M83 rgb

[multiweb]

Not really happy with that one given the ROI with the time spent on it but that's color from my Bortle 9 backyard last Sunday and Monday night. What makes it even more painful for me is that it's shot at 2.6m FL so I did put my back into it.

So this is 59x300s with a QHY8/LUM filter with the CN-212 at prime so F/12.4. Seeing was average to good(ish). Better the first night. Thankfully the wind was down so guiding wasn't impacted.I didn't need any help with that. Sometimes it was quite tight around 0.7" but you could see the changes in seeing quite easily from one sub to the other. Image scale is 0.61asp. The QHY8 has big pixels at 7.8um so it helps a bit. In hindsight I should have gone to 10min exposures but a lot can go wrong in an open field at that FL and I wasn't game. I lost a few subs as is. ASCOM gemini driver disconnecting randomly.

I'll have to try a contrast booster or LP filter instead of LUM next time.
Anyway enough whinging.

1:1 crop [1270x1123 - 468KB] (http://www.astropic.net/astro/M83_CN-212_RGB_c_121.jpg)
HD full field [1920x1273 - 3.16MB] (http://www.astropic.net/astro/M83_CN-212_RGB_HD.jpg)

[h0ughy]

Dust lanes coloured bits and knots, what's not to like, you have done well with the Pepsi Max bottle

[strongmanmike]

There is something unusual about this image Marc, can't quite put my finger on it, it's like...like you have added colour or something..? Hmm? :shrug: :question: Cool idea :thumbsup:

:P

Mike

[kosborn]

That's a great image, especially from Bortle 9. Really nice detail in the spiral arms.


Kevin

[ChrisD]

Your image has good detail, dust lanes are there. Also the visual double star on the edge of the galaxy are separated, most M83 images don't show this level of detail.

I see you used 300 sec subs, have you thought about using shorter subs?

I watched presentation on youtube by Dr Robin Glover the author of SharpCaps. Talks about optimum sub times for different Bortle zones. Recommends very short sub times in Bortle 9 to get lots of subs to make it easier for stacking to improve the signal to noise ratio.

https://www.youtube.com/watch?v=3RH93UvP358

Chris

[gregbradley]

Great detail Marc. You're game imaging at F12+.
Colour though is washed out and needs a boost to get that nice magentaish blue this Galaxy shows.

Greg.

[multiweb]

Thanks mate. Too kind. :thumbsup:



:) I know. It's a slippery slope hey?


Thanks Kevin. :thumbsup: Details are an issue as well with the noise that levels all the fine stuff.


Thanks Greg. :thumbsup: It just happens to be the f/ratio of the scope. I have a reducer to go to f/9.9 but I haven't worked out the spacing and all the hardware changes yet.

It's as pushed as I can. I made a "super lum" from both the lum and the RGB stack. It helps a bit but I need to work out skyglow mitigation and be smarter about the way I capture colour data.

[multiweb]

Thanks for that link Chris. That was a great video. :thumbsup:

It did sound counter intuitive at first to do shorter subs but after viewing this I'm going to give it a go. I got a licence of Sharpcap when I did some planetary imaging with ASI462MC last year which is a CMOS but I'll see if I can use the program to profile my old QHY CCD cameras and get some kind of numbers to decide the optimal subs length for my sky conditions.

I only hope that the galaxy photon count is greater than the skyglow photon count but it should be right? otherwise I wouldn't see it at all. If shorter subs + stacking brings the noise down then I could access the next level of details. Very exciting.

The prospect to do shorter subs let's say 2 or 3min exposures has a lot of appeal as well at that FL. :lol:

[CoolhandJo]

Great close up! I was thinking an Optolong Pro might help tame that Botle 9 wash!

[multiweb]

Thanks Paul. :thumbsup: I have a few things to try with LP. Will see how that goes.

[PKay]

Good one Marc and Cheers!

Just moved onto the port...

It's cloudy here, time for an early night :)

Good effort :thumbsup:

[multiweb]

Sounds like a plan. :thumbsup:

[RB]

LOL, I misread your OP.
I thought you said you’re on Bottle 9....:lol:

I love this shot, don’t know what you’re complaining about Marc.
Well done mate, looks very natural, nothing Artificial.

Great shot imo.

RB
:)

[multiweb]

:lol: Bottle 12 for me after trying to process that. :P


Thanks for the encouragements mate. :thumbsup:
I guess I expected a better more detailed result after two nights on it which is what I have come to expect when I do NB with the FSQ. I'll add up to it next new moon. Maybe from Wiruna :prey:

[multiweb]

After watching this, talking to a few people and re-watching one of Craig Stark old presentations I've come to the conclusion that there's no free beer. The main source of noise is skyglow. I can mitigate that somehow with a filter but the bottom line is that the only way around it is to shoot an "astronomical" amount of subs (100s) to match the same SNR from a handful shot at a dark site.

The argument that shorter subs will yield a better SNR in the stack I'm clearly not convinced because the photon count coming from the galaxy and the sky will proportionally reduce for both. So double the amount of halved subs should be the same as half of subs with double the exposure. The only advantage would be that the SNR in one normal sub or half a sub is the same. So I guess you have less chances of losing a sub and the FWHM could potentially be better as you're guiding for smaller intervals.

[rustigsmed]

nice work Marc - going for some extreme focal length and colour!
LP filter sounds like a goer.

cheers

russ

[multiweb]

Thanks Russel. I have a couple so I'll have to look for the bandpass. I also wonder if the duo band I have would give me some kind of exploitable LUM for blue and red. No doubt the red Hii regions would turn up. Not sure about the blue star forming regions in the arms with the Oiii. Will give it a go anyway next night of good seeing we have.

[rustigsmed]

I saw this video a while ago - might be worth checking out to assist your decision on which filter to go for :thumbsup:
https://www.youtube.com/watch?v=Xorp4f05dhU

[multiweb]

Thanks for the link. I have a 2" Baader Neodynium so will definitely try that. :thumbsup:

[Robert_T]

marc I cant imagine how difficult it must be to image at such focal length and f12.4... incredible. And detail resolevd to the core with very natural looking colour for all features. I'm impressed.

[multiweb]

Thanks Robert. :thumbsup: Booze helps.

[Robert_T]

on that we're agreed... though it does have an unhealthy imapct on my bank account on cloudy nights browsing online astro shops ;-)

[multiweb]

:lol: Clear tonight and good seeing. Moon is up and might be a little smoky but I'll be out to try that LP filter with a mono. Give it a go. Can't be worse than what I've got so far.