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M33 Triangulum

astrophotography CMOS imaging
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#1 craine

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Posted 20 September 2020 - 11:04 PM

Friday night I was able to head south by about an hour and set up in the middle of a corn field outside of Rochester, MN, This was the first time I was able to get to a darker site, and was certainly much darker than what I normally get from my backyard in suburban Twin Cities. It was also the first time I was able to really test out my newly completed rig, so one could consider this first light, if you ignore the terrible previous night's attempt. 

 

I ran a sequence in N.I.N.A. for 100x300s lights through an Astronomik L2 UV/IR cut filter at -10C. I had a little trouble nailing the focus since I seem to have lost my bahtinov mask, but managed to get it close enough. N.I.N.A.'s optimal exposure calc told me to shoot for 432 seconds, but I thought that was a tad optimistic, and to be honest I don't have that much faith in my mount just yet. The next morning, I ran 128 flat frames, because I had time, so why not. I've previously shot and stacked master biases and darks at the same gain and temp, so I reused those. 

 

All in all I had a successful night. The skies were very clear all night long, and we didn't have much of any haze or smoke like we have been recently (yes, we've been getting smoke from the PNW all the way in MN). I was able to sit down and process my data. After running through Siril, ASTAP, Nebulosity 4, and DSS (which kept crashing), I settled on my second run of ASTAP and ended up with this as the result. I'm happy with what I have, though I think I can eek out a bit more detail with time and experience. 

 

Click on the photo for a link to AstroBin. 

M33, 2020-09-19, 62x300L , AT72ED II, LumL2, ZWO ASI183MC Pro  (cloudynights).jpg

 

 

Gear List:

  • iOptron CEM25P
  • Astro-Tech AT72EDII
  • ZWO ASI183MC Pro
  • QHY miniGuideScope and QHY5III-224MC
  • Starfield Optics 1.0x Field Flattener
  • Dew heaters for both scopes

 

Acquisition Details:

  • Lights: 100x 300s @ 50 gain, 10 offset, -10C temp
  • Flats: 128x 0.025s @ 50 gain, 10 offset, -10C temp
  • Biases: master @ 50 gain, 10 offset, -10C temp
  • Darks: master @ 50 gain, 10 offset, -10C temp

Stacking and Processing:

  • Stacking in ASTAP
    • Analyze and uncheck worst 2 stdev
      • Ended up with 62 keepers out of 100. I had an issue with reentering after the meridian flip, so that is probably where the bulk of the lost ones went
    • 2x2 mean master flat
    • Sigma clip average
    • Bayer-Simple de-bayer method (AstroC resulted in weird colors)
  • Processing in Photoshop
    • Adjusted output level maximum down to 174
    • Set black point on background 
    • Reduced exposure by -0.56, offset by -0.0004, applied gamma correction of 0.98
    • Hue +15, saturation +20
    • Adjust RGB curves
    • Export to PNG

  • elmiko, Michael Harris, AstroFrankMontana and 9 others like this

#2 clusterbuster

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Posted 21 September 2020 - 01:45 AM

Very nice !

 Mark



#3 t-ara-fan

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Posted 21 September 2020 - 02:38 AM

Nice shot. That is the target I am after if the smoke is still gone away tomorrow.   Since it is low in the east at dark I can shoot it all night long. I have about 8 hours of true darkness, that should be enough.

 

How does the NINA optimal exposure calc work? Does it work with SharpCap?

 

I usually just shoot 5 or 10 minutes depending on how cooperative my guiding is on a given night.

 

My theory, which is mine, is that a really long sub is going to catch a bunch of photons from faint stuff that only yield a photon to a given pixel every few minutes.  In a 2 minute sub, that hit or miss photon will be stacked out as noise.  Change my mind!



#4 TinySpeck

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Posted 21 September 2020 - 06:09 PM

My theory, which is mine, is that a really long sub is going to catch a bunch of photons from faint stuff that only yield a photon to a given pixel every few minutes.  In a 2 minute sub, that hit or miss photon will be stacked out as noise.  Change my mind!

I was puzzled by this some time ago too, and wrote up an analysis here you might find interesting.  I don't know if it will change your mind though!



#5 craine

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Posted 22 September 2020 - 08:32 AM

Very nice !

 Mark

Thanks!

 

Nice shot. That is the target I am after if the smoke is still gone away tomorrow.   Since it is low in the east at dark I can shoot it all night long. I have about 8 hours of true darkness, that should be enough.

 

How does the NINA optimal exposure calc work? Does it work with SharpCap?

 

I usually just shoot 5 or 10 minutes depending on how cooperative my guiding is on a given night.

 

My theory, which is mine, is that a really long sub is going to catch a bunch of photons from faint stuff that only yield a photon to a given pixel every few minutes.  In a 2 minute sub, that hit or miss photon will be stacked out as noise.  Change my mind!

Thank you. One of the reasons I chose it as a target is that it stays in the sky for so long before crossing the meridian. Normally I'm imaging from the back deck of my house, and only can see objects for about 30-60 minutes after they cross the meridian. 

 

For the N.I.N.A optimal exposure calculator, as I understand it you need three things: 

  1. A SharpCap sensor analysis
  2. A sensor bias reading (taken in N.I.N.A.)
  3. A test exposure of the sky you are imaging (also taken in N.I.N.A.)

From there, I think it is looking at the test exposure, bias, full well, and read noise numbers and doing some form of wizardry to tell you that you can expose for X seconds without blowing highlights and/or losing subtle details. 

 

Up until this night I had not successfully guided longer than 120 seconds with my mount. I bought it second-hand here, and there ended up being a lot of backlash in both RA and Dec which I needed to tune out. A few weeks worth of fiddling and ordering replacement parts has gotten it to the point that I can trust to guide 5 minutes. 




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