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04-13-2018, 11:44 AM - 2 Likes   #1081
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K-5 at ISO 80 : Very Best APSC Sensor 4 Long Exposure

QuoteOriginally posted by gbeaton Quote
... you can get Pentax and other sensor data here: Sensorgen - digital camera sensor data
.
You've had a good idea, gbeaton !... I already know Sensorgen.info, but...
it reminds me a nice way to understand how easily the K-5 detects very faint lights at ISO 80 !
Sensorgen calculations from DxOmark Full-SNR

Open the K-5 in DxOmark Database
- Open it in a New Tab at Measurements / Full-SNR tab...
- Open the Eos 7D & Eos 1D Mk IV at Measurements / Full-SNR in 2 more Tabs
the 3 Cameras Sensor I've compared in 2011

Everything you need to know about a Camera-Sensor's Behavior in Low-Light is here

Let's Compare their Detection Threshold at -1) base ISO -2) ISO 1600
Base ISO Detection Threshold - PK-5 0,008% - C1DM4 0,036% - C7D 0,045% of Gray Scale
ISO 1600 Detection Threshold - C1DM4 0,097% - PK-5 0,109% - C7D 0,193% of Gray Scale

=> Pentax K-5 is far more Sensitive at Base ISO than a Good & Expensive Canon PRO cam.
Subtracting tens of Bias-Maps & Dark-Frames from the Eos CR2 files will lower their Noise
but they will Never Detect 0,008% Gray Details unless you Stack tens+tens of RAW files
while Pentax K-5 and its Very Low Noise only needs from 3 to 6 RAW files at ISO 80
Don't forget final results are worse than theory, Canon Banding is Not Measured :
https://en.astronomike.net/deep-sky/nebulae/162986.html

The Eos 1D Mk 4 is slightly more Sensitive than the Pentax K-5 at ISO 1600
ISO 1600 difference could be worse if shooting with Newer Canon cams

3 Re-Scaled DxOmark Full-SNR Charts Comparison posted in 2011 :
Pentax K5 vs Canon 7D : comparaisons et raisons
.
Re-Scaled DxOmark Full-SNR Charts with base ISO & ISO 1600 Detection Thresholds :
.

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Last edited by geo444; 04-18-2018 at 03:50 AM.
04-18-2018, 05:07 AM - 3 Likes   #1082
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Long Exposure @ Base ISO : a Pentax K-5 !... what else ?

.
To answer the "what else" question, I summarized :
- the Top-8 Cameras with lowest Detection-Threshold < 0,01% @ 0dB SNR, from DxOmark
same as in my previous post, ordered by Measured-ISO
- the Top-8 Cameras with lowest Noise-Levels in 5 min. Dark-Frames
from The Sensor Noise DB. Brendan Davey Photography
ordered by their Noise-Mean-Value

Pentax K-1, the 95 Top Measured-ISO with a Detection-Threshold of 0,009% @ 0dB SNR
+ the 2nd Noise-Mean-Value just behind the Pentax K-5 in 5 min. Dark-Frames (+5ev)

The very Low Dark-Current levels of the Sony imx071 explain the Pentax K-5 Top position
= the 1st lowest Noise-Mean-Value in the 5 min. Dark-Frames (+5ev) test
the Dark-Current Chart is from the Zwo Astro imaging site :
https://astronomy-imaging-camera.com/products/asi-cooled-cameras/asi071mc-pro/
Same Sony sensor, at a $1700+ price !

Then the Asi071(K-5) compared to the Asi294 and Asi1600
= two Astro-Cams with 4:3 ~22,7mm diagonal sensors

High ISO settings are mandatory to lower the Exposure Time to 1 sec. or less
this to cancel the Atmospheric Turbulence effect with long FL.
the only way to operate with Lucky Imaging !

But finally, what do you lose from Base-ISO to ISO 10K :
- Dynamic Range value from 14 ev down to 7 !
- Tone Values from 16384 down to 128 !
- SNR to be Half the Base ISO SNR
- your RAW File Size doubles
- for the same final IQ, you'll have to Stack much more RAWs...
- with Dark-Frames !
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Last edited by geo444; 04-21-2018 at 12:32 PM.
06-19-2018, 09:11 AM - 5 Likes   #1083
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Eagle Nebula and Lagoon/Trifid Nebulas with Webb's Cross

I had the IR-cut filter and anti aliasing filter removed a couple months back, and now have a capable astronomy camera with a bare sensor. I think it was about $250 conversion at spencer's camera, and is now a capable atro-photography camera.

The Eagle Nebula with the Pillars of Creation in the center I shot 90 lights and 30 darks at 45-second exposures and ISO 400 with my Skywatcher Maksutov-Newtonian 190.
The Lagoon/Trifid Nebulas with Webb's Cross in the top right corner I shot 90 lights and 30 darks at 30-sec exposures and ISO 400 with my Takahashi FSQ106ED.
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06-19-2018, 10:57 AM   #1084
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QuoteOriginally posted by Eric Seavey Quote
I had the IR-cut filter and anti aliasing filter removed a couple months back, and now have a capable astronomy camera with a bare sensor. I think it was about $250 conversion at spencer's camera, and is now a capable atro-photography camera.

The Eagle Nebula with the Pillars of Creation in the center I shot 90 lights and 30 darks at 45-second exposures and ISO 400 with my Skywatcher Maksutov-Newtonian 190.
The Lagoon/Trifid Nebulas with Webb's Cross in the top right corner I shot 90 lights and 30 darks at 30-sec exposures and ISO 400 with my Takahashi FSQ106ED.
Congratulations Eric! They did a good job obviously

07-11-2018, 01:48 PM   #1085
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Those results now have me really considering getting the recently aquired "slightly used" K-5 I grabbed from Adorama modded. Being on the fence has now become to almost the jumping off point. I don't have the cam in my possession as of yet though..
08-26-2018, 06:58 AM   #1086
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After reading through this thread, it got me interested in seeing what my K-5 could do last night. Considering that it was unmodified and horrible astronomy conditions with haze, cloud and the night before a full moon; I'm actually impressed with what it was able to do with my 28mm @ f2.8 & ISO 1600 with a 20 second exposure. It's enough to make me wonder if I should go after a faster 28mm.
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08-26-2018, 03:12 PM - 1 Like   #1087
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QuoteOriginally posted by DrMindbender Quote
After reading through this thread, it got me interested in seeing what my K-5 could do last night. Considering that it was unmodified and horrible astronomy conditions with haze, cloud and the night before a full moon; I'm actually impressed with what it was able to do with my 28mm @ f2.8 & ISO 1600 with a 20 second exposure. It's enough to make me wonder if I should go after a faster 28mm.
Until you decide what to do, here is a slightly different approach. You can stack any number of images, which would combine all the captured light together. Just aim the camera to the sky and take multiple images. It would be better to have the mirror up and just put the body in burst mode. I would probably go with 10 second exposures to keep the star trails at a minimum.Then use a program like sequator (free download), to align the images together and then stack them.
08-26-2018, 06:17 PM   #1088
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QuoteOriginally posted by interested_observer Quote
Until you decide what to do, here is a slightly different approach. You can stack any number of images, which would combine all the captured light together. Just aim the camera to the sky and take multiple images. It would be better to have the mirror up and just put the body in burst mode. I would probably go with 10 second exposures to keep the star trails at a minimum.Then use a program like sequator (free download), to align the images together and then stack them.
Thanks for the pointers. Fortunately, or unfortunately, I'm in no rush to do anything other than aim up and shoot thanks to the full moon. So it will be a few days before I try the "burst and stitch" method.

09-28-2018, 02:55 PM - 3 Likes   #1089
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Here another couple shots taken with my modified K-5 camera... Helix Nebula and Comet 21P Giacobini/Zinner in conjunction with Messier 37
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09-29-2018, 04:00 AM   #1090
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QuoteOriginally posted by Eric Seavey Quote
Here another couple shots taken with my modified K-5 camera... Helix Nebula and Comet 21P Giacobini/Zinner in conjunction with Messier 37

VERY! nice, Eric! Congratulations!!!
09-29-2018, 07:22 AM   #1091
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Visually stunning, Eric. I particularly like the comet and the star cluster. Nice colors in the Nebula. Very well done. If you already haven't done so -- you should cross-post the images over on the CN digital photography forum -- just to show those guys the capabilities of a Pentax camera.
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