Advice: more aperture

[Basementboy]

Hi everyone,

It has been a while since I posted, because I haven't been doing much stargazing – the reason for which is why I come to you, now, humbly seeking wisdom.

My situation is that, because I live in London, I have to drive out of the city to get any decent dark skies.

Even when I do, however, I think I've reached the limit of what I can see with my current setup (a lovely 115mm ED triplet and a 6" Newt mounted on an Ercole Giro above a heavy steel tripod). Unless it's a perfect night, most of my faint fuzzy targets elude me, and I'm not having much fun showing my friends anything except the planets. (They also really struggle to use the Ercole themselves, so there's a lot of standing around waiting for me to show them things ... and it's always less fun when you can't use a machine yourself.)

But, leaving aside the mount, the main issue is – cliche alert – I think I need more aperture.

(Ideally I'd also want to be a bit lighter and nimbler, too... the steel tripod+Ercole is a beast to lug around. But life is full of hard choices.)

One more obstacle: my car is a Fiat 500, so space is something of an issue.

Esteemed ones, what do you recommend? 

Is a collapsible truss Dob the easiest way to get more aperture with portability? And, if so, is it unrealistic to imagine I could get 12" or 14" or even 16" that still fits in the boot of the Fiat?

Or is it wiser to aim at an 8"/10" cassegrain of some variety?

Or am I missing another more obvious option?

Assuming for now that money is no object (though of course it is – did I mention the Fiat 500?), where would you go next?

Chris

[vlaiv]

15 minutes ago, Basementboy said:

My situation is that, because I live in London, I have to drive out of the city to get any decent dark skies.

Before getting any new equipment, I would revisit this bit.

How far away are you driving and where?

Can you find your favorite spot on this map:

https://www.lightpollutionmap.info

And what is the reading on it?

5-6" of aperture is quite plenty under really dark skies - it will show you hundreds of objects if you get dark adapted properly.

Find a spot on above map that is green or at least green/yellow transition (SQM > 21.3-21.4) and see what can be seen from such location. Don't forget to get properly dark adapted.

[Stu]

One point to make is that larger aperture rarely (never) goes along with nimble, cheap or light! Certainly a bigger cassegrain would still need the Ercole, possibly bigger.

How are you finding things with your current setup? A TelRad alongside a 9x50 RACI finder can make life a lot easier.

The 115mm should be fabulous for wide field targets under dark skies; objects like the Veil and North America nebula will be great when using an OIII filter for example.

Do you think you need goto? Even with larger apertures you still need to find things, and they generally have narrower fields of view so it can be as tricky as with a smaller scope. None of the goto mounts capable of holding a bigger scope are going to be lighter than your Ercole though, heavier if anything so I would think carefully about what is important to you.

My thoughts are either something like a 8” Classical Cassegrain on your existing mount, or on a goto Alt az mount. Or, something like a 12” truss dob (Sumerian type) which will pack down into a relatively small car.

Budget is a big question though, so giving an indication of what you are prepared to spend would really help.

 

[Cosmic Geoff]

A Celestron C8 SE would give you more aperture +GoTo in a portable package. The GoTo would save a lot of time spent standing around and aiming the scope. Not cheap though with the recent price increases, unless you buy used (and there are lots of them around.)  I have used mine for galaxy viewing in dark Devon to great effect.

One has to say though that 'faint fuzzy objects' are only well seen from a really dark site.  One can see a lot more detail by imaging and EVAA, even with a small scope.

Edited July 23, 2022 by Cosmic Geoff

[happy-kat]

Random thought, what about just the ED on say a goto mount but use with EVAA to say a tablet if windows tablet then sharpcap live stack, there's a post where an existing dslr was being used as they had it already, can't recall the brand of dslr 

[ScouseSpaceCadet]

This is tricky. Are you trying to satisfy yourself or your friends? Are they just along for the ride waiting for you to show them stuff? If so, you don't need more aperture. With patience, 4" - 6" under dark skies will provide an inexhaustable number of objects to observe.

Increased aperture will obviously allow you to go deeper but, will a truss dob or similar actually speed things up so they get their eye in?

Your friends need kit of their own. Three people with binoculars, simultaneously sharing an experience is more fun than one person trying to find objects while two others queue up.

Edited July 23, 2022 by ScouseSpaceCadet

[SthBohemia]

Iffn ya got the 'dough' how about a Meade LX850? Maybe a bit heavy, then again all Meade SCT's are heavy 😞

 

[PeterC65]

I've also been hankering after more aperture with the aim of seeing more (new objects and more detail). I've considered a 10-12" Dobsonian but currently I'm trialling EEVA and that might be an alternative for you to try.

I'm using my existing 72mm Apo refractor and AZ GOTO mount with an Altair GPCAM2 327C camera that I acquired second hand (to keep the trial costs down). I'm a visual astronomer looking for a near live view and I'm not interested in taking photographs, so I've kept things simple by using just the camera connected via USB to a laptop running SharpCap.

I also want to be able to share the experience (with my wife and with friends) and EEVA makes that much easier.

It's still early days for me (only one session so far and that was frustrating due to my lack of experience) but from what I've read I can expect to see images similar to trebling the scope aperture (!) and I should be able to use filters to remove light pollution (not really a problem for me but sometimes removing Moonlight would be helpful).

 

[Elp]

Your experience sounds similar to when I want to quickly view things from my light polluted garden. Other than planets it's next to impossible to find any dso targets as there's few reference stars other than the main ones, a slight fraction of a degree out and you won't see it, more so if you need to use averted vision.

My solution? Well it's easy when you've got the equipment, due to my LP I'm more of an imager and doing what you are looking to do very easy. With my asiair I simply choose a target (or input a set of coordinates from telescopius) and the mount will slew the telescope (there is now also an in built basic stellarium so you can frame targets how you choose), plate solve via the camera and make adjustments until the target is dead centre. No more waiting or faffing around. With the live view mode it will also continue to take images and stack them in real time improving the image over time of which you can also save, all this being viewable on your mobile phone. If you want to compare the camera view with a real view you can use a flip diagonal mirror to switch between the two.

[cajen2]

I have a 150 Flextube dob and it's amazing for aperture v. portability. I also have a StellaLyra 200mm and it's amazing for views v. £.

If it were me, the best compromise might be a Flextube 8"

https://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-200p-flextube-goto.html

It has go-to as well. Flo doesn't quote folded sizes, so maybe check with them to see if it'll fit your car.

Edited July 23, 2022 by cajen2

[niallk]

A compact truss dob could be nice... links to 12", and they have big brothers too

https://www.teleskop-express.de/shop/product_info.php/info/p15130_Taurus-T300-S-12--f-5-Classic-Dobson-Telescope--Professional-optics.html

 

https://www.teleskop-express.de/shop/product_info.php/info/p6879_Explore-Scientific-Ultra-Light-Dobsonian---aperture-305-mm---Generation-II.html

 

https://www.teleskop-express.de/shop/product_info.php/info/p2236_Geoptik-Nadirus-12-Truss-Dobsonian-Telescope---12-inch-Aperture-f-5.html

[Basementboy]

On 23/07/2022 at 12:46, vlaiv said:

And what is the reading on it?

Hey Vlaiv. This is the closest spot I can get to for camping without driving for more than 1 hour:

Coordinates

51.33408, 0.38007

SQM

20.09 mag./arc sec2

Brightness

0.991 mcd/m2

Artif. bright.

820 μcd/m2

Ratio

4.80

Bortle

class 5

Elevation

185 meters

I know that there are darker places (the South Downs for eg) within 2 hours of South London, but there is a certain degree of compromise needed here between darkness v ease.

It's already difficult enough to pack up the car and drive out of the city without making it a 4 hour return journey.

I guess that's why I'm trying to find some help here. Yes, if I'm in a perfect situation (deepest countryside, no moon, peak nighttime darkness, clear seeing) I can see good stuff.

But, in practice, it's often not a perfect situation. Hence why I'm hoping for a more powerful device. Does that make sense?

[Basementboy]

On 23/07/2022 at 12:49, Stu said:

One point to make is that larger aperture rarely (never) goes along with nimble, cheap or light! Certainly a bigger cassegrain would still need the Ercole, possibly bigger.

How are you finding things with your current setup? A TelRad alongside a 9x50 RACI finder can make life a lot easier.

The 115mm should be fabulous for wide field targets under dark skies; objects like the Veil and North America nebula will be great when using an OIII filter for example.

Do you think you need goto? Even with larger apertures you still need to find things, and they generally have narrower fields of view so it can be as tricky as with a smaller scope. None of the goto mounts capable of holding a bigger scope are going to be lighter than your Ercole though, heavier if anything so I would think carefully about what is important to you.

My thoughts are either something like a 8” Classical Cassegrain on your existing mount, or on a goto Alt az mount. Or, something like a 12” truss dob (Sumerian type) which will pack down into a relatively small car.

Budget is a big question though, so giving an indication of what you are prepared to spend would really help.

 

Hey Stu,

I'm using a 9x50 RACI, and I have a Rigel, but tbh I don't use it much – generally if my RACI is properly aligned I don't find the Rigel adds a whole lot to the equation.

I haven't tried using an OIII filter but maybe will give it a whirl.

As for GOTO – yes, I'm starting to think that might help. One thing that puts me off a lot is all the prep that needs to go into finding objects yourself ... researching in advance, writing down notes (to avoid having to flip through the book in the middle of a field – the last thing I want to start doing is bringing a bloody table along too) ... and then not finding 80% of targets anyway. At least GOTO would help me speed that up.

As for weight, I'm totally aware that there's always a tradeoff. Weight isn't really the most important thing for me here. It's a nice to have, not a must have.

Are the truss dobs easy to collapse and reassamble? Or is it a total faff?

Budget wise I'm thinking about £1k but could stretch to £2k by selling off a few older pieces of kit.

[Basementboy]

On 23/07/2022 at 13:14, Cosmic Geoff said:

A Celestron C8 SE would give you more aperture +GoTo in a portable package. The GoTo would save a lot of time spent standing around and aiming the scope. Not cheap though with the recent price increases, unless you buy used (and there are lots of them around.)  I have used mine for galaxy viewing in dark Devon to great effect.

One has to say though that 'faint fuzzy objects' are only well seen from a really dark site.  One can see a lot more detail by imaging and EVAA, even with a small scope.

These are pretty good suggestions. I'll check them out. (I hate the silver colour of the Celestrons but hey.) And will investigate EEVA

[Basementboy]

On 23/07/2022 at 13:30, happy-kat said:

Random thought, what about just the ED on say a goto mount but use with EVAA to say a tablet if windows tablet then sharpcap live stack, there's a post where an existing dslr was being used as they had it already, can't recall the brand of dslr 

Yeah not random at all really – a few other people here have suggested EEVA ... it hadn't occured to me before tbh 

[Basementboy]

On 23/07/2022 at 15:26, SthBohemia said:

Iffn ya got the 'dough' how about a Meade LX850? Maybe a bit heavy, then again all Meade SCT's are heavy 😞

 

As it happens, my father in Canada has one of these (or a very similar model) from the 1980s! So that's what I intend to use when I go back to visit him. I wouldn't want to replicate his kit though, no point doubling up really

[Basementboy]

On 23/07/2022 at 15:27, PeterC65 said:

I've also been hankering after more aperture with the aim of seeing more (new objects and more detail). I've considered a 10-12" Dobsonian but currently I'm trialling EEVA and that might be an alternative for you to try.

I'm using my existing 72mm Apo refractor and AZ GOTO mount with an Altair GPCAM2 327C camera that I acquired second hand (to keep the trial costs down). I'm a visual astronomer looking for a near live view and I'm not interested in taking photographs, so I've kept things simple by using just the camera connected via USB to a laptop running SharpCap.

I also want to be able to share the experience (with my wife and with friends) and EEVA makes that much easier.

It's still early days for me (only one session so far and that was frustrating due to my lack of experience) but from what I've read I can expect to see images similar to trebling the scope aperture (!) and I should be able to use filters to remove light pollution (not really a problem for me but sometimes removing Moonlight would be helpful).

 

This is super helpful, Peter! I think you understand my issue. You've inspired me to try out EEVA. 

Is it necessary to keep dark-adapted vision when doing EEVA? One persistent problem I have with my phone is that when using Stellarium in red-light mode, the phone itself constantly throws out white light – eg a keyboard or a notification – and ruins my dark vision. So I imagine a laptop would have the same issue. Unless that's no longer part of the equation when doing EEVA because you're not viewing the objects directly ... ?

[Basementboy]

On 23/07/2022 at 16:49, Elp said:

Your experience sounds similar to when I want to quickly view things from my light polluted garden. Other than planets it's next to impossible to find any dso targets as there's few reference stars other than the main ones, a slight fraction of a degree out and you won't see it, more so if you need to use averted vision.

My solution? Well it's easy when you've got the equipment, due to my LP I'm more of an imager and doing what you are looking to do very easy. With my asiair I simply choose a target (or input a set of coordinates from telescopius) and the mount will slew the telescope (there is now also an in built basic stellarium so you can frame targets how you choose), plate solve via the camera and make adjustments until the target is dead centre. No more waiting or faffing around. With the live view mode it will also continue to take images and stack them in real time improving the image over time of which you can also save, all this being viewable on your mobile phone. If you want to compare the camera view with a real view you can use a flip diagonal mirror to switch between the two.

This sounds cool – you're talking about EEVA here right? I must admit I didn't understand everything you've said, but I get the picture  

[Basementboy]

On 23/07/2022 at 17:28, cajen2 said:

I have a 150 Flextube dob and it's amazing for aperture v. portability. I also have a StellaLyra 200mm and it's amazing for views v. £.

If it were me, the best compromise might be a Flextube 8"

https://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-200p-flextube-goto.html

It has go-to as well. Flo doesn't quote folded sizes, so maybe check with them to see if it'll fit your car.

Looks brilliant actually. And within my budget. 

Do you know if it's easy to collapse and reassamble, or is it a faff? And does it hold collimation? (I'm assuming not)

[Basementboy]

On 23/07/2022 at 20:19, niallk said:

A compact truss dob could be nice... links to 12", and they have big brothers too

https://www.teleskop-express.de/shop/product_info.php/info/p15130_Taurus-T300-S-12--f-5-Classic-Dobson-Telescope--Professional-optics.html

 

https://www.teleskop-express.de/shop/product_info.php/info/p6879_Explore-Scientific-Ultra-Light-Dobsonian---aperture-305-mm---Generation-II.html

 

https://www.teleskop-express.de/shop/product_info.php/info/p2236_Geoptik-Nadirus-12-Truss-Dobsonian-Telescope---12-inch-Aperture-f-5.html

Whoa. Taurus and Nadirus! Never heard of them. Love the wooden styling ... Are they well-regarded scopes?

Yeah I mean I'd love these but I'm not sure they'd fit in my Fiat 500 even when collapsed. 

Do you know if they're easy to collapse and reassamble? Or it is a pain?

[PeterC65]

42 minutes ago, Basementboy said:

This is super helpful, Peter! I think you understand my issue. You've inspired me to try out EEVA. 

Is it necessary to keep dark-adapted vision when doing EEVA? One persistent problem I have with my phone is that when using Stellarium in red-light mode, the phone itself constantly throws out white light – eg a keyboard or a notification – and ruins my dark vision. So I imagine a laptop would have the same issue. Unless that's no longer part of the equation when doing EEVA because you're not viewing the objects directly ... ?

From my limited experience so far, EEVA does not require dark adapted vision. I sit at the dining table with a laptop just inside the patio door, with the scope just outside connected via a single USB cable. I have the lights on and use the laptop in normal mode (not red light mode). I've been viewing the camera output (with SharpCap) and controlling the mount (with Stellarium) from inside and that's mostly worked out fine.

I ended up aligning the mount with an eyepiece the first time I trialled this kit but I think I should be able to carry out alignment with the camera (I just hadn't got the hang of viewing stars with the camera). The only other thing I needed to go outside for was to focus (which is only needed when you change the setup - changing filters / Barlow / reducer) and then I took the laptop with me.

This is still early days for me but there is the definite possibility of much better views, and I like the idea of observing from inside when its cold out, and sharing the experience with my wife.

I don't have a problem with light pollution here but but I believe that EEVA could allow very narrow band fitters to be used such as the Optolong L-eXtreme which seem to be capable of filtering out almost any amount of light pollution, so you may be able to get good views even in central London.

Edited July 25, 2022 by PeterC65

[Elp]

5 minutes ago, Basementboy said:

you're talking about EEVA here right?

Essentially its how a fully automated astrophotography setup works, once the scope+mount is physically aligned to polaris via a polar alignment routine the asiair (or whatever computer is being used) knows where objects in the night sky should be and where the scope+mount is pointing toward, so you can select an object you want to point to and the asiair moves the mount to point the scope at the target. It then takes an image with the main camera attached to the back of the scope and plate solves (it analyses the image for stars), checks this against its internal database and if the mount is not pointing dead centre it repeats this process until it confirms it is centred. You can then set a tracking rate to it'll keep the target in the centre of the view. If you've got a guidescope connected with a separate guide camera, this setup will track surrounding guide stars to keep the target in centre.

Essentially EEVA utilises the same process but can be simplified by not needing the computer controller if you don't want to and using the goto mounts in built alignment routine which you'll have to align to 2 or 3 stars prior to issuing a goto command. The camera then becomes your "eyepiece". Or if you don't have a goto mount you can just use a camera attached to the telescope but you'll find stars begin to trail after a few seconds. At a modest focal length of around 100-200mm you'll get star trailing after around 10s or so so better to get a mount which has goto/motor drives which control the RA and Dec axis, RA motor control is essential, dec not so much, and setting up in equatorial mode is preferred to alt az mode.

If you do venture into a fully automated setup (costs can ramp up a lot though) it becomes very easy to browse the night sky viewing multiple targets in one session. Scopes such as EVscope and Stellina utilise all this what i've described into one unit.

[cajen2]

1 hour ago, Basementboy said:

Looks brilliant actually. And within my budget. 

Do you know if it's easy to collapse and reassamble, or is it a faff? And does it hold collimation? (I'm assuming not)

I can't comment on that particular scope but the only structural difference between it and my 150p Flextube is that it has three supports for the head instead of two. This should make it even sturdier. My 150p is very easy to deploy: slide it out to full extension and tighten two hand knobs - 10-second job. It also holds collimation well - no worse than my solid-tube 8".

Edited July 25, 2022 by cajen2

[happy-kat]

What tripod do you currently use your ED triplet on? 

[ollypenrice]

Running an astronomy gite for nearly 20 years, I have some experience of trying to impress the non-astronomer. On the planets, it's easy, in almost anything.  On the deep sky, it's almost impossible - even with a 20 inch.  And... I live at a very, very dark site. I recently introduced some absolute beginners to the deep sky with a 14 inch and found some objects which I think they really enjoyed, but they were seriously interested and had booked an astronomy holiday. For many, most things remain faint fuzzy blobs. M42 is a common exception, as is M31, but that's a winner in binoculars guided by a laser pointer (not in London!)

So, as already suggested, I would concentrate on yourself.

The SCT is compact but the long focal length, in many cases, defeats the object of the exercise by cramping the field of view and excluding many targets you might enjoy. (Rosette, Veil and many, many more.) Personally I'd go for a  collapsible Dob as big as possible.

Olly