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Quasar 11.6Bly Distant - Magnitute 21.7 in Short Exposures

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So conditions around mid night last night were excellent (or rather as good as it gets here... NELM 4 -4.25 at zenith), low humidity. So decided to give my Quasar hunt one more try.

Managed to get down to mag 21.7 using short exposures 10x25s (average stack) using the Ultrastar mono x2 binned. This was using the C8 at F5. No LP filter.

The NGC4666 (Superwind field is littered with Quasars as per Martin's deep maps). I identified and marked 3 but there are more in the image if anyone wants to give it a go.

The most distant one in the image that I marked is barely visible and required an aggressive stretch. It has a magnitude of 21.7 and a redshift of 2.25 which puts it at 11.6 Bly.

Note the dark circle you see in the center is not technically vignetting that you see at high focal reduction. It is actually a reflection I am getting off the optical system. I suspect it is due to the clear filter I use to keep dust off the sensor. I will take flats next time which should fix this.


superwind 10x25s.png

Edited by Astrojedi
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Amazing work - into m21 quasars at the edge of the universe - deeper than I managed - must try harder!  Wonder if the sensors near-IR sensitivity helps -assuming quasars at this range emit in these wavelengths?


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Thank you all for the likes.

Thanks Nytecam. Yes IR sensitivity and a naked sensor are important to capturing maximum photons and these faint ones. But the 13 micron pixels with high QE and low read noise are in my view what make this possible in such short exposures.

Edited by Astrojedi
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A picky technical note about these very distant objects.  As z gets large (like more than 1) the divergence between the light travel time from an object (extrapolated from observed z and known c) and the "true" cosmological comoving distance to the object (distance you would measure with a ruler today) starts to become significant.  The graph I'm going to try and attach here shows "lookback time" (how long the light has been traveling) asymptoting at around 13.8 Gy (light can't travel for longer that the whole age of the universe), while line-of-sight comoving distance to objects reaches nearly 40 GLy (at z=10000, the CMB).  Your z=2.25 equates to a light travel time of 11.6 billion years, but due to the expansion of space, that object is presently closer to 20 billion light years away from us.  Pretty cool stuff.



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Superb capture Hiten! As you say, there are a few more in the field. I'd say you've just about caught a slightly more distant mag 20.8 redshift 2.35 object too (SDSS J12453−0021). Very impressed you can get to mag 21.7 -- gives the rest of us something to aim for! I nowadays routinely shoot through a clear filter but for this kind of ultra deep stuff its probably worth removing it ;-)


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That is correct. I ignored the expansion of space which is expanding faster than the speed of light. It is sad to know that certain part of the universe will never be a accessible to us due to this expansion.


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2 hours ago, Ain Soph Aur said:

Hi Hiten. Since these were binned, I assume they were not captured and stacked with Starlight Live?

Correct. For this capture I used Maxim DL for image capture and AstroToaster for stacking.

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