An imaging obs, in Northumberland

[DrRobin]

Hi,

I have been nagging Mrs DrRobin to let me have an obs for some time and after we came back from holiday in August, I showed here this picture

To my amazement she said I could have one!  Even better, I could have it on the site of her veggie plot, which is just about the best location I could hope for.

Now buying a small obs is not as easy as it might seem, especially when they are made in the USA and my present mount (an EQ6) won't fit, or at least won't fit very well.

Fortunately, the obs itself was reasonably easy, I emailed Technical Innovations (Home Dome) and they had one in stock.  A few emails later and a telephone call, it was ordered and then TI ordered a packing case and had it shipped to Baltimore for it's sea journey to Liverpool.  So far so good, it arrived at Liverpool last week and after having open wallet surgery for the import duty, VAT, onwards delivery and importers fees (added about 40% to the purchase price plus shipping) it is now on a wagon somewhere and is going to be delivered tomorrow.

The next problem was the mount.  I thought about trying to modify my EQ6 to fit, but until the dome is here, it is difficult to know how much work that might entail.  I know I would need to shorten the counterweight bar, but I was still worried that the turning circle for my C11 would be too much.

I managed to find a second hand CPC1100 fork mount for sale, but it was over in Canada.  Okay, not a problem, buy it and get it shipped across (the owner was quite happy to ship to the UK).  The cost of shipping it to the UK started going up with every email and the package was just too big for a standard delivery.  The final hurdle was that the C11 and CPC11 OTA are drilled differently and I was left trying to make some brackets to make it fit.  All was not going well.

Enter a Knight in shining armour in the shape of a second hand Avalon M-Uno.  That is a single sided fork mount crafted out of pure gold/titanium/un-obtainium or at least the price tag suggests this.  Actually it is very well made and carries my C11 with all the grace and style of an Italian suit.  Pity it is an EQ6 control board and Skywatcher could probably knock these out for about £3.50, sorry £900.

Although I have bought a dome there is still a load of work to do, like making the base and concrete column for the pier, which I will cover in part 2.

Robin

[night_owl]

Lots of work and effort done so far but, some way to go, so hope it all works out for you soonest, it look the dogs ****** and I'm green with envy. Good luck and would love to see it once completed

[DrRobin]

Part 2, The ground works (the build starts)

Okay, dome ordered and mount on it's way, time to get on with the ground works.  First the site, the former veggie plot;

I have mains power in the rear of the summerhouse and a cable was put in for the greenhouse, although it has never been used.  So, I took up the decking found the cable and pulled a new longer cable through (ah benefit of installing ducts), ready for trenching to the obs.  The cable installed under the decking;

Now a short trench to the power inlet point on the obs.  I hate digging cable trenches, it has to be 600mm down and is hard work, mostly getting the soil out of the trench.  To make life easier I even bought a trenching shovel (£20 well spent).  I put in a Steel Wired Cable (SWA) in a 30mm trunking, both offcuts from work.  If it ever needs to be changed then it will just pull through.  The slightly curved path was to avoid telescope pier and obs foundations.

And finally filled in, the best bit as far as I am concerned.

I decided to mount my dome on a wood deck, so next is the supports and basic frame (About £50 of joists).  I went for a slightly odd shape to follow the lines of the path and the existing decking.  Note the hole already dug for the pier foundations;

I went for a base 600mm x 600mm x 100mm deep with a hole dug under the pier to give added support.  I made up reinforcement from three bars, laced together.  These bars are 1m long and will go from the bottom of the pit to the top of the concrete pier.

 

In section 3 I will look at the pier design in more detail.

Robin

[DrRobin]

Part 3 - The Pier

I decided to opt for a concrete pier and started looking for a former for the pier.  I considered a pipe and also making a square former out of plywood, but the ideal solution turned up in the shape of a stainless steel pedal bin.  The one I bought (£16 from Homebase) is 300mm in diameter and 640mm long, just about the perfect height for me.  An added bonus was the plastic bin inside, that now sees service in my workshop.  The pedal bins don't have a base and the mechanism is easily removed to leave a stainless steel tube.

The pier plate was made from a 300mm diameter 19mm thick disc of aluminium purchased as an off cut for around £20 (Aalco via ebay).

I drilled 6 holes around edge with a 8.5mm drill to take an M8 threaded rod.  I then drilled and taped 6 holes to match the mount plate with a small milling/pillar drill at work.  Aluminium drills and taps really easily, just take it nice and slow.  You can see the 6 taped holes in the next picture.  I aligned it North, so it had to be put in reasonably accurately.

I then fitted 6 off M8 x 500mm studs in to each of the outer holes and bent the bottom of each stud over in the vice.  I also drilled two wooden discs (from a cable drum) so the whole lot could be bolted up to keep the studs straight.

I poured the concrete in two stages, first the pit and concrete plinth were poured after about 30 minutes the stainless tube was pushed in to the concrete base and held upright with planks of wood.  The concrete base and unfilled tube was then left for around 3 hours until the concrete was beginning to set.  This was to allow the base to be stable and for the tube to remain upright when the final concrete was poured.

Finally the concrete was poured in to the tube and then the top plate with M8 studs was pushed into place and aligned.

The spirit level was used to align to true north.  I used Google Earth to find true north and drew a line through my mount location extending north and south.  To the north the line intersected the corner of the greenhouse, to the south the corner of next door's house.  So all I had to do was line up the spirit level on the plate and then sight from the corner of the greenhouse to the corner of the house.  When the spirit level was in line, the pier plate is aligned to true north.

I couldn't get sightings as far as I would have liked, but reckon that the plate is within 5 degrees and there is at least +/-10 degrees in the mount AZ adjustment.

All of the supports were left in place for another couple of days, but the next day the surface of the concrete had dried.  I poured 7 bags of ballast and a fair amount of cement using a 6:1 ratio so reckon there is around 150kg of concrete in my pier.  The rebar and pier plate weighs another couple of kilos and then the mount weighs about 17kg so around 170kg of weight for a scope weighing 12kg, not a bad ratio.

Finally, with the supports removed ready to get on with the decking and dome (part 4).

[ArmyAirForce]

How big is the floor foot print?

[DrRobin]

Hi Stephen,

As it is from the USA, it is imperial, the floor plan is oval with dome diameter 40 inches and length 50 inches. That's about 1m x 1.3m. The dome is oval in the vertical direction and gives a radius of 25 inches. According to the manufacturer a C11 will fit, but not on an EQ mount. I have tried my C11 on the fork mount and it fits, but I have yet to test every angle and it looks very close in some places.

A dob would probably fit quite well, especially if you limit the ALT to say 15 degrees.

Robin

[DrRobin]

Part 4 The deck and dome

It's a little while since I last posted, construction of my obs has been going on, but I have had very little time to post.

So, the pier is done, the frame work for the obs dome base in, so next in with the decking.  This was relatively easy, just cut the deck boards to the right size and screw in place.

Note the pier coming through the deck, with around 40mm clearance all round.

With the deck done, its time to wheel in the dome, of course it was raining.

To get the dome in the right place the mount was put in and it was measured and then measured again (still didn't get it right though).

The dome is secured using a threaded insert and M6 bolt.  These get a really good grip, just drill an 8mm hole and screw the insert in.  I drilled the base of the dome in 10 places, drilling through the fixing flange to mark the deck boards underneath.

Finally, 10 bolts in place and silicone sealant around the dome/deck board interface, this isn't going to move in a hurry.

Robin

[DrRobin]

Part 5 - A pier gasket

I wanted to seal the deck boards round the pier, but didn't want to transmit any vibration to the pier, enter my own custom designed rubber gasket.

Step 1, take two pieces of plywood the correct size to fit the deck boards.

Step 2, cut a hole approx 50mm larger diameter than the pier.  I used a router, attached through a centre hole using the guide as a radius.  I lightly screwed both plywood sheets together to ensure that the hole was in the same place in both.

Step 3, cut a piece of 3mm sheet rubber, the same size as the plywood and then cut a circular hole about 20mm smaller than the pier.  I added some wood around the edge to stop things rolling into the gasket.

Step 4, fit it.  The rubber is quite a tight fit around the pier, a bit like the neck seal on a divers suit and the plywood is a tight fit in the deck boards.

In the next part I will look at a false floor with under floor insulation and the power/data feeds.

Robin

[DrRobin]

Part 6 - The power and false floor

I had laid a swa power cable to the base of the obs, but wanted to have a sealed isolator and distribution box, so procured a cheap IP67 distribution unit, which I then made a partition so I could use one side for mains and the other for low voltage and data.  I mounted the distribution box on to some marine ply and made it fit under the deck joists.  I put three holes in the base, one for swa main in, one for mains out to the obs and a third for data cables.  All three are 30mm flexible conduit.

And then the mains board inside the dome.  You can also see the low voltage conduit, with the remote control cable for the hand controller.

At this stage I decided to make a false floor with under floor insulation.  I bought 12mm marine plywood and to make a template, I used a roll of wallpaper.  The rather odd shape will be revealed later, but I needed two of these, one with the cable cut outs and the other plain.

The ply was cut with a jig saw and then sanded to fit.  I had to make the floor in two pieces, otherwise it would have been impossible to fit.

The ply sits on floor batterns, the gap in between has been filled with closed cell foam, we get loads of this at work in packing and it is that or it goes in the landfill.

The two floor boards are then fitted and screwed in to the batterns.  Note the cut out for the pier gasket and then the rectangular cut out at the right.  This is a trap door and is removable to allow access to underneath for maintenance.

The trap door gets it's false floor and then with the mains disti board in place, I am ready to start putting in the mount and get a scope in.

Robin

[jambouk]

Looks like a wonderful project. Exciting to see it evolve.

James

[David Smith]

Looks very professional Robin, well done. I shall be following progress with interest.

[laser_jock99]

Fantastic looking project.

[wayneh]

looks great cant wait to see it all up 

[DrRobin]

Thanks everyone.

I got a mount, scope, computer and cameras in last night and started to align and take a few test images.  Unfortunately, I had a few teething problems so didn't get too far, but at least it is getting there.  Oh and as it was dark there was no chance for a picture.

My set up is currently:

PC running XP, CdC, EQDirect, PHD, Digital Dome Works (Dome control, also ASCOM), APT.

The PC is connected to the mount (USB EQDirect cable), the dome (Serial port), a QHY5 (Finder/Guider), a Canon 600D and a USB focuser.  There is also a weather station connected on USB and I have a Cloud/Rain sensor to attach to another serial port.

I installed all of the software on to the PC in the house, check it worked before putting the computer in the obs and then found a variety of things that didn't work.  EQMod seemed to want me to upgrade ASCOM and then when I connected the QHY5, PHD wouldn't connect to it.  I un-installed all of the drivers and software, re-installed, still wouldn't connect, so I shut everything down, re-installed all of the QHY stuff and at the second attempt it went through.

Now I have the same problem with APT and my Canon 600D, I have un-installed and re-installed several times, but to no avail.  The camera works in the Canon software, but APT is now not playing ball, although I tested it okay before.  I ran out of time and patience and just ran APT on my laptop to get things going.

The final straw was after measuring my scope carefully to check it fits, the camera hit the side of the dome, it sticks out a long way when focused.  Fortunately, I can solve this by turning the OTA round so that the camera faces the mount and dovetail rather than sticking out the side.

I did manage to do some alignment tasks and did take a couple of un-guided pictures so I guess you could say it has had first light, but there is still a long way to go.

I should have said that I polar aligned the mount on Sunday night, not an easy task when you can't see through the polar scope.  Fortunately a cheap Xbox camera, Sharpcap and an adapter made out of an old case gave me a polar-cam which worked a treat.  I used EQMOD's polar alignment routing, seems to work very well.

I will get a few photos taken this weekend and hopefully update the success/failure record at the same time.

Robin

[DrRobin]

Hi,

I got a clear night last night and with a large bright moon, it was never going to be any good for imaging, but it was a good night for aligning my mount and checking the cameras, scope and software.

I managed to get around 8 alignment points in to EQMOD (via CdC), before the temptation to try imaging M31 came too much.  Using a 8" Quattro and Canon 600D with coma corrector, I ran 120 shots 30 seconds, unfortunately, they are nearly all useless as the moon was just to close.  You can see the central core and the stars around M31 are nice and sharp with no star trails, but that is it.

I next had a quick go at Jupiter with the same set up, over-exposed, but it is there and finally settled for 25 shots at 10 seconds (ISO 400) on M42 to get the picture below.  I am really pleased with this given how bright the moon was, but it does show that my set up is already tracking nicely.  The GOTO was fairly close as well.

It is nice having everything permanently set up, when I finished imaging at around 11:45, I took a few flats and bias frames (I had already taken the darks) and then just shut it down and went inside.  If it wasn't for waiting for the memory stick to be written, I would have been finished in 5 minutes.

Hopefully this weekend I can finish the decking, MrsDrRobin wants a fence up round it and I can start on some of the automation tasks.

Robin

[DrRobin]

Part 7 Putting it all together

With the false floor finished, it was time to put the mount and a scope in to check it all fits.  The mount has to be polar aligned before a scope is attached and since the polar scope is only a few inches from the floor there was never any chance I was going to be able to look through it.

Enter an Xbox camera and the plastic case from an old barlow.  The barlow case just fitted over front of the Xbox camera and the 1.25" end of the barlow fitted over the polar scope.  The lock screw allowed me to tighten it in place.  The Xbox camera is sensitive enough to see Polaris and still pick up the reticule.

Mount in and polar aligned, time to put a scope in.  The first to go in is my Quattro 8" F/4, it is slightly longer than my C11, but is narrower, so it should be a good test of the space available.  To my horror, when the scope was swung from north it hit the side of the dome, it was then that I realised I had put the dome in the wrong place.  The thing is, the centre axis of the scope is offset from the centre of rotation, so I set the centre of the scope as the centre of the dome.  This turned out to be 80mm to far south, hence the scope hit the dome wall when swung.

There was only one solution, take up the false floor, unscrew the dome and move it 80mm to the north.  This would have been easy apart for two things, the power and data inlets had to move, which meant re-cutting the floor panels to suit and my trap door was partly outside the dome, so it had to be altered as well.  In the end it took all weekend, just to move the dome 80mm, but I am happy to report the scope now doesn't touch anywhere.

Robin

The cables are still to tidy up, but note the computer at the back, running CdC, the dome control and APT and also notice the focuser is facing downwards, to stop my camera hitting the dome wall.

[DrRobin]

Part 8 Test runs

Scope in and polar aligned, Monday night was very clear so after aligning on 8 or 9 stars I decided to test the lot, Quattro 8", CdC and ASCOM with a QHY5 finder/guider and my Canon 600 with the brilliant APT.

I had to find objects away from the moon and I am pretty pleased with the results.

M27, 32 frames at 60 seconds, ISO 800

M29, 3 frames at 60 seconds, ISO 800

M57, 24 frames, 30 seconds, ISO 800

Robin

[DrRobin]

Hi,

Very clear early evening, but it turns out my obs PC has a faulty memory board and would not boot.  In the end I took it out, got my PC booted, found my target, M33 and then started my imaging run after 90 mins messing about.  Unfortunately for me the cloud was already rolling in so only got one frame that was any good.  It doesn't seem to improve with darks, so here is a single frame of M33, shot with an 8" newt, Canon 600d, ISO800 & 240 sec exposure.

It can only get better.

Robin

[DrRobin]

Tasks completed this weekend

Okay not much progress this weekend.  Mrs DrRobin doesn't like looking at my obs so I have constructed a small fence out of left over fencing.  I have also added some more insulation and fitted my USB focuser system, but whilst it works from Sharpcap and focusmax, it won't work from APT.

I got two more deck planks put on the side and that was it for a full weekend's work.  Hope you like the fence, it took a fair bit of doing.

Robin

[Earl]

Have you got as link for the dome manufacturer?

[DrRobin]

Hi Earl,

Robodome is made by Homedome in the US, link below

http://www.homedome.com/store/product_robodome.htm

Gerry Smith is the guy to email/speak to, they make it really easy to get one over here.

Robin

PS USB focuser now working with APT, I loaded the wrong driver, then couldn't figure out how to change it.

[Gina]

Very interesting system though not cheap   Remote controlled little dome - very nice

[Gonzo]

I was thinking of one until I saw the price.... but I still like this mini dome.

[DrRobin]

It has worked out about the same price as a Pulsar dome once you add the motors and PC control to one. Actually it was a fair bit less, but import tax, shipping, UK delivery and VAT on top of everything added close to £1,400. In other words for $ read £.

I would have bought a Pulsar dome had MrsDrRobin not said no chance, I could have kept my EQ6 and saved a fair bit on the mount.

Gonzo, pity about the price, it would have suited your German project.

I always had in mind that I would run it at home for a year or two and then re-locate at a dark site in Northumberland, but we will have to see how well it goes.

Robin

[Gina]

That little dome would probably have suited me for my second imaging system if it wasn't for the price.  I shall be running mine remotely except for opening the roof (unless I can find a way to power that).  My widefield DIY mount design even has remote PA adjustment, though I shall be using the NEQ6 at first and may try to add remote PA motors to that (should be fun ).