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EAA observations: Hickson 44, VV 242 and NGC 4449 + quasars


Martin Meredith

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I had a chance to observe more objects last week with a bright moon in the same quadrant, hence pretty poor SQM readings of under 18.

Hickson 44. Although the Hicksons are generally quite compact, there are exceptions, and Hickson 44 has, I think, the largest angular size of any of the catalogue. I've observed it before but this configuration of 4 very different galaxies never fails to impress me.

77321993_anon15Mar19_21_21_44.jpg.5282014566fe4df2215145624e06aba6.jpg


VV 242. It was quite hard to extract much detail from what looks to be a highly-irregular pair of galaxies (NGC 3447 and NGC 3447a), presumably resulting from a recent interaction. This galaxy pair is right next to an Abell galaxy group (to its upper-right). 

750074102_anon15Mar19_20_41_32.jpg.93da86c8212228092479b9b98ac9990d.jpg

Here's a close-up of the pair (oriented with N at top) showing lots of knots and the hint of a halo/spiral arm around the main galaxy:

566276838_anon15Mar19_20_32_26.jpg.3d295b137223d7ae01f3ab2dc666a5e5.jpg

 

 

A much brighter irregular galaxy is NGC 4449. Further to the recent debate(s) on the links between NV, EAA and visual, I often take inspiration from what people with large scopes are looking at through the eyepiece, and this object is one of those, based on an interesting thread on CN: 

https://www.cloudynights.com/topic/654013-observations-of-ngc-4449s-super-star-cluster/

This is a really interesting irregular object with loads of structure. Not only does the interior have lots of star-forming regions, but there is a clear outer halo shaped a bit like one of those shark egg sacs you sometimes find on the beach (or maybe a bow-tie). 

I'm looking forward to revisiting this object in H-alpha, or doing a luminance + h-alpha combination, as it looks like it will be revealing. This object benefits from a very strong stretch in order to see the knots and 'halo' at the same time.

1843535898_anon15Mar19_22_14_39.jpg.c3f7e393ae0779c9b73b08d496267844.jpg

 

I've also marked the locations of 3 quasars. I was observing this for a full 50 mins = 100 subs@30s while looking online for more information about the object and ensuring I could identify the quasars. The three are quite different in terms of magnitude and distance. I applied the SNR calculations from another thread on monochrome sensors to these to work out whether theory and practice meet.

The mag 18.3 quasar has a redshift z=0.66 hence around 6-7.5 billion LYs distant. This is clearly visible on a single 30s sub (peak SNR 5.4).
The 20.2 quasar has z=3.14 ~ 9.5-11.5 BLYs and needs 40-50 x 30s to be sure of detection (peak SNR after 30 subs=5.0)
Although I've indicated the location of the really faint mag 20.9 z=3.82 ~ 10-12 BLYs, I wouldn't count this as a positive detection and in fact it is very marginal even after 100 subs (peak SNR after 50 subs=3.2). Still, all this is with a relatively mediocre sky, simply pointing to the incredible feats some of the modern sensors are capable of coupled with a modest reflector.

Thanks for looking

Martin

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Hi Martin,

Just enjoyed reading your latest report. Impressed with the detail you have captured in all the images and the professionalism of your report. Hickson 44, you also captured PGC 1657031 and PGC 86788. I recently visited Hickson 44 but could only get three of the galaxies in the fov. Is it etiquette to post my image at this point as a comparison (not interested in one up man ship , simply to learn from and enjoy each others achievements or failures). Your image is smooth, mine tends to be grainy. I know SLL live does dark frame subtraction but I assume you go to some other software to do flat and bias (not that I know what they are). I used linear and sum in my stack but I must give your combination of arcsinh and mean a go.

Like you I note what the visual folk are doing and then see what I can capture.

Cheers

Mike

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Thanks Mike. Sure, please do post your image. I'm using the Jocular app that I'm developing (release soon) to handle flats/bias/darks automatically (this was a sky flat I'd take some weeks back). Linear tends to blow out the core so I typically use one of the others. Arcsinh is good because it handles not just the upper end (compression) but also the lower end near the black point smoothly. This can make a lot of difference to the noisy appearance of an image. Sum/mean ought to produce the same result.

cheers

Martin

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8 hours ago, RobertI said:

Very nice result Mike. What camera were you using? 

Hi Rob, I use the SX Ultrastar Mono, on my C9.25. I have experimented using the scope at F10 but seem to have settled to using it at F5 (camera plus Altair Astro focal reducer).

Mike

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Hi Martin, Last night was clear so I pointed the C9/Ultrastar  again at Hickson 44 and used your advice. Very pleased with the result, many thanks. I went for 30sec subs which caused slightly elongated stars. Ignore the caption which says C9 at F4, it was at F5. Conditions were good enough to operate at 1x1, no need to bin. I am not sure I would want to normally do a 5 minute run but delighted to discover what is possible. Image is exactly what I saw on the screen.

I tried doing a run with a saved dark frame and all I got was a dark black background with bright star like objects and no image. So I had to turn the camera off and reboot SLL and abandon the idea of a dark frame.

All the best

Mike

HICKSON.44_2019.3.24_20.45.59 10x7 at 300.png

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