Guide scope/camera advice

[Anthonyexmouth]

Evening fellow nerds, 

Just upgraded my 9*50/asi120mm to an st80 with the same camera. Now, I have an asi290mc that was an impulse buy last year just sitting around until I get my mak90 out or purchase a something bigger for planetary imaging. In the mean time, would there be any advantage to using the 290 colour as a guide cam or is the 120 mono the best choice and leave the colour one looking unloved on the shelf.

Also, I've attached the st80 like this

Is there any problem just screwing the rings together?

[cjdawson]

Looks ok to me.  Give it a go and see how it works

[david_taurus83]

Not knocking your setup but if it were me, id have put another dovetail on top of your main scope and bolted the ST80 to that. Just for extra rigidity. But as above, give it a go. If it's rock solid already then should be sound!?

[Anthonyexmouth]

My thinking was that the less joints would add to the stiffness. It won't be out for a while as I'm in the middle of building my pier. Steel plate should be here this week so I can do the final pour at the weekend. 

Thoughts about the camera choice?

[drjolo]

ASI120 mono is not as sensitive as recent CMOS cameras, maybe even less sensitive than 290 color, but with 80/400 scope it will be perfectly ok. You should have no problem with finding guide star. Since this tube have significant chromatic aberrations some filter for mono camera would be advised. IR cur at least, but for my guide setup (80/400 + ASI290 mono) I use Fringe Killer that significantly reduces guide star size. 

[Anthonyexmouth]

The 120 mono with the SW 9*50 was fine for finding stars and guiding with PHD. Just felt there was a lot of flex as it was on the foot mount and wobble with with rubber gasket. Hope this new setup sorts that. Think I'll keep using the mono and use this as an excuse to buy a bigger mak for the colour 290.