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Expectations and The Grey Smudge

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#1 dcweaver

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Posted 05 February 2021 - 10:59 PM

Conversation with my wife this morning:

   
Wife:  Why were you up until 4AM
Me:  Check out this image I captured

   
Wife:  Yep, it's another smudge
Me:  But this smudge is special.  Do you see anything unusual about it.

   
Wife:  There's a streak coming out of it
Me:  Bingo! (with a big smile)

   
This conversation illustrates a difference of expectations that can ultimately drive satisfaction with the hobby.  My wife has the expectation that images should look like Hubble Space Telescope images.  My expectations are significantly lower, because I tried to look at DSO through an eyepiece from my light polluted back yard, and saw a grey smudge, or nothing at all.  Funny thing is, she was usually looking through the eyepiece with me, and you would think her expectations would be lower now as well.  I think she just likes to keep the grey smudge harassment going.  Regardless, expectations stand between us and our money.  The law of expectations demands that one must be reduced to reach equilibrium; expectations, or money.  Most often the latter is what gets reduced.  We throw money at equipment trying to satisfy our expectations.

   
The smudge I was so exited about was the galaxy M87.  It's a rather uninteresting target unless you know what to look for.  On the surface, it's just a bright smudgy looking galaxy, among many others that have more interesting features.  But as I told my wife, this one is special.  She noticed it immediately.  This galaxy contains a black hole at its center, that is feeding, or at least it was feeding 55-60 million years ago when the photons captured in the image left home.  That hungry black hole spit out some of what it consumed at near the speed of light, forming a relativistic jet that stretches across 700+ light years of its neighborhood.

   
M87 was a fun target for me that was inspired by the following threads on the forum. 

   

https://www.cloudyni... seen at f10
   

https://www.cloudyni...e-jet-from-m87/

   
The thing that caught my attention was the fact that people were capturing the jet with apertures ranging from 16 inches to 70 mm.  They were also having better luck with short exposures than long exposures.  My 15 year old, Costco Joe Nextar4, is a small 102 mm Mak paired with one of the lowest cost goto mounts Celestron offered at the time.  It has trouble capturing anything longer that 4 seconds due to tracking jitter, so basically, the M87 jet is right in my sweet spot!

   
I captured the image below in the wee hours of the morning between midnight and 3:30AM.  Atmospheric transparency was excellent, seeing was average, and light pollution was bad.  To try for the best pixel scale, 0.6 arcsec/pixel, no reducer was used initially.  Capturing the galaxy easy enough, but the long focal length (1325 mm) bounced it around the sensor enough to smear any fine detail where the jet was supposed to be.  The long focal length was always a problem with the mount's tracking jitter and small ASI224 sensor, so I added a GSO 0.5x reducer and a 1/4 inch (6.5 mm) spacer.  That combination gave optical parameters close to a typical 4 inch refractor, which was the second reason for chasing this target.  I wanted to know if it was possible to see details like this with a small refractor on a solid EQ mount.  To me, this combination feels like the most portable, fiddle free imaging solution, EAA or otherwise, for my situation, which means setting up and tearing down each night to preserve my wife's backyard Feng Shui.  I wanted to get a feel for the interplay between Dawes/Raleigh, seeing limits, and pixel sampling with 102 mm aperture.  After all, the best images of the jet were coming from 8-16 inch Howitzers.

   
The image was a "save exactly as seen" from SharpCap's live stacking tool.  It was built from 300 one second exposures.  I tried shorter and longer, but one second worked out best.  I also tried "lucky imaging" by setting the FWHM filter toward the middle of the range that was being captured, stacking only the best frames.  It wasn't any better than the "kitchen sink" stacking after a couple of minutes so I stopped.  It was already 3AM and I wasn't feeling "lucky".  There is a reference line between two nearby objects to cross check I was looking in the right place and not at a random diffraction artifact.  So while I've seen better, the smile I got from my wife this morning tells me this exceeded her expectations.  I know it exceeded mine!

   

Annotated Final.JPG

   

M87 Feb-5-2021, 300 sec subs, 300 sec total, 0.5x reducer, ZWO ASI224, Celestron Nexstar4, 737 mm focal length, f/7.2


Edited by dcweaver, 06 February 2021 - 01:10 AM.

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#2 colinrasmussen

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Posted 06 February 2021 - 12:09 AM

Way better conversation than ... WIFE: Where were you until 4 am? ... YOU: ... uhhhh ....


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#3 SanjeevJoshi

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Posted 06 February 2021 - 02:31 AM

Great job!  Really amazing what you can do with focus and determination!



#4 RarePepe

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Posted 06 February 2021 - 04:18 AM

This is stunning result for such a small scope and 1sec exposures! Gives me hope that my 130mm F5 newton will catch the jet in M87 too.



#5 alphatripleplus

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Posted 06 February 2021 - 09:12 AM

Nice story. Yep, the M87 jet is a good candidate for this sort of very short exposure stacking with a low read noise camera. I'm impressed that SharpCap was able to align the 300 x 1sec exposures - sometimes if the field is very small it will complain about not enough alignment stars  when using very short sub-exposures to live stack.



#6 iantaylor2uk

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Posted 06 February 2021 - 09:24 AM

I've also recently been experimenting with short exposures (with an ASI 071 Pro MC camera) - in my case they were 10 second exposures with a 110 mm Starwave ED-R refractor (with a 0.72x focal reducer). 

A single frame just shows a small grey smudge, but after stacking 50 or so frames, and then processing, you do see something that does resemble the crab nebula: 

 

single frame: https://chesterastro...rame.jpg?w=1024

final image: https://chesterastro...ssed.jpg?w=1024


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#7 Rickster

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Posted 09 February 2021 - 12:34 AM

From roughly this time last year...

 

M87 relativistic jet  2-29-2020

16in SW on GEM.  No coma corrector, flat, darks, or filters.  432x1sec.  Saved as viewed and cropped.

[ZWO ASI183MM Pro]
Binning=1
Colour Space=MONO8
Gain=320
Exposure=1
Temperature=-2
Cooler Power=0
Target Temperature=0
Cooler=On
TimeStamp=2020-02-29T08:18:38.2757316Z
SharpCapVersion=3.2.6232.0

 

 

Attached Thumbnails

  • m87 423x1s crop.jpg

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#8 dcweaver

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Posted 09 February 2021 - 02:05 AM

Rick,

 

That is an awesome shot!  It's actually what inspired my "16 inch Howitzer" reference.  The detail you captured with that combination of big aperture and small pixel size is amazing.  You can see the jet rolling up like smoke from a good cigar as it gets further from the core.  Thanks for adding it to this thread!


Edited by dcweaver, 09 February 2021 - 02:08 AM.

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#9 Astrojedi

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Posted 09 February 2021 - 02:17 AM

You don’t always need a 16” to capture the jet wink.gif

 

Here is mine with an EdgeHD 8 from my Bortle 8/9 skies.

 

m87-jet-apr-2019.jpg


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#10 alphatripleplus

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Posted 09 February 2021 - 08:42 AM

I always love seeing  those high resolution captures of the M87 jet!



#11 Rickster

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Posted 09 February 2021 - 08:46 AM

Good point AJ.  M87 is a relatively bright target.  What one really needs is exceptional seeing.  In my case, there was a brief calm period right before a front passed through.  Short subexposures also help.  And, of course, your rig needs to be well tuned.


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#12 dcweaver

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Posted 09 February 2021 - 11:50 AM

Lol.  Thanks AJ!  Your shot was my reference to the "8 inch".  You and Rick had the best captures I found.  I actually ran yours through nova.astronomy.net and worldwide telescope to make sure I was looking in the right place for the jet.  It had enough other stars to get a good reference.  Amazing that you got that level of detail with the 8 inch SCT and reducer.


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#13 Jeff Lee

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Posted 10 February 2021 - 09:41 AM

I think this is a great post and discussion and should give hope to all who live in LP areas where they do most of their viewing. While visual at dark sites is a treat, EAA in LP means that one can explore space with EAA in a manner that is both fun and fulfilling. Great job all who posted.


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