Blog


2016 Starts

I’ve been lazy and not posted a blog for ages - not that anyone seems to be complaining!

Havent observed much either! My last outing was to the Winterfest at Kelling last November, which wasn’t good. Strong winds forced me to quite early. I did manage to upgrade my friend Gain’s dobsonian drive to the production standard of ScopeDog. He has a fine 24” that is very stable, but with that came heavy and stiff to move. So I replaced the PTFE pads with ball bearings and added the encoders and stepper drive I had developed for my own 18”.

ScopeDog provides full tracking and goto control with a built-in wifi link to any pc, tablet or smartphone. The drive is now available as a DIY kit and installation advice is now available for almost any large Dobsonian.More details here.

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Farewell Brian

Over the last few years I became good friends with Brian Johnson. Very sadly he passed away this week.

He had been hooked on practical astronomy late in his life and I was more than happy to help him a little as he built and commissioned a superb observatory,The Ironpan Observatory.

He was a supeb craftsman, and had a nice little workshop with mill and lathe where he produced extrememly high quality pieces. He played a vital part in the restoration of the Rev Ellison telescope. Without his ability to expertly rework the metal tube and make some replacement parts I dont think the restoration would have been possible.

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He loved photography too, and combined his interests into astrophotography. Despite the severe light pollution at his home, he took some fantastic images. I have taken the liberty of reproducing one here - The Rosette Nebula, which he was rightly proud of and was one of his favourites.

All those who new Brian will miss a man who felt he couldnt do enough to help others. I have great memories of our time together and will miss him greatly too. My sincerest sympathies to his family.

2015 Winter Star Party

This year’s WSP was a mixed bag. There were a three great nights, but they were really cold! The Florida Keys arent supposed to be 42F (5C)! One night we had the biggest and loudest thunderstorm I have ever known - quite an experience in a tent!

I had persuaded my wife to join me this year, along with a crowd from the Texas Star Party. Although I had been careful not to promise warm weather - it had been expected and they were all a bit disappointed.

Here’s a shot of the sun going down behind a palm tree. Note the guy in the foreground (Craig) wearing a warm jacket and hat!

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Jan & I started the trip with stays in Key West, and ended on Ocean Drive, Miami Beach. Both places can behighly recommended for sightseeing and fun.

Not long to the Texas Star Party, lets hope the weather is better there!


Kelling Star Party success

I went up to Kelling a full week before the main weekend and was rewarded by two very good nights and a couple of average ones.

The new scope worked very well overall. Optically it was a dream and I had great fun just looking at all those faint objects at the limit of what can be expected at this aperture. The tracking was also spot on, maintaining objects in the centre of the field of view for more than 30 minutes. GoTo’s stil have some bugs, needing sometimes 2 or 3 iterations to get to the target. This is probably down to the stepper motors being slightly under driven on the fast slew rate. Not a big problem as the Nexus maintained a very accurate fix on scope position, and so it just needed another hit or two on the SkySafari GoTo button to complete the goto, usually putting the object very near the centre of the field of view.

I had to use my Mac to drive the scope, as the RaspberryPI had a problem calculating Local Siderial Time. Craig is working on this!

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18” Dobsonian Drive Finished

I finished the last bits of integrating the Raspberry Pi into the system today. I had to build a little 12V to 5V converter to power the rPI and this is now mounted on the inside of the lid. The GPS antenna is also on top of the lid, fixed down with some velcro.

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After powering up the system, I log into the rPI from my MacBook Air using an ethernet cable and run the scope control programme from the rPI command line. Once it is up and running I can unplug the cable to prevent “cord wrap” problems. I’m going to see if a wifi dongle can be used instead of the cable, but I suspect it will interfere with the Nexus wifi. The rPI has its own separate power switch so I can reboot it if necessary without resetting the Nexus and Phidgets.

All I need now is some clear nights at Kelling Heath in a couple of weeks!


Time for some Raspberry PI

At last it was time to add the Raspberry PI to the system. There was just enough space in the servo box for the rPI, plus a “level converter” needed to provide a serial port to talk to the Nexus DSC.

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I have arranged it so that the Phidget drive system is controlled by a USB lead that loops out of the box. I can plug it back into the rPI for local control, or plug it into my Mac Book Air via an extension lead.

New scope hardware just about done

The hardware build of the new 18” scope is just about finished. The code is almost there too but needs a few good clear nights to check it out. Meanwhile Craig is converting the control softweare from Objective-C to Java so that it will run on the Raspberry PI. Clever guy!

I knew it should fit, but today I tried packing the scope into the boot (trunk) of my car. It went in even better than I had expected. It will just need a few hard foam packing pieces to protect the paintwork. The truss poles will go between the seats in side.

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Scope takes up about 1/2 of boot space

There is quite a lot of spare room left, including under the scope which with judicous packing can be used for sleeping bags etc. I have a roof box and so the rest of my star party gear should go in OK.

Telescope shroud attracts visitor!

I uncovered my scope the other morning and was fairly surprised to see an enormous “spider” on the shroud.

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It measured 12 cm (5”) tip to tip. OK it has a tiny body (about 8mm) but nevertheless it was quite a shock. I had never seem one like this before. Doing some research it is not a spider, but a member of the Opilione family, this one being commonly called a “Harvestman"

Making real progress

The scope got completely re-assembled yesterday and the new bearings are superb. In fact they run so easily I will now have to add some form of damping for when I want to use in manual “push to” mode.

The encoders were installed for the first time and hooked up with the Nexus and SkySafari. Worked perfectly!

Were still having fun with the code. I think we are on version 21, which still has a bug or two, or three, or four….!

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Complete scope. Shroud is only pinned on temporarily at the moment.

Getting back on track

Fortunately, replacing the PTFE with ball bearings turned out to be fairly easy and I didnt have to remake any major parts. New photos are here.

It now glides very freely in both axes and I shall reassemble the scope now to try them under some clear skies.


AstroKeith 2014