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  #21  
Old 18-03-2018, 06:00 PM
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AstroJunk (Jonathan)
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Thanks Jonathon, nice review. Still a two-person job to set up you reckon?

I'm interested (and jealous) of your seeing conditions - we were at Watt's Bridge Airfield past Esk last night, and anything higher than 50x was like looking through a kiddies wading pool.
I was Jealous of our seeing too. My normal location in Samford is usually very poor. Last night we were at 500x on Jupiter without too much deterioration.

None of the individual components were particularly heavy, so one person could put it together from scratch. Of course its much quicker to leave the base and rocker assembled and only remove the poles and UTA - then it becomes more of a 2 person lift.
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  #22  
Old 18-03-2018, 09:40 PM
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Cool as a cucumber !~ I have had the liberty to view with 22 and 20 inch scopes in Darwin , and yes here they are being set up ,, there aint nothing better from a dark site , here is my mate putting his secondary spider on his awesome 22 inch f 4 ? Newtonion and John setting up the structure of the 20 inch f4.3 .

Brian.
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  #23  
Old 18-03-2018, 09:51 PM
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Here is another for the people that think 20 inches is BIG ,, hell yes they are but with todays design's .
Brian.
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  #24  
Old 18-03-2018, 09:54 PM
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You get lost in the Virgo cluster with these bad boys ! .
Lewis ?>

Brian.
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  #25  
Old 18-03-2018, 10:03 PM
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Yes a 20 inch is a monster that will show you more than you could imagine ,,, a sweet 5 inch refractor is up an running ,,, sorry guys .

Brian.
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  #26  
Old 18-03-2018, 10:45 PM
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You get lost in the Virgo cluster with these bad boys ! .
Lewis ?>

Brian.
Errrr? Yes?
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  #27  
Old 21-03-2018, 06:55 PM
raymo
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I notice that since the session with the two scopes was posted here by
Jonathon, that the comparison of the scopes seems to have been studiously ignored; is that because most posters were unhappy that the Chinese can produce a scope that is seemingly optically competitive with an SDM
scope?
raymo
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  #28  
Old 30-05-2018, 09:03 PM
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gaseous (Patrick)
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Hi Graeme, any further thoughts / comments on the 20" Skywatcher now that you've hopefully had some extended viewing with it?
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  #29  
Old 23-07-2018, 09:19 AM
Joves (Aaron)
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Hi Graeme, any further thoughts / comments on the 20" Skywatcher now that you've hopefully had some extended viewing with it?
What are your most recent thoughts of your 20”, Patrick? It sure is a lot of scope for the money. Are you still happy with it?
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  #30  
Old 23-07-2018, 10:11 AM
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Hi Aaron,


by and large, yes I'm very happy with it. Only had it to a dark site once since I bought it, but the effort it puts in on DSO's is pretty impressive. Had a few collimation issues which I believe I've sorted, and very bright stars still give spectacular diffraction spikes, but I didn't buy it for looking at very bright stars so I'm not too concerned about that. It's currently poor on planets too (very very bright as you'd expect), but I'm in the process of making an aperture mask - again, not that planets are the main target, and I've still got an 8" for that.



I'm just on 6' and can put it together myself without too many issues. A stepladder is needed for putting the secondary cage on top, and some upper arm/shoulder strength is required, but nothing too onerous. The two base components are probably 30kg each, at a guess, and are a little awkward to get off the ground, but reasonably movable once you've done that providing you're not moving them too far.



Once broken down, it takes up less volume than my old 16", and the circular base is only about 600mm across (as opposed to nearly 900mm on the 16"), so a trolley is a lot smaller too. Not including the time spent on lugging the various pieces all over the place, it can be put together and ready to go in under 30 minutes, with a bit of practice. It's a lot easier to use than the 16" as well, as the narrow base lets you stand next to the eyepiece, rather than having to lean in quite a bit which is a pain in the back. Graeme mentioned some of the quality issues with the fixings which are valid, but overall, it seems to be a very solid and well-built setup.
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  #31  
Old 23-07-2018, 04:54 PM
Graeme Bluestar (Graeme)
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Hi Patrick & Aaron,
Been flat out on my double star work with the 16", and I have not used mine in a while now, hope to have it out and working early August weekend (4th & 5th). Should be well after full moon, so will hopefully get some good hours using it. Last outing we had some spectacular planetary views - Jupiter's GRS was just amazing...

To avoid assembly hassles I modified a Kinchrome moving trolley from Bunnings to move it around on as an assembled unit. So at present it is stored under cover with a large plastic bag covering it. Once I have it out I am going to work out some suitable cooling fans to suit the the primary mirror cell which already has provision for three of them.

Will let you know what I come up with.
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  #32  
Old 23-07-2018, 05:03 PM
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I'll be very keen to see your fan solution Graeme, and also to find out where you got a bag big enough to cover it!
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  #33  
Old 24-07-2018, 12:16 AM
Joves (Aaron)
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Hi Patrick and Graeme,

Thanks so much for your replies.

I have a number of what I feel are nice telescopes, but have never owned a Dob. To add context, my current largest scope is a “measly” 10” LX90. To be honest, I’ve not really ever had a hankering for a dob until now but, for some reason, the mood has recently struck me. There are plenty of options available between this and what I currently own, I know, but I figure if I’m going to go the dob route for mere aperture purposes (which is pretty well the appeal) I might as well go relatively large compared with what I already have. The 20” Skywatcher Synscan seems a pretty decent option at “trying out” a significantly larger aperture than I’ve ever experienced. I know there are higher quality and more premium options out there, but this actually seems like a pretty decent consideration. To be honest, irrespective of the differences a higher wave mirror from a highly regarded maker might provide, I’m pretty certain I’d be impressed with almost anything an even “reasonable” mirror at this aperture might show in the right conditions and under reasonable skies. The fact that the optics of this particular scope (aside from those reviewed under extremely critical analysis, which I’m far from qualified to comment) seem to have received mostly positive, and sometimes glowing, reviews is pretty well enough for me. I’m not expecting the creme de la creme. Just a much larger aperture option, should the mood strike on any given night. This seems a pretty decent option, and with go-to/tracking, for a great price (still expensive, but cheap in most respects).

I guess all I really hoped to hear from you both is that these things aren’t complete duds, which I never expected that they were going to be.

Patrick, really glad to hear you’re happy with the scope. Whilst I know that this type/aperture scope is probably ideally suited to DSO’s, it’s interesting to hear that you’re not overly impressed with it on planets. I’d be keen to use it on both planets as well as DSO’s, but predominantly the latter. I have other scopes ideally suited to planetary observing.

Graeme, thanks for kicking off this thread to begin with. Your initial impressions (both positive and potentially negative) are appreciated and the subsequent replies, particularly with regard to your thermalised mirror holding its own against an SDM, are encouraging. It leads me to think I will purchase one of these and immediately get started on upgrading the items you kindly detailed as requiring attention. Great to also hear that you have, in fact, enjoyed some decent planetary views through yours.

Don’t you just love astronomy and telescopes... horses for courses and vice versa.

Again, thanks fellas. The fact that you’re both still reasonably satisfied with this particular scope with the limited amount of time you’ve each had to spend with it leads me to think it’s worth a shot. Where/how else is one going to get a go at observing with this kind of aperture, and complete with a fully functioning go-to system, other than this at this price point?! If the optics are good and the functionality of the scope works, that is fine for me. I have the rest of my life to “upgrade” to an Obsession, SDM, Starstructure, etc. etc. should I all of a sudden decide to become a dobsonian “connoisseur”!

Thanks again fellas.

Aaron
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  #34  
Old 24-07-2018, 05:36 AM
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Good luck Aaron. In fairness to the scope, the only time I tried it on planets was a night my collimation was a bit off, so with that corrected and maybe an aperture mask, hopefully the views will be good like Graeme had.
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  #35  
Old 24-07-2018, 06:43 AM
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AstroJunk (Jonathan)
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Good luck Aaron. In fairness to the scope, the only time I tried it on planets was a night my collimation was a bit off, so with that corrected and maybe an aperture mask, hopefully the views will be good like Graeme had.
Here's my aperture mask!

My local seeing is truly rubbish most of the time and it kills definition across a large mirror surface. The aperture mask certainly helps sharpen up the image when those stars are twinkling and reduces glare of that scattered light. On the very odd occasion though, the seeing firms up and a 20" view of the planets is truly stunning
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  #36  
Old 24-07-2018, 08:25 AM
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Here's my aperture mask!

My local seeing is truly rubbish most of the time and it kills definition across a large mirror surface. The aperture mask certainly helps sharpen up the image when those stars are twinkling and reduces glare of that scattered light. On the very odd occasion though, the seeing firms up and a 20" view of the planets is truly stunning



I like this! I've got a couple of large pieces of black foamcore that I'm hoping will do something similar.
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  #37  
Old 24-07-2018, 07:00 PM
Joves (Aaron)
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Good luck Aaron. In fairness to the scope, the only time I tried it on planets was a night my collimation was a bit off, so with that corrected and maybe an aperture mask, hopefully the views will be good like Graeme had.
Thanks Patrick. I’m thinking I might as well bite the bullet and purchase one. I’m sure it will get very limited use, with my ordinary skies and lack of real time/motivation for setup, but on those such occasions where I feel like spending the better part of the night at the scope and the seeing is decent it seems that it could be a lot of fun! 4 times the light gathering of the largest aperture scope I’ve ever actually looked through should provide somewhat of a wow factor under the right conditions!
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  #38  
Old 24-07-2018, 07:04 PM
Joves (Aaron)
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Here's my aperture mask!

My local seeing is truly rubbish most of the time and it kills definition across a large mirror surface. The aperture mask certainly helps sharpen up the image when those stars are twinkling and reduces glare of that scattered light. On the very odd occasion though, the seeing firms up and a 20" view of the planets is truly stunning
Looks great, Jonathan... I also particularly like that you’ve labeled the mask the way you have.

Can I ask, was there a specific reason or calculation that had you make the mask to 6”? That’s a lot of stopping down, which makes sense if the seeing is poor or the object too bright, but is there a reason you didn’t choose, say, 8” or even 10”? 8 inches seems to be a pretty well performing aperture for a lot of scopes under most conditions.
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  #39  
Old 24-07-2018, 08:37 PM
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Looks great, Jonathan... I also particularly like that you’ve labeled the mask the way you have.

Can I ask, was there a specific reason or calculation that had you make the mask to 6”? That’s a lot of stopping down, which makes sense if the seeing is poor or the object too bright, but is there a reason you didn’t choose, say, 8” or even 10”? 8 inches seems to be a pretty well performing aperture for a lot of scopes under most conditions.
Very little thought went into it.

I have a mate who swears by his 6" refractor - I thought I'd look at Saturn without all those pesky moons getting in the way, just like him
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  #40  
Old 24-07-2018, 10:09 PM
Joves (Aaron)
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Very little thought went into it.

I have a mate who swears by his 6" refractor - I thought I'd look at Saturn without all those pesky moons getting in the way, just like him
Haha... as good a reason as any, I guess!
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