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Distant Galaxies and Clusters

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#176 Redbetter

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Posted 09 September 2019 - 05:20 AM

I have not observed that many near 3 billion light years.  I covered the main ones that I recall in the thread about it and they are all massive galaxies.   I go past 2 at times when I start targeting some of the dimmer Abell clusters or if they happen to be in the field, but I really haven't kept track of them as a class. There was one recently at a little under 1.75 billion light years, PGC 200336. tucked between another pair with another gx forming the group VV129 in Hercules.  The PGC runs somewhere in the 17+ g mag range. 


Edited by Redbetter, 09 September 2019 - 05:21 AM.


#177 quazy4quasars

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Posted 09 September 2019 - 12:13 PM

I have not observed that many near 3 billion light years.  I covered the main ones that I recall in the thread about it and they are all massive galaxies.   I go past 2 at times when I start targeting some of the dimmer Abell clusters or if they happen to be in the field, but I really haven't kept track of them as a class. There was one recently at a little under 1.75 billion light years, PGC 200336. tucked between another pair with another gx forming the group VV129 in Hercules.  The PGC runs somewhere in the 17+ g mag range. 

Yeah, these suckers are darn faint.  I keep wanting to try for a little further, but I find I need ideal conditions to have even a hope of a (mostly direct) view of anything around or beyond z~.2... maximum contrast and high-power seeing both required.  Next up for me is  SDSS J215541.97+123128.5  (Ogle 0023) BCG of Abell 2396- at z~.193 - when I get back "up the hill", along with a (barely) direct sighting of A2261, hopefully...   meantime, I'm revisiting deep QSOs (easier) and soaking up Summer Milky Way splendors (easier and prettier!), anyway, thanks Red.  Sure hoping the smoke holds off. 

   

We'll see...


Edited by quazy4quasars, 09 September 2019 - 04:06 PM.


#178 Knasal

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Posted 09 September 2019 - 10:25 PM

I use Naglers, typically 9T6 or 7T1 and if the seeing is good enough and the target small enough, a 5T6 or 3-6 TV zoom for the most distant targets at 2 to 3 billion light years.  I could probably use an 8mm...there are times when going from the 9 to the 7 is a little beyond what conditions really support. 

Can you tell us the magnification you get with the 9T6 and 7T1 in your 20”, and whether you use a TV Paracor with them?

 

What would Mag be with the above EPs if that’s the case?

 

Thanks, just trying to compare with my setup.

 

Kev



#179 Redbetter

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Posted 10 September 2019 - 12:32 AM

With my scope the mags are: 9mm = 278x, 7mm = 357x, 5mm = 500x.  6mm (in zoom) = 417x. 

 

I don't have a Paracorr. 

 

I use 278x most of the time for galaxies since my dark sites will typically support that.  When they don't I will use the 11 for 227x, or even a 13 for 192x if it is particularly bad (the latter is usually limited to winter observing in the Valley.)

 

For the most distant galaxies and smallest cluster members I will go as high as seeing permits but 357x is a typical limit on a decent night, perhaps 500 or more during the most stable time of the year at my more stable site. 

 

When I say "when the seeing supports it" I am referring to the level of blurring/flaring/rapid focus movement that renders the smallest/dimmest galaxies nearly indistinguishable from 16, 17, or 17+ mag stars...or pairs or trios of the same.  If the seeing is several arc seconds further magnification only increases the moving blur and it is hard to distinguish a bloated dim star from a the semi-stellar core of a galaxy that is itself is perhaps 10 arc seconds across. 



#180 quazy4quasars

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Posted 10 September 2019 - 11:49 AM

  I'd add that (less than ideal) seeing and LP sky glow (less than ideal transparency) both place effective limits on the usable magnification for these most distant and reddened BCGs: When faint stars become "Fuzzy Li'l Nuthins", the already really dim and very small real  FLNs (the barely visible BCG cores) begin to become mere INs -"Invisble Nuthins"; -they're never very far from that threshold. Even in a very dark sky, in great seeing, they are (those featuring AGNs excepted) close to the practical limit of visible scotopic SB contrast - For me they are, anyway- cool.gif    


Edited by quazy4quasars, 10 September 2019 - 01:23 PM.


#181 NGC7702

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Posted 02 October 2019 - 08:37 PM

Hi All,

In terms of "normal" galaxies (ie not QSOs) a possible target for southern hemisphere observers with very large telescopes is ESO 146-8 near the Indus/Tucana border. I haven't had a crack at it as yet but will do so in the next couple of months with my 25" f/5. It has a nice set of nearby marker stars that should make identification of the precise location pretty easy. My observing site in central NSW, Australia typically has SQM-L readings near zenith of about 21.7 - 21.8 this time of year on moonless nights. Even so, I think it would be pushing the edge of the envelope.

ESO 146-8 has a B mag of +16.7  coupled with V(km/s) +48400 [~] / z(~) 0.176884 [~] implying a look-back time in the order of 2.2 Gyr (assuming a Hubble constant of 71.5 kms/sec/Mpc).

http://simbad.u-stra...ubmit=submit id

It is found only a couple of high-power fields away from the somewhat brighter but still very distant ESO 146-5 (I have seen ESO 146-5 in my 18" f/4.9) that has a B mag of 15.75, V(km/s) +28711 [99] / z(~) 0.10083 [0.00033] and therefore resides probably about the 1.3 Gyr look-back time.

http://simbad.u-stra...ubmit=submit id

 

 

Best,

L.

Hi All,

 

I can add that I was successful in observing ESO 146-8  on 25th September 2019 with my 63.5cm f/5 at x260 and x347. The observing note follows:

x347: Very to extremely faint and tiny -- probably no more than 15" diameter if that spot of V/LSB ephemeral mist with no visible internal brightening. No structure visible. Can be glimpsed with A/V every several seconds. Must pinpoint location exactly. Not visible at x196, detectable but less certain at x260.

 

I might also add that following on upon that successful sighting, several days later using a friend's 50cm f/5 at x277 (different, but similar quality observing site) we were able to detect it at x277 at least several times per minute.

I had previously observed ESO 146-5 (which is one of the, if not the most massive galaxy in the "local" Universe) with my own 46cm f/4.9 at x185. I observed it again and the note follows:

x185: Very small to tiny and very faint spot of mist about 15" diameter 1.5' SE of a magnitude 12.5 star than can be just held continuously using A/V. Consistent S.B halo, no other visible structure.

 

ESO 146-5 weighs in about 30 trillion solar masses and is the dominant galaxy in AGC 3827.

Best,

L.


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#182 quazy4quasars

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Posted 02 October 2019 - 10:51 PM

Hi All,

 

I can add that I was successful in observing ESO 146-8  on 25th September 2019 with my 63.5cm f/5 at x260 and x347. The observing note follows:

x347: Very to extremely faint and tiny -- probably no more than 15" diameter if that spot of V/LSB ephemeral mist with no visible internal brightening. No structure visible. Can be glimpsed with A/V every several seconds. Must pinpoint location exactly. Not visible at x196, detectable but less certain at x260.

 

I might also add that following on upon that successful sighting, several days later using a friend's 50cm f/5 at x277 (different, but similar quality observing site) we were able to detect it at x277 at least several times per minute.

I had previously observed ESO 146-5 (which is one of the, if not the most massive galaxy in the "local" Universe) with my own 46cm f/4.9 at x185. I observed it again and the note follows:

x185: Very small to tiny and very faint spot of mist about 15" diameter 1.5' SE of a magnitude 12.5 star than can be just held continuously using A/V. Consistent S.B halo, no other visible structure.

 

ESO 146-5 weighs in about 30 trillion solar masses and is the dominant galaxy in AGC 3827.

Best,

L.

I wish, that for just even one night per month, the Earth really were flat. Then we all could see those behemoths.

 

I'd give my eye teeth to see them in my big scopes!  But- the eye teeth market is saturated.  A3827, A2744 etc; and some great QSOs, not to mention all the glories of the Southernmost reaches of the Milky Way and the 3 best Globulars in the whole sky!  Darn Spherical Earth!   At least we have the internet for the pics. But you're there, mate. Lucky Dog!  How I envy you.


Edited by quazy4quasars, 02 October 2019 - 10:52 PM.

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#183 sgottlieb

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Posted 03 October 2019 - 06:35 PM

  There were a number of quite distant Galaxies (Super Spirals and BCGs) that I didn't manage to attempt this Spring due to weather and my dark sites being snowed in;  All are low surface brightness and generally they need to be attempted near their culmination, under decently dark skies: Now many are falling into the West; and the Summer -the inner- Milky Way is rising to its late Summer prominence. 

   

  For those who are smitten with the Deep Galaxy bug and want to get a jump on the ones on the other side of the Milky Way, through the Southern Window, I offer this small selection: Some of these are 10-12" and up, others are more like 18-20" class, but dark sky is the main limiter of course:  These are among the most likely visually detectable at such distance; complied from multiple catalogs. You can check CDS, NED, HyperLeda for details:  

 

PGC 188874

PGC 97447
PGC 1480586
PGC 1013135
PGC 71834
PGC 1008418
PGC 97456

 

Fall is coming...Happy hunting!

I thought I would follow up on a few of your suggestions at last week's central California star party (CalStar) at Lake San Antonio.  Both transparency (SQM 21.4-21.5) and seeing were off from previous years, though dark enough to easily surpass the 1 billion l.y. threshold with my 24" Starstructure.

 

PGC 97456 in Aquarius and PGC 71834 in Pisces have similar redshifts (z = .083 and .084) and light-travel times of 1.1 billion years.  PGC 97456 is the BCG (brightest cluster galaxy) in the Abell cluster 2448 and PGC 71834 is the BCG in the SDSS cluster [GMB2011] 1462.  Although their listed magnitudes are similar (about V = 14.5), I found PGC 97456 more prominent (visible continuously), despite being nearly 10° further south.  But I logged PGC 71834 as larger (~0.3' diameter) than 97456 (~0.2' diameter).

 

LEDA 188874 is also in Aquarius and well placed this time of year.  This one is over a magnitude fainter (B mag close to 17) and quite small.  At z = .137, the light-travel time is ~1.8 billion years.  It only popped intermittently for me, though the galaxy is partially "masked" by a mag 15.7 star only 20" NE.  The position was pinpointed using a nearby galaxy (CGCG 375-048) 8' E and 9th magnitude HD 204738, a similar distance NE.  LEDA 188874 forms the southwest vertex of an equilateral triangle with these two objects.

 

As far as distant galaxies, I also took a look at IC 1757 = LEDA 174458 in Cetus, which was discovered visually by Barnard, probably with the 36-inch refractor at Lick.  Its redshift is similar to the first two, so tops the 1 billion year threshold.  This galaxy is just 1.5' east of IC 1756 = UGC 1429, a faint (but brighter) edge-on that lies in the foreground.  The SDSS image of the pair is here.  HyperLEDA and SIMBAD don't recognize the IC designation, but NED does.


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