NGC 7331: The Good, the Bad and the Ugly

[tomato]

For once I was determined to give a DSO the integration time it deserves, so here is 609 x 2 mins on NGC7331 with the dual Esprit150/IMX571 OSC rig, captured over several sessions in September/October. I also got about 6 hrs of Ha/NBZ data but I can't seem to make this work with the RGB image, so it is not included here.

The Good

The only thing I like about the image is that the long integration and minimisation of the foreground stars has given the sprinkling of distant small galaxies in the FOV more prominence.

The Bad

I have always had a rather cavalier attitude to precise framing, I don't worry about losing sensor real estate since my targets are usually galaxies so my approach has been "I can always crop the rough stuff out". However, there is no excuse for my initial stack looking like this when I have plate solving and auto centering  in NINA. My only defence is the cameras came off numerous times during the month, and I didn't want to lose too much clear sky time realigning them but even so... I think this poor frame alignment has significantly contributed to the other issues with this image, you will also note from the dust motes present that I lost my way with the calibration frames assignment, on at least one occasion.

The Ugly

The background is really blotchy. You can see it more clearly on this stretched image. Is it real dust or IFN, or a consequence of poor alignment and/or calibration, I'm not sure.

This experience has dented my enthusiasm for spending ages on one target, but I will try again at some point with more disciplined framing.

Thanks for looking

 

 

[glafnazur]

You're certainly right about the background galaxies, there's a whole host of them. It might not be perfect but I like it anyway  

[Elp]

Nice smooth look. I tend to not spend much time on galaxies but it's essential for capturing the fainter ones in greater detail. Don't worry about blotch, I think it happens a lot.

[Tomatobro]

Here is mine.....

LRGB @ 23 mins total 40 frames each at 8.6 seconds

Ha Oii @ 41 mins total 40 frames each at 30.8 seconds

[Ratlet]

Looks like you've got a decent number of frames over Stephan's quintet too.  Might be a nice wee crop there

[geeklee]

1 hour ago, tomato said:

on NGC7331

That's a stunning outcome @tomato

A spot too much blue/purple in the galaxies colour and maybe a little sharpening of the galaxies added?  Both personal things though.

Love the framing output combination! 😅

1 hour ago, tomato said:

The only thing I like about the image is...

...Everything.

Edited October 28, 2022 by geeklee

[Whistlin Bob]

I wonder if your reaction to this image is a result of the level of investment that you've put into it? I can see the flaws you describe, but overall I really like it. You've captured a tremendous amount of signal from those galaxies- I love all the faint areas that come through strongly that are not usually seen.

[Paul M]

All great images. This area is perhaps one of my favorite galaxy groupings. 

As interesting as the Quintet is (are?), I always think the wider field including Deerlick gives it (them?) greater appeal. And all those lesser galaxies! Can't say I've noticed a lot of that stuff previously.

 

[Ratlet]

12 minutes ago, Paul M said:

All great images. This area is perhaps one of my favorite galaxy groupings. 

As interesting as the Quintet is (are?), I always think the wider field including Deerlick gives it (them?) greater appeal. And all those lesser galaxies! Can't say I've noticed a lot of that stuff previously.

 

I imaged this area earlier in the year with my 130pds and it is absolutely hoaching with galaxies.

[tomato]

Thanks for all of the appreciative feedback. I suppose by investing over double the integration time I usually manage on an object I had high expectations for the outcome, but to my eye there was not much improvement over the 11 hr version.  It depends on the target I guess, but maybe somewhere around 15 hrs would be the optimum from my location.

[tomato]

Thanks @Paul M, for the Stephan's Quintet crop suggestion, I suppose there might not be this level of detail on the 11 hr version so that's a positive.

[The Lazy Astronomer]

On 28/10/2022 at 18:55, tomato said:

Thanks for all of the appreciative feedback. I suppose by investing over double the integration time I usually manage on an object I had high expectations for the outcome, but to my eye there was not much improvement over the 11 hr version.  It depends on the target I guess, but maybe somewhere around 15 hrs would be the optimum from my location.

To double the SNR you need quadruple the integration time. Logically, I would guess doubling the integration time boosts SNR by about 1.5x, which obviously is an improvement, but maybe not as much as you think you should have got for your time (and maybe not even particularly noticeable).

That said, it's a lovely image with some great detail and a myriad of background galaxies. As already mentioned, l think the colours are shifted a bit towards purple, and for me, l think the stars have been pushed a bit too much into the background -  that is a personal thing though, and l appreciate you've done it in order to allow all the galaxies to jump out more.

Unrelated question: I'm thinking about the possibility of setting up a dual rig (2 x Esprit 100s, so a baby version of yours) and was wondering how you dealt with the mounting of both scopes to get them aligned with each other? 

[tomato]

Thanks, you are right about the colour, it is way too purple. Again, I was hoping with 20 hrs of OSC on the board, getting a decent colour rendition would be straightforward, but not so. I need to have another go at the processing, but hopefully not the whole calibration and stacking routine, it took around 6 hrs on my PC...

For a dual rig you will need some kind of adjustable saddle, I use an ADM item which I think would be sturdy enough for a couple of Esprit100s but is right on the limit of acceptable stability for the 150s.

The trouble is the height of the adjustment saddle puts the COG of the second scope well away from the mount which is not good. The inherent flexing that occurred causing image shift between the two scopes was largely fixed by fabricating an aluminium bracing plate which bolts across the top of the two sets of tube rings. This has to be loosened off to allow adjustments to align the cameras and then very carefully tightened up so that the alignment is not thrown out too much by tightening down the plate. It's a bit of an iterative process and take the best part of one session to get right. Hopefully you could get away without one on the Esprit100 setup.

But I wholly recommend dual rigs. The feeling you get when you can multiply the time spent capturing subs by 2 is for me, well worth the cost in time and money.

[Tomatobro]

Here is a picture of the top plate under construction.

[The Lazy Astronomer]

2 hours ago, tomato said:

But I wholly recommend dual rigs. The feeling you get when you can multiply the time spent capturing subs by 2 is for me, well worth the cost in time and money.

That's exactly the feeling I'm looking for! I'm a paradox of wanting long integration times (around 20hrs) and impatience - it honestly it feels like a dual rig setup is the only way to go with UK weather...

[tomato]

Yes, there are two schools of thought on dual rigs in the UK, the first is “why waste your money on a dual rig when we get so little imaging time” and the second is “we have so little imaging time in the UK, a dual rig makes perfect sense”.

I think we are in the second category👍🏼

[Ratlet]

Why stop at 2? I'm sure there was someone on Astrobin who had a quad setup with 4 x takumar 200mm doing mono.

[tomato]

I’ve tried a triple scope set up, the mount could cope and it sort of worked but in my experience the degree of difficulty in getting it all to run harmoniously goes up disproportionately to just adding another scope. I have had more success setting up the third scope on a second mount and running it separately.

[tomato]

Here is another rendition. I have bumped up the stars a bit and tried to fix the purples. I might have clipped the data in trying to sort out the uneven background though.

[AstroMuni]

22 hours ago, tomato said:

Here is another rendition. I have bumped up the stars a bit and tried to fix the purples. I might have clipped the data in trying to sort out the uneven background though.

I prefer the first one. Great shot