Question about Skywatcher Collapsible Dobsonians

[AEAJR (Ed)]

This link goes to an example of the Skywatcher collapsible Dobs.
http://www.skywatcher.com/product/bk...0-collapsible/

While I am not in the market for a telescope at this time I might be in the future. I might consider one of these.

It is an interesting design in that you don't remove the supports to the secondary, you merely slide the pipes in to reduce the size of the system when you are done for the day. That looks extremely convenient as compared to other truss dobs.

The question is how well do they hold collimation? We have moving parts and the secondary is only supported by three struts. As you tip and turn the scope the potential for that secondary to move out of alignment seems real.

How accurately does it place the mirror when you extend it? Focusing problems?

Owners, what is your experience?

Great design?

Doesn't work as expected?

Need to collimate every time you use it? (NEED, not seems a good idea)


Inquiring newbie minds would like to know.

[gaseous (Patrick)]

Hi Ed,

I've got an 8" model. In my experience, if you're a perfectionist then you'd probably want to collimate every time you use it - I find it's normally out by a smidge every time you extend/retract the poles. I can't say for certain how badly this slight non-collimation affects viewing, but in all honesty it only takes a minute or two to tweak it back so I'd say it's not a big deal. Make sure your laser collimator is properly collimated itself! I've got the goto version so I'm not constantly nudging it into position, so I still find collimation is pretty good at the end of a viewing session. A trick (which I've not tried yet) is to have the laser collimator in the focuser as you extend the tubes, then lock them into place when you've got your red dot in the middle of the primary - it might take a bit of jiggling the pole positions, but it might be easier than collimating if you're not a fan of allen keys.

As far as focusing goes, I find that 2" eyepieces only just have enough outer travel, requiring the eyepiece to be only just held inside the outer rim of the focuser, and using an extension tube (which I tend not to do), means you have not enough inward travel. Again, not a major issue and I may need to get a different extension tube not so long. The focuser itself is serviceable - the 14" and 16" models have a dual speed focuser, whereas the 6"-12" models are single speed, but generally do the job. 1.25" eyepieces work fine. Overall, and having not used/owned any other scopes, I really enjoy the relative simplicity and ease of movement - it's easy enough to move as one piece, or easier if you take it out of the base. I'm currently awaiting arrival of the 16" version so the ease of movement might be a thing of the past.

Cheers,
Pat.

[Allan_L (Allan)]

Hi Ed,
Fairly regular question.

I had my doubts before buying one too.
But price (bang for buck) and convenience helped me take the plunge.

Disclaimer: I can only speak of my experience, and that of several other friends who have these scopes. Which is all good! But I imagine there are others who may not have been so lucky. (Such is the way of mass produced scopes)

As Pat has said, collimation holds Surprisingly well.

I have previously owned a 10" SW collapsible and now a 12" SW GoTo Collapsible.
Although I do run the laser collimator over it every time, (and it is a very good Hotech self centering with cross hairs), it is only ever out a "smidgen". Even after travelling over very rough roads to our remote dark sky sites. (Albeit sitting upright in the passenger seat for safety)
Occasionally I double check with a Cheshire. Yes. I am that perfectionist.

It always holds collimation through the night session.
And I do use Televue eyepieces and paracorr of weight. Occasionally with counter weights.

I have never had in focus or out focus problems with any eyepieces.
(Making sure your collimation screws on the primary are not fully one way or the other may help here. That did it for one friend)

I can't speak highly enough of the quality of the scope, or the convenience of the collapsible feature.

I have no hesitation in recommending it. And if buying new, there is a good warranty to safeguard against a "dud".

[BeanerSA (Paul)]

I have a fixed tube, but I observe with a very experienced, very knowledgeable old guy, who has a collapsible. He says he tweaks it maybe a couple of times a year. It always looks sharp to me.

[AEAJR (Ed)]

Thanks guys. Very encouraging reports.

[raymo]

I had the 10" collapsible for about 5 yrs, and I tweaked it even less often than
beaner's friend. All these people that worry themselves sick about collimation being a little off should try miscollimating their scopes in steps, and see
how far out it has to be to become noticeable for visual use.
raymo

[steve.garner (Stephen)]

I had the 8" version and found it to hold collimation really well ( although I'm not a perfectionist ). Seemed really good. I liked it so much I would have liked to upgrade to the 10" although I ended up getting the full tube because of cost.

[AEAJR (Ed)]

Originally Posted by raymo

I had the 10" collapsible for about 5 yrs, and I tweaked it even less often than
beaner's friend. All these people that worry themselves sick about collimation being a little off should try miscollimating their scopes in steps, and see
how far out it has to be to become noticeable for visual use.
raymo

Interesting point. I may try that some time.