Rob`s Obsy Build

[red dwalf]

Concrete not poured yet, but I think if I do get any problems I could put some rubber matting underneath which will provide tension and if you think that the original mount only has one bolt to secure the mount head and it's very secure, also the bolt on the skywatcher mount is smaller than the one I'm going to use, we will see what happens and make adjustments if nessasary.

[jambouk]

Rubber matting again would limit gross movement, but won't stop minor rotation around the central bolt. Any additional bolts in the lower plate wouldn't need to be massively big (diameter or length) or need to be sunk too far into the concrete to provide absolute prevention of any rotation around the central bolt. They could be shortened with a hack saw once the plate was fixed so they would just sit a nut height proud of the plate itself, so not hindering you getting your hand in for the mount bolt.

The plate could be lowered onto the concrete as it set with the central bolt through it and the three anti-rotation bolts dangling beneath to ensure they were all in the correct position; thin wooden spacers could be used to lift the plate off the concrete by a few mm to prevent it fixing to the concrete if you wanted.

It's all very exciting. I've found a local chippy (carpenter not fish and chip shop) who is going to come and give me an idea how much it would cost to make me an observatory as yours Rob has really impressed me.

James

[yesyes]

... and if you think that the original mount only has one bolt to secure the mount head and it's very secure...

That's not quite correct. It has 2 bolts, one is the one you secure the mount to the tripod, the other is the azimuth adjustment bolt. The latter doesn't secure the mount but it prevents rotation around the middle bolt. You won't have that for your bottom plate with only one bolt. I too would be concerned about rotation and therefore losing polar alignment...

[yesyes]

... and if you think that the original mount only has one bolt to secure the mount head and it's very secure...

That's not quite correct. It has 2 bolts, one is the one you secure the mount to the tripod, the other is the azimuth adjustment bolt. The latter doesn't secure the mount but it prevents rotation around the middle bolt. You won't have that for your bottom plate with only one bolt. I too would be concerned about rotation and therefore losing polar alignment...

[yesyes]

ooops, double post, sorry...

What you could do is drill another hole into the bottom plate now. Then fasten it with only that one bolt and when you have done your rough alignment, you can mark in the concrete where the hole is in the plate, drill a hole in the concrete put a wall plug in and then secure the plate with a normal screw into the plug.

[red dwalf]

I like that idea,

[Gina]

Those plates look rather big and I suggest you check carefully that a large scope will not collide with one if the object you're tracking goes vertically above. This has happened with my rig and terminated an automated imaging run prematurely - as I found out in the morning after leaving everything running overnight while I went to bed No damage but several hours of valuable imaging time lost. So it looks like I should re-engineer my mount to pier construction. Nuisance!

As for the PA adjustments on these Synta mounts - I think it's very poor. To rely on a short leverage with relatively coarse threaded bolts is far from satisfactory, particularly with the very fine adjustment you need for good PA, and I can see why several people have re-engineered this aspect. Indeed I would like to do this myself as I have had to redo my PA after the central bolt came loose and I lost PA through bumping into the scope As mentionmed above, you can't have this too tight or you can't adjust the azimuth. So I do mine up finger tight. The altitude adjustment is even worse - all that weight and the dreadful adjustment system makes altitude adjustment almost impossible.

What is needed is much longer adjustment levers for the PA - maybe with a coarse and fine adjustment. A coarse azimuth adjustment could be simply slotted holes in a mounting plate. The altitude can be set coarsely from the latittude of the obsy site, a spirit level and a protractor. I guess the Synta adjustment and scale could be used for coarse and something else arranged for the fine adjustment though I'm not altogether happy that the Synta adjuster is up to the job without flexing. This could be one reason for needing guiding on long subs.

I'm going to be thinking about this in the coming days (or weeks) and see if I can come up with something which will not cause collisions and provide fine PA adjustment. I'll probably start a thread about this in the "DIY Astronomy" forum.

[laser_jock99]

I'd be tempted to do away with the plates and the bolts altogether.

Three reasons:

1) Contrary to popular belief the pier head does not need 'leveling' all the adjustments required can be done with the EQ5 mount's mechanics.

2) Those long bolts connecting the plates are sometimes nicknamed 'wobbly bolts' for obvious reasons....

3) As Gina mentioned your scope and/or counterweights could clash with those plates at some point. I have occasionally come close to hitting the pier with attached cameras & other gear and I don't have any plates on my rig.

There should be some way of fitting your blue puck directly to the pier?

[Astrokev]

I'm going to be thinking about this in the coming days (or weeks) and see if I can come up with something which will not cause collisions and provide fine PA adjustment. I'll probably start a thread about this in the "DIY Astronomy" forum.

Look forward to seeing what you come up with there Gina.

I'm planning on using quite a wide tube for my pier (can't remember the exact size without remeasuring, but it's something like 250mm). I'm intending doing some calculations to see in what OTA positions the tube may hit the pier before I finally commit. Important factors that need to be considered are the distance between the inner side of the OTA and the RA axis; the height of the Dec axis above the top of the pier; and the distance between the Dec axis mounting point on the OTA and bottom of the OTA (ie the length of the tube below the Dec axis). It also obviously depends on where the scope is pointed! Paper calculations are actually quite difficult to do I think, so I'm considering making a simple scale model of my set-up. Better to know in advance how this will perform before starting the build !

Red Dwalf - Regarding your plate mounting design, I agree with other posters that a single bolt to attach the plate to the pier is risky. It's difficult to assess the rigidity of your design without putting a fully loaded OTA on the mount, as doing so will generate a much larger turning force than the mount alone. Forgive me for saying so but I also think using a rubber sheet is a very bad idea IMHO.

Regarding pier plates, my design will use a single plate with 4 corner bolts sunk into the pier concrete, with the mount (NEQ6) bolted through a central hole in the plate. Access to the central bolt will be achieved by fabricating an "owl's nest" arrangement at the top of the pier when I pour the concrete. The wider tube design should make this relatively simple and effective.

Kevin

[red dwalf]

I'd be tempted to do away with the plates and the bolts altogether.

Three reasons:

1) Contrary to popular belief the pier head does not need 'leveling' all the adjustments required can be done with the EQ5 mount's mechanics.

2) Those long bolts connecting the plates are sometimes nicknamed 'wobbly bolts' for obvious reasons....

3) As Gina mentioned your scope and/or counterweights could clash with those plates at some point. I have occasionally come close to hitting the pier with attached cameras & other gear and I don't have any plates on my rig.

There should be some way of fitting your blue puck directly to the pier?

there`s no way of directly attaching the puck to the pier which would be nice, reason being is that you need access to the underside in order to bolt the mount to it.

it is a difficult one to sort but if push comes to shove i can simple and always make adjustments to stop it rotating if this does happen.

fingers crossed the plates are not too big, i have done alittle research with professional pier builders and one i looked at had a 8" pier width with a 10" plate on top, then fitted with a puck, they sell alot of them but cost a fair amount so if there design is ok i should be fine as regards to scopes and equipment missing the top plate, i only use a 8" sct and a 80mm short focal length refractor anyway so should be fine.

famous last words L.O.L.

[laser_jock99]

there`s no way of directly attaching the puck to the pier which would be nice, reason being is that you need access to the underside in order to bolt the mount to it.

it is a difficult one to sort but if push comes to shove i can simple and always make adjustments to stop it rotating if this does happen.

fingers crossed the plates are not too big, i have done alittle research with professional pier builders and one i looked at had a 8" pier width with a 10" plate on top, then fitted with a puck, they sell alot of them but cost a fair amount so if there design is ok i should be fine as regards to scopes and equipment missing the top plate, i only use a 8" sct and a 80mm short focal length refractor anyway so should be fine.

famous last words L.O.L.

Access to the to the mounting bolt is an issue with solid concrete piers granted. One of the reasons I decided to buy a piece of steel tube for the pier was to allow easy access to the mount retaining nut (via an 'owl hole'). I can only just fit my hand in the hole- but I can get all the wiring up the pier and out the hole as well.

[Astrokev]

There's no reason why you can't put an owl's nest in a concrete pier if it's wide enough. Needs a bit more thought perhaps, but I don't see that it's impossible. This is what I'm planning for my pier.

[Gina]

My 10" round plates were fine with the ED80 and everything else I had on the mount but the MN190 fouls the plates when the scope goes up to vertical just past the meridian. It's OK if I do a meridian flip at the appropriate time but I want to be able to run my imaging unattended. I need to get my sleep as I'm currently caring for my OH as he recovers from a broken hip during the daytime as is somewhat immobile.

So I'm looking at replacing my 10" plates with something smaller. The problem is that the threaded rods in the pier are on about a 5" diameter circle and the extension tube is 5" diameter. So it seems I will need two plates with the lower one on the rods and connected to an upper plate with bolts that will clear the 5" extension tube. If the rods had been right near the edge of the concrete I might have got the extension tube inside and then only needed one plate.

As for improving the PA adjustments, I'm thinking in terms of a lever inside the 8" extension tube to tilt the tube (or the top plate) by something like one degree using a fine threaded bolt - maybe M6. The bolt (or rod) could have a large knob on the outside of the tube to turn it.

Oh BTW - on second thoughts, the most appropriate forum for discussing this is this one

[yesyes]

Gina, if you're using EQmod you can set limits. You still would miss out on a bit of sky around the zenith but at least the scope wouldn't hit the pier plates and you could run unattended.

[Astrokev]

My 10" round plates were fine with the ED80 and everything else I had on the mount but the MN190 fouls the plates when the scope goes up to vertical just past the meridian. It's OK if I do a meridian flip at the appropriate time but I want to be able to run my imaging unattended. I need to get my sleep as I'm currently caring for my OH as he recovers from a broken hip during the daytime as is somewhat immobile.

So I'm looking at replacing my 10" plates with something smaller. The problem is that the threaded rods in the pier are on about a 5" diameter circle and the extension tube is 5" diameter. So it seems I will need two plates with the lower one on the rods and connected to an upper plate with bolts that will clear the 5" extension tube. If the rods had been right near the edge of the concrete I might have got the extension tube inside and then only needed one plate.

As for improving the PA adjustments, I'm thinking in terms of a lever inside the 8" extension tube to tilt the tube (or the top plate) by something like one degree using a fine threaded bolt - maybe M6. The bolt (or rod) could have a large knob on the outside of the tube to turn it.

Oh BTW - on second thoughts, the most appropriate forum for discussing this is this one

Hi Gina,

I'm struggling to visualise your problem and plan (it's late and I'm tired!) - could you perhaps post a quick sketch to illustrate your post above?

thanks

kevin

[Bas]

having talked with a electician at work and asking about the best way to run power to the obsy without major works, he surgested this system.

Did he really suggest using not one, but two widowmakers? I find that impossible to believe. Connectors of the correct genders would have been no more expensive - please change yours before you, or someone else, gets killed.

[dmahon]

Yes - make sure you have it wired up so that the male plug (prongs) can never be live when disconnected - it looks like the receptacle on the shed is female, which would be bad.

[Bas]

Similar badness in the garage - he has a lead with a BS1363 plug on one end and a male 60309 on the other.

[red dwalf]

Did he really suggest using not one, but two widowmakers? I find that impossible to believe. Connectors of the correct genders would have been no more expensive - please change yours before you, or someone else, gets killed.

many thanks for the posting on another forum Bas, much appreciated.

your comments are founded but vague in the absent of any helpfully imformation, but another helpfull forum member has shown me where i`ve gone wrong

i do now see the problem with the blue 16 amp campsite female connector which is attached to the obsy and will rectify it once i find a male connector unit which do seem hard to find, so if anyone can help with finding one please do.

apart from that problem i don`t see any other fault in the system.

[RF Lighting]

You can pick up appliance inlets very easily.

http://www.tlc-direct.co.uk/Products/GW240slash16slash3A.html

Here's one.

Or search eBay for "16A appliance inlet"

I think the larger branches of B&Q might even sell them too.

[red dwalf]

many thanks for the help, manage to find a few of these now on the internet, only concern is that the pins are open to the weather, would like them to be sealed or covered when not in use.

[dmahon]

http://uk.rs-online.com/web/p/mains-connector-accessories/4787694/?origin=PSF_435647|cav

Might work.

[dmahon]

Or how about this page (top or bottom items)

http://essentialsupplies.co.uk/acatalog/Online_Catalogue_16A_Inlets___Mounted_Sockets_141.html

[red dwalf]

a little update of the pier build.

having some time available before the winter season sets in, i have now stared work on the pier build.

firstly digging out a 24" deep hole in the trap door of the obsy floor, and concreting in a galvanised post which should help to stablize the pier,

also ive made a few holes in the bottom of the pier to help the concrete bond better which the concrete fill of the tube and also have screwed a few 6" screws into the bottom of the tube to help stablize the tube. they look flimsy but belive me they are very well screwed into the plastic waste pipe, the pipes are fairly thick.

[red dwalf]

managed it concrete the pier into position today, took 8 bags of ballast, mixed by hand, my back is killing me !

feels very sturdy so far, so fingers crossed,

i also added a two threaded bars to the bottom of the pipe to help stablise the pier alittle better, the screws looked alittle light weight on there own.