Stuck on Next Steps for My Astrophotography Setup – Need Input!

Adding a screenshot of gradient corrected images for comparing Seagull Nebula, and what to expect out of galaxy (a mess!). Just Graxpert applied after WBPP, no other changes. I have experience mostly with Narrowband imaging, so quite possible the flats are an issue when I created them for RGB (no filters ) - They were only 0.0015ms exposure. I have only these 2 hour of experience on broadband targets.

First two images on top are without filters
Bottom single image is with L-extreme filter

Hi. In a Bortle8-9 I would suggest ( based on being told this by others for years and personal experience! ) you stick with NB. Broadband in 8-9 Bortle is incredibly difficult. Secondly, and this matters more than anything else…invest as much time as possible into post processing. A great post processed image using rubbish data will nearly always look better than great data post processed rubbishly! 

As a side note, you can always save up more money in the medium/long term and just buy that Newtonian, more filters, basically add to your existing gear over time, then you won't have to make difficult choices anymore my friend. I've been slowly building up my gear over 6 years and I'm STILL buying new gear!! LOL.

Clear Skies from Wes, Liverpool, England.

Wesley Robert Donnelly:
just buy that Newtonian, more filters, basically add to your existing gear over time

That is where I am most inclined towards. Just read about the cassegrains, how they can be F/12 at 2400mm focal lengths and you could use reducers to get them to F/6 at 1200mm. This got me tempted, but fiddling with the optical train with the reducer will certainly be something to keep in mind. F/6 is poorer than a F/5 Newtonian at 1000mm and if the planetary imaging at 2400mm isnt a great reach, then the F/6 also ends up with a compromise - both on planetary imaging as well as on DSO. Hence want to really hear it out from people who may have used it.
If it is a scope, I will get a dedicated astro-cam and set of filter/wheels (later over time, hopefully!) to avoid fiddling with the optical train every time. Ofcourse, there isnt a spare mount to keep both of them going through the night - that is where there is always limited finances to manage! Currently I have a iOptron CEM40 (18kg maximum load as per specs), I hope it will handle a 8kg Newtonian OTA with accessories.

I love my Skywatcher Quattro 10".  For your mount, the 8" should be OK and get you reasonable 1.1"/pixel which is good for average seeing.    I've not found collimation to be that challenging at all, and I also just bought a Nexus 0.75x coma corrector/reducer at f3 and didn't have to fuss with collimation at all for my first light several days ago (https://www.astrobin.com/wd3bxa/C/).  That was about the same pixel scale (>1"/pixel) and my guiding was just horrible (>1" rms) due to wind and horrible seeing. 
If it's windy where you are, a warning that larger newts will act as sails and guiding will suffer.  I usually check collimation if I bump it a lot, but it's usually good for months.  

Bortle 8-9 does mean narrowband for the most part or planetary.

Going mono will get you better spatial resolution, but that's a large investment from where you are.

andrea tasselli:
A good 8" f/4 newt is the way to go but I can't recommend the cheap ones in light of their poor mechanical features, notably their primary cell design/construction.

Two follow-up questions please:
1. Is collimation of f/4 a big issue (compared to f/5) and how does it hold.
2. Any recommendations on good newtonians? What do you think about Sky-watcher tubes?

I’ve run a 925 on a CEM40 for 3 years now with terrific results. 

my traveler is the GT 71 on HAE29 and carbon fiber sticks. 

The entire 925 rig weighs 90lbs

The entire traveler rig weighs 25lbs, as you may know. 

This matters if the 925 is not in a permanent location. 

I love the 925!  I can’t imagine recommending a telescope more highly. It’s in a good sweet spot at 2350mm. You’ll get lots of utility out of it. But its rewards are diminished if you have to take it anywhere other than the end of the driveway.

Your biggest problem is light pollution, so Narrowband and lot of integration time…

For narrowband, shooting mono is superior, so if you will be shooting mostly from a bortle 8.  If I were in your shoes.. I would go mono..   In fact, I was in your shoes.. my first astronomy camera was a mono.  Then I moved to a darker location.

So have you looked into that? Is your area particularly windy? Is the setup balanced well enough? I'd definitely ask CEM40 users to see what's realistic and if they have suggestions.

I forgot to add Periodic Error Correction (PEC)  to that list to investigate.

If your main issue is light pollution, and you are looking at one major upgrade, a different scope is irrelevant of course.  Narrowband filters are the best solution.

You have a high quality 294MC camera - fine pixel size that probably is an excellent fit with your APO.  Now the choice becomes whether:

1) a decent set of SO and HO filters with your OSC camera (perpaps add an electronic filter wheel)-
it's the simplest upgrade, and if you choose wrongly and later opt for mono, you're only out of the cost of the filter (sounds like you already have HO?).
2) mono camera with L R G B (when you go to dark skies) and S H O. 

If you are critical about color mapping your S H and O channels from the OSC, there's a lot of postprocessing (so I hear, I haven't touched that yet with my OSC setup) to account for color channel cross-talk (H and S showing up on your green and blue O data, for example). But if you get enjoyment out of the result of  your efforts, even though it may not be technically correct, you will enjoy the OSC option.

I'll let the more experienced get into the fine points of postprocessing NB OSC vs mono

With the light pollution you are forced to deal with going to anything over F/6 will cause you more stress. I shoot at  F/10 in Bortle 5 and deal with light polluted images. 

Have you looked into moving your scope to a remote observatory?  $30 a month in Bortle 1 skies has me thinking.