Sky-Watcher Star Discovery AZ GoTo Mount - Adaptation to Heavier Loads

Introduction | My Attempt... | Photos | Preliminary Conclusions | Links

On this page, I describe how I tried to adapt my Sky-Watcher Star Discovery AZ GoTo mount so that it is able to carry heavier loads than the 5 kg that are listed by the manufacturer.

See here my experiences that I made so far with "overloading the mount with a 6" Newton tube."

See also: Sky-Watcher Star Discovery AZ GoTo Mount Information | Sky-Watcher Star Discovery AZ GoTo Mount - First Experiences | Sky-Watcher Star Discovery AZ GoTo Mount - General Experiences and Thoughts

 

Introduction

According to the manufacturer, the Sky-Watcher Star Discovery AZ GoTo Mount can carry a load of up to 5 kg. In the meantime, a variant of this mount is being sold by Orion (Orion Mount StarSeeker IV SynScan GoTo), which costs 100 EUR more and is reported to be able to carry a load of up to 6 kg. When I asked my astronomy dealer about this mount, he advised me that both mounts are identical. Thus, the technical data with respect to the load that can be carries seem to be somewhat arbitrary - as I also found in other cases...

I had bought a 6" Newton tube (Sky-Watcher Explorer 150PDS), and all dealers listed its weight as 5 kg. This was the reason why I bought exactly this tube, since all other tubes, except for carbon tubes, were listed as being heavier. Shortly after having bought the tube, I went to the Sky-Watcher Website, and there I found a weight of 6 kg for the tube (BKP 150 DS). I was really embarrassed by this, since in this case I might have bought any other tube as well. When I measured the tube's weight myself, I found a weight of 5.5 kg, just the mean of the two weights that I had found... Having made these experiences, I am unsure, which technical data I can trust in, and in which I cannot trust... A mount that would be able to carry 6 kg would, of course, have been ideal in my case, but it looks as if the price difference between the Sky-Watcher and the Orion versions of the mount is based on reasons that I do not know...

Now, the question was, whether my GoTo mount would tolerate 1-2 kg more weight than listed or not... My dealer answered this question with a fairly definitive "yes" (there is no "fairly definitive", I know...) - at least if you adapt the mount a little to heavier loads. This requires that you increase the friction somewhat, so that the motors do not coast, but also do not have too much friction so that they drain the battery. When I tested my 6" Newton tube on the GoTo mount for the first time, the horizontal motor sometimes coasted, but not so during the second test. By the way, the dealer himself even uses an 8" Celestron C8 tube (5.7 kg) on this mount, but this is more or less in the same weight category as my Newton tube. He describes how to adapt the mount to heavier loads on the following Web page (in German):

 

My Attempt...

Because I had forgotten to take the GoTo control with me when I visited my astronomy dealer (yes, my age shows...), I decided to make an attempt at adjusting the control myself to heavier loads. For this, I had received a couple of tips from the dealer and additionally had his description with photos on a Web page at my disposal. The page briefly describes how the mount can be adapted to heavier loads (in German):

So I opened the mount case, figured out how to tighten the nuts without the use of a wrench by employing a long screw that I screwed into a screw hole in the nuts (see the photos below), and then tried to turn the nut with this "lever." It showed, however, that the upper nut was already very tight and I only bent the screw without really turning something. Maybe I moved the upper nut a little bit, but I am not sure anymore... I did not even attempts this at the lower nut, because I was unsure about what was to be done.

So I put the cover on again, tested my 6 " Newton tube on the mount - the horizontal motor did not coast this time - and I will observe whether everything works fine or whether there are coasting issues. In the latter case, I will probably send the control unit to the dealer for adjustment, because he has so much more experience than me...

The whole affair turned out like the famous "Hornberg shootout," that is, without any decisive result, but at least I found taking a look at the innards of the control very interesting. I took a lot of photos during this procedure and present them in the following section - maybe some other owners of the GoTo mount are interested in this.

 

Photos

Below, I present photos of my attempt at adapting my Sky-Watcher Star Discovery AZ GoTo mount for heavier loads (larger versions appear in a new window/tab if you click the photos).

Further photos and information about this topic (text in German):

    
    

Everything is ready for the adaptation to higher loads.

Four Phillips screws at the base have to be removed so that you can ...

...remove the cover.

Cover removed - you have to push it to the side.

Removed cover with screw

Look at the gear wheels - the electronics are located at the right side.

Above and below the white plastic gearwheel there is a nut which can be tightened to adjust the mount to higher loads.

The upper nut has two flat sides so that it can be tightened with a wrench. In addition, it has a hole with a thread.

The lower nut also has two flat sides for a wrench and a threaded hole, which is not visible here.

View from another direction; the upper nut can be seen better here.

Ditto, here the lower nut can be seen better...

Here you can see the hole with thread in the lower nut. Instead of using a wrench, I screwed a long screw into the hole in order to be able to tighten the nuts more firmly. Here, the screw sits in the hole of the upper nut. This nut was, however, already very tight, and I do no longer know, whether I was really able to turn it.

Now the screw sits in the hole of the lower nut, but I did nothing else here...

Well, I cannot recognize whether something has really moved...

Cover reapplied, but not yet closed.

Ditto

Here you can see the plastic lids, which must be inserted correctly, so that the cover fits.

Cover back in correct position, screws not yet fastened.

Here I found the effects of a "screwdriver attack." Perhaps my control was adapted before delivery...

Ditto, detail

Unfortunately the screw has suffered somewhat from its use, the nut was already sitting very tightly before I applied the screw...

 

Preliminary Conclusions

Since my "project" ended like the famous "Hornberg shootout," that is, without any decisive result, I even cannot offer a preliminary conclusion here. I've learned a lot, but not quite as much as what I need to know. For example, I would like to know, what functions the two nuts exactly serve (one for horizontal, one for vertical turns?).

I will therefore continue to observe whether my 6 " Newton tube will work properly on the GoTo-mount or whether there will by coasting issues one day. In the latter case, I will probably not touch the control again. Instead, I will send it to the dealer for adjustment, because he has much more experience than me...

See here my experiences that I made so far with "overloading the mount with my 6" Newtonian tube."

 

Links

 

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gerd (at) waloszek (dot) de

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01.09.2017