Gina's Observatory Build - Abbreviated - Pier Head Adapter

[Gina]

This is where things were left from the Pier Construction thread with the pier adapter made and levelled - though I've since learnt that levelling is not becessary as it's covered by polar alignment. This thread will describe how I made the adapter, materials used etc.

[Gina]

The pier adapter consists of 3 metal plates - 2 mild steel discs of 250mm diameter x 10mm thick and 1 aluminium 200mm square x 5mm thick. The materials were dictated by what I found on-line at the time whilst being suitable for purpose. I rounded the corners of the ali plate to match the steel plates. The bottom steel plate was drilled with 4 holes to match the threaded rods protruding from the concrete pier plus another 4 for bolts to attach the top plates. The top plates were drilled with matching holes. The top steel plate was drilled in the centre with a 30mm hole to match the stem of the NEQ6 mount and the ali plate with a 60mm hole to match the boss on the mount. A hole was also drilled for the post used for azimuth PA adjustment. Additional small holes were used to align the plates.

Here are some photos of the plates during construction plus sectional diagrams showing how the mount fits on the adapter and of tthe complete pier adapter with pier threaded rods and mount together with nuts, bolts and washers.

[Gina]

The smaller holes were drilled using standard drill bits in a belt driven electric bench drill press. The 16mm holes used blacksmiths drills and I used a very old hand driven geared bench drill press which was a heavy duty piece of equipment - much heavier than the electric drill press. To cut the 30mm hole in the 10mm thick mild steel plate I used a 25mm blacksmith's drill bit and then a 16-30mm taper reamer to open it out to 30mm. This hole took several hours by hand but the electric pillar drill just wasn't up to it. The 60mm hole in the ali plate was cut with a trepanning tool in the electric drill - very carefully with the workpiece well clamped down.

[floppygoose]

Nice job Gina, looking forward to seeing the next phase of development - Phil

[Gina]

Thank you Phil

[Gina]

After the hole drilling etc., all the sharp edges were filed smooth and the plates given a couple of coats of smooth white Hammerite paint to match the mount. Once thoroughly dry everything was assembled and the mount and adapter attached to the pier. It was then ready for use

[Gina]

That was before the obsy was built and due to a change in the floor design as work proceeded, the whole "shed" ended up about 6" higher than originally planned. This meant that the pier and mount were no longer at the designed height and the scope wouldn't be able to see the southern and eastern horizon over the walls. Plus the area of visible sky over the roof when open would be further restricted. The problem was later solved when I picked up an NEQ6 pier extender second hand. This meant I could raise the mount and scope by 8". It also meant a slight change in adapter design. Now the mount would go directly on top of the extender, which included the PA adjustment post and the aluminium plate on the top of the pier adapter would be redundant. I could have saved myself some work if I'd had a crystal ball

The diagram and photo below show the new arrangement. I used a whole heap of washers to pad out the special bolt with waist to get it to fit. And this is now things are to date

[laser_jock99]

This probably makes polar aligning easier now- you can probably turn the azimuth adjuster screw without hitting any plates! Something I kind of overlooked (although I'm using a standard hex bolt & 17mm spanner now).

[Gina]

Yes it is easier to get to the azimuth knobs without a plate right beside them. Azimuth is not too bad but I've found altitude difficult to adjust with so much pressure on the UP bolt. I'm really far from impressed by the NEQ6 PA adjusters. I've been wondering if I can work out a better adjustment method. The new - not yet available - NEQ8 looks quite a lot better.

[nightvision]

Gina have you considered replacing your plate bolts with longer ones and then tilting the whole extender and mount so that it appears to the NEQ6 alt adjustment that you live somewhere a lot further south (maybe about 25 degrees) and the mount alt bolts can be relieved of all that mechanical stress arising from poor design?

I am considering doing something like that when my obsy is complete, for rigidity I may engineer a pivot/bearing opposite two large alt adjustment bolts at the adapter plates, I may need to check the balance of the mount so that the loads pass straight down through the pier so as to prevent flexing.

[Gina]

Gina have you considered replacing your plate bolts with longer ones and then tilting the whole extender and mount so that it appears to the NEQ6 alt adjustment that you live somewhere a lot further south and the alt bolts can be relieved of all that mechanical stress arising from poor design?

I am considering doing something like that when my obsy is complete, for rigidity I may engineer a pivot/bearing opposite two large alt adjustment bolts.

Yes, I did consider that but having modified the bearing point of the adjusting bolt on the lug I can now adjust the altitude without a problem. I think using moly grease helps too (less friction). That problem is solved to my satisfaction.

What isn't quite solved yet is the azimuth. With the standard SW pier extension the slack between the central collar of the mount and the matching hole in the pier extender means that if I knock the scope or mount it can move a little bit. Probably up to a degree - far too much when polar aligning to a few minutes of arc or better. The adjuster bolts can be tightened against each other but the pivot is slack. I need a way of tightening that or some other adjustment method as well. I have some ideas and the coming week looks like a suitable time for mods - weather forecast is dreadful!

Having got the azimuth right, I can lift the mount and extender top off the tube and tighten the central bolt fully. Then I'll need an adjustment at my pier adapter 'cos 10:1 the adjustment will have gone a bit out.

Watch this space ...............

[nightvision]

Looking forward to seeing your innovations.

[Gina]

I lifted imaging rig and then mount plus top section of pier extender off the tube part and tightened the central bolt. Then tried adjusting the azimuth - no problem, so I tightened it up some more until it was pretty tight. Tried adjustment again and though somewhat stiff I could still do it. So I put the mount etc back on the tube and tested again. I found I could adjust the azimuth but unless I gave it a very hard knock the central hub didn't move. I think I may have fixed it adequately. Time will tell - bunping into the scope or whatever is something to be avoided At least PA is much less bother with AstroTortilla if I should blunder into the scope.