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Trip to Argentina and Chile with Night Vision

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#1 Gavster

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Posted 07 July 2019 - 03:19 PM

I’ve just come back from an 8 day trip to Argentina and Chile to see the recent total solar eclipse. The eclipse was awesome with fantastic blue skies from our viewing location in Bella Vista in Argentina.

However, this post is not about the eclipse. smile.gif

I’ve never observed the Southern Hemisphere night skies with a scope before, so I couldn’t resist also taking my 95mm Baader refractor with me. Coming from Europe my pvs-14 is also itar-free so I also took along my Photonis 4g intens with me.

Unfortunately due to the trip scheduling, there was only one night I was able to observe which was the night of the actual eclipse itself - this turned into quite a long day! The skies were very dark at this pretty remote location in Argentina but unfortunately the hotel lights were quite bright bringing the sqm reading down to around 21.

 

Initially I just scanned with Milky Way at 1x with the nv, both unfiltered and with my 5nm ha chroma filter. The Milky Way was just stunning unfiltered, with the heart of our galaxy directly overhead. The detail and contrast of the dark lanes with the white fluffy bits was something to behold. By a large margin the best views I’ve ever had of the MW. I also scanned with the ha filter attached and a little surprisingly for me, there wasn’t massive amounts of emission nebulae visible in the south. But what there was did rather stand out (in particular eta carinae, of which more later).

 

I then set up the 95mm Baader. I had limited time since it was getting late and I had to catch an early coach in the morning. Therefore I decided to focus on a couple of showcase objects.

 

First up, using the 41mm panoptic, 0.75x reducer and 5nm chroma ha filter was eta carinae itself. The fov was around 3.5 degrees with a magnification of 10x. The object just fit into the fov but wow the view was just filled with nebulosity - one of my very best night vision views I’ve had, surpassing the vast majority of northern sky emission nebulae. The attached phone image is 15 seconds exposure.

 

Just above this was the so called ‘running chicken nebula’. Not as stunning or bright but still a lot of fun to observe. Phone image attached is again 15 seconds exposure.

 

I searched around for the LMC or SMC but unfortunately they were too low in the sky and obscured by some trees.

 

With it getting quite late, I went for my final showcase object, the Omega Centauri globular cluster. I decided to increase the magnification to 30x by using an 18.2mm delite (fov just over 1 degree). Even with the relatively low magnification, this globular looked incredible - like nothing else I have seen before. The image attached is an 8 second exposure, the eyepiece views were more impressive since the core didn’t blow out. 

 

Coincidentally when I got home I stumbled upon an image I took of m13 using the exact same setup of 95mm Baader, 18.2 delite and nv monoculars. The side by side comparison (see final

image of m13, 10 second exposure with the phone) did make me gasp - I didn’t realise that omega centauri was so much bigger than m13. Just shows what us northerners are missing... 

 

A great trip to see a fantastic total solar eclipse, topped off by a lovely few hours under the southern skies with nv. I don’t think I’m going to get another opportunity anytime soon but I certainly won’t forget the views I got.

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#2 TOMDEY

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Posted 07 July 2019 - 03:25 PM

Wow!    Tom



#3 Anduin

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Posted 07 July 2019 - 03:37 PM

Nice! I was in Bella Vista too, and the event was awesome! You should come back to TSE in South America, in december/2020.
Then you will be able to observe 47Tucanae , the Tarantula and pthers.
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#4 Jeff Morgan

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Posted 07 July 2019 - 05:00 PM

Just shows what us northerners are missing... 

 

No doubt about it, astronomers in the Northern Hemisphere got the short end of the stick.



#5 Jim4321

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Posted 07 July 2019 - 05:33 PM

Great report, Gav!  I've seen Omega Centauri with NV fairly low on the horizon from our club's mountaintop observatory, and yes, it is big and mind blowing!  (My meditative thought while falling asleep that night was about living on a planet orbiting a star there.... )

 

Jim H.



#6 chemisted

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Posted 07 July 2019 - 06:42 PM

I've been trying not to make this comment but I just can't help myself.  I have seen the glorious NGC 5139 from the mountaintop of Kitt Peak through a 16" reflector and from the Caribbean shores of Costa Rica and yes, it is big.  However, with my NV views I find a 30 arcmin framing of M22 every bit as appealing as the image Gavin shows here. That's the beauty of NV for globulars.  The cluster doesn't have to be 17,000 l-y away and an enormous brute on top of it to be made visually a show stopper.  All one has to do is go to an appropriate image scale and enjoy the presentation of innumerable pinpoint stars in breathtaking clusters.

 

Great trip, Gavin, and thanks for sharing the images.  We are all jealous that you can take your device outside the country.


Edited by chemisted, 07 July 2019 - 06:45 PM.

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#7 Eddgie

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Posted 07 July 2019 - 08:29 PM

Great report!

 

Images are all terrific.  Thank you for sharing them. 



#8 Gavster

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Posted 08 July 2019 - 06:49 AM

I've been trying not to make this comment but I just can't help myself.  I have seen the glorious NGC 5139 from the mountaintop of Kitt Peak through a 16" reflector and from the Caribbean shores of Costa Rica and yes, it is big.  However, with my NV views I find a 30 arcmin framing of M22 every bit as appealing as the image Gavin shows here. That's the beauty of NV for globulars.  The cluster doesn't have to be 17,000 l-y away and an enormous brute on top of it to be made visually a show stopper.  All one has to do is go to an appropriate image scale and enjoy the presentation of innumerable pinpoint stars in breathtaking clusters.

 

Great trip, Gavin, and thanks for sharing the images.  We are all jealous that you can take your device outside the country.

Ed, I completely agree that getting an appropriate image scale is important for globs. I’ve viewed m13 with my 16 inch dob and nv and it looked fantastic. But I only had my little 95mm refractor with me and I personally feel there’s only so far I can push the image scale up before the nv views are adversely affected on globs. I took on board your suggestions and brought the 18.2mm delite with me to triple the image scale compared with my normal 41mm pan plus reducer. This made the system around f9 and I think that’s as slow as I’d want to go. The photonis has significantly less gain than my 3G harder so potentially I could use a slower system and hence more mag with the harder.


Edited by Gavster, 08 July 2019 - 06:50 AM.

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#9 GeezerGazer

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Posted 09 July 2019 - 12:32 AM

I've been trying not to make this comment but I just can't help myself.  I have seen the glorious NGC 5139 from the mountaintop of Kitt Peak through a 16" reflector and from the Caribbean shores of Costa Rica and yes, it is big.  However, with my NV views I find a 30 arcmin framing of M22 every bit as appealing as the image Gavin shows here. That's the beauty of NV for globulars.  The cluster doesn't have to be 17,000 l-y away and an enormous brute on top of it to be made visually a show stopper.  All one has to do is go to an appropriate image scale and enjoy the presentation of innumerable pinpoint stars in breathtaking clusters.

 

Great trip, Gavin, and thanks for sharing the images.  We are all jealous that you can take your device outside the country.

 

Ed, I completely agree that getting an appropriate image scale is important for globs. I’ve viewed m13 with my 16 inch dob and nv and it looked fantastic. But I only had my little 95mm refractor with me and I personally feel there’s only so far I can push the image scale up before the nv views are adversely affected on globs. I took on board your suggestions and brought the 18.2mm delite with me to triple the image scale compared with my normal 41mm pan plus reducer. This made the system around f9 and I think that’s as slow as I’d want to go. The photonis has significantly less gain than my 3G harder so potentially I could use a slower system and hence more mag with the harder.

 

I agree with both of you, so I pulled some of my old phone photos for a visual comparison to see differences in aperture and focal length.  But first, I checked on the apparent size of M13 at 20 Arc Minutes (AM), M22 at 32 AM and NGC 5139 at 55 AM.  Below is all three in a collage, from L to R:

NGC 5139, taken with an ST 120 achro, iPhone 6+, ISO 1250, 1/2s averaged 4s

M22 (center), taken with ST 120, iPhone XR, ISO 8000, 1/2s averaged 20s

M13 ®, taken with ES 208 + 2x barlow, iPhone XR, ISO 1250, 1/4s averaged 10s

 

Although M22 is bigger than M13 (32 AM vs 20 AM), it appears smaller in the photo comparison because a barlow was added for the M13 image.  If I take another image of M22, I will absolutely add a barlow to glean more detail... and I know it will support the slower focal ratio.  

 

glob comparo.jpg

 

I also pulled two images of just NGC 5139 taken with vastly different scopes, both in May 2018 using my iPhone 6+: 

Left, taken with ST 120 achro, ISO 1250, 1/4s averaged 4s

Right, taken with 20" Teeter w/Lockwood mirror, ISO 64, 1/6s averaged 5s

 

5139 Comparo.jpg

 

Now these are really compressed to present in each photo, but they do show similarly even with very different scopes being used, in spite of the very big difference in their apparent size.  Focal length, either scope focal length or apparent focal length when using a barlow, is the equalizer.  The really nice thing about globs is how well they hold up as point sources of light in NV.  There are limitations as Gavster points out, but they can be pushed way beyond nebular subjects, both for visual and imaging purposes.  


Edited by GeezerGazer, 09 July 2019 - 12:44 AM.

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#10 Gavster

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Posted 09 July 2019 - 01:14 AM

I agree with both of you, so I pulled some of my old phone photos for a visual comparison to see differences in aperture and focal length.  But first, I checked on the apparent size of M13 at 20 Arc Minutes (AM), M22 at 32 AM and NGC 5139 at 55 AM.  Below is all three in a collage, from L to R:

NGC 5139, taken with an ST 120 achro, iPhone 6+, ISO 1250, 1/2s averaged 4s

M22 (center), taken with ST 120, iPhone XR, ISO 8000, 1/2s averaged 20s

M13 ®, taken with ES 208 + 2x barlow, iPhone XR, ISO 1250, 1/4s averaged 10s

 

Although M22 is bigger than M13 (32 AM vs 20 AM), it appears smaller in the photo comparison because a barlow was added for the M13 image.  If I take another image of M22, I will absolutely add a barlow to glean more detail... and I know it will support the slower focal ratio.  

 

attachicon.gif glob comparo.jpg

 

I also pulled two images of just NGC 5139 taken with vastly different scopes, both in May 2018 using my iPhone 6+: 

Left, taken with ST 120 achro, ISO 1250, 1/4s averaged 4s

Right, taken with 20" Teeter w/Lockwood mirror, ISO 64, 1/6s averaged 5s

 

attachicon.gif 5139 Comparo.jpg

 

Now these are really compressed to present in each photo, but they do show similarly even with very different scopes being used, in spite of the very big difference in their apparent size.  Focal length, either scope focal length or apparent focal length when using a barlow, is the equalizer.  The really nice thing about globs is how well they hold up as point sources of light in NV.  There are limitations as Gavster points out, but they can be pushed way beyond nebular subjects, both for visual and imaging purposes.  

Very interesting Ray. In the second set of images what was the respective magnification and f ratio of each setup (ie for the 120 and 20 inch dob)? I assume the dob was running at a much faster speed since the iso was only 64 compared to 1250? Given this was the actual eyepiece view in the 120 quite a bit dimmer compared to the dob? 

Does using a relatively high iso of say 1250 as most of your images above are brighten the images relative to the actual eyepiece views?

 

I also notice that my longer exposure image of ngc 5139 looks quite different to your short exposure by with averaging images. The core of my image has blown out whereas yours hasn’t.


Edited by Gavster, 09 July 2019 - 01:25 AM.


#11 GeezerGazer

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Posted 09 July 2019 - 08:06 AM

Gavin,

I'll try to answer your questions about FR and specs when I get home.  But what I totally ignored above was the other half of the equation when looking at any subject visually or for imaging... the apparent magnitude... our perceived brightness of the subject we are looking at.  While M13 is pretty bright in a pair of binos, M22 is not, even though it is substantially bigger, and NGC 5139 is naked eye visible, much bigger (2x) and brighter!  When light is spread out over a bigger angular area, it is just harder to see, which is why our beloved nebula with narrow transmission bands spread over such a big area are tough nuts without NV providing the huge increase in perceived brightness.  

 

Visual magnitude:

M13             +5.78   20 arc minutes

M22             +5.09   32   "

NGC 5139   +3.68   55   "

 

I have photographed nearly all of the Messier globs, and they are all quite apparent as globs in my modest aperture objectives with NV.  But without NV, many are just barely visible and often do not resemble a glob.  The biggest and brightest though, like above, are quite glorious with NV.  My experience reveals that point light sources are more easily enhanced by the power of NV than very dim nebular clouds, which also require filters.  Filters do not enhance the light as Edggie and others have explained many times; they only block light, so the NVD is left with a weaker signal to enhance.  Globs require no filters and their broad spectrum of starlight is fully acquired and enhanced by NV.  They are definitely a win/win.  


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#12 GeezerGazer

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Posted 09 July 2019 - 07:07 PM

Gavin,

To answer your question, yes, the Teeter 20" Dob was working at f:3.6 using a Lockwood mirror, so the FL was 1829mm.  The ST 120 has a native FL of 600 at f:5 but was used with a 2" 2x barlow, so about 1200mm FL at a very slow focal ratio, thus the difference in ISO settings for the images.  

 

The visual image of Omega Centauri through the 20" Dob was breath taking, with stars resolved throughout the core with a glass eyepiece WITHOUT NV.  With NV, the core was much more dense as demonstrated in the photo which does approximate the visual image.  Using the 120mm achro with 2x barlow, the visual image of this massive globular was much more dim than the visual image through the big Dob, but it was still much, much brighter than when using a glass eyepiece and seemed very amenable to the slower FR.  

 

The short exposure times for these bright globs is really all that is needed when using NV.  Averaging the images in NightCap does not brighten them; it only eliminates extraneous noise.  For example, in Aug 2017, I took an untracked snapshot of M22 with my iPhone 6+ using the phone's automatic camera settings.  It wasn't great, but it showed me that the phone could do an adequate job for some NV targets.  So here is that iPhone snapshot using the phone's automatic settings (several months before I started using NightCap for NV phonetography).  Metadata shows this image of M22 was taken on 28 Aug 2017, and was a 1/4s exposure at ISO 500.  The point of this old image is to show that many globs do not require a really long exposure when using NV.  With NightCap, I often use higher ISO with even shorter exposures that I then average to rid the image of noise.  With Android, you might try setting your ISO to the lowest setting for the least noise and then use a sub-second or 1 second exposure.  The great thing about digital imaging is you can take as many images as needed to get them just right... or use any results as a reminder of what you saw visually.   I save my old images mainly to see if I can improve on them.  

 

IMG_6917.jpg  

 

You are also correct about a higher ISO in my images reflecting a dimmer subject.  As you know, the iPhone is limited to a maximum 1s exposure.  To make a dim subject brighter, I adjust ISO up.  Then I use NightCap to average multiple short exposures to eliminate noise acquired from the higher ISO.  The Android system allows longer single exposures, so as a rule, does not need averaging.  In the near future, I'll be experimenting with longer single exposures that are not averaged; this will be new to me with new parameters.  🤔


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