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Miranda and the Four Other Moons of Uranus

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#1 james7ca

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Posted 23 September 2019 - 07:10 AM

A few weeks ago during the full moon I did an update to the PEC curves on my mount (not the story here). Then, not wanting to waste the remainder of a night of clear weather I decided to go after some targets that would not suffer (much) under the bright, full-moon skies. I ended up taking some images of both Uranus and Neptune using a Stellarvue SV80ST2 80mm refractor with a ZWO ASI178MM camera. I didn't expect to record any surface details, but I thought it could be interesting to image the moons.

 

So, job done and when looking at the images I wondered whether it would be possible to record more of the moons using a larger scope or with longer integration times. I decided that Neptune was a no-go since after Triton (magnitude 13.6) the next brightest moon was Nereid with a current magnitude of 18.7 (possible, but maybe not easy under the full moon or my normal red/orange zone light pollution).

 

However, Uranus has four moons that are all fairly easy and I did record all of those with the SV80. Then I started wondering about the moon Miranda that was discovered in 1948 using McDonald Observatory's 82-inch reflector which was at that time the second largest operational telescope in the world. Right now Miranda has a magnitude of 16.5 (according to JPL's Horizons website) which doesn't sound that difficult until you consider that its apparent separation from Uranus currently varies from only 6.5 to 9.4 arc seconds. So, best case you have a 16.5 magnitude object that is 9.4 arc seconds from the center of an object (Uranus) that is almost twenty-one thousand times brighter than Miranda.

 

Next night I was lucky to have some more clear weather and I tried my Celestron C6. Didn't find anything other than the four brightest moons but on researching my next attempt I noticed that Miranda was going to reach its maximum elongation from Uranus on the morning of September 21 as both were passing through my local meridian. By a near miracle that morning was also clear and I set about imaging using a 9.25" EdgeHD and my ASI178MM camera with a Baader Semi-APO filter (the latter somewhat like a strong luminance filter). During this session I was actually able to see Miranda very fleetingly and intermittently on the preview images from within my capture application (or, at least I believed that I could see it -- certainly not easy).

 

Okay, so long story somewhat shortened below you will see one of the images that I created from a selected stack of 32 subs that were exposed for 4 seconds each using the lowest read noise gain setting on the ASI178MM camera (with the 9.25" EdgeHD at f/10). The moon Miranda is definitely recorded (close to and immediately below the overexposed image of Uranus) along with the moons Ariel, Umbriel, Titania, and Oberon (with respective magnitudes of 14.1, 14.9, 13.9, and 14.1). The image scale on this is approximately 0.3 arc seconds per pixel (a 67% reduction on the original).

 

The image capture was done using SharpCap with image processing in PixInsight (image selection, registration, and adjustments) and Photoshop CC2019.

 

Because confirmation of a capture like this can be, well, somewhat controversial I've included a "finder" chart that was created with an overlay of a plot done with the Uranus Viewer website and my image. The correspondence between my image of Miranda and the plot positions produced by the website seems to be perfect. I've also marked several field stars ("A" through "E") that were also recorded as those can be used as magnitude references.

 

This kind of magnitude check is really required for two reasons. First, you need to eliminate the chance that what you've recorded is actually a moon and not some brighter star that just happened to be close to Uranus (more on this in a following post/image). Second, you need to make certain that your image has recorded to a magnitude that would actually include the target moon (in this case, Miranda, at magnitude 16.5). If you can't find field stars that are similar to or fainter than the target then you can be pretty certain that what you've recorded isn't a moon.

 

Here are the estimated magnitudes for the labeled field stars (as determined using the website WikiSky.org on images based upon the Palomar/AAO Digitized Sky Survey II  or DSS2):

 

A: 14.95
B: 15.15
C: 16.25
D: 16.6 (the star USNO A2 0975-00500312, about the same magnitude as Miranda).
E: 17.5 (the star USNO A2 0975-00500283, one full magnitude fainter than Miranda).

 

The bright star at the top of the image is TYC 0637-1209-1 which has a magnitude of 10.4 (this star was used as a reference point for the overlay done on the Uranus Viewer plot).

 

You need to look at this "finder" chart at full size and perhaps when using a display in a darkened room, since it is an overlay of my image and the plot from the Uranus Viewer website. What you should see is a dark dot in the center of each bright moon. That dark spot is from the Uranus Viewer plot that was aligned and scaled to match my image (using the field star TYC 0637-1209-1 as a rotation and scale reference).

 

*** Updated some of the text for greater clarity and for typos at 2PM PDT ***

Attached Thumbnails

  • Uranus and Its Moons (Small).jpg
  • Uranus Finder Chart.jpg

Edited by james7ca, 23 September 2019 - 04:01 PM.

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#2 james7ca

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Posted 23 September 2019 - 07:15 AM

Here is the star field surrounding the then location of Uranus as taken from the DSS2 images on WikiSky.org (the position of Uranus is noted by the small icon near the center of the image). Note, there are no stars brighter than magnitude 18 in the location of Uranus that could have produced a false detection in my image of Miranda. This image also includes the labels for the stars that I identified in my earlier overlay plot.

 

I've also included an image of Uranus that I tinted with a blue/green photo filter in Photoshop that was taken using a series of much shorter exposure times (80ms). This was done with a 1.5X drizzle in AutoStakkert! using the best 20% of 2000 frames. Again, I didn't expect to record any details on the surface of Uranus, but it's interesting to note that an extreme stretch of this image shows what appears to be the moons Ariel, Titania, and Oberon (and a suspect that could be Umbriel). The scale on this image of Uranus is about 0.14 arc seconds per pixel.

Attached Thumbnails

  • WikiSky DSS2.jpg
  • Uranus 1_5X Drizzle Color Tinted.jpg
  • Uranus High Stretch 400 x 80ms.jpg

Edited by james7ca, 23 September 2019 - 07:32 AM.

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#3 james7ca

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Posted 23 September 2019 - 07:22 AM

Finally, here is an animation that I created using two sequences that show the movement of the moons over a 30 minute period (first sequence taken at 10:28 UTC or 3:28AM PDT, the second at 10:58 UTC, both on September 21, 2019). This is yet another confirmation on Miranda, since it shows movement that is consistent with the other moons of Uranus. This animation used the native image scale of the capture, that being 0.21 arc seconds per pixel (2350mm focal length, camera pixel size 2.4 microns).

 

Now, one may ask why I've made such an effort to confirm my image of Miranda. One reason is that it's part of my astronomy "bucket list" of things to image (which includes my earlier posts on Jupiter's Amalthea and Saturn's many moons).

 

Secondly (and this may verge on political incorrectness), I've found only four general categories of images of Miranda.

 

In the first category the author admits that what they've recorded may NOT be Miranda and I'd fully agree (in fact, it's probably not Miranda). In the second category the author claims to have captured Miranda but in an image of dubious quality and presented without any supporting documentation so that one can't really be sure of what they are being shown (it may or may not be Miranda).

 

Next, you will find the occasional image that has been manipulated so highly that it's more of an artistic expression of what MIGHT be Miranda than an actual image of the moon itself.

 

Lastly, there are a few images that seem credible, but they are in the great minority and some are not really that compelling.

 

Now, I'm sure someone can point me to a really great and verifiable image that was taken by an amateur that clearly exceeds what I've managed, but I do have some hope that no one has yet provided as much documentation as I have in order to remove any doubt about the veracity of their image. smile.gif

 

But, as always YMMV.

Attached Thumbnails

  • Uranus-Moons-Animation.gif

Edited by james7ca, 23 September 2019 - 05:03 PM.

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#4 descott12

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Posted 23 September 2019 - 07:28 AM

Very cool. Thanks for posting.



#5 psuaero

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Posted 23 September 2019 - 07:53 AM

Fascinating. I'm no expert (newbie, actually). I've used this site before to find the positions of Galilean and Saturnian moons.

 

When I plug in Sept. 21 @ 10:28 UTC with a reduced FOV of 0.03 deg I see the following:

Uranus Sept21 1028
 
If I rotate the image 90 degrees to the right then the moons line up pretty nicely. For some reason I was unable to post the rotated image.
 

 

 


Edited by psuaero, 23 September 2019 - 09:05 AM.


#6 happylimpet

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Posted 23 September 2019 - 07:54 AM

Nice detection, Miranda is never easy. I expect you had very good seeing that night.



#7 WarmWeatherGuy

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Posted 23 September 2019 - 08:06 AM

Thunderf00t made an animation showing Uranus and some of its moons moving against the background stars. The video is 1:08 and the animation starts at 0:45. At least you can determine which are stars versus moons. The video was posted in 2011.

 

Looking at URANUS!



#8 Rouzbeh

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Posted 23 September 2019 - 08:37 AM

Finally, here is an animation that I created using two sequences that show the movement of the moons over a 30 minute period (first sequence taken at 10:28 UTC or 3:28AM PDT, the second at 10:48 UTC, both on September 21, 2019). This is yet another confirmation on Miranda, since it shows movement that is consistent with the other moons of Uranus.

 

Now, one may ask why I've made such an effort to confirm my image of Miranda. One reason is that it's part of my astronomy "bucket list" of things to image (which includes my earlier posts on Jupiter's Amalthea and Saturn's many moons).

 

Secondly (and this may verge on political incorrectness), I've found only four general categories of images of Miranda.

 

In the first category the author admits that what they've recorded may NOT be Miranda and I'd fully agree (in fact, it's probably not Miranda). In the second category the author claims to have captured Miranda but in an image of dubious quality and presented without any supporting documentation so that one can't really be sure of what they are being shown (it may or may not be Miranda).

 

Next, you will find the occasional image that has been manipulated so highly that it's more of an artistic expression of what MIGHT be Miranda than an actual image of the moon itself.

 

Lastly, there are a few images that seem credible, but they are in the great minority and some are not really that compelling.

 

Now, I'm sure someone can point me to a really great and verifiable image that was taken by an amateur that clearly exceeds what I've managed, but I do have some hope that no one has yet provided as much documentation as I have in order to remove any doubt about the veracity of their image. smile.gif

 

But, as always YMMV.

I really liked this one! Very interesting to see. Thanks.



#9 james7ca

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Posted 23 September 2019 - 12:38 PM

Dave, psuaero, happylimpet, Steve, and Rouz thanks for the notice.

 

As for the animation by Thunderf00t, I think you have to be careful about what you find on the internet. Without any date or information about how that image was created you can't really be certain about much of anything (or even what you are being shown). I don't know anything about Thunderf00t except that he seems to run a YouTube channel (with over 800K subscribers) where he posts a lot information on conspiracy theories and his debunking of "fake news" or vaporware products. Yes, he joined CN in 2008 but has apparently made only 4 posts since that time (none of which are apparently still available). Is he now active under a different name?

 

Although the image looks somewhat credible it has some oddities.

 

First the field apparently isn't wide enough to show all of the moons of Uranus (as far as I can tell, but without the type of information that I outlined earlier you really don't know for sure). The reason I say this is that there appears to be only three moons in the image (maybe, see below) and yet Thunderf00t claims that the image recorded Miranda. So, if that animation really shows Miranda there should/could be four other moons that might have fallen within any reasonable field of view for a camera (since the orbital planes of the moons never cross either in front of or behind Uranus). In mid-2011 (when that video was posted) the moon Ariel passed as close as 3.8 arc seconds to Uranus (Miranda gets a little closer -- maybe 3 arc seconds, but the other moons are further out, the next closest is Umbriel getting within 5 arc seconds). Thus, Ariel may have been hidden in the glare of Uranus (so, that would mean that only one other moon is "missing," either out of field or too close to Uranus to be seen).

 

Another oddity is that the two other objects that seem to be tracking with Uranus never seem to move much in relation to the planet itself. The only logical explanation for that is that their movement was just too slow to record. That's possible but it seems somewhat unlikely given that the object identified as Miranda moved quite noticeably (which, admittedly is also possible since Miranda's orbit is closer to Uranus).

 

All that said, I can't really be certain one way or the other as to the validity of that animation. It's possible that a certain set of conditions could have satisfied what is shown in the animation so it could be a shot of Uranus and several of its moons, or it might not. It might show Miranda or it might not.

 

I should add that I was a little uncertain about whether I should have posted my own animation since quite frankly I was somewhat surprised by how clearly it showed the motion of the moons in just 30 minutes of elapsed time. I then measured the motion of Miranda and found that it seemed to be displaced by about 4 pixels which at my native image scale would have been slightly under one arc second. I then used SkySafari Pro to measure the predicted motion in relation to Uranus and that came out to 0.7 arc seconds (so, if SkySafari and my math were correct then my animation seems plausible).

 

However, I went ahead and did two simulations using the Uranus Viewer website and below is an animated plot that shows what the motion of the moons should have looked like. It seems quite similar to what was shown in the animation based upon my two images and it is shown at exactly the same scale and with the same event times. So, my animation seems correct with no bias from the imaging methods or image processing (IMO).

 

 

 

Attached Thumbnails

  • Uranus-Viewer-Animation.gif


#10 WarmWeatherGuy

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Posted 23 September 2019 - 01:33 PM

Thunderf00t (Phil Mason) is a scientist. Many years ago he posted videos showing what he has captured with his CPC 1100.

 

Free Your Mind!

 

He has another YouTube channel beautyintheuniverse which he hasn't uploaded to for 7 years.

 

I have no reason to think he faked his video but it is quite possible he misidentified Miranda.

 

 



#11 james7ca

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Posted 23 September 2019 - 02:28 PM

Thunderf00t (Phil Mason) is a scientist. Many years ago he posted videos showing what he has captured with his CPC 1100.

 

Free Your Mind!

 

He has another YouTube channel beautyintheuniverse which he hasn't uploaded to for 7 years.

 

I have no reason to think he faked his video but it is quite possible he misidentified Miranda.

I don't know. That animation by Thunderf00t looks far too sharp for the scale that it would have to represent. Plus, from the defects that show up in each frame and the flare around Uranus it kind of looks like each frame is a single exposure (or maybe the stack was just processed poorly).

 

If you look on Astrobin you will find no truly credible images of Miranda (IMO). I checked several of the ones that seemed somewhat plausible and the moons aren't even in the correct position for the time the person said the image was captured. One person who posted an image that claimed to show Miranda even suggested that one of the brighter moons wasn't visible because it was being eclipsed by the rings around Uranus! A few others suggested that they had also imaged the rings of Uranus (in addition to Miranda). Simply put, you need to be careful about some of the images that you find on the internet.



#12 Tom Glenn

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Posted 23 September 2019 - 02:30 PM

James, that's a nice capture, and good supporting evidence, particularly the animation.  Last year I posted an image in which I claimed to have identified Miranda.  I think it probably is, but I don't have nearly the supporting evidence that you do.  I'll have to go back and check to see how large my field of view was to see if there are any stars, because I can't remember how much this image was cropped, versus using a small ROI to begin with.  I'm also fairly certain (unfortunately) that I don't have a sequence of images to test an animation.

 

https://www.cloudyni...vember-27-2018/



#13 james7ca

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Posted 23 September 2019 - 03:24 PM

Tom, yes I saw your image after I started working on mine. One thing I should mention is that my images didn't use any masking or local modification to show the five moons. All I did was a very mild deconvolution and a simple histogram stretch (no masking, no AdaptiveStretch, ArcsinhStretch, LocalHistogramEquilization, or anything similar). Quite frankly I didn't think the image needed that, although I could certainly go in a do some masking and local brightening to make the image look "better."

 

By the latter I mean no critique on your final image, since you also showed a version that had no local adjustments. A testament, I think, to the honesty in your presentation.

 

I have found a few other images that have been so heavily modified or processed that they fell under my category of "artistic expression."

 

In any case, thanks for your comments.



#14 Tom Glenn

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Posted 23 September 2019 - 03:40 PM

James, yes, in my unmasked and less processed image, Miranda barely materializes from the noise.  My attempts at capturing the moons was done as an afterthought after a "normal" imaging run of Uranus, and I only did 10x2s exposures.  Looking at your data, it's obvious that a 32x4s scheme produces a much better result.  At the time of imaging, I wasn't even thinking about Miranda, and only discovered it during processing.  My tracking was also not very reliable, and so 2s was about as long of an exposure as I wanted to go, although in retrospect I could have captured far more than 10 frames.  In any event, your account here provides good motivation to revisit this target.  Well done and an informative analysis.  



#15 james7ca

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Posted 23 September 2019 - 04:53 PM

Tom, I'm sure that someone can do better than what I've shown. In fact, I may try again at my local mountains to get darker and better skies than I have at my home where I work under red/orange zone light pollution from a spot that is surrounded by concrete, roof tops, asphalt, and a pretty extreme set of neighborhood lighting.

 

I guess my search capabilities on the internet are not as good as they should be as I can find no really compelling images of Miranda that were taken from earth-based telescopes. I've looked here on CN and on Astrobin and there aren't that many good images (a few on CN, but none on Astrobin). Then I just did a Google search for "Uranus moon Miranda images" and nearly everything that Google displays is either an illustration/drawing or an image taken by one of the space probes. Notably, your image shows up on Google but the only truly compelling image that I can find using Google was taken with ESO's Very Large Telescope in Chile (which none of us could hope to match).

 

Then, I've found a nice image that was taken by CN's Kokatha man that seems to have been posted only to his website:

 

http://momilika.net/...2016-18Pics.htm

 

Frankly, however, that image looks pretty highly manipulated although I'm sure that given the author it is a valid capture. Kokatha man also says the following here on CN:

 

 

faint Miranda can only be obtained in a single-exposure capture when the sky is exceptionally transparent/clear...good seeing is also needed of course to do this, as well as pick up the belts/banding on Uranus!

Maybe the problem is that Miranda just hasn't been attempted that often by experienced planetary imagers.


Edited by james7ca, 23 September 2019 - 04:54 PM.


#16 Tom Glenn

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Posted 23 September 2019 - 05:09 PM

fwiw, I've found that the "Search" function on the CN website is not nearly as good as typing the same search feature into Google, and then appending "Cloudy Nights" to the end of the search.  Even still, it can be difficult to find what you're looking for, and amateur images of Uranus are definitely less common than the NASA images or simulations that come up in many searches.  Even more so for the Moons of Uranus, and the types of data you are looking for with complete documentation would be rarer still.  If the goal was peer review for publication, then everyone would always have to post an exact list of the equipment and methods used for processing, as well as accurate time stamps, and access to the raw data.  A much higher bar then the routine internet post provides.  


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#17 WarmWeatherGuy

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Posted 23 September 2019 - 06:27 PM

If you want to restrict your search to cloudynights.com append a site:cloudynights.com to the search string. Ensure there is no space on either side of the colon.

 

miranda site:cloudynights.com

 

Edit - use colon, not equal sign.


Edited by WarmWeatherGuy, 23 September 2019 - 06:29 PM.

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#18 Kokatha man

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Posted 24 September 2019 - 01:07 AM

 

Then, I've found a nice image that was taken by CN's Kokatha man that seems to have been posted only to his website:

 

http://momilika.net/...2016-18Pics.htm

 

Frankly, however, that image looks pretty highly manipulated although I'm sure that given the author it is a valid capture. Kokatha man also says the following here on CN:

 

Quote

faint Miranda can only be obtained in a single-exposure capture when the sky is exceptionally transparent/clear...good seeing is also needed of course to do this, as well as pick up the belts/banding on Uranus!

 

 

Maybe the problem is that Miranda just hasn't been attempted that often by experienced planetary imagers.

Good to hear some complimentary words amongst your comments James...particularly as they pertain to our images..! rofl2.gif

 

I'll start from the bottom wink.gif - I don't really know any "experienced planetary imagers" who bother with the moons teribly much on any planet unless they figure prominently within the capture &/or they need especial handling such as WJ integrations, as per the Ganymede shadow transit in my most recent thread...they're just not that interesting to me tbh & I personally don't think Miranda is as challenging as some might think, given good transparency...with no inherent criticism of your efforts per se, I hasten to add - & this pastime is so incredibly diverse that there's plenty of room for folks to delve into all sorts of objectives & challenges, even if it does seem that this forum has a predominance of planetary imaging activity concentrating on disk features!

 

For my money merely increasing the exposure/lowering the fps & using sufficient gain in the conditions I describe in your quote of mine should make it relatively easy to capture it...but as said, not something I find sufficiently challenging.

 

As per my quote you've used, the most principal point is "in a single exposure capture" meaning those parameters utilised to maximise the possibility of picking up atmospheric features on the planet itself where exposure needs to play "second fiddle" somewhat to frame-rates.

 

I'm quite happy for some folks to debate/differ on what constitutes "proof" but I do think anyone should be prepared to back up any claims that they post with their "rationale" should the necessity arise (I've been involved in plenty of that over the years) so I've spent an inordinate amount of time this morning trying to dig up something since I read your thread: not easy I might add with all my older HD's packed away & my labelling not too good with many of them...

 

I found one from November 2014 (no idea what camera, this was not listed in the .txt files) & as I say quite often here on CN, I first make a duplicate copy of the RAW or sharpened tif stack & raise the levels (enormously if I think Miranda might be buried in the background) & make a 1 or 2 pixel selection of any that I see, delete this layer whereby the selection is still visible in the "background layer" & then raise the levels there: here is an example of this where I have "inverted" the image for greater clarity.

 

Uranus_091114_124105_IR610nM_uberlvls.png

 

Now I'm sure you'll try to say that the lowest delineated spot in the image above is far too similar to the many identical features of background noise etc - but my simple response about something rather inconsequential to my major objective is "if I detect something this way that is in the position of something tangible then it satisfies my own criteria for its probable likelihood of being "real" - more so if earlier/later captures provide additional support! wink.gif

 

Q60Nm100_Uranus_091114_124105_IR610nM&WinJUPOS-Moons_overlay.gif

 

Here I've rotated the WinJUPOS graphics display (Eq orientation) 2° ccw to better align this WJ display to my inverted & delineated Uranus & Miranda etc image to assist me further in my appraisal of the veracity.

 

OurUranus-UT1241&1319Nov9th2014.gif   WinJUPOS_Graphic-UT1241&1319Nov9th2014.gif   WinJUPOS-Graphics&Captures-MirandaRotationalDisplacement.png

 

Lastly, I show a simple animation using the WJ graphic displays from 2 of the captures times of that night (12:49:51 & 13:28:41) alongside that animation of those 2 actual capture stacks where I have annotated the position of what I (confidently) ascertain Miranda to be in...& another side-by-side of said images showing very roughly the angular displacement of Miranda at said times: noting that the WJ graphics animation (2nd last image) & the last image of the positional movement of Miranda in the WJ (lhs) display have not been rotated apropos the rhs capture image...

 

I'm quite happy for you to promote the superiority of your own exercise James - but as I've said I personally do not think this is a terribly challenging exercise whatsoever if one uses capture parameters to assist faint satellite captures...but using parameters predicated upon maximising disk "resolution" for the ability to pick out very faint moons - from the perspective of "if it looks like a moon, it's in the right position & it repeats itself in further captures" - I'll confidently make the claims I have here! lol.gif

 

I've always presented myself as a "nuts & bolts" planetary imager: ie, I focus on outcomes regardless of whether they conform with mainstream approaches or even (supposed) resolution etc limitations...this applies to the capture durations we employ (this comes up regularly - or at least has me wondering why so many people use very short timespans, especially when very few of them refocus between them either, regardless of the amount of guff I read on forums about how focus hardly varies rofl2.gif ) - or to another "furphy" that occasionally surfaces concerning WJ's maximum integration capabilities...or how to focus on the Ice Giants etc...etc... wink.gif

 

The very few instances on our website where Miranda appears (& all images on our website have been posted at one time or another here on CN James) indicate that it is not something easily accomplished under the capture parameters I refer to...but then again we were amongst the handful of imagers to capture the only verifiable recent Uranus "storm" back in late 2014...as well as picking up BWC's on Neptune only recorded by the HST...as well as another where the pros had not bothered to issue "alerts' to AA'ers, believing that our equipment was not capable of detecting them so early in that apparition...or of course the - or I really should say "our" - discovery of long-lasting Eq. storms, well before the Keck in June of 2017... wink.gif

 

Perhaps I really am a bit of a maverick employing methods & rationales that might not sit very well with quite a lot of folks - but we've been proved correct independently enough times by irrefutable sources to suspect we have something going for us therein...whatever anyone might think of our own specific "manipulations" of the highly-mediated outcomes that are all images presented by AA'ers...although I do like to think we are pretty constrained on that aspect overall! smile.gif


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#19 Marco Lorenzi

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Posted 24 September 2019 - 02:53 AM

Finally, here is an animation that I created using two sequences that show the movement of the moons over a 30 minute period (first sequence taken at 10:28 UTC or 3:28AM PDT, the second at 10:58 UTC, both on September 21, 2019). This is yet another confirmation on Miranda, since it shows movement that is consistent with the other moons of Uranus. This animation used the native image scale of the capture, that being 0.21 arc seconds per pixel (2350mm focal length, camera pixel size 2.4 microns).

 

Now, one may ask why I've made such an effort to confirm my image of Miranda. One reason is that it's part of my astronomy "bucket list" of things to image (which includes my earlier posts on Jupiter's Amalthea and Saturn's many moons).

Excellent result James, it is nice and inspiring to see people like you chasing these challenging targets! waytogo.gif

 

Clear skies

Marco



#20 james7ca

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Posted 24 September 2019 - 03:22 AM

Kokatha man, thanks for your comments. Yes, the animations are a good way to confirm your capture and as I said earlier I was actually surprised that a sub-arc-second displacement could actually be seen so easily (in the animation that I posted earlier).

 

That said, I think that one other useful and sometimes required verification method is to actually look at the background star field to confirm that there aren't any stars that could be mistaken for a moon. I've had to do that on a number of occasions when imaging the fainter moons of Jupiter or when trying to capture Saturn's Phoebe.

 

In the case of Saturn it was a real hassle last last year when Saturn was in one of the most dense parts of the Milky Way and the star field surrounding and behind Saturn was literally overloaded with 16, 17, and 18th magnitude stars. In that case even doing an animation can be difficult because you may find similar magnitude stars almost directly on top of or very near to the target moon during each session. For Phoebe it actually took several attempts before I had a night where all of the moons were cleanly separated from any background star or group of stars.

 

Fortunately, Uranus is currently in a relative star-poor area of the sky, so these conflicts are less likely to happen. But, I've learned from past experience that it is best to carefully check the background star field before you assume that you've captured a faint moon. In fact, I've found that this seems to be a fairly common error found in many purported images of the fainter moons.



#21 Kokatha man

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Posted 24 September 2019 - 03:55 AM

That said, I think that one other useful and sometimes required verification method is to actually look at the background star field to confirm that there aren't any stars that could be mistaken for a moon. I've had to do that on a number of occasions when imaging the fainter moons of Jupiter or when trying to capture Saturn's Phoebe.

 

In the case of Saturn it was a real hassle last last year when Saturn was in one of the most dense parts of the Milky Way and the star field surrounding and behind Saturn was literally overloaded with 16, 17, and 18th magnitude stars. In that case even doing an animation can be difficult because you may find similar magnitude stars almost directly on top of or very near to the target moon during each session. For Phoebe it actually took several attempts before I had a night where all of the moons were cleanly separated from any background star or group of stars.

 

...in case it didn't come across - I applaud your efforts in these endeavours James waytogo.gif waytogo.gif  & I can well understand satellites such as Phoebe would need scrupulous examination in those particular fov's...after assembling all that stuff earlier I also thought that the next time I image the Ice Giants (which will be as soon as an opportunity presents itself) I'd better test my comments about how easy it should be with capture parameters set for the satellites - I might have to swallow some humble pie blush.gif lol.gif but I'll try & put my own animation together to test my bravado above..! ;)



#22 happylimpet

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Posted 24 September 2019 - 04:47 AM

One of my better (there arent many) images of Miranda here:

 

https://www.cloudyni...anus-sept-2018/

 

It needs very good seeing to show up in stacks intended for planetary detail - one throws away a lot of signal/noise in trying to get the sharpest details with high frame rates.

 

I'll say it again -your image is very good and one of the best Ive seen for showing all the moons so clearly.

 

EDIT: just realised my moon shot linked above is with 1.5sec subs! Not a standard 30fps for Uranus. I was clearly moon-hunting that night.

 

post-222909-0-85551000-1543104899.png


Edited by happylimpet, 24 September 2019 - 04:49 AM.

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#23 james7ca

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Posted 24 September 2019 - 05:05 AM

Marco, Kokatha, and happylimpet, thanks for the further comments.

 

 

...in case it didn't come across - I applaud your efforts in these endeavours James waytogo.gif waytogo.gif...

 

I'm primarily a DSO imager and I guess that being so I'm a little hesitant to resort to very targeted and local modifications to my images. Thus, I actually prefer to see my attempts at "deep"planetary images having as little local modification as possible (if the selections were done by purely manual methods, algorithmic being something else and perhaps a bit less subjective in manner). But I can understand a desire to make an image appear as if it were simply captured by the eye (on a VERY large telescope) or by a camera that had nearly infinite dynamic range.

 

One of the "problems" I have with my image is that the bright star at the top has a very non-circular appearance (I could actually fix that in Photoshop, but I decided not to do that given that I wanted the image to be as close as possible to the raw data). I'm not sure why this happens, it may have something to do with a small amount of relative movement between the star and Uranus during the several minutes over which these images were captured. The registration (I used PixInsight's FFTRegistration script) probably tracked mainly on Uranus and in fact when I tried to register these subs using AutoStakkert! the results were not as good (you could see a greater amount of movement or blurring in the moons). That said, I probably need to go back to AutoStakkert! and try some different parameters to see if I can improve things even further. In fact, another "problem" is that the saturated parts of the disk of Uranus are not really that symmetric, that's either an optics problem or another issue with the registration.

 

I also used a manually selected subset of the best of the images (using the Blink tool in PixInsight), since I've found that Autostakkert! sometimes doesn't do the best frame selection when it grades the frames (after all, it's not really designed to work on DSOs or stars, or even grossly overexposed images of the planets).

 

That latter issue (non-circular disk of Uranus) caused some issues when I was doing the animation (which was based upon a registration done in AutoStakkert!). What I found was that it was somewhat difficult to get the animation of the disk of Uranus to match exactly between the two frames, so there may have been a pixel or more of misplacement between the true disk of Uranus and the moons (resulting in an incorrect placement of the moons). That said, I tried very hard to insure that the overlay was as exact as possible (by minimizing any difference between the apparent location of Uranus between the two frames of the animation).


Edited by james7ca, 24 September 2019 - 05:09 AM.


#24 aeroman4907

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Posted 24 September 2019 - 07:36 AM

James, I appreciate the level of effort you made in confirming your capture of Miranda.  I think it was well developed and presented in a manner I am not needing to interpret whether it is a moon detected or simply another bit of noise that just happens to be located close to the calculated location of Miranda.  If the sampling is of sufficient resolution, it is evident that light was of course collected by the telescope that includes light reflected from Miranda.  The light is collected by the telescope, but it is captured, processed and presented in a manner that we can clearly say Miranda was imaged?  Well, that is another story.  In this case, you have done an excellent job!

 

I also appreciate your efforts in an area that don't get as much interest, even if imaging Miranda isn't a personal goal of mine, I do enjoy seeing others branch out from imaging the 'typical' targets.



#25 KpS

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Posted 24 September 2019 - 03:08 PM

Good preparation, very nice results and consistent documentation. Well done!

 

James, let me ask you a question. Five years ago I sent a post called Uranus and Miranda width C11. Which of your categories does it belong to? Only in addition: Video 2000x0.5 sec, North up using WinJUPOS, resolution 0.1734 ".




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