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First Saturn of the year, July 21, 2019

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#1 Tom Glenn

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Posted 21 July 2019 - 07:57 PM

I finally got an image of Saturn for this season.  Now I'm just wondering if I'll be one and done!  This was a race to see which happened first.....clouds rolling in (which they did), or the dew shield on my scope hitting the fence in my yard because the angle is so low.  I got five captures recorded, but as often is the case, only one of them was worth processing, and the others (including Winjupos variations) were all inferior.  This is a six minute capture, using a C9.25 Edge and ZWO ADC, with a Televue 2x barlow, and ASI224mc (in that order in the imaging train....focal ratio is still on the long end at about f/25, but that's better than the f/30 that results if I put the barlow first).  For those interested, this capture had a shutter speed of 15ms and gain of 410 (transparency was not good, hence needed higher gain), recording at 66 fps for a total of 23,989 frames.  3000 frames were stacked in the final image.  

 

Saturn_July21_2019_TG.png


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#2 Toddeo

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Posted 21 July 2019 - 08:08 PM

Tom, that's a very nice capture!



#3 Tulloch

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Posted 21 July 2019 - 09:06 PM

A great result for a low altitude, how high is Saturn for you now?

 

Andrew



#4 Helvetios

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Posted 21 July 2019 - 09:28 PM

That's an excellent result!  You can even make out the polar hexagon.

 

Richard



#5 Tom Glenn

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Posted 22 July 2019 - 02:41 AM

Thanks Toddeo, Andrew, and Richard.  Much appreciated.  

 

Andrew, Saturn crosses the meridian at 35 degrees in San Diego.  While this is "low" by my standards, it won't garner much sympathy from my colleagues who are much farther north.  Nevertheless, good results at 35 degrees are more difficult to come by than even if just 10 degrees higher.  In my experience, which is based largely on lunar imaging (since the Moon cycles between maximum and minimum declination each month), anything above 60 degrees is basically the same, as in I don't notice much improvement once you pass 60 degrees.  Below 60 but above 45 degrees can still give good imaging with reasonable regularity.  Once you drop below 45 degrees, and especially into the 30's (and heaven forbid below that!), things are basically very bad most of the time.  And this is assuming good seeing at zenith.  In bad seeing, even high elevation won't help you.

 

One additional problem with low elevation, aside from the seeing, is simple logistics.  At my house, I have numerous obstacles that conspire to limit my viewing of low altitude objects to a narrow corridor.  These include houses, trees, and fences.  For anything below 60 degrees altitude, I have about an hour in any given night during which I can image, and this corresponds to the hour just after culmination.  For objects above 60 degrees, all of these obstacles are out of the way and I would have multiple hours of good imaging.  Currently, this only applies to the Moon, and the occasional asteroid or Uranus if I choose to target that.  Fortunately, next year Mars will join my "60 degree club", which will be a nice change.  



#6 Tulloch

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Posted 22 July 2019 - 04:10 AM

Thanks Tom, I can certainly understand your pain, and have admiration for those of you still imaging in adverse conditions,

I’ve only started doing this a few months ago, and in Melbourne Australia at the moment the planets are peaking at a bit over 70 degrees, in fact so high that I needed to reposition my scope on the mount so the camera wouldn’t crash into the base! I’m certainly in the right time and place to begin this hobby, and should be right on top of my game when mars reappears next year.

The only down side here right now is that it’s the middle of winter, so the number of clear nights is limited, however I don’t expect much sympathy from anyone in the northern hemisphere.lol.gif 

Andrew


Edited by Tulloch, 22 July 2019 - 04:43 AM.


#7 Tom Glenn

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Posted 22 July 2019 - 05:24 PM

The only down side here right now is that it’s the middle of winter, so the number of clear nights is limited, 

 

Everyone is in a similar boat there......once Saturn reaches its maximum declination in the north (many years from now), it will be winter here as well during opposition.  By definition this is true for any object on the ecliptic plane....the point on the ecliptic opposite the Sun is highest in the sky in the winter.  


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#8 Tulloch

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Posted 22 July 2019 - 05:40 PM

Ha! I hadn’t even considered that, not that I’d given it much thought, but that makes perfect sense.

Thanks for the lesson.

Andrew.

#9 Kokatha man

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Posted 22 July 2019 - 07:53 PM

A very nice image Tom, especially from your elevation! waytogo.gif waytogo.gif waytogo.gif



#10 Tom Glenn

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Posted 23 July 2019 - 03:05 AM

Thanks Darryl!  Much appreciated.  It's been a relentless string of cloudy nights this summer, so planetary imaging has been slow going so far, but I was happy with this result.  



#11 Peregrinatum

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Posted 23 July 2019 - 10:16 AM

That's a great image!!!

 

With exp = 15ms and gain = 410 where did that put the histogram?



#12 Tom Glenn

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Posted 23 July 2019 - 01:32 PM

That's a great image!!!

 

With exp = 15ms and gain = 410 where did that put the histogram?

Thanks for the comment.  My Firecapture log file says 49%, but I frequently question the accuracy of the histogram report in the FC log file, at least with my ASI224, because for some reason it will often report a value of 0%, when this is obviously not the case.  I've wondered if there is a bug in this FC version (I'm using the Mac version) or if there is some other explanation for it.  49% isn't too far off, but it was hovering around 60% when I started the recording, and maintained approximately that value throughout.  So I would say 60% is closer to the truth.  



#13 Achernar

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Posted 23 July 2019 - 05:39 PM

I can see the polar hexagon clearly, and this is an amazingly sharp image considering the conditions you recorded the video under.

 

Taras



#14 kevinbreen

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Posted 23 July 2019 - 06:09 PM

Thanks Tom, I can certainly understand your pain, and have admiration for those of you still imaging in adverse conditions,

I’ve only started doing this a few months ago, and in Melbourne Australia at the moment the planets are peaking at a bit over 70 degrees, in fact so high that I needed to reposition my scope on the mount so the camera wouldn’t crash into the base! I’m certainly in the right time and place to begin this hobby, and should be right on top of my game when mars reappears next year.

The only down side here right now is that it’s the middle of winter, so the number of clear nights is limited, however I don’t expect much sympathy from anyone in the northern hemisphere.lol.gif

Andrew


No sympathy.
They’re 15 degrees here..

Aaaargggh
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#15 kevinbreen

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Posted 23 July 2019 - 06:13 PM

Really nice image, Tom. Congrats. It must be some relief, being July.

#16 Tom Glenn

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Posted 23 July 2019 - 06:23 PM

Thanks Taras and Kevin.  It's important to keep in perspective, however, that although conditions haven't been great, the Cassini division was still visible in the live view throughout the recording, despite having more wavering than I'd prefer.  This is basically a prerequisite for getting anything substantial out of Saturn, yet I've seen many examples of raw videos from others (usually beginners asking questions about expectations) in which the Cassini division cannot be clearly seen.  That's basically a non-starter for imaging, so I can't complain about my situation.  The primary problem here has been clouds.  The Jupiter opposition came and went and I only have one decent image out of that, although there is still time left for both.  



#17 DMach

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Posted 24 July 2019 - 11:35 AM

Very nice capture Tom, congrats!



#18 Tom Glenn

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Posted 25 July 2019 - 06:36 PM

Thanks Darren!  And thanks to all for the extra "likes".  




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