Advice on GSO RC 10" or 12" set up with EQ8

[John K]

Hi guys,

Doing some research on a potential new set up revolving around either a GSO RC 10” or 12” with an EQ8 and something like an ASI1600 camera.
It will need to be a portable and be used at a Dark sky site.

For those currently using the GSO RC’s, my questions are:

- Is a GSO RC 12 scope at 23.7kg considered portable for one person?

- How does the Astro-Physics AP-CCDT67 go with reducing focal length to f/6

- Would like a lighter version of the EQ8 tripod – the Sky Watcher tripod weights a hefty 30kg. Are there any alternatives out there? E.g. https://www.altairastro.com/skywatcher-eq8-mount-with-starbase-cnc-tripod.html

- Can someone recommend a good focuser option for a mono, filter wheel and OAG set up. Does something like a Moonlite CSL 2.5" Large Format SCT/RC Focuser do the trick and what accessories will it need?


Look forward to everyone's advice.

Clear skies.

John K.

[Paul Haese]

John my answers in descending order:

Lifting 23kg up to shoulder height can be a bit of a problem. It's not an easy lift when you are trying to slip into the dove tail saddle. However, yes you can use it portable but it would not be my preference with a 12"

I have not used that reducer but I hear it is good with APS size sensors. Though a few tell me that it is ok for a larger sensor. I would say it would be fine with the APS sensor but would be wary about using full frame with it.

Don't know about the tripod.

I found that only two focusers worked well with a big camera on the back of the RC12. The Atlas or the Feather Touch 3". I don't know about the Moonlite. My recent use of a Moonlite CRL 2.5" with my QSI showed considerable movement when used with a Newtonian. It might actually be ok for use on the back of the RC but I suspect you would need something bigger. To that end I am waiting on a Moonlite Night Crawler (heavy) to use with my RC12. My policy now with focusers is go heavy duty.

Hope some of that helps.

[John K]

Thanks Paul - good info.

For a 12" I might need this approach:

https://www.youtube.com/watch?v=Ge1zG8-Y1kA

John K.

[lazjen]

I've got an RC10, a Moonlite focuser, the ASI 1600MM and the Astro-Physics AP-CCDT67 - on a G11.

I can just comfortably handle the RC10 onto the mount, so going heavier would not be an option for me.

The Moonlite focuser works very well and holds the gear well. If you get a heavier camera, you might need something a bit stronger. For an ASI1600 though it will not be a problem.

For the reducer, I mostly used that with an ST8XE and it gave a flat field. I think I've used it with the ASI1600 as well (I got a refractor around the same time and have been using that more recently) and again I seem to recall no issues with the field.

I've been using 1.25" filters with the ASI1600, but I'm in the process of switching to 36mm to hopefully reduce the vignetting a bit more (and they should be better quality filters, etc).

For an OAG, I use the TS OAG - it's about 9mm? in width I think - very thin.

For the ASI1600, most people tend to use the ZWO FW with it. I went Xagyl instead as at the time the ZWO version wasn't quite ready. I think either should be fine.

[doppler]

I find it easier and safer to take the tube out of the ring cradle and fit that to the mount first. It's quite easy to lift the optical assembly into an open cradle. Works for me with my 10" f5 newt.

[John K]

Thanks - I'm afraid the GSO RC's I'm looking at have a Truss tube with the attachment plate attached for the mount.

[Paul Haese]

John, I would not buy the tubed version, the truss version is better and holds focus for a lot longer. I found that the tube version was a pain in holding focus, whereas once cooled the truss version gives about 2 hours before needing a refocus.

[DJT]

Hi John

I can’t talk to the weight of the scope as I have the RC8 but I use the moonlight focuser and I can happily hang an MMOAG with an STL6303e plus filter wheel for 8 2” filters. It will have no problem with the imaging train you are thinking about. It will hold focus pretty much all night with the CF Tube.
I also have the ASI1600, OAG and ZWO filter wheel. Again, no issue with that configuration.


I don’t use a flattener and with the smaller chip it’s not needed.
Ron at Moonlite will help with accessories but would suggest threaded connections wherever possible. He has a few options there as well

PS: just read Paul’s comments. My experience is my experience with a CF tube RC8. Others may have different ones :)

Cheers

[John K]

Thanks for all of the advice everyone - appreciated.

I would only be looking at a Truss tube not a walled tube so not an issue. The video I shared was more in terms of the use of a scissor lift. I guess an extra thick CF tube could work, but that would require re-tubing the scope if I wanted to use the video method of moving a heavy scope around.

I guess from a portability perspective, the GSO RC 10" on a G11 rather than EQ8 could be a lower cost alternative, and perhaps I would also then save a bit on the focuser as Moonlite seems a bit cheaper than Feathertouch.

As always, everything is about compromise in some way - cost vs weight vs stiffness vs portability vs aperture/focal length!

One other issue for me is imaging at F/8 with a portable set up where most images will have to be gathered over 2 nights (my typical dark sky get away: Night one polar align and get Luminance Channel; Night 2 More Luminance and then R, G, B). This is why I would love the 12" but with a focal reducer at f/6.

Any other comments are welcomed.

[Star Catcher]

Well John I have the RC10 CF, moonlite and STL6303 running on my field G11. Lifting the tube is about as heavy as I would want to lift. I also have the CCDT67 which doesn't fully handle the 6303 sensor size. So I tend not to use it. The moonlite handles the weight fairly well (using the focus motor and locked shaft) and I have not noticed any great focus shift over several hours, but then my imaging "radar" may not be switched on as intensely as other imagers. :)
Ted

[John K]

Thanks Ted - I think the 10" is the way to go with portability and might just bite the bullet and go with the EQ8. I would rather have a heavier mount and save my weight lifting for that rather than the tube assembly. I would then upgrade to what I really want which is a 14" RC when I can set up a permanent arrangement.

Bummer about the AP focal reducer. I'll do some more calcs - I think even with even a smaller chip CCD camera it may provide the type of field I am looking for and give me the f/6 ratio for faster captures.

[RickS]

I successfully used the A-P 27TVPH reducer with an RC10, albeit with an Atlas focuser (which helped a bit with back focus.)

Cheers,
Rick.

[John K]

Thanks Rick - good info.

[John K]

Did forget to ask on my original post - is there anyone who is Melbourne based who has either a 10" or 12" truss tube GSO RC?

John K.