Moving on from RASA 8

What is your budget? If no concern you could consider a PW DeltaRho 350.

The options you listed aside from the RASA 11 and Starizona Nexus are more or less lateral moves that allow you to use a filter wheel. The RASA 11 gets you more focal length, but then you are still stuck changing the filters. The only way the Nexus allows you to increase your focal length is if you use it on a large newtonian, think 250mm+ of aperture.

I have no experience with the Nexus so I cannot speak towards its quality. I would suggest searching astrobin for newt + nexus combos to see if you like the image quality.

You might just have to accept that with current 'budget' options, a higher focal length comes at the cost of a higher focal ratio.

I have the Epsilon 160 and it is a fantastic scope. The two biggest issues people have with the Epsilon series is 1) Collimation and 2) Tilt. 

Collimation gets easier and easier the more you do it and understand how the scope works. If you go this route the Takahashi collimation tools are absolutely required.

Since you have found a way to mitigate tilt with the RASA the Epsilon shouldn't be hard to deal with. I use the ASG Photon Cage and adjusting for tilt is super easy with it. The Octopi is another device people use for the Epsilon to deal with tilt.

If you do decide on an Epsilon I recommend the 160. It has the newest corrector and it the best adjusted for small pixel cameras like your ASI2600. The 130 is nice since it is a little bit lighter and easier to grab and go but I had no issues taking my 160 along with me to my imaging site. 

I love my Epsilon so much that it is currently at a remote facility so I can actually use it since it is so cloudy where I am!

The Sharpstar HNT13028 or 15028 is alternative for the Epsilon series but I have no firsthand experience with them. Just by browsing images of them on here, I think the Epsilon series produces sharper images.

So you guys are saying I'm probably nuts to consider moving from a TAK TSA-120 to a RASA 8?

Because that's exactly what I began daydreaming about a little while ago and decided to see what RASA users were saying and came across this thread!

FXF

A real upgrade would be something like a 12" F/4 ONTC newtonian or similar quality newt, optical/mechanical quality wise and resolution wise. 

The Epsilons are just that… taks (not really an upgrade over RASA8 especially aperture wise)
RASA 11 is just bigger but without filter wheel and automation its not that "big" of an upgrade. 
I would avoid the nexus reducer, for a newtonian you are better off with a quality F4 native that can correct a nice large sensor than a "faster" but smaller correction. 

For 6k budget a nice quality newt is probably your best bet for what you are looking for.

Go the Epsilon (I have the 130) - you can use a filter wheel and there is a 1.5x extender if you want a little more reach.

I'll second George's RASA11 comments.   Not sure why anyone would voluntarily give up f/2 speed for longer focal length.   If what you mean is that you want more resolution for chasing smaller objects, then a RASA11 + 183 camera might fit well.   The native resolution of a RASA11 + ASI183mcPro (OSC) is 0.799 arcsecs, drizzled 0.399 arcsecs, with a field that's ~1 degree.   That seeing limited resolution + medium sized field is a joy to work with.  Image quality can be nice as you'll tend to crop close to the optical axis.   If you ignore the classic Mono vs OSC food fight, and you have access to dark skies, you might discover that OSC work can actually be quite acceptable with the combo.   If you're stuck in the city, then of course you'll need a mono/filters approach that would lead in another direction.

From your page, I see you've imaged a lot of wide fields.   A RASA11+183 combo is suited for smaller nebula and galaxies.   You can do larger planetaries as well.   For typical examples of a RASA11 + 183 OSC targets/fields, you might search out pages with this combo (including my page).   Best of luck as you consider your options...  DougS

https://www.astrobin.com/users/dmsummers/

A RASA with an OSC camera is significantly slower than an F/3 newtonian with a mono camera and is more similar in speed to a mono camera on an F/5 refractor.

I think we should try and avoid this debate (OSC vs Mono).  It's just old and frankly boring.   Luka, you might want to spend some time on cloudy nights looking at all the posts there to see if you really want to reassert this old argument.   What's undeniable is that given equal aperture, equal QE cams, and equal integration time, an f/2.2 reflector will produce an image that has 5.2x more photon conversion vs an f/5 reflector.   A similar comparison of f/2.2 against an f/3 will produce 1.9x in favor of the f/2.2 rig.   It's just physics.  Adding a refractor to the mix doesn't really change the outcome much as the reflectivity loss (mirror vs lens) isn't large.  Now, since mono cams have different QE vs OSC for the same sensor, the QE chart for any mono vs osc camera needs to be evaluated to complete the story (sans resolution, which has other factors to debate/ignore).   While typically OSC "deep" violet/blue QE will have appreciable loss vs mono, the same isn't true as we move up toward green and red.   That said, OSC blue QE isn't going to be 1/5th of mono!   

It's just not as easy to back up the argument as it is to make the generalized statement, and the volume of debate on CN, to include some detailed calculators that have been developed, should be sufficient to avoid the rehash here.  Compare the QE of a 183mm vs 183mc sensor between 400 and 700nm to get a feel for this.  Also, there are plenty of online calculators for differential f-ratios to round out support against the argument.    Hope this helps, and CS,  Doug

Doug Summers:
I think we should try and avoid this debate (OSC vs Mono).  It's just old and frankly boring.   Luka, you might want to spend some time on cloudy nights looking at all the posts there to see if you really want to reassert this old argument.   What's undeniable is that given equal aperture, equal QE cams, and equal integration time, an f/2.2 reflector will produce an image that has 5.2x more photon conversion vs an f/5 reflector.   A similar comparison of f/2.2 against an f/3 will produce 1.9x in favor of the f/2.2 rig.   It's just physics.  Adding a refractor to the mix doesn't really change the outcome much as the reflectivity loss (mirror vs lens) isn't large.  Now, since mono cams have different QE vs OSC for the same sensor, the QE chart for any mono vs osc camera needs to be evaluated to complete the story (sans resolution, which has other factors to debate/ignore).   While typically OSC "deep" violet/blue QE will have appreciable loss vs mono, the same isn't true as we move up toward green and red.   That said, OSC blue QE isn't going to be 1/5th of mono!   

It's just not as easy to back up the argument as it is to make the generalized statement, and the volume of debate on CN, to include some detailed calculators that have been developed, should be sufficient to avoid the rehash here.  Compare the QE of a 183mm vs 183mc sensor between 400 and 700nm to get a feel for this.  Also, there are plenty of online calculators for differential f-ratios to round out support against the argument.    Hope this helps, and CS,  Doug

Tell me that you don't understand the Bayer matrix without actually telling me. Please don't give advice to people trying to make good choices when your sources are based outdated equipment, and not relevant to a mono discussion.

Tell me that you don't understand the Bayer matrix without actually telling me. Please don't give advice to people trying to make good choices when your sources are based outdated equipment, and not relevant to a mono discussion.

Well, the same could be said right back at you.   Maybe do yourself a favor and read the following and then do some calculations.   Here's a good place to start:
https://www.cloudynights.com/topic/682340-monochrome-vs-one-shot-color-%E2%80%93-by-the-numbers-please/

CS  Doug

Doug Summers:

Tell me that you don't understand the Bayer matrix without actually telling me. Please don't give advice to people trying to make good choices when your sources are based outdated equipment, and not relevant to a mono discussion.

Well, the same could be said right back at you.   Maybe do yourself a favor and read the following and then do some calculations.   Here's a good place to start:
https://www.cloudynights.com/topic/682340-monochrome-vs-one-shot-color-%E2%80%93-by-the-numbers-please/

CS  Doug

The post you've sent is based on very old and outdated cameras, and also, discredited by the first reply. lol
https://www.cloudynights.com/topic/682340-monochrome-vs-one-shot-color-–-by-the-numbers-please/?p=9743345
You ought to read the discussion and not just the OP...

Edit: Also CL is not a good source. It is 2-3 years behind the curve in AP knowledge.