The skywatcher Syn Scan Dobsonians discussion

[N3ptune]

I am looking at the Canadian Skywatcher website and reading about the SynScans dobonian base models, comparing them just for fun. (I always wonder if someday I'll be sitting while sketching)

http://ca.skywatcher.com/product/series/dobsonians/

8" SynScan GPS 1 548USD / 1 996CAD (F5.9)

10" Synscan GPS 1 970USD / 2 541CAD (F4.7) +545 +2"

12" SynScan GPS 3 049USD / 3 932CAD (F4.9) +1391 +2"

14" SynScan GPS 3 831USD / 4 941CAD (F4.5) + 1009 +2"

16" Synscan GPS 5 269USD / 6 796CAD (F4.4) + 1885 +2"

Just looking at price, size and F ratio, I find this interesting especially for the first 3 models the 8", 10" and 12" 

In these deals the 12" is F 4.9, is it a big difference with a F5 honestly?  With the same eyepieces I use right now with my F5, Xcel LX, Starguider, Explore scientific 68 and 82 and orthoscopic eyepieces, I don't fell any need for a coma corrector very much.

If anyone ever compared a F5 with a F4.9

Also, looking at the prices, the 10" it not much more expensive then the 8", but at F4.7, I believe it needs a coma corrector which will raise the price of a few bills and you get more glass behind the eyepiece.

============

(Simulation) My first goal would be to upgrade to something I can sit while sketching and that has a tracking system, that's mandatory. The 3rd thing, the aperture has to be 8" or more naturally, It's the least important need in the 3 but it's still there.

The choice is not really easy:

8": PROS: Not to heavy, generous F5.9 focal ratio, decent price, not too high to watch while sitting CONS: No aperture upgrade.

10": PROS: interesting 2" aperture gain, probably still low enough to watch while sitting CONS: F4.7, Coma corrector required 200$GSO / 400$ Baader, more lens behind the EP

12": PROS: Maximum and massive aperture upgrade, F4.9 perhaps no coma corrector required.  CONS: heavy weight, perhaps too high to watch the zenith while sitting, quite expensive. 

if you want to share your opinion, what telescope do you guys thing is the very best of the 3 and why?

[Geoff Lister]

I went for the 10". I wanted the largest aperture that would also be relatively easy to store in my garage, and move out, through a standard doorway with single step, to an adjacent patio. I have no regrets, and have not felt the need for a coma corrector.

Geoff

[vlaiv]

12" ?

Dobs are about aperture, so if you have the funds (and storage space)....

Personally I would probably go for non goto version. Tracking is something that I would want, especially for planetary but goto does not appeal to me in terms of finding stuff. That is something I like to do on my own (star hopping, or alternative - looking at the sky, pointing in general direction of target and hoping for the best - you would be surprised how often this turns out to work well).

That 12" is really F/5 so no much different in terms of coma. It is quoted to be F/4.9 because they used 12" measure for primary, while staying in metric for focal length - 12" is 305mm rather than 300mm and focal length is 1500mm, so actual "speed" of telescope is F/4.92. However I believe that there is some variance in real focal lengths of mirrors produced - couple of mm at least, and maybe even full cm +/-, so again for all purposes it can be said it is F/5 scope.

Depending if you want the goto or just tracking - I think there could be cheaper alternative (I would go for that for example, over goto):

Regular non tracking 12" SW dob - still F/4.92 (or maybe GSO one, cheaper still and lighter), everything the same except:

1. Weight

No much real gain, but it "disassembles" in 3 rather than 2 pieces - probably easier to carry (each piece, and rocker box is somewhat lighter).

2. Price

Price cut would be from goto / non goto version + eq platform, something like this:

https://www.teleskop-express.de/shop/product_info.php/info/p10564_TS-Optics-EQ-Dobsonian-Telescop2-Drive----Platform-for-45--N-S.html

Since "barebone" version is about 66% of goto version, and EQ platform is less than 1/3 of goto version (there are even DIY plans floating around the web).

 

[N3ptune]

@Geoff Lister thanks for the interesting insight about coma and weight. Good to know.

@vlaiv Yes the storage and weight are an issue with the 12" and perhaps even with the 10".  I am not a fan of GOTO, after 3 years of only star hopping with my equatorial mount, the benefits of learning the sky, it's part of the whole experience for me too.

-->It's the tracking while sketching.. this is not optional for me, I would be very unhappy with anything manual today ?. (also, good to know F4.9 ~ F4.92 is the same thing has F5)

The solution of a manual dobson, 12" with an equatorial platform is something I highly consider. But I am quite afraid with the equatorial platform because at my various observation spots, the ground is very uneven with rocks, slops and everything. My actual equatorial mount is a charm to set up on any terrain but with the equatorial platform I don't know how easy and quick they would be to set up, I don't quite understand how to polar align them yet.

'Ill watch some Youtubes but it seem like one needs to  lay flat on the floor to look trough the polar reticle.

The second problem is to build such a precise device myself.

Still, it's an intelligent idea to install a manual 12" on an equatorial platform especially with the DIY solution.

[vlaiv]

46 minutes ago, N3ptune said:

@Geoff Lister thanks for the interesting insight about coma and weight. Good to know.

@vlaiv Yes the storage and weight are an issue with the 12" and perhaps even with the 10".  I am not a fan of GOTO, after 3 years of only star hopping with my equatorial mount, the benefits of learning the sky, it's part of the whole experience for me too.

-->It's the tracking while sketching.. this is not optional for me, I would be very unhappy with anything manual today ?. (also, good to know F4.9 ~ F4.92 is the same thing has F5)

The solution of a manual dobson, 12" with an equatorial platform is something I highly consider. But I am quite afraid with the equatorial platform because at my various observation spots, the ground is very uneven with rocks, slops and everything. My actual equatorial mount is a charm to set up on any terrain but with the equatorial platform I don't know how easy and quick they would be to set up, I don't quite understand how to polar align them yet.

'Ill watch some Youtubes but it seem like one needs to  lay flat on the floor to look trough the polar reticle.

The second problem is to build such a precise device myself.

Still, it's an intelligent idea to install a manual 12" on an equatorial platform especially with the DIY solution.

Don't think you need to do precise alignment with EQ platform, usual compass + latitude of observation site would be quite enough (actually many platforms don't even have latitude adjustment, they are pre build for specific range). Sure you would not be able to do long duration precise tracking, and you might need to nudge the scope every 5 to 10 minutes to recenter the target, but that is much better than having to nudge it every minute or less. You would also need to "rewind" the platform every hour or so.

As for flatness of the base and ground - I guess if one can put dob on ground, then EQ platform is much the same. Just make sure you have some sort of adjustable legs so you can go relatively level - that is more than I've got on my 8" dob - it has only 3 small rubber legs.

[pipnina]

1 hour ago, vlaiv said:

Personally I would probably go for non goto version. Tracking is something that I would want, especially for planetary but goto does not appeal to me in terms of finding stuff. That is something I like to do on my own (star hopping, or alternative - looking at the sky, pointing in general direction of target and hoping for the best - you would be surprised how often this turns out to work well).

I would never consider GOTO a bad feature to have. After all it can be used with goto turned on or off, better to have the ability to quickly get to the target you want to see before the clouds come in while maintaining manual control when you want it, even if that's most of the time.

The directional controls on the handset would no debut be a godsend as well. I've found my 10" sw dob to be great, but maneuvering it to relatively high position can be a pain. something about the movement can be "sticky". Both altitude and azimuth wise. Motorized directional control as with synscan would be a large improvement IMO.

Obviously you still have to pit that convenience against cost, but if I were buying a dob again I'd be looking at a goto.

[N3ptune]

? I could probably live with 10 minutes but 5 is not enough to my taste ? It should be able to reach even more then 10 minutes if built and installed correctly.. for that reason. like you said, it should have adjusters. I would want a bubble level, the right angle for my region and some kind of polaris finder. Am used to good performance with my equatorial mount, it can hold the image for more then 20 minutes easily when well adjusted.

 

[N3ptune]

@Geoff Lister

How is the height of the eyepiece with your 10" dob? Do you have a special bench and is it tall enough to look at the eyepiece when it's at the highest position? 

[vlaiv]

57 minutes ago, pipnina said:

I would never consider GOTO a bad feature to have. After all it can be used with goto turned on or off, better to have the ability to quickly get to the target you want to see before the clouds come in while maintaining manual control when you want it, even if that's most of the time.

The directional controls on the handset would no debut be a godsend as well. I've found my 10" sw dob to be great, but maneuvering it to relatively high position can be a pain. something about the movement can be "sticky". Both altitude and azimuth wise. Motorized directional control as with synscan would be a large improvement IMO.

Obviously you still have to pit that convenience against cost, but if I were buying a dob again I'd be looking at a goto.

Yes, I get what you mean, but I've read couple of reviews of this goto and tracking feature, and while everyone agrees that tracking is good, not everyone is impressed with goto, its precision and the work involved to properly set it up. Also, at least once it has been mentioned that manual motion of goto version is not as smooth as regular/manual version.

Using external power source seems to cause problems, because scope always uses quickest route between objects - sometimes causing power cable to get wrapped around the base. It is recommended to use power tank / battery type of power supply and to put it on base (inside), so it rotates with the scope.

I do like the idea of having both tracking and hand controller that you can use to center/slew while looking at the eyepiece. My concern is whether it is sound option given cost premium and mixed reports. I would like to have "no glitches" option at affordable price - then it would be my first choice - but if I look at it this way: questionable goto or eq platform for tracking and manual finding things with a bit more aperture (for the same amount) - I must say I prefer other option.

[N3ptune]

I was not aware they were that bad these goto Synscan systems.. this discussion is a good one. The 10" collapsible Dob is around $1 022USD while the same thing with Synscan is around 1 970USD. The GOTO / tracking system is an option of almost 1000USD. The price of a Nagler 31mm

http://ca.skywatcher.com/product/product/bk-dob-10-collapsible/

http://ca.skywatcher.com/product/product/bk-dob-10-synscan-gps/

 

 

 

[vlaiv]

1 hour ago, N3ptune said:

I was not aware they were that bad these goto Synscan systems.. this discussion is a good one. The 10" collapsible Dob is around $1 022USD while the same thing with Synscan is around 1 970USD. The GOTO / tracking system is an option of almost 1000USD. The price of a Nagler 31mm

http://ca.skywatcher.com/product/product/bk-dob-10-collapsible/

http://ca.skywatcher.com/product/product/bk-dob-10-synscan-gps/

 

 

 

Not necessarily bad, but more like quirky, have a look at few reviews (some have issues, some report goto fine, but almost all mentioned that manual movement is harder than non goto version), see what other people think, it maybe helpful for your decision.

http://www.iceinspace.com.au/forum/showthread.php?t=78143

http://www.iceinspace.com.au/forum/showthread.php?t=72836&highlight=GOTO

https://www.skynews.ca/review-sky-watcher-synscan-goto-dobsonian/

http://scopeviews.co.uk/SW400P.htm

 

 

[Geoff Lister]

12 hours ago, N3ptune said:

How is the height of the eyepiece with your 10" dob? Do you have a special bench and is it tall enough to look at the eyepiece when it's at the highest position?

I am 5' 8" and I find the eyepiece position, for viewing close to the zenith, OK when standing. I have the base on the ground, and use a small wedge under one of the feet to level it.

Goto is useful for the more difficult objects, and the tracking is excellent for high-magnification viewing.

Geoff

[N3ptune]

@Geoff Lister

If you need to stand during observation of the Zenith with your 10", do you use a chair like this one bellow? they say it can be has high has 33 inches from the ground.

This Vestil chair we are looking at is the lowest priced one on this list and at first glance it does tick all the boxes for what you would want in a good adjustable astronomy observing chair. The seat can be adjusted from 18 inches all the way up to 33 inches so it going to be very easy for you to adjust it so that you are nice and comfortable. It can take up to 300 pounds and when you are not using it, it can be folded up flat and stored away somewhere out of the way.

@vlaiv

Thanks for the links, I started to look at them, Ill do this over the next days slowly but I see many good points about these dobson based telescopes, they seem to have a good reputation.

But ? looking at all the factors and everything, I am stonewalled by one odd particular thing, has a "do it yourselfer" and a pessimistic type of person, I have a bad feeling about ordering electronic spare parts from Skywatcher, for the Goto/tracking system. Considering the electronics only are worth almost 1000$ stock with the scope, the trouble of maintaining these for a lifetime seems impossible, while the mirrors and the rest of the telescope can probably last for many decades.

Mirrors can be re coated.. but ordering a remote after 20 years, not very likely. 

Just thoughts.

[Geoff Lister]

On ‎26‎/‎05‎/‎2018 at 18:32, N3ptune said:

If you need to stand during observation of the Zenith with your 10", do you use a chair like this one bellow? they say it can be has high has 33 inches from the ground.

I have a variable-height office stool, but it is not high enough to sit on when the eyepiece is towards the top. I may well buy a dedicated observing chair, similar to the one in your photo.

Geoff