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S/W 8 inch GOTO Dob.


Astro Imp

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I've had the Dob since January but due to poor weather and issues with the mount, (documented here:- https://stargazerslounge.com/topic/288505-make-the-most-of-the-clear-skies-ive-organised/) I have waited 'til now to give a review as I wanted to have some eyepiece time before commenting.

The kit arrives in two well packed boxes, the base in one and the OTA in the other.

Assembly of the base is quite straightforward and took me a couple of hours or so.

I chose to power the unit with a Tracer battery, I know this isn't the cheapest option but being compact it sits on the baseboard behind the front panel with the power lead threaded through the side panel. This way there are no leads to trip over and the whole unit moves as one.

In use I have had some excellent views of the moon and earlier Venus but limited DSOs as it has been either cloudy or washed out with moon light.

However on a couple of occasions I've set the GOTO up and was very surprised at the accuracy. I had been a little worried having read numerous tales of woe on the forum from members who had trouble getting their GOTO to go to. I can only conclude that feeding the handset the correct information and taking trouble with the initial alignment, which takes less than five minutes, is the key. I find I can get objects very close to the centre of an 18mm eyepiece which gives x66.6 mag. and a TFOV of just less than one degree. To me this seems remarkable for an old technology and I'm well impressed.

Overall I am very pleased with my new kit but (there's always a but) there are a couple of niggles.

i) The focuser is only single speed and there is image shift when focusing, I intend to update this when funds allow and will be asking for advice.

ii) I find a lot of flare when viewing bright objects. Placing the moon just out of the FOV the view is very light. I hope a dew shield will help with this, I shall be making one as a first priority. I know a lot of you will suggest flocking the tube but I don't have the confidence to do a good job.

iii) This a personal niggle and not the fault of the equipment. Previously I had used a 150P on an equatorial mount and adjusted the eyepiece position in the rings to suit my sitting position. The Dob is not mounted in rings so the eyepiece position is determined by the elevation, as I use a fixed height garden chair for observing this needs replacing.

iv) The first thing I did was replace the straight through finder with a RACI I already had, next was attach the Telrad. Well no there isn't enough room for the Telrad so a Rigel Quickfinder was installed. Personally I found the Telrad a lot easier to use as I had it on a riser but no doubt I will cope.

I hope you found my ramblings interesting and informative and look forward to your thoughts.

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great report Alan, agreed mate we havnt had the DSO weather or seeing mate but I'm sure it wont be long until the skys get better. glad your getting on well with your new scope. thumbs up for tackling your goto, ive had it for years and never used mine, your post has reminded me I should have a go " you don't buy a dog and bark yourself" comes to mind as my grandmother used to say.  thanks, charl. 

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On 4/28/2017 at 01:32, Astro Imp said:

Thanks mate, looking pretty dire at the moment.

I know your pain, the amount of times that I have nothing more than clouds on free and moonless nights and clear night during work nights is enough to drive a man totally insane.

I'm hoping for the next 3 nights to be nice and clear to do some observing with my 14" dob. Wish me luck.

 

 

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Nice one Alan. I've got the 10" SW dob and I know what you mean about flare around bright objects. After a few months, I flocked the tube and focuser tube which made for a worthwhile improvement on the moon and Jupiter.

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2 hours ago, Size9Hex said:

Nice one Alan. I've got the 10" SW dob and I know what you mean about flare around bright objects. After a few months, I flocked the tube and focuser tube which made for a worthwhile improvement on the moon and Jupiter.

Did you just flock the uper tube or both.

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Mine is the solid tube version. I took out the primary and secondary mirrors and did the whole lot, plus the focuser tube and I also blackened the back/sides of the secondary. I can't say I noticed any difference when observing faint targets under dark skies, but the distracting flare around the moon and Jupiter were improved. It was a bit awkward to get the primary back into the tube, but other than that it wasn't too tricky. I've read other folks have just done the area opposite the focuser, but I figured if I was taking the secondary out anyway, I might as well get the whole thing done, plus it was a chance to chance to give the primary a careful clean.

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Thanks Paul, I'll have to give careful consideration how to proceed but I already have an old camping map with which to make a dew shield so that will be my first line of attack.

I'll be sure to post my thoughts.

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On 4/29/2017 at 20:52, Astro Imp said:

Hope you manage some eyepiece time and enjoy your observing.

Thanks.. Yeah, I had a awesome night of observing.... saw awesome details on Jupiter and Saturn, and heaps of DSO. I spent 6.5 hours outside, when I packed up it was after 3:30am.. its like time was on fast forward. 

 

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  • 1 month later...

I went down down the camping mat dewshield route.  Its a lot of fiddling to get it to fit and then you may find that the added weight prevents the system from driving vertically.  In the finish after an exhaustive search for alternative cheap materials  I managed to source an 8" Astrozap.  Once I had it I wished I had had it from the start.  However, it still isn't light and if you have a heavy EP or camera attached it may still affect the vertical drive.  I found what helped more was my home made collapsable baffle to fit aound the three trusses.  It also had less effect on the weight.  Since making it I've used it each time where the Astrozap gets less use esp. If I have the weight of the Mopheus on the go too.

N.B. Putting the plastic baffle with the small hole in place helps enormously  with the glare.

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