What’s the Best Option for Bigger Aperture?

[PeterC65]

The 5kg payload of my SynScan AZ GOTO mount limits me to smaller aperture scopes, so far:

• the Skymax 127 which is my main and longest serving scope and a good all round performer,
• a 72mm Apo for widefield, but it does a good job on most targets, albeit at lower magnifications,
• a 150mm Newtonian which is the biggest aperture my mount can handle (just) and to try out the Newtonian (standing) eyepiece position.

I keep hankering after more aperture but the next step up will require a major investment so I want to get it right. GOTO is important to me, both for finding things and for tracking them, so the options seem to be:

• 10” GOTO Dobsonian
  Dobsonians being what most people seem to choose for more aperture.
• 10” Newtonian on a 15kg AZ Mount
  On the face of it this seems like a better choice as the mount would be useful for other scopes and the eyepiece orientation would be adjustable (via the tube rings), but very few people seem to go down this route.
• 8” Schmidt-Cassegrain / Classical-Cassegrain on a 15kg AZ Mount
  This may be a bit left field but it allows seated observing and I think it’s important to be comfortable to properly concentrate on an object.

Leaving aside the price differences between these three, what do others think?

Would anyone recommend a Newtonian (on a conventional mount) or a Cassegrain for bigger aperture?

 

[Cosmic Geoff]

You could have a 10" Dob Newt, but from what I've read the Goto Dobs are suited to visual only (check the imaging threads).

A Newtonian on an AZ-EQ mount would work, but the mount would be a bit pricey.

I have an 8" Celestron Schmidt-Cassegrain and am quite pleased with it.  You can buy the Celestron C8 with a choice of bundled mounts, both Alt-AZ goto and equatorial GoTo. Or put it on any other mount you like (it's not a heavy OTA).  Used, they are quite reasonably priced - half the price of new last time I checked.  The SE mount is portable but a but flimsy, the Evolution is said to be better and the CPC800 package is great for visual and some kinds of imaging and solid as a rock, but a bit heavy.

CC has good reports if you want a visual or planetary imaging scope, but never seen one.  Apparently heavier than the Schmidt-Cassegrain of same aperture..

[Zermelo]

I'm in a similar position and I'll be interested in the responses.

I've decided (more or less) that it's not worth going 6">>8", I want at least 10".  A motorized goto mount for that will probably be too pricey for me, so I'll probably be looking at a Stellalyra dob.

How important for you is the pointing capability, relative to the tracking? Have you considered getting by with just push-to on a dob, either by retro-fitting some digital encoders or cannibalizing a Starsense from a cheap refractor? I do like the goto/tracking too, but I'm considering push-to, combined with some decent widefield EPs to reduce the nudging.

[Louis D]

Combine push-to with an equatorial platform, and you can have both computerized object finding with tracking.  Since the tracking is equatorial, some astrophotography is also possible.

[PeterC65]

15 hours ago, Cosmic Geoff said:

You could have a 10" Dob Newt, but from what I've read the Goto Dobs are suited to visual only (check the imaging threads).

A Newtonian on an AZ-EQ mount would work, but the mount would be a bit pricey.

I have an 8" Celestron Schmidt-Cassegrain and am quite pleased with it.  You can buy the Celestron C8 with a choice of bundled mounts, both Alt-AZ goto and equatorial GoTo. Or put it on any other mount you like (it's not a heavy OTA).  Used, they are quite reasonably priced - half the price of new last time I checked.  The SE mount is portable but a but flimsy, the Evolution is said to be better and the CPC800 package is great for visual and some kinds of imaging and solid as a rock, but a bit heavy.

CC has good reports if you want a visual or planetary imaging scope, but never seen one.  Apparently heavier than the Schmidt-Cassegrain of same aperture..

I should have mentioned that I only do visual astronomy which is why all of the mount options are AZ.

The 15kg AZ mount that I have in mind is the SW AZ EQ5-GT. It is quite pricey but still the cheapest of the 15kg AZ GOTO mounts. What I like about this option is that the mount would provide benefits for all of my scopes (more stable mount, freedom find capability) which goes some way to justifying the cost. If I get a Dobsonian then my existing mount / scopes remain the same. An Explorer 250PDS weighs 14.5kg though which is right on the mount limit, and I think attaching one to then mount is probably a two person job. I'm guessing this is why most people choose a Dobsonian over a Newtonian on a standard mount.

I have looked at the Celestron NexStar 8SE. The OTA seems to be a basic version. The C8 XLT may be better but is more expensive. Some reports say that the 8SE included mount is operating at its limit with this OTA and it is a very similar mount to the SynScan AZ GOTO that I have already, just a little taller to accommodate wider scopes, so it doesn't gain me anything for my other scopes. Having said all this, I do like to sit while observing which is why an 8" Cassegrain is so appealing.

 

 

[Cosmic Geoff]

1 minute ago, PeterC65 said:

I should have mentioned that I only do visual astronomy which is why all of the mount options are AZ.

 

I have looked at the Celestron NexStar 8SE. The OTA seems to be a basic version. The C8 XLT may be better but is more expensive. Some reports say that the 8SE included mount is operating at its limit with this OTA and it is a very similar mount to the SynScan AZ GOTO that I have already, just a little taller to accommodate wider scopes, so it doesn't gain me anything for my other scopes. Having said all this, I do like to sit while observing which is why an 8" Cassegrain is so appealing.

 

 

All the C8 OTA's are essentially the same - the only differences are the various colours and that some have a grab handle - it depends on what mount it is bundled with. (There is also the Edge HD, but that is intended for imaging as well as visual). As for the SE mount, it is on the limit, but good enough for visual use in a sheltered location, and on the plus side is portable enough for you to pick up the whole setup and carry it through a domestic doorway. The SE 6/8 mount is a little more substantial than the SE 4/5 mount, or your Synscan AZ GoTo, but I suggest you reserve it for the C8 only as you don't want to be detatching and re-attaching the fat and handle-less C8 OTA unless it's really unavoidable. It's alto the wrong shape for long OTAs. 

The Celestron Schmidt-Cassegrains have been in production for at least 40 years. Some people have re-mounted the really old ones and found they work as well as ever after a bit of maintenance.

As I mentioned, you have a choice of bundled mounts for the C8 OTA (and Celestron also do their Schmidt-Cassegrains in larger sizes).

If you have no interest in imaging, either a Schmidt-Cassegrain or a Classic Cassegrain, or a GoTo Dob should suit you.

[PeterC65]

15 hours ago, Zermelo said:

I'm in a similar position and I'll be interested in the responses.

I've decided (more or less) that it's not worth going 6">>8", I want at least 10".  A motorized goto mount for that will probably be too pricey for me, so I'll probably be looking at a Stellalyra dob.

How important for you is the pointing capability, relative to the tracking? Have you considered getting by with just push-to on a dob, either by retro-fitting some digital encoders or cannibalizing a Starsense from a cheap refractor? I do like the goto/tracking too, but I'm considering push-to, combined with some decent widefield EPs to reduce the nudging.

I've seriously considered the Stellalyra 10" Dobsonian. It seems to me to be the best of that type and is certainly the lowest cost way to get bigger aperture. I just don't know how I would get on without GOTO. I value both the finding and the tracking. I keep meaning to use my existing mount manually but it always seems like such a faff so I haven't tried it yet.

With a manual Dobsonian I was thinking I could add a setting circle and an inclinometer for finding but that would still be quite a faff and wouldn't help with tracking. Push-to kit costs about half the cost of adding GOTO and an equatorial platform (as @Louis D suggests) about the same again. So it would cost the same to add GOTO as to add both of these.

I think it's important to spend several minutes observing a target and to be still and relaxed, so I value being seated which I can only do with a diagonal enabled scope. I recently bought the Explorer 150PDS in part to see how I get on with Newtonian eyepiece positioning (standing up). So far it's better than I was expecting but I've only had one proper session with it. I have my tripod / mount set permanently at the right height for seated observing with diagonal enabled scopes. When I attach the Explorer 150PDS and set its rotation appropriately the eyepiece is at just the right height for me to observe standing with just my neck bent. The zenith height of the eyepiece from the ground is 1500mm. Comparing this with Dobsonians, the Skyliner 300P is about the same but the Skyliner 250P is shorter at 1250mm so I'm thinking that the 12" may be a better height (and of course a bigger aperture).

 

[Cosmic Geoff]

3 minutes ago, PeterC65 said:

I keep meaning to use my existing mount manually but it always seems like such a faff so I haven't tried it yet.

I wouldn't - it is clearly designed to slew under power only.

With a manual Dobsonian I was thinking I could add a setting circle and an inclinometer

I tried using manual setting circles and inclimometer with a 8" Newt and EQ5 manual mount, and soon decided it was a waste of time and I wanted a used C8 SE (which cost me £650).

[Astro_Dad]

Whilst not professing to be an expert, I've tried a number of the options mentioned here in various ways, and have concluded that the Nexstar 8SE is a great scope for comfortable sitting and observation but not easy to use "manually" - one has to engage the electronics to actually use - and that combined with fairly long cool down time and the need for dew shield for me limits its ease of use (to some extent - its all relative). I think you need to step up to the Evolution range to have the option to disengage the gears. For me being forced to use electronics rather than it being there as an option is less appealing. Basic AP possible though - especially planetary.

My main stay scope and by far most used is the heritage 150p, and I generally enjoy the purity of manual star hopping with that, but I do like to have the option of some form of GOTO/Push-to occasionally- especially when time is precious juggling kids , work and waiting for gaps in the clouds! So my big aperture scope has been a 10" Dob - (I personally have not noticed much extra bulk/weight/hassle using a 10 vs an 8, so may as well go for 8...there is a noticeable difference vs the 150). Where I am going with this is that I have been looking at doing some mods to my SW 250p Classic to give Push to capability (Asterion kit, https://www.firstlightoptics.com/astronomy-mount-upgrade-kits/asterion-push-to-kit-for-sky-watcher-dobsonians.html) plus a couple of others, but I then had the idea of selling off unneeded or rarely used kit (and my scope) to see if I could go for the admittedly expensive new Celestron Starsense 10 inch Dob for about the same overall financial outlay.... This has worked out, and I have the new scope arriving today! The Starsense tech is really very good (my first scope was the 130mm reflector version) and I'm looking forward to having the option to manually star hop "the proper way" but also have assistance that may be useful at parties, at my local society or for when needing to show the kids stuff - plus my own benefit of being able to track down some of those tricky DSO's.

There are cheaper ways to do it - DIY projects using the Starsense kit from the cheaper models in the range as has been noted, but I've taken this route, and looking forward to  unboxing later 🙂

 

[Zermelo]

49 minutes ago, PeterC65 said:

I've seriously considered the Stellalyra 10" Dobsonian. It seems to me to be the best of that type and is certainly the lowest cost way to get bigger aperture. I just don't know how I would get on without GOTO. I value both the finding and the tracking. I keep meaning to use my existing mount manually but it always seems like such a faff so I haven't tried it yet.

With a manual Dobsonian I was thinking I could add a setting circle and an inclinometer for finding but that would still be quite a faff and wouldn't help with tracking. Push-to kit costs about half the cost of adding GOTO and an equatorial platform (as @Louis D suggests) about the same again. So it would cost the same to add GOTO as to add both of these.

I think it's important to spend several minutes observing a target and to be still and relaxed, so I value being seated which I can only do with a diagonal enabled scope. I recently bought the Explorer 150PDS in part to see how I get on with Newtonian eyepiece positioning (standing up). So far it's better than I was expecting but I've only had one proper session with it. I have my tripod / mount set permanently at the right height for seated observing with diagonal enabled scopes. When I attach the Explorer 150PDS and set its rotation appropriately the eyepiece is at just the right height for me to observe standing with just my neck bent. The zenith height of the eyepiece from the ground is 1500mm. Comparing this with Dobsonians, the Skyliner 300P is about the same but the Skyliner 250P is shorter at 1250mm so I'm thinking that the 12" may be a better height (and of course a bigger aperture).

 

Yes, I certainly agree about the value of being seated, it's one reason that my Skymax usually gets put out ahead of the Newt.
I too keep promising myself to go starhopping one evening, but when I bring up an ambitious  list of targets, and factor in the chance of some cloud, and a grim forecast for the following week, I always want to spend my time observing rather than searching. Actually, my goto is usually temperemental enough to provide me with a bit of a challenge in the finder.

[Captain Scarlet]

I seem to be in the minority that uses a newt on an alt-az mount. And at the big end of things too: a 12” on an AZ-EQ6. Although I now have reduced the weight of the OTA with a carbon tube, it used to be a full-blown SW 300p with steel tube, coming in at over 27kg including eyepieces finder etc. I was and am able to attach it to the mount without risk on my own: I attach the rings first, then with clutches locked and OTA horizontal held with one hand at each end, I “walk” the tube into the open rings, close the rings whilst gently holding the tube in place with my body and I’m done.

A 10” being so much more wieldy should be even simpler should you go down that route.

Cheers, Magnus

Edited May 27, 2022 by Captain Scarlet
i before e except after c

[Carbon Brush]

My take, which is not necessarily correct.

A goto dob (I used to own one) can mean storing and carrying everything in one lump.
I used to separate the mount and tube on my 10" SW flextube.
But you can only use the mount for this scope. Alright depending on your DIY skills and patience, you can put something else on there.

If you buy a big goto mount, you swap scopes as often as you like, without having to learn a new goto system.
It is as easy as dropping something different into the dovetail. Are you really only going have one scope - ever?

EQ is a littlle less intuitive than AZ. But you only have to learn once.
This choice opens the door to astro. Whether it is low cost wide field DSLR, or money pit is your choice.
I have in the past used EQ5 with a DSLR on 800/1000mm FL 8" newts for a couple of minutes with good (to me) results.
This was unguided and before all this complicated fiddling and stacking in the computer was so popular.

Most important whichever you choose. Is it still easy enough to set up quickly?
The best scope is the one used most and all that.

HTH, David.

 

[Mr Spock]

Dob on an EQ platform. The best of both worlds 

[Starwatcher2001]

6 hours ago, Astro_Dad said:

I think you need to step up to the Evolution range to have the option to disengage the gears.

The Evolution has Alt and Az clutches that can be disengaged, but once you do that it forgets where it is for both tracking and goto. It then requires an alignment process again. I wouldn't star hop like that, but I do star hop using the motors. The advantage being that the tracking ensures things "stay put" whilst you consult the charts for the next hop.

Edited May 27, 2022 by Starwatcher2001
tryping

[Zermelo]

4 minutes ago, Starwatcher2001 said:

The Evolution has Alt and Az clutches that can be disengaged, but once you do that it forgets where it is for both tracking and goto. It then requires an alignment process again.

That's why I like my SW mount. It's hardly the most expensive, but the dual encoders let me do most of the work myself (well, with a little help from SkySafari). As long as I get it reasonably close, it won't use the higher slew speeds, and I won't wake the neighbours.

[Mr Spock]

The 12" 'Beast'

[catburglar]

7 hours ago, PeterC65 said:

The zenith height of the eyepiece from the ground is 1500mm. Comparing this with Dobsonians, the Skyliner 300P is about the same but the Skyliner 250P is shorter at 1250mm so I'm thinking that the 12" may be a better height (and of course a bigger aperture).

Just one comment on observing comfort…The eyepiece height on a 10 or 12 inch dob will vary with altitude much more than it will with your 150- a longer tube and balance point closer to the mirror will almost guarantee it… I suspect you’d need to swap between standing/seated observing as you move between objects…In my experience a mak/SCT or short focus refractor is most likely to give you observing comfort across a broad swath of sky.. 

You could stick a 10inch SCT on an AZ-Eq5 if your budget would allow…or the Evolution9.25… and both would give you an beefier mount for your other scopes if you wanted it.

[ollypenrice]

The SCT is admirably compact and the views are between good and excellent. (My own experience says that the bigger they are the better they get relative to Newts of the same aperture. That's just my feeling.  The not inconsiderable downside is the restricted field of view.

A 10 inch on an EQ5?  Just this afternoon I've put a 10 inch Meade on an EQ6 for visual and I have four counterweights on there...

Olly

Edited May 27, 2022 by ollypenrice

[Paz]

This is a difficult one as it involves trading off different things,  but I would say a big Newtonian on an eq mount would be a serious undertaking, quite difficult and physical to set up due to weight, bulk, awkwardness, more hassle balancing everything off, the eyepiece rotating all over the place, etc.

I think there's a lot to be said for a go-to dobsonian although it may not tick every box perfectly. 

It is true eyepiece height varies a lot on a big dobsonian but my observing chair (a bog standard skywatcher one) allows me to go from almost sitting on the floor to almost fully standing just fine.

Edited May 27, 2022 by Paz

[catburglar]

The OP referred to an AZ-EQ5GT which in altaz mode has a weight limit of 15kg per side. The 10inch SCT should come in a little under 15kg- according to the spec on FLO the C11 OTA is 12kg.

I have used a 10kg mak newt on an AZ-EQ5 in altaz with just 2 counter weights and it handled the weight fine although the longish OTA and some free play in az that some examples of this mount seem to show made it a bit irritating for me, although goto and tracking were fine. I didn’t try in EQ mode.

[Mr Spock]

My view on SCTs is, and I had a good quality C9.25, they are more susceptible to seeing conditions than a Newt. I've had more nights of excellent seeing with the 12" Dob in the last six months than in the whole 8-10 years I had the C9.25.

Quite often it was the same procedure. Put the cat out, let it cool for a few hours (it was stored in a cool place anyway), see how rubbish the seeing is, pack it up for the night. A very frustrating scope!

[PeterC65]

9 hours ago, Cosmic Geoff said:

All the C8 OTA's are essentially the same - the only differences are the various colours and that some have a grab handle - it depends on what mount it is bundled with.

That's really useful to know - thanks!

[PeterC65]

8 hours ago, Cosmic Geoff said:

I wouldn't - it is clearly designed to slew under power only.

I meant try using the mount under power, controlled via the buttons, but without using the find function and with tracking switched off. I think this may not be representative of a manual Dobsonian though which can be moved by hand much more readily than my mount can be moved under power via the controller buttons.

 

[Chaz2b]

I would’ve thought that top priority in this debate would be MUSCLES, what ever you decide on in achieving large aperture, it ain’t going to be light!

I’ve had four Orion 10” dobs in this flat, just moving them around had me knackered, and that’s without moving the bases! They ain’t light either!!

seriously, at least an 8” whatever, but do consider weight.

The 8” CapeNEWISE I have is the carbon tube version, lightish…ish.

chaz

Edited May 27, 2022 by Chaz2b

[PeterC65]

9 hours ago, Astro_Dad said:

Whilst not professing to be an expert, I've tried a number of the options mentioned here in various ways, and have concluded that the Nexstar 8SE is a great scope for comfortable sitting and observation but not easy to use "manually" - one has to engage the electronics to actually use - and that combined with fairly long cool down time and the need for dew shield for me limits its ease of use (to some extent - its all relative). I think you need to step up to the Evolution range to have the option to disengage the gears. For me being forced to use electronics rather than it being there as an option is less appealing. Basic AP possible though - especially planetary.

My main stay scope and by far most used is the heritage 150p, and I generally enjoy the purity of manual star hopping with that, but I do like to have the option of some form of GOTO/Push-to occasionally- especially when time is precious juggling kids , work and waiting for gaps in the clouds! So my big aperture scope has been a 10" Dob - (I personally have not noticed much extra bulk/weight/hassle using a 10 vs an 8, so may as well go for 8...there is a noticeable difference vs the 150). Where I am going with this is that I have been looking at doing some mods to my SW 250p Classic to give Push to capability (Asterion kit, https://www.firstlightoptics.com/astronomy-mount-upgrade-kits/asterion-push-to-kit-for-sky-watcher-dobsonians.html) plus a couple of others, but I then had the idea of selling off unneeded or rarely used kit (and my scope) to see if I could go for the admittedly expensive new Celestron Starsense 10 inch Dob for about the same overall financial outlay.... This has worked out, and I have the new scope arriving today! The Starsense tech is really very good (my first scope was the 130mm reflector version) and I'm looking forward to having the option to manually star hop "the proper way" but also have assistance that may be useful at parties, at my local society or for when needing to show the kids stuff - plus my own benefit of being able to track down some of those tricky DSO's.

There are cheaper ways to do it - DIY projects using the Starsense kit from the cheaper models in the range as has been noted, but I've taken this route, and looking forward to  unboxing later 🙂

 

I'm the opposite, I'm happy to just have GOTO with no manual adjustment (other than via the controller buttons). My SynScan AZ GOTO cannot be moved manually in azimuth anyway, only under power, and I have tightened the altitude friction clutch so that it is hard to move manually. This is because if it slips the mount looses alignment and that can happen too easily with the Explorer 150PDS fitted!

It's good to know that you rate the Nexstar 8SE for seated observing and that you think there is a noticeable difference between 6" and 8".

One of my concerns is that if I sacrifice 10" standing for 8" seated observing I may be left wondering what I could have observed with 10" or even 12" standing!