Gina

Pier with mount fitted.  ATM I'm just collecting photos to see which I want to include - it can't be all of these.

On 18/07/2011 at 19:51, Gina said:

It stopped raining for a while this evening so feeling "stir crazy" I went out to the site and tried to level the remains of the soil heap outside the "shed" area but even with the rain we've had, it was still very hard and I made little impression.

However, having levelled off the underfloor area (thereby reducing the tripping hazard) I thought I'd try the mount on the adapter. So having uncovered the pier I lugged the mount outdoors and up onto the pier adapter. Once I'd undone the azimuth screws it sat down on the adapter with a nice close fit but still easily adjustable. But as soon as I'd taken a couple of photos, down came the rain again! So back on went the cover. But this time over the mount as well.

Here are the photos I took of the mount. Only had time for the two.

On 15/07/2011 at 07:26, Gina said:

I've removed the pots - did it yesterday evening. No problem Must say, the pier looks a lot better without them. There are no voids and the concrete surface is absolutely smooth - moulded by the smooth plastic

Photos attached (it wasn't as dark as it looks - the automatic flash kicked in) :-

1. Smaller pot removed.

2. Larger pot and most of the duct tape removed.

3. North side view with discarded pieces of plastic pot.

A bit of humour.

On 12/07/2011 at 16:36, nightvision said:

That looks great, coming on nicely, it certainly must be tempting to try it out especially if you get a clear night, you could easily piggy-back your DSLR for some wide-field shots. You would find it a refreshing change from all that slog you are putting in!

I wont be covering the block and pier build in any detail and might not include it at all.

On 03/07/2011 at 12:49, Gina said:

Photos of the pier and base hole concreting :-

1. Equipment set up for pier base hole filling.

2. Pier base hole about half full (15" deep).

3. & 4. About 4" to go.

5. Pier base filled and levelled off ready to take top shuttering.

6. Base top shuttering screwed on and plant pots filled with concrete.

7. & 8. Pier filled with concrete.

On 28/06/2011 at 19:55, Gina said:

More photos

On 24/06/2011 at 19:37, Gina said:

The rain's come in now so that's it for today. 3rd beam cut to length, soil removed to accommodate it and it's more or less in position. Needs level and height checking - to do tomorrow.

Now at last beginning to look as if something's happening

Here's a cropped webcam image - too wet to use DSLR!

On 24/06/2011 at 19:37, Gina said:

The rain's come in now so that's it for today. 3rd beam cut to length, soil removed to accommodate it and it's more or less in position. Needs level and height checking - to do tomorrow.

Now at last beginning to look as if something's happening

Here's a cropped webcam image - too wet to use DSLR!

On 21/06/2011 at 21:56, Gina said:

Here's some more photos :-

1. Pier base hole - finished - 30" square (at bottom) x 27" deep.

2. Hole 1 of 6 for floor supports - 18" square by 10" deep.

3. Hole 2 of 6 for floor supports - 18" square by 10" deep.

4. Covered up for the night - rain forecast.

On 19/06/2011 at 20:32, Gina said:

The forecast isn't good but could be worse. Yes making progress gradually

Here's a couple more photos, taken this evening :-

1. The pier base hole.

2. the ever increasing spoil heap. This is all hand dug out of the pier base hole.

Conclusion - even without going into technicalities, astro imaging simply won't go into this short a talk!  I'm going to have to leave a lot out.  Some things could be left for the following Q&A session.

Hmmm...  I think I'm going to be hard pressed to cram all I want into 40 minutes.  It would be nice if I could cover all these :-

1. Types of telescope including camera lenses
2. Types of observatory
3. Types of camera
4. Methods of supporting the imaging system - tripod, pier etc.
5. Different sorts of night sky object - moon, planets, galaxies, nebulae...
6. Solar imaging - white and NB
7. Image processing - stacking - colour processing...

It simply won't go into a mere forty minutes!

Why do you have an observatory?  Taking night sky pictures needs a lot of equipment, very carefully set up and though some people set up and take down every time they do any astronomy this takes a lot of time and is a problem when the equipment needs very careful setting up.  With an observatory all the equipment can be set up virtually permanently and you only have to open the roof to be ready to go.

Why is your observatory like a strange garden shed when "proper" observatories are dome shaped?  This leads to the sorts of observatory and a very quick discussion of types of amateur telescope covering.  This could take up half the time itself if I let it. 

I think I have an idea of how to explain a telescope and the need for a solid mounting (pier/tripod and mount).  "I think most of you will have used binoculars and realised how difficult they are to hold still and the more magnification the more difficult this is.  Now consider a very much higher magnification of say, a hundred times rather than eight or ten times and you can see why telescopes need a good solid mounting." 

Of course, this doesn't mention time exposures but I don't want to get too much into that as it gets technical.  Nor does it cover widefield imaging but again this has to be outside my brief.  There is so much to cover without covering widefield.  I think the same may apply to NB imaging - explaining very narrow band optical filters would be far too technical.  I may be able to explain NB imaging by saying that there are special coloured filters that only let light through from particular glowing gases.  I can say that hydrogen produces a deep red glow and oxygen a bluey-green or turquoise, glow.  I could demonstrate this with two-colour images such as the Cygnus Loop (thought there is some SII in this).  I think I really need to offer some sort of explanation of NB imaging as this is my main sort of imaging.

40m is not long to describe astro photography.  Indeed 40m wouldn't be long to describe terrestrial photography.  We had a talk on photography at a WI meeting last week which lasted an hour.  I got the impression that that tended to be too technical.

Back to thinking about my talk.  This will be practically all pictures with minimal explanation to avoid any technical stuff which much of the audience wouldn't understand (or so I've been told).  So apart from pretty pictures of nebulae and galaxies I plan photos of the astro kit and construction of my observatory.  The trouble is, I have hundreds of photos of the site excavations, concrete work and construction that will need a really serious prune.  I need to sort out a time-line of pics to show the build without overdoing the photos.  I think it would be good to include the various weather conditions with a bit of humour showing a waterlogged building site.

It has been suggested that I include image processing and mainly I agree.  The problem is that this is very technical so I shall need to work out how to describe this as simply as possible.  One thing I would like to show is the improving image as more and more subs are added to the stack.  Explaining the stacking process in lay terms is not going to be easy but this is the principle that is the main part of astro image processing.  Another important part is combining monochrome images to form a colour image.  How does one explain this to people whose only knowledge of photography is pointing the camera at something and pressing the button?  Few people will know how coloured pictures are formed from different coloured dots/pixels or the photographic colour film process of layers on monochrome images derived using colour filters.

Some improvements made to the chain drive including adding a tensioning spring and adjustment.  The eastern attachment bracket remains the same but the western end block has been replaced by an eye bolt through the end frame of the roof and a heavy duty spring.  Also the smaller chain pulley has been replaced by a bigger and stronger 3D printed version employing two ball bearings and an 8mm coach screw into the motor baseboard.  This was to cure the chain climbing up onto the edge of the pulley and to improve the chain movement generally.

Two screenshots of the new small pulley design.

New pulley installed.

Spring and eye bolt, which provides for tensioning the chain.

The chain is now attached to the blocks on the ROR framework and both roof and window now open and close from the motor drive though ATM the window needs pushing open at first before its weight takes over.  There is still the motor control unit to design and build.

That galvanised clothes line pulley wasn't good enough - the cord rode up over one of the cheeks.  Replaced with a 3D printed one which works fine.

After applying geometry to the idea of using 8mm plaited cord to open and close the window from the ROR I set it all up and tested it.  It worked perfectly.

The pulley system shows the situation with roof and window closed (vertical).  When open the cord from floor over pulley to window is straight floor to pulley and window is lowered to horizontal position.  This arrangement has the advantage of evening out the pull needed to close the window a bit.  Operating the window doesn't add much to the force required to close the roof.  If I want to open the window without opening the roof, I can unhook the pulley block from the window cord.

Stiffened up the fold-down window frame with blocks on the top joints and pinned the axle brackets to the axle (1.25" aluminium tube).

Screenshot of CAD design of the fixed pulley that will take the cord from the ROR frame.  Again with a deep groove to stop the cord coming out of the groove.  This is the smaller, left-hand pulley in the diagram above.

The 70mm diameter main cord pulley for the window (the RH larger pulley in the diagram above) had a rather shallow groove and the cord tended to come off so I've printed another with a deeper groove.   Also printed a pair of plates to stiffen the window frame.

Chain end brackets fitted to ROR.  Now waiting for the penny washers to secure the chain.

Back to the chain drive for the roof.  Designed and printed the bracket to attach the west end of the chain to the roll-off-roof.

I think I have a design for opening the window when the roof is opened  using 6mm diameter braided cord and a couple of pulleys.  This can be disconnected if I want to open the window without opening the roof.  This dispenses with the traditional wooden lever system so the guttering downpipe will not be in the way.  I can stiffen the window frame using wooden blocks screwed to the corner joints.

This diagram shows the roof and window open.  As the roof closes the cord and pulley system pulls the middle of the diagonal cord upwards and the geometry is arranged such that when the roof is closed the window is pulled up to the vertical position and closed.  The reverse happens on opening the roof.  The window will have a weight on a bracket to make it open.  This geometry also means that the stronger pull needed to start closing the window is compensated by pulling on the middle of the diagonal providing extra leverage.