Would you buy Skywatcher 20” Dobsonian Collapsible GOTO?
This is once in life time opportunity, for me anyway, to buy such a big scope.
I wanted to buy 16” $6000 and was showing it to my wife and how it would be impossible to fit the base (unless dismantled) into my Corolla station wagon. And the price is a bit too high as well.
Then I showed her 20” $12000 and how nice and portable that one is. She said: “Well get that one then” WOW!
Now I am thinking every day about it with a lot of questions in my mind. Should I buy it, or is there something better and not costing so much?
Your suggestions and opinions are welcome!
I used to have 8” Dob, sold it and got Bintel 12” Dob. Loved it, especially for deep sky observing. Then looked through 16” Meade Lightbridge and was blown away.
Then I cooled down, sold my 12” Dob and bought early 8” NexStar Celestron for planets mainly.
Now I got again very interested in deep sky observing and 8” simply can’t give me views that I used to see with 12” Dob.
They a pretty darn good value for what they are. I've spent a lot of time looking into these and I've concluded it isn't really portable which is important to someone who lives in Sydney and needs to travel to darker skies for a better visual experience.
Furthermore, the size of the ladder required due to the eyepiece location also needs to be factored in for travelling with it. With the 18" non-goto you can get by with a short step stool. One of our club members has one. The 20" goto dob telescope is collapsible perhaps, or should I say dismantlable, but what about the ladder you require to actually use the thing.
Location: '34 South' Young Hilltops LGA, Australia
Posts: 1,481
HI Bob,
If you live in Perth then portability is a key issue. I have an 18" f5 with a Galaxy Optics mirror. It's very similar construction to an SDM. It is portable but not as portable as the SW20".
I live on a a rural property with Bortle 1-2 skies and the scope lives here all the time so portability is not an issue for me. .
Yes you can use big instruments from the light polluted city for planet observing. But they won't give you much advantage for observing faint details in DSO's. Doesn't matter how big the telescope is, if the object is fainter than the light pollution, you won't see it.
I have seen some amazing planetary and lunar detail through the 18" but where they really shine (no pun intended) is on deep sky objects under a really dark sky.
Some examples: - the Dumbbell nebula is a full orb, not just a dumbbell, you can see the Orion nebula fully loop and close up again and on nights of high transparency, I can see a hint of red in the brighter parts of the nebula. Look at Markarian's Chain and you'll easily see 9 galaxies. Globulars like Omega Centauri and 47 Tuc just blow apart.
If you live in Perth's LP, I would place a high premium on the portability.
Yes, portability is very important. I live near Perth Airport, so travelling to dark site and ability to fit scope in my Corolla wagon is a must.
Availability is another issue, scopes are advertised but they don’t have them in shops. Would have to put deposit and wait.
You raised good point about how high the eyepiece will be on those big Dobs. I have seen some nice solutions on YouTube. I could make it myself.
Thinking about it too much and it’s a lot of money as well.
Maybe I shouldn’t make big jump from 12” I used to have to 20”
I could get 16” Meade Lightbridge that is advertised for $2,500 here in Perth.
It’s portable, base would fit in my car without dismantling it, and there is no need for steps or ladder to rich eyepiece.
Firstly I am in a very similar position to Joe and have the SW 18" goto Dob under excellent dark, steady and transparent skies and it is simply fantastic viewing!! Were I not permanent and was keen on a dob for dark sky viewing that required pack up and significant travel and was keen to make the most of my trips out to great skies, I would snap up the biggest scope that would fit in my car and one of these SW20 goto dobs would be perfect . The way to look at it is and certainly if you have received the finance go ahead () why go to all that trouble to travel to a dark sky, only to get there and set up a piddly 10 or 12"..?just becasue it takes 10min less time to setup, and three steps less to view the eyepiece!? (although I do have one of those too) the views will be well worth the slightly extra setup and packup time! I've looked through a few large dobs over the years, under some of the best skies on the planet and a 20" class dob under a truly dark sky is truly amazing, you wont regret it!
So, if you can indeed fit it in your car and that's your main method of use, go for it I say, the views will be worth it!
“Just when I thought I was out, they pull me back in” – The Godfathe
I have to admit you make perfect sense. Now I have to read more about dimensions and reviews of SW 20” GOTO.
Weight doesn’t bother me, still deadlift every now and then 230kg for reps.
Not bad for 61 year old f..t
Do you still lift Mike, just for keeping fit I mean?
Cheers
Bob
You're welcome
230kg for reps at 61 is bloody awesome mate! wow! I don't know what I might be able to pull if I went back into a gym today..? Pretty sure I would struggle to match you, maybe after a couple of months getting back in to it. I'm 57 now and I haven't lifted in a gym since 2005. At my peak in 2001, in the full deadlift (with no straps or suit) I did a set of 10 with 275kg and a single on 325kg (regular stance not summo), but my real bazar forte was the so called, silver dollar deadlift (bar 19" off the floor) in which I pulled 475kg without straps or a suit and a whopping 500kg with straps (but no suit!), it was World class at the time easily top 5, still is really ...I was just even more disproportionately strong in that particular reduced range than everyone else. Here is Rauno Heinler, the current best in the World at this event, doing the current Silver Dollar Deadlift World Record last year, with an amazing 580kg.
Ah sigh....those were the days, I do sweet FA now and my body is already starting to develop some arthritis, mainly shoulder, and old age body aches
Now go get that 20" Dob, I really want to upgrade my 18" to it too but my finance minister is pretty well at her limit
Location: '34 South' Young Hilltops LGA, Australia
Posts: 1,481
Bob,
The SW 20" dob is a 20" f3.9. When viewing the zenith & looking at the design, I would guess that the eyepiece would be no more than 1.8m off the ground. Most of the time it will be lower. Depending upon your height, it may well be more comfortable than a 12" f5 and you won't need a ladder, maybe a step if you are shorter than 1.8m.
At age 61, your maximum pupil dilation is probably around 4.8mm. I and 3 friends are all in the 58-62yo age group and we have all recently measured our pupil dilations at 4.7-4.9mm.
Assuming you, at age 61, are similar, the longest eyepiece focal length you can use for 100% light transmission to your eye is: -
Pupil diam x f ratio =. 4.8 x 3.9 = 19mm.
Using the supplied 28mm LET eyepiece to attain a wider field, the light transmission will be equivalent to a 14 inch diameter scope. So you will want a wide field <19mm eyepiece such as a 17mm Nagler as your killer DSO eyepiece. Of course you can use the longer focal length eyepieces if you accept the light loss. A 31mm Nagler will give you the light transmission equivalent to a 12-13 inch aperture.
Providing you are aware of the interactions between pupil dilation & exit pupil, you can gain great enjoyment from such an instrument as Mike and I and many others do.
That’s some crazy weight you moved around! I was more on bbuildung side of it but liked to lift heavy especially deadlifts. I still believe deadlift is the best overall exercise you can do. I watched that video 580kg!!!
In my best days only once I lifted 380kg 12 times so called partial reps in power rack setting pins higher and with wrist straps.
Good old days mate.
Joe,
You are pushing right buttons too I already have 17mm Nagler and am 185cm tall.
Listen to you old lifters cracks me up.The joys of youth.But seriously Bob good to see you still training.Go the big scope.I have a SW 16” and my best moment was when the kids were younger and they saw the moon through it.As Mike said you won’t regret it.Time is ticking enjoy the view.
Cheers Derek
The SW 20" dob is a 20" f3.9. When viewing the zenith & looking at the design, I would guess that the eyepiece would be no more than 1.8m off the ground. Most of the time it will be lower. Depending upon your height, it may well be more comfortable than a 12" f5 and you won't need a ladder, maybe a step if you are shorter than 1.8m.
The 20" has an eyepiece height of 2 meters at zenith. OK we don't often observe at zenith, but the GOTO has extra height added on top of that due to the mechanics of the motors.
Sky Watcher themselves stated that number. Once again a decent ladder is required for these larger Sky Watcher dobsonian's. We don't observe from the tops of out heads.
At least the 20" the focuser is at a 90 degree angle. Some genius thought it was a good idea to have the 18" focusers at a 45 degree angle.
These big scopes are certainly rewarding with the views they give and a 20” that can still be portable is excellent way to go.
I went from an 18”F5.6 to my current 18”F3.5 “ Excalibur “ DIY job as I needed a more compact scope to fit into my motorhome through a hatch. In the process I brought the focuser down almost a metre and saved a lot of weight. Sit down viewing even at zenith is a nice bonus and it fits in the back of my Subaru XV Hatchback. Though as I’m getting closer to 70 I’m now considering building a baby version of Excalibur using my 13”f4.3 mirror set….
Our society has a 16inch collapsible goto dob skywatcher which i look after its a great scope but is heavy i built a purpose built trailer for transporting it with a fiberglass lockable top and i just have a ramp into the trailer to it goes and straps in ,the views with the scope are terrific and the goto works so well last public viewing night we tracked the moon for 3 hrs and it just worked they are lovely scopes
Hey Mike,
Nothing wrong with a “piddly” 12” under my darkish B3 skies down South
My SW 12” Goto using my array of TV eyepieces is unbelievable no
matter what you observe
However I’d imagine a 20” would be absolutely another world under even darker skies as you said ……..
I use an adjustable gas strut bar stool for comfy viewing plus from my garage to my car bay observing location is only 6m away. Very convenient
The 20” is very enticing !!
Cheers
Martone
Hey Mike,
Nothing wrong with a “piddly” 12” under my darkish B3 skies down South
My SW 12” Goto using my array of TV eyepieces is unbelievable no
matter what you observe
However I’d imagine a 20” would be absolutely another world under even darker skies as you said ……..
I use an adjustable gas strut bar stool for comfy viewing plus from my garage to my car bay observing location is only 6m away. Very convenient
The 20” is very enticing !!
Cheers
Martone
Oh yeah, I have a 12" goto Skywatcher too, it has provided great views for sure! ...buuuut still piddly, compared to a 20" I am afraid, especially under true dark skies!
These big scopes are certainly rewarding with the views they give and a 20” that can still be portable is excellent way to go.
I went from an 18”F5.6 to my current 18”F3.5 “ Excalibur “ DIY job as I needed a more compact scope to fit into my motorhome through a hatch. In the process I brought the focuser down almost a metre and saved a lot of weight. Sit down viewing even at zenith is a nice bonus and it fits in the back of my Subaru XV Hatchback. Though as I’m getting closer to 70 I’m now considering building a baby version of Excalibur using my 13”f4.3 mirror set….
God damn it! that's a beautiful scope Matt ...you need to bring it up to Eagleveiw one clear Moonless night...we could have two 18"ers hammering away
Yes, we were lifting some serious iron And still bloody do, those young guys have no idea
I knew I could rely on you to convince me to buy it.
I was like a frog sitting on the rock above beautiful lake thinking should I jump into it or not
Now, the question, where to buy it from?
I checked a few websites and Andrews communications has the best price. Just called them and confirmed $11,499 plus delivery, will let me know on Monday how much.
Yes, we were lifting some serious iron And still bloody do, those young guys have no idea
I knew I could rely on you to convince me to buy it.
I was like a frog sitting on the rock above beautiful lake thinking should I jump into it or not
Now, the question, where to buy it from?
I checked a few websites and Andrews communications has the best price. Just called them and confirmed $11,499 plus delivery, will let me know on Monday how much.
Cheers
Bob
For that money you could almost buy my Excalibur…… almost ……
) why go to all that trouble to travel to a dark sky, only to get there and set up a piddly 10 or 12"..?just becasue it takes 10min less time to setup, and three steps less to view the eyepiece!? (although I do have 
) the views will be well worth the slightly extra setup and packup time! I've looked through a few large dobs over the years, under some of the best skies on the planet and a 20" class dob under a truly dark sky is truly amazing, you wont regret it! 
wow! I don't know what I might be able to pull if I went back into a gym today..? Pretty sure I would struggle to match you, maybe after a couple of months getting back in to it. I'm 57 now and I haven't lifted in a gym since 2005. At my peak in 2001, in the full deadlift (with no straps or suit) I did a set of 10 with 275kg and a single on 325kg (regular stance not summo), but my real bazar forte was the so called, silver dollar deadlift (bar 19" off the floor) in which I pulled 475kg without straps or a suit and a whopping 500kg with straps (but no suit!), it was World class at the time easily top 5, still is really 
...I was just even more disproportionately strong in that particular reduced range than everyone else. 
...ah yes, the good old fishing stories, ala the 
...you need to bring it up to Eagleveiw one clear Moonless night...we could have two 18"ers hammering away 
