150mm Newtonian on a Sky-Watcher SynScan AZ GOTO Mount?

[PeterC65]

The Sky-Watcher SynScan AZ GOTO Mount is the only one I have and I like it for the tracking and its ability to find objects.

I have a 127mm MAK and a 72mm APO and struggle to see fainter objects with these two such as most nebulae (apart from M42, M27) and most galaxies (apart from M31, M81, M82), so I've been thinking about how I might increase aperture.

One option is to get a 150mm Newtonian such as the Orion Optics VX6 which weights 4.5kg, just under the recommended load for the current mount.

I have two questions ...

• Is it sensible / usable to mount a 150mm Newtonian on the Sky-Watcher SynScan AZ GOTO Mount? I'd be interested to hear from anyone who has done this.
• Will I see noticeably more faint objects with a 150mm Newtonian as compared with the 127mm MAK? In theory the Newtonian is gathering only 40% more light although I've read that the aperture of the Skymax 127 is actually less than 127mm so the difference could be greater. For comparison, the MAK gathers 310% more light than the APO and I can notice this difference.

If the mount cannot handle a bigger aperture and I need to abandon GOTO then I would instead choose a 10" Dobsonian such as the StellaLyra 10" Dobsonian and just go big on aperture.

 

[Cosmic Geoff]

To see galaxies beyond those you mention you need dark skies. What are the skies like at your location?

I took my 8" SCT to rural Devon a couple of times and could see far more galaxies than at home.

I also put together a video- assisted astronomy outfit with a 102mm Startravel, an ASI224MC planetary camera and a GoTo mount, and this proved startlingly effective at detecting faint objects at my home location, detecting a whole lot of galaxies I could not see visually even with an 8" SCT at my home location.

22 minutes ago, PeterC65 said:

If the mount cannot handle a bigger aperture and I need to abandon GOTO then I would instead choose a 10" Dobsonian such as the StellaLyra 10" Dobsonian and just go big on aperture.

I assume you mean abandon GoTo on grounds of cost. If you are working in light-polluted skies you may be disappointed at the number of galaxies visible with a 10", and also frustrated at the difficulty of finding anything without a GoTo. Your choice, of course.   I recently uprated my EEVA mount to a EQ5 Synscan and added software for platesolving and resync, which quickly places objects (visible or not) right in the middle of the FOV.

[PeterC65]

On 08/01/2022 at 10:20, Cosmic Geoff said:

To see galaxies beyond those you mention you need dark skies. What are the skies like at your location?

I live in a semi-rural location with Bortle 4 skies, so not dark but pretty good. I'm unlikely to take the scopes elsewhere.

On 08/01/2022 at 10:20, Cosmic Geoff said:

I also put together a video- assisted astronomy outfit

The thing I like is seeing objects with my own eyes so astrophotography or EAA doesn't really do it for me I'm afraid.

On 08/01/2022 at 10:20, Cosmic Geoff said:

I assume you mean abandon GoTo on grounds of cost.

Yes. To have GOTO on an AZ mount with a load capacity of more than 5kg the lowest cost option seems to be the Sky-Watcher AZ EQ5-GT GOTO Mount which is £1200. So quite a big spend just for the mount and then I'd need a suitably large OTA.

Edited January 9, 2022 by PeterC65

[Cosmic Geoff]

21 minutes ago, PeterC65 said:

Yes. To have GOTO on an AZ mount with a load capacity of more than 5kg the lowest cost option seems to be the Sky-Watcher AZ EQ5-GT GOTO Mount which is £1200. So quite a big spend just for the mount and then I'd need a suitably large OTA.

There is an Ioptron alt-az GoTo mount which is a little cheaper.

Check out the price of a used Celestron C8 SE GoTo outfit.  This is an 8" SCT with alt-az GoTo and if you are only interested in visual should tick several of your boxes.  They often go for far less than the cost of a new one.

[PeterC65]

1 hour ago, Cosmic Geoff said:

There is an Ioptron alt-az GoTo mount which is a little cheaper.

The iOptron AZ Pro Mount with a tripod is slightly more expensive than the Sky-Watcher AZ EQ5-GT GOTO. It can carry 15kg + 4.5kg whereas the Sky-Watcher can carry 15kg + 15kg. So I think the Sky-Watcher is still the best option, but quite an investment!

[Zermelo]

1 hour ago, PeterC65 said:

1 hour ago, Cosmic Geoff said:

To see galaxies beyond those you mention you need dark skies. What are the skies like at your location?

I live in a semi-rural location with Bortle 4 skies, so not dark but pretty good

I'm in the same situation as you regarding skies, and I use a 127 Mak and 150mm Newtonian on a 5kg AZ goto platform (the Star Discovery in my case, with a 1.25" leg tripod).  I've pushed close to the 5kg by substituting finders, diagonals and heavier eyepieces. As far as I can tell, the mount is still performing nominally, though perhaps I've had to pay more attention to balance than I did with the vanilla configuration. The smaller moment of the Mak does help when you're at the limit. I'm sure that if I had a sturdier mount that I'd see some improvements in, say, the settle time when I'm focusing and resistance to wind. But like you, I decided that the next step up (with goto and tracking) was a bit pricey at the moment. I will stick with my existing kit until (or if) I decide to get an OTA that demands a new mount.

With the Newt I've now seen 97 Messiers, including more difficult ones like M33, M100 and M101 from my back garden, though many are just smudges. I've not done a systematic comparison of light grasp between the Mak and reflector because I tend to go out with the larger scope whenever it's moonless. But interestingly my best double star splits are currently the same on both, though the resolving power of the reflector ought to be better.

 

[PeterC65]

On 08/01/2022 at 14:08, Zermelo said:

I'm in the same situation as you regarding skies, and I use a 127 Mak and 150mm Newtonian on a 5kg AZ goto platform (the Star Discovery in my case, with a 1.25" leg tripod).  I've pushed close to the 5kg by substituting finders, diagonals and heavier eyepieces. As far as I can tell, the mount is still performing nominally, though perhaps I've had to pay more attention to balance than I did with the vanilla configuration. The smaller moment of the Mak does help when you're at the limit. I'm sure that if I had a sturdier mount that I'd see some improvements in, say, the settle time when I'm focusing and resistance to wind. But like you, I decided that the next step up (with goto and tracking) was a bit pricey at the moment. I will stick with my existing kit until (or if) I decide to get an OTA that demands a new mount.

With the Newt I've now seen 97 Messiers, including more difficult ones like M33, M100 and M101 from my back garden, though many are just smudges. I've not done a systematic comparison of light grasp between the Mak and reflector because I tend to go out with the larger scope whenever it's moonless. But interestingly my best double star splits are currently the same on both, though the resolving power of the reflector ought to be better.

 

We do seem to have similar kit and the same attitude to larger capacity mounts! The Sky-Watcher AZ EQ5-GT GOTO is very tempting though!!

It's good to know that attaching a 150mm Newtonian to my existing AZ GOTO mount is practical. How do you find the Sky-Watcher OTA? It's considerably cheaper than the Orion Optics VX6 that I mentioned but doesn't have the dual speed focuser that I am finding essential with the APO. There is the 150PDS which has a dual speed focuser but that seems to be a shorter version specifically for astrophotography.

 

Edited April 2, 2022 by PeterC65

[Zermelo]

11 minutes ago, PeterC65 said:

It's good to know that attaching a 150mm Newtonian to my existing AZ GOTO mount is practical. How do you find the Sky-Watcher OTA? It's considerably cheaper than the Orion Optics VX6 that I mentioned but doesn't have the dual speed focuser that I am finding essential with the APO. There is the 150PDS which has a dual speed focuser but that seems to be a shorter version specifically for astrophotography.

You may know that the version of the 150mm that's bundled with the Star Discovery is optimized for weight (because of the 5kg limit) and for cost.
The primary mirror is the same as any other SW 150mm mirror, but it's glued into its base and has no adjustment. The secondary is adjustable in the usual way, but I've not had any problems with it holding collimation. The focuser is a very basic, single speed rack-and-pinion job. I added a helical focuser to it, for finer control, but some would say that an F/5 calls for a proper dual-speed focuser. I've not used another reflector that I could compare with it for performance, but I think it was the right choice for me at the time I bought it. Yes, the P-DS version is for imaging. It has a much more robust focuser and slightly adjusted optical path to achieve prime focus. The 'P' and 'PL' versions are intended for visual and are somewhere between the version I have and the 150P-DS. You can get away with the cheaper mount for the 150P, but the longer 150PL really should have an EQ5.