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PhotoGav

The Deer Lick Galaxy Group

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Well, it has nothing to do with animals and there are no tongues involved... it is also pretty much all about one galaxy, though it is a visual group. NGC 7331 is the main galaxy, 47 million light years away in the constellation of Pegasus. It is a nearly edge on unbarred spiral galaxy with very evident dust lanes. It appears quite uneven with an off-centre galactic core - perhaps the result of previous galactic encounters? The Deer Lick Galaxy Group comprises NGC 7331 and the four smaller galaxies above it; NGC 7337, NGC 7335, NGC 7336 and NGC 7340, known as 'The Fleas'. These smaller galaxies are far more distant at around 310 million light years from Earth, though the right hand of the four, NGC 7336 is even more distant at around 430 million light years away. So, why the Deer Lick Galaxy Group? Though originally discovered by William Herschel in 1784, it was given the name by astronomer Tomm Lorenzin in honour of the Deer Lick Gap in the mountains of North Carolina, where he had a particularly good view of the group! Fair enough. As for The Fleas - perhaps dancing on the back of the deer? Oh, I don't know! Anyway, enough words, here's the image:

 

DeerLick-LRGB-13-Final.thumb.png.4a17e2aacf4e048eada323e7d84418b5.png

 

Tech details:

Celestron EdgeHD 8", QSI 683-WSG8, Baader 1.25" filters, HEQ5 Pro

L = 21 x 1200s
RGB = 12 x 600s each
TOTAL = 13 hours

All in all I am pretty happy with this one, it's an interesting target and the main galaxy is visually very pleasing. I think the Luminance could have done with even more data as the background seems quite noisy. Possibly that also has to do with a few sub-optimal subs due to not such good atmospheric conditions? It suffers from the usual SCT softness, but I have to tolerate that, unless some kind soul would like to lend / give me a 2032mm focal length refractor, please!?!! I have just put my Esprit100 back on the mount tonight and the sharpness, clarity and contrast that it offers compared to this is outstanding!

I hope you like the image and I look forward to your comments.

Clear skies to you all!

Edited by PhotoGav
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Gav,

That's a beautiful image - definitely benefiting from a very long exposure time! This is on my list of must-do targets. The first thing I think when I see your image is "wow", not "that's soft" - I don't think it is. (Have you tried some subtle deconvolution if it bothers you a lot?)

A question... Have you done a side-by-side comparison of your 100ED and Edge 800 with eyepieces in the two 'scopes, so that they're both providing the same or similar magnification? I've had my TOA150 co-mounted and aligned with both my C11 and Edge 14 (not all three together!) and did that experiment - swapping quickly between two scopes on the same target. My TOA is a very good example - it's been to Es Reid who reported as much. It gives the classic refractor views, and I definitely consider myself to be a "refractor guy" with unashamed bias. But... my conclusion from that experiment was that much of what people refer to as softness in SCTs, is just a consequence of operating at such long focal lengths and large plate scales. Just my subjective opinion - I think if you did find that monster frac and imaged the same target from the same site in the same seeing as this Edge 800 image, the improvement may not be as significant as extrapolating the 100ED experience might suggest.

in any case - lovely image - well done!

Nigel

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Nigel, thank you for your comments. You are absolutely right about that softness, it is the huge focal length and inadequacy of the tracking that gives that softness, not the scope. The 8” and QSI are operating at an image scale of 0.55”/pixel, whereas the Esprit100 and QSI are at 2.03”/pixel. My HEQ5 and OAG guiding manages around 0.66” RMS performance at best, which is steady enough for the Esprit, but way too poor performance for the 8”. So, thank you for sticking up for the 8”! The only problem is that I now realise that what I really need to upgrade in my system is the mount. I need a system that can guide to an accuracy of around 0.3”...! Any kind souls out there who would like to lend / give me a Mesu 200, a 10Micron or perhaps just an EQ8 to try out?!

And also, thank you for your kind comments about the image itself!

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That’s a mighty fine image, lots of detail visible, in the debate of the refractor vs reflector for imaging detail, the mirror fights back!

And a solid performance from the HEQ5, I’ve used one recently as part of a portable set up to take to a dark site and was guiding at 0.7” RMS, after PA with Sharpcap. A quick, easy, process, I was very impressed.

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9 hours ago, tomato said:

That’s a mighty fine image, lots of detail visible, in the debate of the refractor vs reflector for imaging detail, the mirror fights back!

And a solid performance from the HEQ5, I’ve used one recently as part of a portable set up to take to a dark site and was guiding at 0.7” RMS, after PA with Sharpcap. A quick, easy, process, I was very impressed.

Thank you! I think that my HEQ5 is probably the ‘weak link’ in my imaging set up, but it never ceases to amaze me with how well it performs. I gave it the Rowan belt mod upgrade and that certainly helps. Then the Polemaster system for PA, which is ridiculously quick and easy to achieve impressively accurate PA. The HEQ5 will be hard to actually replace, i think it is the only piece of kit that I still use from when I started my astrophotography journey some five or six years ago!

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On 17/09/2018 at 22:50, PhotoGav said:

it has nothing to do with animals and there are no tongues involved...

Excellent image.

Yes, the name is a misnomer.  Labelled by some amateur astronomers in the US that had a 'great view' of the group from that location once.  Unfortunately it somehow got into The Sky software and its use spread.

It used to be referred to as NGC 7331 and 'The Fleas' a much more descriptive visual term...

...your image is great whatever we chose to call it  
Cheers

Paul

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Is the main galaxy NGC 7331 or NGC 7731? It is identified as the former on Stellarium.

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Just seen this, Gav.  

Nice one!  

I also like to use long focal lengths (my deforked CPC1100) to get shots of far away stuff.  I also hit 0.55sec/pixel using my old Atik 4000, so I usually bin the subs.  

So I know it's not easy, especially to avoid the softness of the stars.  And I have the benefit of using my EM200 mount which gives around 0.4 secs RMS.  But I do use some very slight deconvolution (as NigeB suggested above) to try to tighten the stars.

You say that the softness is not due to the scope.  Well, looking very carefully at your full image, there seems to be a problem with some of your stars.  They seem to be elongated, especially in the top left.  This should not be due to tracking which should surely give round (but bigger) stars - especially given the relatively long sub times?  Also there seems to be some colour mis-alignment on some of the stars, as well as some misshapen stars.  Is the OAG well clear of the light path?

I think that the long total time was well spent - you have remarkably little noise in the main galaxy, and I think that the image is very well processed.

Chris

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2 hours ago, tomato said:

Is the main galaxy NGC 7331 or NGC 7731? It is identified as the former on Stellarium.

 

6 hours ago, clarkpm4242 said:

It used to be referred to as NGC 7331 and 'The Fleas' a much more descriptive visual term...

Well spotted, it is of course NGC 7331. I bungled the typing, sorry - all corrected now. 

 

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1 hour ago, cfpendock said:

Just seen this, Gav.  

Nice one!  

I also like to use long focal lengths (my deforked CPC1100) to get shots of far away stuff.  I also hit 0.55sec/pixel using my old Atik 4000, so I usually bin the subs.  

So I know it's not easy, especially to avoid the softness of the stars.  And I have the benefit of using my EM200 mount which gives around 0.4 secs RMS.  But I do use some very slight deconvolution (as NigeB suggested above) to try to tighten the stars.

You say that the softness is not due to the scope.  Well, looking very carefully at your full image, there seems to be a problem with some of your stars.  They seem to be elongated, especially in the top left.  This should not be due to tracking which should surely give round (but bigger) stars - especially given the relatively long sub times?  Also there seems to be some colour mis-alignment on some of the stars, as well as some misshapen stars.  Is the OAG well clear of the light path?

I think that the long total time was well spent - you have remarkably little noise in the main galaxy, and I think that the image is very well processed.

Chris

Thank you Chris, that’s some great feedback and definite material for investigation. You are right about the dodgy stars, I will try and suss out where that is coming from next time the 8” is on the mount. The OAG is well clear, so I’m sure that isn’t a contributing factor. I have noticed that my guiding is always worse in the same one axis, but can’t remember which now! I have always thought that that could contribute to misshapen stars? That would also give some star misalignments, if the star shapes are not the same? With regards to deconvolution, what do you use to do that?

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54 minutes ago, PhotoGav said:

I have always thought that that could contribute to misshapen stars? That would also give some star misalignments, if the star shapes are not the same? With regards to deconvolution, what do you use to do that?

Well, I suppose it could.  I am always very careful about getting the balance slightly off so I am generally guiding in only one direction, mostly because I suspect that with the weight of the C11 + bits then I am close to the weight limit for the mount. Otherwise I don't think that just bad guiding would lead to the shapes which you have.  I presume collimation is OK?  Not tilt I suppose?

I use Fat-tail Richardson-Lucy deconvolution plugin for Maxim: https://vanderbei.princeton.edu/images/deconv/deconv_MaximDLnew.html .  It needs a lot of experimenting to get right, but when it works, it works.... And I only use it very sparingly, and only on those bits of the image I think need it.  It can sharpen up the stars nicely, without giving them hard edges, but as I said, it takes some time to get right.

Chris

Edited by cfpendock
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Thank you Chris. I will reopen the misshapen misaligned stars case when the C8 is on the mount next and the Moon is bright!

I don’t use Maxim... I use Astro Pixel Processor and PhotoShop on a Mac. I am almost at the point of purchasing PixInsight, solely for the deconvolution and the annotate script. Expensive for not a full use, but when I have the spare funds, I will do it.

Btw - ‘Fat Tail Richardson Lucy Deconvolution’... you don’t hear that down the pub very often!!!

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17 hours ago, PhotoGav said:

 

I don’t use Maxim... I use Astro Pixel Processor and PhotoShop on a Mac. I am almost at the point of purchasing PixInsight, solely for the deconvolution and the annotate script. Expensive for not a full use, but when I have the spare funds, I will do it.

 

I have APP and PS and also Startools. I am starting to use APP increasingly for processing but it doesn't seem to have an equivalent to Startool's noise reduction tool which I think is brilliant. With my general  lack of integration time, background noise is always a problem and this feature has rescued many of my images from the bin. Unfortunately I don't seem able to export the partly processed APP image into Startools and  get the same results, it always works best if the entire workflow is carried out in the same software (which is what you would expect, I guess). Trouble is APP always seems to do a better job with the colour!

Sorry to go off thread, I think I will eventually purchase PI also, just so I have a complete toolbox, but it is a big outlay compared to the other packages.

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