<p>If you have a good camera, a steady hand, good conditions and a lot of patience, you might.</p>
<p>The <a href="https://esahubble.org/images/heic1920a/" rel="noreferrer">Sunburst Arc</a>, at a magnitude of around 17, has been observed with a 132mm refractor by Ian Woodward at astrofotato.blog, by stacking more than 22 hours of exposure with his camera.</p>
<p><img src="https://i0.wp.com/astrofotato.blog/wp-content/uploads/2021/04/LRGB_SCNR-architectural-scale-6_00x-gigapixel.jpg" alt="The Sunburst Arc as seen by Ian Woodward." /></p>

CC BY-SA 4.0
2022-05-23T19:11:24.140Z
*Beautiful!* Nicely done! Some amateurs have reflectors with ten times the aperture area which naively suggests one tenth the exposure time. But for very low *surface brightness objects* very close to bright objects refractors have the advantage of unobstructed apertures so no diffraction from secondary mirrors and/or their supporting structure and much less scattered light from optical surface imperfections, cf. [Dragonfly](https://astronomy.stackexchange.com/q/18074/7982) and [TESS](https://astronomy.stackexchange.com/q/39572/7982)
uhoh
CC BY-SA 4.0
2022-05-23T19:11:54.920Z
and [What are the benefits of a large refracting telescope?](https://astronomy.stackexchange.com/q/34235/7982)
uhoh
CC BY-SA 4.0
2022-05-23T18:42:17.870Z
2022-05-23T18:42:17.870Z
Thriveth
<p>The cosmic horseshoe is beyond amateur instruments. It is a magnitude 20 object. In a large (2.5 m) professional telescope it looks like:</p>
<p><a href="https://i.sstatic.net/SvMcO.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/SvMcO.png" alt="enter image description here" /></a></p>
<p>This image taken from the SDSS III data.  It is small (10'', half the size of Mars at opposition) but that is not insurmountable for amateur equipment. But is it very dim.  If an object like this was visible in moderate telescopes, it would have been found long ago.  It is really only the sky surveys, and computerised searches of the survey data that allows for such objects to be found.</p>
<p>Processsing the SDSS data can bring out more detail, as can be found on the discovery paper <a href="https://arxiv.org/pdf/0706.2326.pdf" rel="nofollow noreferrer">https://arxiv.org/pdf/0706.2326.pdf</a></p>
<p>While this isn't visible, another example of gravitational lensing can be: the <em>Einstein cross</em> is a gravitationally lensed quasar, and it is at the limits of amateur equipment.  It is even smaller, but as it is composed of four point-sources it can be seen. <a href="https://observing.skyhound.com/archives/sep/Q2237+0305A.html" rel="nofollow noreferrer">Skyhound</a> recommends at least 18 in telescope, but practically 24'' to see the four components, exceptional dark skies, fully adapted eyes and perfect conditions (especially perfect seeing: this object is small). Your reward for this is &quot;four smudges of light embedded in the galaxy&quot; The <a href="http://www.wikisky.org/?ra=22.67508300000001&amp;de=3.358611&amp;zoom=14&amp;show_grid=1&amp;show_constellation_lines=1&amp;show_constellation_boundaries=1&amp;show_const_names=0&amp;show_galaxies=1&amp;img_source=SDSS" rel="nofollow noreferrer">SDSS view</a> gives an indication of how hard this object is.</p>

CC BY-SA 4.0
2021-05-15T19:41:33.227Z
But "to observe" doesn't necessarily mean by passive instruments. Lots of amateurs do astrophotography which might be able to image some objects too dim for human eyes.
Ruslan
CC BY-SA 4.0
2021-05-27T13:19:19.227Z
Update: Mike Merrifield managed to image QSO0957+561 with his telescope: https://www.youtube.com/watch?v=nLSBGuPm-DQ :)
2080
CC BY-SA 4.0
2022-05-23T19:15:03.723Z
@2080 consider posting that as an answer, it will nicely complement [this answer](https://astronomy.stackexchange.com/a/49423/7982)
uhoh
CC BY-SA 4.0
2021-05-01T15:16:52.800Z
2021-05-02T07:57:02.763Z
2021-05-02T07:57:02.763Z
James K
<p>Strong gravitational lens systems like the <a href="https://en.wikipedia.org/wiki/Cosmic_Horseshoe" rel="noreferrer">Cosmic Horseshoe</a> have been imaged by scientific space telescopes, but have any amateur astronomers accomplished this?</p>
<p>Or are amateur/small ground based telescopes not suited for this?</p>

CC BY-SA 4.0
2021-05-01T15:08:28.390Z
*Cool question!*
uhoh
CC BY-SA 4.0
2021-05-02T21:51:13.640Z
I would not have been so quick to accept an answer. I usually give it a week or longer to let the whole community have a chance to think about the question. Just because a few famous objects are far and dim does not mean it's impossible to see something closer and brighter. For example, [these little telescopes](https://astronomy.stackexchange.com/q/43520/7982) discovered a particularly interesting type of black hole in our neighborhood. Why not wait for an answer that discusses what's possible from a scientific viewpoint, rather than a "here's two you can't see" answer?
uhoh
CC BY-SA 4.0
2021-05-03T06:28:24.723Z
I can still accept a new answer, but I found that this one showed a major limiting factor, the apparent magnitude. I found this list of gravitational lenses and it suggests that the Einstein Cross seems to be the best there is right now in this regard: https://lweb.cfa.harvard.edu/castles/
2080
CC BY-SA 4.0
2022-05-23T22:57:27.780Z
I remeber seeing a photo in an astrophotography newsgroup (long ago) of one of the Abell clusters showing obvious lensing.  He said he spent two weeks in the desert in his RV taking it.
Greg Miller
<telescope><amateur-observing><gravitational-lensing>
Is it possible to observe strong gravitational lensing with amateur telescopes?
2080
# Is it possible to observe strong gravitational lensing with amateur telescopes?

(Asked by: username_0 on 2021-05-01)

Strong gravitational lens systems like the [Cosmic Horseshoe](https://en.wikipedia.org/wiki/Cosmic_Horseshoe) have been imaged by scientific space telescopes, but have any amateur astronomers accomplished this?

Or are amateur/small ground based telescopes not suited for this?

**Tags:** telescope, amateur-observing, gravitational-lensing

> **Comments:**
> **username_1**: *Cool question!*  
> **username_1**: I would not have been so quick to accept an answer. I usually give it a week or longer to let the whole community have a chance to think about the question. Just because a few famous objects are far and dim does not mean it's impossible to see something closer and brighter. For example, [these little telescopes](https://astronomy.stackexchange.com/q/43520/7982) discovered a particularly interesting type of black hole in our neighborhood. Why not wait for an answer that discusses what's possible from a scientific viewpoint, rather than a "here's two you can't see" answer?  
> **username_0**: I can still accept a new answer, but I found that this one showed a major limiting factor, the apparent magnitude. I found this list of gravitational lenses and it suggests that the Einstein Cross seems to be the best there is right now in this regard: https://lweb.cfa.harvard.edu/castles/  
> **username_2**: I remeber seeing a photo in an astrophotography newsgroup (long ago) of one of the Abell clusters showing obvious lensing.  He said he spent two weeks in the desert in his RV taking it.  

---

## 2 answers

### Answer by username_4 on 2021-05-01. Score: 11 | Accepted answer

The cosmic horseshoe is beyond amateur instruments. It is a magnitude 20 object. In a large (2.5 m) professional telescope it looks like:

[![enter image description here](https://i.sstatic.net/SvMcO.png)](https://i.sstatic.net/SvMcO.png)

This image taken from the SDSS III data. It is small (10'', half the size of Mars at opposition) but that is not insurmountable for amateur equipment. But is it very dim. If an object like this was visible in moderate telescopes, it would have been found long ago. It is really only the sky surveys, and computerised searches of the survey data that allows for such objects to be found.

Processsing the SDSS data can bring out more detail, as can be found on the discovery paper <https://arxiv.org/pdf/0706.2326.pdf>

While this isn't visible, another example of gravitational lensing can be: the *Einstein cross* is a gravitationally lensed quasar, and it is at the limits of amateur equipment. It is even smaller, but as it is composed of four point-sources it can be seen. [Skyhound](https://observing.skyhound.com/archives/sep/Q2237+0305A.html) recommends at least 18 in telescope, but practically 24'' to see the four components, exceptional dark skies, fully adapted eyes and perfect conditions (especially perfect seeing: this object is small). Your reward for this is "four smudges of light embedded in the galaxy" The [SDSS view](http://www.wikisky.org/?ra=22.67508300000001&de=3.358611&zoom=14&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=0&show_galaxies=1&img_source=SDSS) gives an indication of how hard this object is.

> **Comments:**
> **username_5**: But "to observe" doesn't necessarily mean by passive instruments. Lots of amateurs do astrophotography which might be able to image some objects too dim for human eyes.  
> **username_0**: Update: Mike Merrifield managed to image QSO0957+561 with his telescope: https://www.youtube.com/watch?v=nLSBGuPm-DQ :)  
> **username_1**: @username_0 consider posting that as an answer, it will nicely complement [this answer](https://astronomy.stackexchange.com/a/49423/7982)  

---

### Answer by username_3 on 2022-05-23. Score: 7

If you have a good camera, a steady hand, good conditions and a lot of patience, you might.

The [Sunburst Arc](https://esahubble.org/images/heic1920a/), at a magnitude of around 17, has been observed with a 132mm refractor by Ian Woodward at astrofotato.blog, by stacking more than 22 hours of exposure with his camera.

![The Sunburst Arc as seen by Ian Woodward.](https://i0.wp.com/astrofotato.blog/wp-content/uploads/2021/04/LRGB_SCNR-architectural-scale-6_00x-gigapixel.jpg)

> **Comments:**
> **username_1**: *Beautiful!* Nicely done! Some amateurs have reflectors with ten times the aperture area which naively suggests one tenth the exposure time. But for very low *surface brightness objects* very close to bright objects refractors have the advantage of unobstructed apertures so no diffraction from secondary mirrors and/or their supporting structure and much less scattered light from optical surface imperfections, cf. [Dragonfly](https://astronomy.stackexchange.com/q/18074/7982) and [TESS](https://astronomy.stackexchange.com/q/39572/7982)  
> **username_1**: and [What are the benefits of a large refracting telescope?](https://astronomy.stackexchange.com/q/34235/7982)  

---

