The whole project took one year to plan and four months to build working pretty much one day on weekends. Odessius is nothing like my first idea. I designed it to follow all the principles of what makes a dobsonian mount work, and the stiffness requirements of a good OTA. The poles are 50mm, and are held in place first from the over engineered mirror box and with very strong clamps. Without good clamps the design wouldn't work. The secondary cage looks flimsy, but once its clamps are actuated it is rock solid. Once collimated, I can focus on something at zenith, drop it to something on the horizon and nothing shifts.
My perspective is a little different- I now put tracking ability above GOTO or setting circles, on my wish list. Having tracking is just like adding a few inches of aprture as you brain really has a chance to intergrate faint details.
Yep, there's no wrong or right with astro. It's what you want from it.
I found pointing accuracy adequate but clearly the more you calibrate it to work in the area of sky you are working the better it points.
Quote:
Originally Posted by Waxing_Gibbous
I've only had a go with this scope but it was very accurate - once trained
Revisiting this area ... a few more quesitons if I may ...
So, assuming a reasonably level base and that care has been taken with the 2-star alignment, what sort of GoTo accuracy can be expected for the 12" SW Dob? What about tracking drift? And does it change significantly in other parts of the sky, say the opposite side to the two alignment stars? Does it degrade during the evening?
How does it compare to an EQ6 Pro that has done 3-star alignment? (I have one of those, so am familiar with it's performance).
mental, I understand your thinking a bit. I have played around the edges with imaging and I'm seriously thinking of going back to pure visual observing again. I am looking at a standard 18" Obsession or Telekit build with no bells or whistles, but I have heard many good reports about the Aussie made Argo Navis so might have to look into it further.
I don't have time to perfect my alignment technique and while I find photography and astronomy exciting, the thought of sitting out there in the cold playing chase the star in the reticle for hours then NOT looking through my scope while I babysit and image is extremely unappealing. And for what? There are people who are spending crazy time and money doing the same. There are much larger telescopes and better more expensive tracking in research instruments.
Please note I am not putting down the stunning work that others do here. I'm just saying it's not for me.
So I went with my 12" Dob and intend to do a lot of visual. On the imaging side I've decided to learn to reduce images from the big instruments. I've downloaded and played with my first couple of sets of Hubble data using FITS Liberator and GIMP and though the results are just a beginning I'm pleased that after all these years I finally did it. I even posted one of these first attempts here.
FiTS Liberator instead of IRAF - which is what I touched on using back in the days I did my astro degree made it much more about getting a good image and much less about learning obscure commands and processing/calibration steps.
My perspective is a little different- I now put tracking ability above GOTO or setting circles, on my wish list. Having tracking is just like adding a few inches of aprture as you brain really has a chance to intergrate faint details.
I could not agree more. When I got my HEQ5Pro mount (my first computerised mount) I bought it for tracking things in the viewfinder that would otherwise be too fleeting to enjoy.
I had previously dabbled with EQ mounts that had just an RA motor but I could never get those to track properly (due to my lack of skill in setting them up properly). I had hoped I could just point the HEQ5 roughly south and the 3-star alignment would detect and compensate for any setup errors. I had wrongly assumed that the mount would use the alignment information for tracking, but it doesn't (it's only used for GOTO).
So, I ended up with a mount that would point with reasonable accuracy after a quick setup, but still track poorly at high magnification unless set up meticulously. This means a lengthy setup involving compass, bubble level, clinometer, sometimes several tries due to SynScan bugs/idiosyncrasies. Plus, I lost the ability to point manually.
This is why those tracking Dobs (which all seem to be GOTO these days) are so attractive to me. Not only do they hold much bigger OTAs than any EQ mount in my price range could ever hope to, they also let me point manually and then track whatever I pointed to. All this after nothing more than levelling the base and doing a two-star alignment. The GOTO and identify functions are nice to have gimmicks, but fast setup and good tracking is what I'm really after.
i own a 12" SW flexi-tube goto. I am quite happy with it.
as for moving it around, there is one bolt to seperate the tube from the mount. easy. i drive a BA falcon, and put the tube in the boot and actually have to put the mount on the front passenger seat. the rear doors on the BA falcon don't open wide enough (i think the BF onwards have more rear door range). I don't think I could transport the 14" with my car!
When moving around i don't dismantle the mount either, i am able to move around easy enough with the mount off, but if you've got a bad back etc / traversing uneven ground / or have to cover more than 50m it may be a struggle.
i enjoy the ease of setup and the clutch setup really is a good feature. setup / imaging etc it really is the LazyAstronomer's perfect scope. i'm still to suss out exactly where the tracking weaknesses are eg zenith or downlow, i think as far as ds imaging goes i think it was struggling well perhaps rotating a bit more directly up than closer to the horizon..
Another thought: I've read conflicting reports as to whether anti-cord wrap is in the Skywatcher firmware. Can anyone confirm that it has anti-cord wrap?
Another thought: I've read conflicting reports as to whether anti-cord wrap is in the Skywatcher firmware. Can anyone confirm that it has anti-cord wrap?
The SW Flex Tube GoTo Dob does not have anti-cord wrap built into its firmware. I purchased a 10m long cord to help prevent the dob from self strangulation.
I discussed my pointing issues in an earlier post. I am still willing to work around the errors and when I have the object in the FOV it will track it very well. Object tracking can be fine tuned on the fly with a setting in the firmware and it will reduce the effects of any drift.
Thanks, Stu. Your info is a help and much appreciated.
I guess I'm looking for quantitative answers to help remove a source of error, that being interpretation of descriptors people use: e.g. one person's "pretty close" is another person's "significantly out".
I guess I'm looking for quantitative answers to help remove a source of error, that being interpretation of descriptors people use: e.g. one person's "pretty close" is another person's "significantly out".
Hey Astro_Bot, I came close to buying a skywatcher GOTO dob, but I too found getting good answers to questions regarding reliability difficult. I know if you search the web you'll always find bad reviews of pretty much any product but I just couldn't convince myself that these scopes were worth the money (to me). There are plenty of good reviews out there and many happy owners, but these are still a relatively new product and talking to a supplier I have found some are having issues already, one owner (of an Orion dob, same system as SW) ditched the electronics and fitted an Argo Navis after repeated attempts to fix pointing errors failed! Also I've owned one of these budget dobs before and their bases aren't the best and end up needing rebuilding after several years (what happens to the goto then....?).
Because of this, I've embarked down the path of ATM. I'm building a dob base for a 10" newt and fitting an argo navis. This will cost approximately half that of a GOTO skywatcher and should perform MUCH better and for many years to come, although without tracking. I could add servocat later down the track if I wanted and only be about $500 more than the SW. The reason I went down this path is that I know the Argo is a great system, and one I can take to my next scope - same goes for the servocat.
So, when I started this thread I was looking to find a quality scope for visual observing, for me I've decided to try an avoid the constant updating cycles by buying some premium components (the argo) and building a premium base. This (I hope) should allow me to upgrade later without having to buy the electronics all over again.
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