M104

[codemonkey]

Time for yet another common / bright / easy target. Not sure I'm really happy with this one, but it's better than my last attempt so that's something. Would have been nice to have gotten the seeing I had when imaging M83 recently, but I had to settle for average seeing on this one.

7.1hrs data, 300s subs, same gear as usual. Full res / high quality / more details available on Astrobin (https://www.astrobin.com/400934).

[strongmanmike]

Well....another excellent galaxy image Lee, the seeing doesn't look like it was toooo bad? Another very enjoyable view of what is a perennial favourite, mate you are on a roll :thumbsup:

You seem to have addressed your previous star issues too? Did you use star processing to deal with that or collimation?

Mike

[codemonkey]

Thanks mate :-)

Well, the M83 L stack was about 1.8" FWHM and this one was 2.3" Wasn't just seeing though, SGP wasn't doing a great job with focus on this target. I also hit this with decon and sharpening to and mitigate it.

I'm still not sure what the cause of the elongation is, since it didn't really manifest much with M83. I suspect astigmatism, possibly due to secondary collimation, which only manifests as elongation when the focus isn't perfect.

I tweaked the secondary last night before capturing some of this data... I think it helped with the elongation, but I might have overdone it, looked like the bottom right corner got a bit more elongated whereas earlier it was the top left that was the worst. I still had some subs which were showing up as high 0.4's for eccentricity (you don't want it any higher than 0.4 for those unfamiliar with the measurement)

When it nails focus it seems to do ok... see the attached aberration inspector output of a 60s sub from last night. Still looks elongated (and switching either side of focus) when out of focus though. Maybe SGP was just doing a better job of focus on M83 so it didn't manifest there...

[strongmanmike]

Still, looks pretty good and once all subs are combined the final image looks good :thumbsup:

I will have to tweak my system when I go out next :scared2: :driving:...I got it right last time I pulled the mirror out, cleaned it and replaced, then collimated using my Catseye tools during the day...but that was nearly 5 years ago :eyepop:. seems I haven't nailed it this time :question:..problem with my scope design is that I have to dismount everything and then remove the whole mirror back plate from the tube if I need to adjust edge and top mirror supports...hopefully tweaks to the secondary and primary collimation and tilting of the Wynn corrector will do the trick...:prey:

Mike

[Geoff45]

Looks good Lee. You’ve done a good job on handling the bright core. Nice detail in the disc too.
Geoff

[gregbradley]

That's a good M104 by anyone's standards Lee.

Greg.

[ChrisV]

That's really nice Lee. That ontc newt is working well

[Camelopardalis]

Great details, Lee, beautifully processed :thumbsup:

[Stevec35]

Not happy with it? I think it looks great!

Steve

[Screwdriverone]

Holy crap Lee,

I don't know what you think is wrong with this image, it is fantastic!

Details in the disc are superb!

Love it!

Chris

[AG Hybrid]

Very impressive. But, 7.1 hours data on an object as bright as M104. At what point does diminishing returns kicks in and how hard?

Don't know. Just trying to gauge this for myself for when I start imaging this object.

[Camelopardalis]

You learn this by stacking your images and deciding for yourself whether or not you’re happy with the noise.

If not, take a lot more subs...

[multiweb]

Superb! :thumbsup:

[codemonkey]

Thanks Geoff :-) I actually clipped the core the L data (but not the RGB). I tried to recover it with the RGB data but wasn't terribly successful. Because of the gradient I can't easily see it's clipped so I'm reasonably content with it.



Thanks Greg :-)



Thanks Chris :-) Yeah, it's doing ok except occasional issues with star shapes that I can never get to the bottom of... might not be the scope though, could be user error or guiding at least in part.



Thanks Dunk :-)



Thanks Steve :) I'm always wishing things were sharper, and after being treated with good seeing on M83 recently I was hoping for better on this one.



haha, thanks Chris, glad you like it :-)





Cheers Adrian :-) I'd agree with what Dunk said, it's all about getting a noise level you're happy with. That said...

7.1hrs isn't really a lot of time, I'd have gone longer if I actually had any patience. I usually aim for about 10hrs on a target these days, but often get too impatient to process it and end up getting less than I planned. I actually used some noise reduction in my final version of it (which I never uploaded), which I don't always do, which I think suggests I needed more data.

One thing to remember is that I'm shooting at 0.5"/px so the light gets spread over more pixels than people often use (I'd guess most imagers use 1"/px or more), so I need a correspondingly longer integration time to offset that.

One day I hope to develop some real patience and start doing 20-40hr integrations. You're right though, M104 is very bright so it lends itself to shorter integrations.



Thanks Marc :-)

[Placidus]

Beautifully acquired and processed. The feeling of transparency in the main galaxy is wonderful. Lots of detail, and lots of galaxies in the far distance showing good structure.

[RobF]

That's a great shot!

[alpal]

Hi Lee,
that is a surprisingly good picture especially since
you have resolved details in the dark edge on dust lanes
with only 914mm of focal length.
It's the kind of pictures I'd expect with over 2000mm of FL.
Please keep them coming.
I only wish I had the time to fire my system up,
that has a 10" ONTC mirror from TS.


cheers
Allan

[alan meehan]

Nice shot Lee nothing wrong with that

[codemonkey]

Thanks mate :-)



Thanks Rob!



Thanks Allan :-)

With the Paracorr I think it's closer to 1000mm (989.39mm according to plate solving), but your point still stands.

I think it's more about aperture and sampling (e.g. arc seconds per pixel) than focal length as such, you don't really need a large focal length these days with such small pixels on cameras.



Thanks Alan :-)

[gb44]

Very nice Lee.

Why did you go for the ZWO178mini for the guide cam?

GlennB

[codemonkey]

Thanks Glenn :-)

I use the QHY178M for the main imaging camera and the ZWO 174 mini for guiding. I'm not 100% sure which one you're asking about, so I'll answer both :-)

I use the QHY178M for my imaging camera because it provides great resolution (in terms of arc-seconds per pixel) with my scope, has low read noise, reasonable number of pixels, and field of view which suits me well since I mostly image galaxies.

I use the ASI174 mini guide cam because it has a good form factor which means it doesn't get in the way of my focuser or anything, it has reasonable size pixels, moderate read noise (reasonably low at high gain), but most importantly because it has a pretty big sensor for a guide cam, which makes it easier to find a guide star and since I use an OAG, that's very important.

[gb44]

Thanks Lee.
And thanks for the inspiration too.

[alpal]

Hi Lee,
I'm aware of the smaller pixels but it is still remarkable.


cheers
Allan

[Atmos]

Very nice detail Lee, the dust lanes are showing up really nicely :thumbsup:
Always like your star colours :)

[codemonkey]

Cheers Allan :-) I hope I didn't come off as patronising, it wasn't my intention, was just trying to get across the point that you don't need big focal lengths these days, technology is changing things on us again.



Thanks Colin! :-) That's one of the areas I think I could improve this... the large stars could probably do with some more colour, and some of the smaller ones could probably do with a bit less.

[codemonkey]

No probs Glenn! :-)