Major rethink ...

[wxsatuser]

If thats peashingle cats will do their business in it for sure.

If it's 20mm shingle they won't.

When I built my garden railway I covered the whole garden in normal 20mm shingle plus decorative stuff.

Never ever had cats doings in 20mm stuff as they really don't like walking on it.

[Demonperformer]

Thanks for the thoughts.

I like the idea of a 'spray gun', but the trouble with anything where I have to be there is that the cats can (and do) just hop back over the fence before I get the back door open and out.  So I need to devise some method of stopping them from escaping too quickly.  Maybe buy a roll of chicken wire and tack it to the fence near the top to make it difficult for them to get purchase as they scramble up the fence. Then a good drenching would provide the motivation they need.  Now I suspect that would definitely encourage them not to come back.  More expense!

Actually, I haven't had any problems since I covered the central sand bit with pea shingle. Or maybe it was the pepper solution that I put down at the same time.  Only time will tell.

[Demonperformer]

I  DON'T BELIEVE IT!!!!!!

Clear skies, so went out to enjoy having the mount on the pillar and being able to get it properly aligned.

It appears that the compass I used to set the pillar up was less accurate than one could have hoped.  I moved the azimuth knobs as far as they could go, and polaris was a fraction outside of the big circle in the polarscope, with no further movement available to bring it into it's correct position.

Which all means that I am going to have to dig up the pillar (with all the measures I put in to make it difficult to remove) and rotate it an appropriate angle.  First thing will be to measure what the angle on the mount it, so that I can get it roughly central.

It shouldn't be too difficult a task, just incredibly tedious in view of the effort put in in the first place.

So I am now settling down for an evening with Sapphire & Steel.

[yesyes]

would it not be an option to drill new holes in the pier top so that you can rotate only the top bit instead of digging it all up again?

[MadAlbert]

'Spose it's a good job you didn't set the pillar in concrete...

Personally, I'd dig it up.

[MadAlbert]

Oh, apart from checking your compass, check your magnetic declination, too.

[Demonperformer]

would it not be an option to drill new holes in the pier top so that you can rotate only the top bit instead of digging it all up again?

I see where you are coming from, but I can see too much opportunity for me to mess it up in a permanent way.

Consider this: the angle produced by the gap in the bottom of the mount is about 50 degrees.  That means I could have been over 20 degrees out in either east or west of the pole and still have been in the catchment area - and I missed it!  OK, by less than 1.5 degrees, but still.

Now I am going to attempt to drill three holes in a steel pillar in an upright position accurately enough for the bolts to match up with all the holes and still have little enough slack so that the mount is held rigidly?  Me??  I think I will pass on that option .

[Demonperformer]

'Spose it's a good job you didn't set the pillar in concrete...

Personally, I'd dig it up.

Oh, apart from checking your compass, check your magnetic declination, too.

Yes, concrete would have been a real disaster.

My magnetic declination is -1d 42'.

[Demonperformer]

OK, a few calculations (PLEASE point out any errors in my thinking):

Polaris was just outside its 'orbit' circle, so I know that rotating the pillar anything over 2 degrees west will put me in a position where I can get it polar aligned.  But it would still be right on the far end of alignment.  It would be better to get it closer to the middle.

The diameter of the mount base is about 130mm, giving a radius of 65mm.

The width of the gap is 45mm.

Let's assume that the gap extends to the rim of the mount base (it doesn't, but calculating it this way will give me the smallest 'limit' angle and I DON't want to overshoot!)

This gives a right angle triangle, hypotenuse is 65mm, side is 22.5mm (half the gap-width).

Side = hypotenuse * sin(a)

sin(a) = 22.5/65 = 0.346154, which means that a is just over 20 degrees.

The whole gap therefore subtends an angle of over 40 degrees.

This means that if I rotate the pillar 20 degrees west, alignment will be close to the middle of the gap.  Actually, because of the limit applied above, the actual figure for the middle will be somewhat bigger, say 25 degrees.  So anywhere between 20/30 degrees will put me in the golden zone.

Now, the mechanics of the operation:

1) remove the majority of the pea shingle from the central 'sanded' area

2) locate the feet (not difficult, as I have a pretty good idea where they are and they are only just below the surface)

3) calculate new position (easy, they are 120 degrees apart, halving it twice gives 30 degrees - the upper limit - so a bit less than that) and mark with canes

4) grub out the sand from the side of the legs in the direction in which they are going to move to the new position

5) rotate the pillar to its new position

6) repack the sand on the other side of each leg

7) replace the pea shingle

I think I should be able to do it without removing the wooden struts I put over each leg, as I am only rotating, not lifting out of the hole.

A tedious, but not complicated task.

So all-in-all, not a total disaster.

[Gina]

How about just clearing a small area in the middle between two of the legs , undoing the clamping screws between the two legs slightly and rotating just the tube?  Take the mount off so the weight is just the tube.  Since you are now left with just a plain tube to turn it should be possible.

[Demonperformer]

Now that is why I need to run my ideas before other people before doing anything.

Thank you, Gina.  That should save me a LOT of work.

[Gina]

Great   I'm pleased I can help.  Good luck - that must have been very annoying.

[Macavity]

I still think (given the effort you have already put into this!) laying FOUR 2x2 Flags in a minimal bed of hardcore / concrete might have given fewer problems? The Pillar weighs 35lb... A 2x2 Flag 50lb? You are buying a (fairly) expensive pillar, burying it in ground where it will RUST out of sight? With one "coronary episode" under my belt, I do appreciate the problem, but managed to (carefully!) lift 2x2 flagstones?

Aside: For significant stuff, a local bloke / MATE does my work. He is a *skilled* Landscape Gardener. Or simply a FIT (younger) guy who appreciates a few quid? lol. A few "drinking tokens"... An escape from the rigours of "family life"! But I do join in and give him a helping hand wherever I can. But Simply, he does a FAR FAR better job than I (a mere Physicist) could ever do? Overall, a win-win situation?

Really not trying to detract from your efforts...

P.S. I do use a Skywatcher Pillar - In (Video Astronomy) Observatory context. All laid

on "standard patio" even. And no, I didn't dig out a "cubic metre" of clay / limestone.

[Tinker1947]

Flag stones are nice and flat, but they will also get nice and icy unless there covered in rock salt, i would go for 20mm shingle to stand on and i would have used the same shingle to cover the mount base as this would allow drainage and slow down the rust process as the sand will just hold water and the rust will do its damage a lot quicker.....but what ever way you go it will be a nice solid mount......

[Gina]

I think I'm going to use concrete blocks for my pillar mount to stand on - just sunk into the ground.  It's heavy and seems very stable just placed on level ground and my NEQ6 mount adds to the weight making it even more stable.  For my widefield use I think it will be quite adequate.

[Macavity]

I think I'm going to use concrete blocks for my pillar mount to stand on - just sunk into the ground.  It's heavy and seems very stable just placed on level ground and my NEQ6 mount adds to the weight making it even more stable.  For my widefield use I think it will be quite adequate.

My (general) feeling too? I am (genuinely) surprised by the stability of traditional, quite SIMPLE constructs.

My Skywatcher Pillar stands on three Breeze-block "plinths" (albeit within a Ro-Ro observatory). But Patios,

"Pavers"... A little bit o' "ready-mix" here and there? Don't "jump up and down" while imaging? etc. etc. 

[Demonperformer]

For me the big advantage of the pillar (ironically in my current situation) is that it is fixed in one place permanently.  And so, once I have this thing polar aligned properly, that will be job done.  I was getting nowhere with polar alignment on a tripod and was on the verge of considering jacking the whole exercise in.

Where I want to go with this is to be able to do some DECENT astrophotography, and so polar alignment is fairly essential - otherwise I might as well have stuck with the alt-az SE & SLT mounts.

Merely putting the pillar on 4 flagstones, where it can be knocked and moved requiring me to start again would IMO be a waste of time - I might as well have stuck with not being able to align the mount on the tripod.

As to how well it will survive, well, only time will tell.  I'll get back to you in five years time and let you know how well it has done.  Alternatively, I may not have another five years and so the matter will be moot.

[Demonperformer]

 that must have been very annoying.

My nomination for 'understatement of the year'

[Macavity]

Alternatively, I may not have another five years and so the matter will be moot.

And indeed (my?) reality! lol. And frankly influencing quite a lot of my recent "more creative" decisions... 

Thinking outside the Box? No bad thing? Good luck with whatever you decide anyway...

[Gina]

I think I might well drill a hole in each concrete block to take the feet or maybe even cement in some threaded pieces.

[Macavity]

I think I might well drill a hole in each concrete block to take the feet or maybe even cement in some threaded pieces.

Heheh. If we are still vaguely on the same topic, I found standard copper "pipe ends" fitted the feet. lol.

Drilled / cemented into over-sized holes into concrete blocks (whatever). But "you'd know" anyway...

[Demonperformer]

Though I say it as shouldn't, I do occasionally have my moments.

Despite all my calculations above, I was not convinced enough to start digging around the pillar ... I could just see me making a mess of it.

Then I had my moment.

So this evening I went outside with the mount and placed it on the pillar.  With the azimuth bolts centrally placed on the mount plate, I rotated the mount on the pillar until Polaris was more or less central in the polarscope.  Now, I plunged a cane into the sand immediately below the polarscope.

Now I know exactly where the bolt in the pillar has to line up when I get out and start digging/rotating the pillar tomorrow, without any guess work or dodgy calculations.

[Demonperformer]

Gina,

Sounds good, as long as:

(1) the blocks are positioned in the correct place before you start drilling [if I had done that I would still have had the same basic problem I have had here], and

(2) there is no risk of your local friendly tea-leaf coming along and unscrewing the feet from the threaded pipe into which they are screwed [unless you have some way of preventing them from being removed?]

[Demonperformer]

Right, that turned out to be a lot simpler than I anticipated. 40 minutes from start to finish.

I did need to loosen all three of the 'foot bolts' to give me enough flexibility to get the pillar to move.  My own fault for packing the pillar in so solidly with the sand!  Maybe my ability to judge angles is seriously screwy, but the angle I had to move the pillar to line up with the cane seemed to be considerably less than the angle I had calculated above.

Be that as it may, I have now repositioned it and it is ready for tomorrow night, when we have been promised clear skies after the rain during the day.  That will be the real test.

[Demonperformer]

Really pleased with the results from my first session using the new setup.

Had a slight issue with the EQMOD polar align program (using just the AZ controls did not move polaris to the "9 o'clock position", more like about 7.40.  Maybe that explains why it managed to lose 7.5 degrees slewing from Polaris to Capella.  Still, then used AT to do ALT alignment and got it within 1.7'.  Even discovered that I can get a lot closer to the celestial equator in the south than I thought (within 10 degrees) and checked the AZ alignment - 4.4' - not particularly good, but then could not decide which bolt I needed to tighten when the mount was the other way round, so decided to leave it like that for last night.  Since then have realised that I can ignore the direction the mount is facing, as the affect of each bolt on the mount/pillar interface is the same whatever the telescope is pointing at.  Live and Learn!  Not too worried about these errors, as I am anticipating being able to get it a lot better in subsequent sessions using these figures as a starting point - and I did want to do something other than just polar align last night.

Then spent the rest of the evening running test shots at various declinations/durations to see what I could achieve.  Was initially rather puzzled by the fact that some of my shorter shots with greater declinations are worse than longer shots at lower declinations.  Then it struck me - if the gear train has a 48 minute cycle (according to the EQMOD analysis program) it stands to reason that some bits of that will be worse than others, so I was obviously running through a worse bit when I was testing the higher declination and so got worse results.  Answer: increase priority of doing a PE recording/analysis.

By ten, I was feeling really grateful that I was not a "brass monkey", and so decided to call it a night.  No great "results" as such, but a really fruitful evening.