


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#33 F.Meiresonne

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Posted 22 November 2019 - 02:23 PM

No!  I believe that refractors, achromats in particular, are vastly underated for lower power deep sky observing.  Inch per inch they excel at light gathering and contrast.  Even the standard Synta 6" sample achromats can provide some truly excellent, low power deep sky viewing.  My 6" F5 Jaegers certainly does.  Trouble is as the inches inch upwards in aperture, refractors can get kinda big and heavy once you get past 6" in aperture.   

 

Jeff

yes, that is true. I have a 120 mm F/5 , really nice images at low power and sharp.

 

Refractors , give a more refined image but for deepsky are very limited. If you are a deep sky lover  , like i used to be, a big newt is a good idea imo.

 

But i also think that every scope is surely usable , guess it is up to the user and the night that decide what to use. Eg if i return from work , tired, i might as well take my 70 mm for a quick look or even binoculars...

Bottom line : if you really like to observe one scope will not do...

 

It is just great that in the market you have so much opportunities these days!


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#34 Jeff Morgan

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Posted 22 November 2019 - 03:54 PM

I've been meaning to check this stuff out.  Would they work well with achromat?

 

Jeff

 

My refractors are APO's, so I can't tell you from experience.

 

Many of the guys on the EAA are using fast achromats with satisfaction. They often recommend fast achros to the guys starting out because of the lower entry cost, faster speeds, and back-focus capabilities for reducers.

 

For nebula a h-alpha filter is used, so just a narrow window is getting in. That's an easy one.

 

On other DSO's I suspect you would want to use a red long-pass to tame the chroma, but best check with some achromat users.


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#35 Redbetter

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Posted 22 November 2019 - 04:27 PM

For me, small refractors don’t offer enough magnification before they run out of exit pupil to be entirely satisfactory as a visual planetary scope, which starts around 6-8 inches in my typical seeing conditions.

Excellent point.  That is the key problem for visual high mag planetary observing, because of the way our eyes handle (or mishandle) small exit pupils, and the way exit pupil sets both image scale and brightness as well as what exit pupil means with respect to diffraction blur.  (Exit pupil is less of a concern for double stars except where companions are becoming too dim.)   A good refractor can be convenient and effective when the seeing is mediocre, but when the seeing is better it hits an exit pupil limit that makes larger aperture considerably more useful.

 

By the same token, exit pupil is the refractor's strength for wide field observing because their small aperture allows very wide fields of view with maximum illumination and image contrast. 

 

It is the middle ground (mid pupil/mid power/mid field of view) where I find refractor's least useful.  Sure I can observe all sorts of things with them, but a larger aperture obstructed scope shows so much more that I don't see much reason to use a refractor compared to other choices.  Even here there is an exception:  some open clusters.  Open clusters, especially ones that are not well differentiated from the surrounding field, are sometimes best seen in some specific aperture range. 


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#36 Wildetelescope

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Posted 22 November 2019 - 04:29 PM

Most posts here are about the Moon, planets and imaging. 

 

Are refractors with their small apertures but excellent optics really only good for detailed views of solar systen objects, and for imaging?

 

I suppose as higher magnification monoculars, taking over from binoculars, the grab & go hassle free side ipof smaller sizes is good. But beyond that, refractors' apertures are limiting.

 

So refractors seem more specialised than average sized Newtonians & SCTs, and less good for general viewing of deep sky.A

A large number of posts in ALL the scope categories involve some sort of imaging.  That is a well established trend.   It has also been often observed that refractor design has really been driven by imaging concerns as well.  Faster focal ratio, Flatter FOV, Drive toward color correction perfection.  That said, I do not think that those changes limit what one can observe visually with a refractor.  Even in light polluted areas, I find that a 4 inch refractor will reveal much on bright DSO's, and much more in dark areas.   My 6 inch refractor gave me the best visual view of Andromeda that I have seen to date from my back yard in an Orange zone.   Sure, there is more detail and brightness in my 10 inch Dob, but the 4 inch gets used more because often my time outside is in quick snippets. 

 

Cheers!

 

JMD



#37 Jon Isaacs

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Posted 22 November 2019 - 05:02 PM

The notable exceptions are large DSOs.  Things like the Double Cluster, Andromeda, the Pleiades are all fantastic in refractors.

 

There's always the Milky Way... a very interesting DSO..

 

Jon


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#38 mikeDnight

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Posted 22 November 2019 - 05:10 PM

For me, small refractors don’t offer enough magnification before they run out of exit pupil to be entirely satisfactory as a visual planetary scope, which starts around 6-8 inches in my typical seeing conditions.

 

I consider small refractors more of a third type of instrument that splits the difference between the capabilities of a handheld binocular that offers great portability and very wide fields, and a larger general purpose telescope that can go deeper for DSOs and can provide brighter high magnification views of planets. 

I've never really thought of the planet's needing very high magnification. Jupiter, Saturn and Venus are comfortably observed below X250. Mars and Mercury can be a bit more challenging but even a sub 6 second Mars can reveal albedo features under X400 in a good 4" refractor. 

58b754a7b9221_2017-03-0121_23_58.jpg.048940880aaa8695f953e27ff09a8577.jpg


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#39 mikeDnight

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Posted 22 November 2019 - 05:19 PM

Jupiter reveals a wealth of detail at medium powers.

 

2019-11-22 22.18.36.jpg

 


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#40 salico

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Posted 22 November 2019 - 05:23 PM

Mike, which Bortle Skies did you have for your DSO sketches?



#41 dscarpa

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Posted 22 November 2019 - 05:24 PM

Nope. I use my WO ZS110 and Vixen 130ED SS for all the doubles and DSOs I view with my cats. Unless Jesus says his hand upon my head I'll not be doing any imaging. David


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#42 mikeDnight

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Posted 22 November 2019 - 06:06 PM

Mike, which Bortle Skies did you have for your DSO sketches?

I've never really paid any attention to the Bortle scale. From my garden I can see the milkyway with ease directly overhead and reasonably well towards the north north east. M31 is easily visible with the naked eye but M33 needs optical aid. I'm situated on the outskirts of a small town in north west England, where although there is some light pollution, it isn't too much of a problem for me. Often, I'll observe from a blacked out run off observatory, and for dso's I often use a blackout hood to block any stray light.

I suppose my Bortle sky is between 6 & 5, but taking measures to maximise my dark adaption can really pay dividends. 

 

1553711713629_IMG_0598.JPG


Edited by mikeDnight, 22 November 2019 - 06:10 PM.

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#43 punk35

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Posted 22 November 2019 - 07:36 PM

Since my main scope for the last 15 or so years has been a 4” refractor, I use it for everything I think I might be able to see/find with it. I actually feel More rewarded viewing DSO’s, even if they’re bright, with my small telescope.  Finding that granulated ball of light, and what it represents,  M81/82 in the same field, or Orion stretching across the fov is very rewarding to me. 


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#44 JIMZ7

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Posted 22 November 2019 - 07:58 PM

. . . depends on who's using the refractor and what their sky is like.

 

I own several refractors.  Each of mine might, possibly, have been used more often for visual deep-sky observation than for any other purpose.  I consider all my refractors to be multi-purpose visual instruments -- suitable for solar, lunar, planetary, and deep-sky visual use.

 

If a 1-inch refractor can provide deep-sky views like the following, what do you suppose could be seen with a 2-inch, 3-inch, 4-inch, etc?

 

 
 
 
 
 
 
 
 
 

 

So far I've observed 83 Messier objects with only 1-inch of (refractor) aperture.  Soon I expect to "catch" most, if not all, of those that remain.

I read somewhere Galileo's famous 30mm refractor was "stopped down or mask" to 15mm to make it sharper & less CA. He didn't have great eyepieces to choose from of course.

Jim



#45 Shorty Barlow

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Posted 22 November 2019 - 08:05 PM

Since my main scope for the last 15 or so years has been a 4” refractor, I use it for everything I think I might be able to see/find with it. I actually feel More rewarded viewing DSO’s, even if they’re bright, with my small telescope.  Finding that granulated ball of light, and what it represents,  M81/82 in the same field, or Orion stretching across the fov is very rewarding to me. 

Your AT102ED seems very similar to my 102mm Altair Starwave.

 

med_gallery_249298_10284_39846.jpg

 

F/7 ED refractors like these are superb all rounders if you ask me.


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#46 gwlee

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Posted 22 November 2019 - 09:51 PM

I've never really thought of the planet's needing very high magnification. Jupiter, Saturn and Venus are comfortably observed below X250. Mars and Mercury can be a bit more challenging but even a sub 6 second Mars can reveal albedo features under X400 in a good 4" refractor. 

attachicon.gif 58b754a7b9221_2017-03-0121_23_58.jpg.048940880aaa8695f953e27ff09a8577.jpg

To clarify, the seeing here usually supports no more than about 150-200x, so that’s about the magnification range that I typically want to use for planets here. Achieving 150-200x without reducing exit pupil below 1mm requires at least a 6 to 8 inch scope.

 

That’s the reason, I don’t consider any 4 inch scope an entirely satisfactory planetary scope: for me, a 4 inch scope starts to run out of usable exit pupil at about 100x. 
 

 

 


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#47 Tyson M

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Posted 22 November 2019 - 10:06 PM

Refractors are my favorite lunar and solar scopes, but for planets you need aperture. 

 

Aesthetics would show that they excel as open clusters sweepers, as well as large extended nebula. Double stars are beautiful as well.


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#48 Shorty Barlow

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Posted 22 November 2019 - 10:35 PM

 

That’s the reason, I don’t consider any 4 inch scope an entirely satisfactory planetary scope: for me, a 4 inch scope starts to run out of usable exit pupil at about 100x. 
 

I can get about 143x (5mm EP) out of my 102mm Starwave for about an 0.7mm exit pupil. That's not bad.



#49 F.Meiresonne

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Posted 23 November 2019 - 05:24 AM

To clarify, the seeing here usually supports no more than about 150-200x, so that’s about the magnification range that I typically want to use for planets here. Achieving 150-200x without reducing exit pupil below 1mm requires at least a 6 to 8 inch scope.

 

That’s the reason, I don’t consider any 4 inch scope an entirely satisfactory planetary scope: for me, a 4 inch scope starts to run out of usable exit pupil at about 100x. 
 

I have the same issue.Rare nights that go over 200x ..Allthough sometimes ...I remember one night years ago in the Dutch countryside just over the Belgian border we stood there observing. My Obsession with my friends N5T6 on Saturn and tack sharp and steady ,450x...best view ever of Saturn



#50 Scott Beith

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Posted 23 November 2019 - 06:24 AM

Although I am a SLAP observer (Solar, Lunar, and Planetary), like others have mentioned, I find my little refractors are great with the larger objects (M31, the DC, M45, M81/M82 in the same FOV) in the night sky as well as some of the smallest (double stars).

 

One thing I believe my smallest refractor does best is sweeping the Milky Way and taking in a really big chunk of sky with a 35 Panoptic.  It is a very relaxing way to spend an evening when I don't feel like cranking up the magnification.

 

Comets are excellent targets for refractors due to their high contrast.

 

One thing I didn't see anyone post is asterisms like the Coathanger.  I think a refractor presents them better than other designs due to the tight stars.

 

Bigger scopes will show more detail, but high quality refractors seem to show what they show better if that makes sense.  

 

 

That said - a C14 Edge will be my retirement scope when I get out of the city and move to a dark site.  


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