<p><a href="https://solarsystem.nasa.gov/resources/13794/titan-beyond-the-rings/" rel="noreferrer">This NASA page</a> says this photo was taken on April 28 2006.</p>

<p>Using <a href="https://celestia.space/" rel="noreferrer">Celestia</a>, I managed to find the picture from Cassini that best lines up with the photo. It doesn't match up precisely, but that's to be expected as the calculated orbital elements of all these moons (and cassini) in the software won't necessarily match up to reality precisely.
<a href="https://i.sstatic.net/y3bvs.jpg" rel="noreferrer"><img src="https://i.sstatic.net/y3bvs.jpg" alt="cassini celestia shot of titan"></a></p>

<p>Below is the zoomed out version of this shot. You can see Titan in the centre and Epimetheus as a dot on top.
<a href="https://i.sstatic.net/CgA1d.jpg" rel="noreferrer"><img src="https://i.sstatic.net/CgA1d.jpg" alt="enter image description here"></a>
And here is the top down shot from Cassini to the moons. Circled are Epimetheus and Titan.
<a href="https://i.sstatic.net/gaaPZ.jpg" rel="noreferrer"><img src="https://i.sstatic.net/gaaPZ.jpg" alt="enter image description here"></a></p>

<p>So to answer your question: Titan is really big compared to epimetheus (about 50x), Titan has an atmosphere and so appears fuzzy (It is actually in focus, everything in space is very far away and so is effectively at infinity for focusing purposes), and the rings are highly oblique, so you only see a small slice of them.</p>

CC BY-SA 4.0
2019-03-29T09:08:05.517Z
Very nice, but we're only half-way there. I've added a cropped version and drawn a rectangle that highlights the rings being almost 40% wider near the left limb of Titan than the right limb. Are you able to adjust the POV of your simulation and make this happen as well? Right now the section of the rings you're showing is so small that there's no slope.
uhoh
CC BY-SA 4.0
2019-03-29T09:16:25.517Z
https://photojournal.jpl.nasa.gov/catalog/PIA08391 and http://ciclops.org/iss/iss.php?js=1
uhoh
CC BY-SA 4.0
2019-03-29T09:28:44.643Z
It's not about the POV, it's about the accuracy of the orbital data in Celestia. There were two conjunctions of epimetheus and Titan on april 28, 2006 from the view of titan, one too early (the one pictured) and one too late (the rings were no longer in view). AFAIK, Celestia does use a database of precise orbital information rather than just using keplerian ellipses, but I guess even that isn't accurate enough to recreate this photo (saturn's moons have very complex orbits). If anybody has other software that tracks these objects with more precision, they're welcome to post an updated answer.
Ingolifs
CC BY-SA 4.0
2019-03-29T09:46:33.680Z
I did a [quick plot](https://astronomy.stackexchange.com/a/30166/7982) . It looks like the distances only match up around `08:30 UTC`. I have a hunch that through the tiny 0.35 degree FOV of the narrow-angle camera we're looking at the very outer edge of an inner ring, which is why it's getting narrow so rapidly.
uhoh
CC BY-SA 4.0
2019-03-29T17:29:34.260Z
Celestia shows me the Encke division in line with the Titan terminator at 08:18 UTC.
Mike G
CC BY-SA 4.0
2019-03-29T20:34:19.090Z
I should have remembered. Epimetheus has a [https://en.wikipedia.org/wiki/Horseshoe_orbit](horseshoe orbit). That's presumably why it's so inaccurate.
Ingolifs
CC BY-SA 4.0
2019-03-29T08:39:15.857Z
2019-03-29T08:39:15.857Z
Ingolifs
<p><strong>note:</strong> This is a supplemental answer adding some details to @ Ingolifs' <a href="https://astronomy.stackexchange.com/a/30164/7982">excellent answer</a>.</p>

<hr>

<p>At <em>roughly</em> <code>2006-Apr-28 08:30 UTC</code> Cassini was both 1,800,000 km from Titan and 667,000 km from Epimetheus at the same time. </p>

<p>I used JPL's <a href="https://ssd.jpl.nasa.gov/horizons.cgi" rel="noreferrer">Horizons</a> and saved the positions in the Saturn body centered coordinates every 5 minutes then ran the python script below to plot. I am not sure how to get the plane of the rings this way easily.</p>

<p><a href="https://i.sstatic.net/dCZzp.png" rel="noreferrer"><img src="https://i.sstatic.net/dCZzp.png" alt="enter image description here"></a></p>

<p><a href="https://i.sstatic.net/pRU08.png" rel="noreferrer"><img src="https://i.sstatic.net/pRU08.png" alt="enter image description here"></a></p>

<pre><code>class Body(object):
    def __init__(self, name):
        self.name = name

import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D

fnames = ['Titan photo Cassini horizons_results.txt',
          'Titan photo Titan horizons_results.txt',
          'Titan photo Epimetheus horizons_results.txt' ]

names  = ['Cassini', 'Titan', 'Epimetheus']

bodies = []

for name, fname in zip(names, fnames):

    with open(fname, 'r') as infile:

        lines = infile.read().splitlines()

    iSOE = [i for i, line in enumerate(lines) if "<span class="math-container">$$SOE" in line][0]
    iEOE = [i for i, line in enumerate(lines) if "$$</span>EOE" in line][0]

    print iSOE, iEOE, lines[iSOE], lines[iEOE]

    lines = zip(*[line.split(',') for line in lines[iSOE+1:iEOE]])

    JD  = np.array([float(x) for x in lines[0]])
    pos = np.array([[float(x) for x in lines[i]] for i in 2, 3, 4])
    vel = np.array([[float(x) for x in lines[i]] for i in 5, 6, 7])

    body = Body(name)
    bodies.append(body)
    body.JD  = JD
    body.pos = pos
    body.vel = vel

Cassini, Titan, Epimetheus = bodies

r_Titan      = np.sqrt(((Cassini.pos - Titan.pos     )**2).sum(axis=0))
r_Epimetheus = np.sqrt(((Cassini.pos - Epimetheus.pos)**2).sum(axis=0))

hours = 24 * (JD - JD[0])

r_Titan_target      = 1.8E+06 
r_Epimetheus_target = 6.67E+05

hours_Titan      = hours[np.argmax(r_Titan &lt; r_Titan_target)]
hours_Epimetheus = hours[np.argmax(r_Epimetheus[30:] &gt; r_Epimetheus_target)+30]

print hours_Titan, hours_Epimetheus
if True:    
    fig = plt.figure()

    plt.subplot(2, 1, 1)
    plt.plot(hours, r_Titan)
    plt.plot(hours, 1.8E+06 * np.ones_like(r_Titan), '-k')
    plt.ylabel('Cassini-Titan distance (km)', fontsize=16)

    plt.subplot(2, 1, 2)
    plt.plot(hours, r_Epimetheus)
    plt.plot(hours, 6.67E+05 * np.ones_like(r_Epimetheus), '-k')
    plt.ylabel('Cassini-Epimetheus distance (km)', fontsize=16)
    plt.xlabel('2006-Apr-28 hours', fontsize=16)

    plt.show()
</code></pre>

CC BY-SA 4.0
2019-03-29T10:30:21.413Z
If I set observer location to Epimetheus, then Titan and Cassini have opposite RA at 08:13 UTC. [Solar System Simulator](https://space.jpl.nasa.gov/) matches the image at [08:12](https://space.jpl.nasa.gov/cgi-bin/wspace?tbody=606&vbody=-82&month=4&day=28&year=2006&hour=08&minute=12&rfov=45&fovmul=-1&bfov=30&showac=1).
Mike G
CC BY-SA 4.0
2019-03-29T10:36:10.280Z
@MikeG that's good news! Can you add an answer with a screen shot?
uhoh
CC BY-SA 4.0
2019-03-29T09:44:56.973Z
2019-03-29T09:50:35.217Z
2019-03-29T09:50:35.217Z
uhoh
<p>The JPL <a href="https://space.jpl.nasa.gov/" rel="noreferrer">Solar System Simulator</a> doesn't show Epimetheus but does show Titan behind the Encke gap at 2006-04-28 08:12 UTC.</p>

<p><a href="https://i.sstatic.net/h0uBz.jpg" rel="noreferrer"><img src="https://i.sstatic.net/h0uBz.jpg" alt="Titan at 08:12, narrow field"></a></p>

<p>The simulated surface texture is probably composed of
<a href="https://photojournal.jpl.nasa.gov/catalog/PIA21923" rel="noreferrer">VIMS images</a>
in infrared wavelengths where Titan's atmosphere is relatively transparent.
On the real Titan, haze scatters visible light so strongly that the surface is indistinct and the edge looks fuzzy.</p>

<p>If we zoom out, we see that we are looking near the outer edge of the rings at a very shallow angle.
This is why they cover less than half of Titan's 10-arcminute apparent diameter.</p>

<p>Since Epimetheus appears above the rings while we are looking from below, it must be in front of them.</p>

<p><a href="https://i.sstatic.net/7ggTn.jpg" rel="noreferrer"><img src="https://i.sstatic.net/7ggTn.jpg" alt="Titan at 08:12, wide field"></a></p>

<p><em>Simulated images courtesy NASA/JPL-Caltech</em></p>

CC BY-SA 4.0
2019-03-29T22:10:36.410Z
Wow I had no idea that JPL had such a Solar System Simulator website.  These are quit helpful, thanks!
uhoh
CC BY-SA 4.0
2019-03-29T19:24:58.190Z
2019-03-30T13:52:11.140Z
2019-03-30T13:52:11.140Z
Mike G
<p>The NY Times article <a href="https://www.nytimes.com/2019/03/28/science/saturn-moons-rings.html" rel="noreferrer">Saturn’s Rings Are Sculpted by a Crew of Mini-Moons</a> is really interesting and links to the recent paywalled paper in Science <a href="http://science.sciencemag.org/content/early/2019/03/27/science.aat2349" rel="noreferrer">Close Cassini flybys of Saturn’s ring moons Pan, Daphnis, Atlas, Pandora, and Epimetheus</a></p>

<p>But I absolutely can't understand one of the photos in the NY Times article, shown below. Titan seems to be...</p>

<ol>
<li><em>behind</em> Saturn's rings, and yet it is</li>
<li><em>huge</em> relative the spacing of the rings, and yet it</li>
<li>appears to be <em>out of focus</em> while the rings and Epimetheus are in focus.</li>
</ol>

<p>Can someone help me understand how all of these can be true at the same time?</p>

<hr>

<blockquote>
  <p>In the foreground, the moon Epimetheus appearing to hover above Saturn's rings. Epimetheus is dwarfed by Titan in the background.CreditNASA/JPL/Space Science Institute</p>
</blockquote>

<p><a href="https://i.sstatic.net/SyQn5.jpg" rel="noreferrer"><img src="https://i.sstatic.net/SyQn5.jpg" alt="Epimetheus, Titan and Saturn&#39;s Rings"></a></p>

<p><a href="https://i.sstatic.net/6UBhU.png" rel="noreferrer"><img src="https://i.sstatic.net/6UBhU.png" alt="Epimetheus, Titan and Saturn&#39;s Rings cropped"></a></p>

CC BY-SA 4.0
2019-03-30T00:05:22.217Z
Something that might contribute to this illusion is the extremely narrow angle used. I know Titan is much farther away than the rings, so I intuitively expect it to look much smaller than it is, so it looks enormous in this picture. Because the focal length of the camera is so high, Titan isn't actually that much bigger than it appears.
DarthFennec
CC BY-SA 4.0
2019-03-30T00:30:19.267Z
@DarthFennec yes, the 2nd link in [this comment](https://astronomy.stackexchange.com/questions/30162/help-understanding-this-unsettling-image-of-titan-epimetheus-and-saturns-ring?noredirect=1#comment55141_30164) shows that the FOV for this photo is only about 0.35 degrees.
uhoh
CC BY-SA 4.0
2019-03-30T20:55:12.673Z
How are the rings so thin if the moons appear to have vastly different inclinations? That's what looks strange to me.
Mazura
CC BY-SA 4.0
2019-03-31T17:43:24.747Z
Beautiful, stunning image. In case you haven't seen it I would like to recommend [Carolyn Porco's classic TED talk about Cassini.](https://www.ted.com/talks/carolyn_porco_flies_us_to_saturn) It's well worth watching; she puts things in perspective ;-).
Peter - Reinstate Monica
<photography><saturn><cassini><saturn-rings>
Help understanding this unsettling image of Titan, Epimetheus, and Saturn's rings?
uhoh
# Help understanding this unsettling image of Titan, Epimetheus, and Saturn's rings?

(Asked by: username_0 on 2019-03-29)

The NY Times article [Saturn’s Rings Are Sculpted by a Crew of Mini-Moons](https://www.nytimes.com/2019/03/28/science/saturn-moons-rings.html) is really interesting and links to the recent paywalled paper in Science [Close Cassini flybys of Saturn’s ring moons Pan, Daphnis, Atlas, Pandora, and Epimetheus](http://science.sciencemag.org/content/early/2019/03/27/science.aat2349)

But I absolutely can't understand one of the photos in the NY Times article, shown below. Titan seems to be...

1. *behind* Saturn's rings, and yet it is
2. *huge* relative the spacing of the rings, and yet it
3. appears to be *out of focus* while the rings and Epimetheus are in focus.

Can someone help me understand how all of these can be true at the same time?

---

> In the foreground, the moon Epimetheus appearing to hover above Saturn's rings. Epimetheus is dwarfed by Titan in the background.CreditNASA/JPL/Space Science Institute

[![Epimetheus, Titan and Saturn's Rings](https://i.sstatic.net/SyQn5.jpg)](https://i.sstatic.net/SyQn5.jpg)

[![Epimetheus, Titan and Saturn's Rings cropped](https://i.sstatic.net/6UBhU.png)](https://i.sstatic.net/6UBhU.png)

**Tags:** photography, saturn, cassini, saturn-rings
> **Comments:**
> **username_1**: Something that might contribute to this illusion is the extremely narrow angle used. I know Titan is much farther away than the rings, so I intuitively expect it to look much smaller than it is, so it looks enormous in this picture. Because the focal length of the camera is so high, Titan isn't actually that much bigger than it appears.  
> **username_0**: @DarthFennec yes, the 2nd link in [this comment](https://astronomy.stackexchange.com/questions/30162/help-understanding-this-unsettling-image-of-titan-epimetheus-and-saturns-ring?noredirect=1#comment55141_30164) shows that the FOV for this photo is only about 0.35 degrees.  
> **username_2**: How are the rings so thin if the moons appear to have vastly different inclinations? That's what looks strange to me.  
> **username_3**: Beautiful, stunning image. In case you haven't seen it I would like to recommend [Carolyn Porco's classic TED talk about Cassini.](https://www.ted.com/talks/carolyn_porco_flies_us_to_saturn) It's well worth watching; she puts things in perspective ;-).  

---

## 3 answers

### Answer by username_5 on 2019-03-29. Score: 12 | Accepted answer

The JPL [Solar System Simulator](https://space.jpl.nasa.gov/) doesn't show Epimetheus but does show Titan behind the Encke gap at 2006-04-28 08:12 UTC.

[![Titan at 08:12, narrow field](https://i.sstatic.net/h0uBz.jpg)](https://i.sstatic.net/h0uBz.jpg)

The simulated surface texture is probably composed of
[VIMS images](https://photojournal.jpl.nasa.gov/catalog/PIA21923)
in infrared wavelengths where Titan's atmosphere is relatively transparent.
On the real Titan, haze scatters visible light so strongly that the surface is indistinct and the edge looks fuzzy.

If we zoom out, we see that we are looking near the outer edge of the rings at a very shallow angle.
This is why they cover less than half of Titan's 10-arcminute apparent diameter.

Since Epimetheus appears above the rings while we are looking from below, it must be in front of them.

[![Titan at 08:12, wide field](https://i.sstatic.net/7ggTn.jpg)](https://i.sstatic.net/7ggTn.jpg)

*Simulated images courtesy NASA/JPL-Caltech*

> **Comments:**
> **username_0**: Wow I had no idea that JPL had such a Solar System Simulator website.  These are quit helpful, thanks!  

---

### Answer by username_4 on 2019-03-29. Score: 30

[This NASA page](https://solarsystem.nasa.gov/resources/13794/titan-beyond-the-rings/) says this photo was taken on April 28 2006.

Using [Celestia](https://celestia.space/), I managed to find the picture from Cassini that best lines up with the photo. It doesn't match up precisely, but that's to be expected as the calculated orbital elements of all these moons (and cassini) in the software won't necessarily match up to reality precisely.
[![cassini celestia shot of titan](https://i.sstatic.net/y3bvs.jpg)](https://i.sstatic.net/y3bvs.jpg)

Below is the zoomed out version of this shot. You can see Titan in the centre and Epimetheus as a dot on top.
[![enter image description here](https://i.sstatic.net/CgA1d.jpg)](https://i.sstatic.net/CgA1d.jpg)
And here is the top down shot from Cassini to the moons. Circled are Epimetheus and Titan.
[![enter image description here](https://i.sstatic.net/gaaPZ.jpg)](https://i.sstatic.net/gaaPZ.jpg)

So to answer your question: Titan is really big compared to epimetheus (about 50x), Titan has an atmosphere and so appears fuzzy (It is actually in focus, everything in space is very far away and so is effectively at infinity for focusing purposes), and the rings are highly oblique, so you only see a small slice of them.

> **Comments:**
> **username_0**: Very nice, but we're only half-way there. I've added a cropped version and drawn a rectangle that highlights the rings being almost 40% wider near the left limb of Titan than the right limb. Are you able to adjust the POV of your simulation and make this happen as well? Right now the section of the rings you're showing is so small that there's no slope.  
> **username_0**: https://photojournal.jpl.nasa.gov/catalog/PIA08391 and http://ciclops.org/iss/iss.php?js=1  
> **username_4**: It's not about the POV, it's about the accuracy of the orbital data in Celestia. There were two conjunctions of epimetheus and Titan on april 28, 2006 from the view of titan, one too early (the one pictured) and one too late (the rings were no longer in view). AFAIK, Celestia does use a database of precise orbital information rather than just using keplerian ellipses, but I guess even that isn't accurate enough to recreate this photo (saturn's moons have very complex orbits). If anybody has other software that tracks these objects with more precision, they're welcome to post an updated answer.  
> **username_0**: I did a [quick plot](https://astronomy.stackexchange.com/a/30166/7982) . It looks like the distances only match up around `08:30 UTC`. I have a hunch that through the tiny 0.35 degree FOV of the narrow-angle camera we're looking at the very outer edge of an inner ring, which is why it's getting narrow so rapidly.  
> **username_5**: Celestia shows me the Encke division in line with the Titan terminator at 08:18 UTC.  
> **username_4**: I should have remembered. Epimetheus has a [https://en.wikipedia.org/wiki/Horseshoe_orbit](horseshoe orbit). That's presumably why it's so inaccurate.  

---

### Answer by username_0 on 2019-03-29. Score: 6

note: This is a supplemental answer adding some details to @ Ingolifs' excellent answer.

At roughly 2006-Apr-28 08:30 UTC Cassini was both 1,800,000 km from Titan and 667,000 km from Epimetheus at the same time. 
I used JPL's Horizons and saved the positions in the Saturn body centered coordinates every 5 minutes then ran the python script below to plot. I am not sure how to get the plane of the rings this way easily.


class Body(object):
    def __init__(self, name):
        self.name = name

import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D

fnames = ['Titan photo Cassini horizons_results.txt',
          'Titan photo Titan horizons_results.txt',
          'Titan photo Epimetheus horizons_results.txt' ]

names  = ['Cassini', 'Titan', 'Epimetheus']

bodies = []

for name, fname in zip(names, fnames):

    with open(fname, 'r') as infile:

        lines = infile.read().splitlines()

    iSOE = [i for i, line in enumerate(lines) if "$$SOE" in line][0]
    iEOE = [i for i, line in enumerate(lines) if "$$EOE" in line][0]

    print iSOE, iEOE, lines[iSOE], lines[iEOE]

    lines = zip(*[line.split(',') for line in lines[iSOE+1:iEOE]])

    JD  = np.array([float(x) for x in lines[0]])
    pos = np.array([[float(x) for x in lines[i]] for i in 2, 3, 4])
    vel = np.array([[float(x) for x in lines[i]] for i in 5, 6, 7])

    body = Body(name)
    bodies.append(body)
    body.JD  = JD
    body.pos = pos
    body.vel = vel

Cassini, Titan, Epimetheus = bodies

r_Titan      = np.sqrt(((Cassini.pos - Titan.pos     )**2).sum(axis=0))
r_Epimetheus = np.sqrt(((Cassini.pos - Epimetheus.pos)**2).sum(axis=0))

hours = 24 * (JD - JD[0])

r_Titan_target      = 1.8E+06 
r_Epimetheus_target = 6.67E+05

hours_Titan      = hours[np.argmax(r_Titan < r_Titan_target)]
hours_Epimetheus = hours[np.argmax(r_Epimetheus[30:] > r_Epimetheus_target)+30]

print hours_Titan, hours_Epimetheus
if True:    
    fig = plt.figure()

    plt.subplot(2, 1, 1)
    plt.plot(hours, r_Titan)
    plt.plot(hours, 1.8E+06 * np.ones_like(r_Titan), '-k')
    plt.ylabel('Cassini-Titan distance (km)', fontsize=16)

    plt.subplot(2, 1, 2)
    plt.plot(hours, r_Epimetheus)
    plt.plot(hours, 6.67E+05 * np.ones_like(r_Epimetheus), '-k')
    plt.ylabel('Cassini-Epimetheus distance (km)', fontsize=16)
    plt.xlabel('2006-Apr-28 hours', fontsize=16)

    plt.show()

> **Comments:**
> **username_5**: If I set observer location to Epimetheus, then Titan and Cassini have opposite RA at 08:13 UTC. [Solar System Simulator](https://space.jpl.nasa.gov/) matches the image at [08:12](https://space.jpl.nasa.gov/cgi-bin/wspace?tbody=606&vbody=-82&month=4&day=28&year=2006&hour=08&minute=12&rfov=45&fovmul=-1&bfov=30&showac=1).  
> **username_0**: @MikeG that's good news! Can you add an answer with a screen shot?  

---

