I hope I've understood your question correctly, but here goes...

If you might print an image, then there could be a case for taking all your pictures at the best resolution the camera can produce.

This is a separate issue from the monitor resolution, which should also be set at the best quality you can. It is also true that CRT monitors will give better quality images than TFT screens. For Photoshop purposes, the colour of the CRT will also be far more accurate. And at a fraction of the price for a given quality level.

I am using a 19" IIyama CRT with a 0.22mm dot pitch and the computer is set at 32 bit colour and 1280 x 1024 resolution. This is the recommended best resolution for this monitor, although it can go to 1600 x 1200. Fortunately, what we see on the screen translates pretty well to what we get on the print.

The extension tube goes between the camera body and the lens - the more you extend the tube the closer you will be able to focus. You can focus and compose your picture through the viewfinder in the normal way. Exposure can also be relied upon.

As a rule of thumb for hyperfocal distance, focus one third of the distance into a scene. So, if you want everything sharp from foreground to background, don't focus on infinity and don't focus on the nearest point, but one third of the way in between. Using a small aperture this will work most of the time.

Centre weighted metering measures the whole screen area, but with the emphasis on the centre of the frame. In experienced hands, this is perfectly predictable and quite satisfactory. Large areas of sky will upset the readings and cause underexposure, but if this is understood compensation can be made.

Matrix metering measures many areas of the screen and the camera's algorithms decide what you are photographing and adjust exposure accordingly. In the example of sky, bright areas at the top of a picture may well be interpreted as sky and the camera could adjust exposure accordingly. The snag is that the photographer does not know what the camera is thinking so although suitable for less experienced users, I question the need for matrix metering in experienced hands.

Personally I use centre weighted and spot metering, very often with manual exposure mode as well.

It all depends what you are doing with the image files. If you are using the camera to e-mail images, make web sites or print small prints then you may not notice much difference. If you are printing A3 then you certainly will and will need all the quality you can get. There is a real difference here between using film and digital - with film you always have the highest resolution original, with digital you can decide the level of quality depending on the final use. However, I always use the highest quality settings as the final use might change if I like the picture. I can always reduce the quality later if needs be.

Are the drivers compatible with the operating system you are using?

I would avoid using a polariser on lenses wider than 24mm because of the uneven polarisation that you get with the large sweeps of sky - it can even cause bands of different coloured sky.

As you go wider still, the natural vignetting of an ultra wide causes darkening at the corners of the picture, which is very nice for accentuating skies without any further intervention. The 15mm is particularly useful for this effect. Sometimes, lens "defects" can be quite useful!

Particularly good is the SMC Pentax-A 35-70mm f4. It has a fairly simple construction (7 elements in 7 groups) which gives good contrast. It has a constant aperture of f4, handy for flash work and exposure calculations. It focuses continuously down to a 1:4 magnification, almost a macro lens. Definition is good at full aperture, becoming excellent as you stop down.

All in all, one of my favourite A series lenses, and ideal for the P30.

On an M42 fit lens the auto/manual switch is a different thing altogether - it relates to the automatic operation of the diaphragm on Spotmatic cameras, something that modern photographers will take totally for granted!

When set to auto, the lens will be at full aperture for viewing and focusing and will stop down automatically when the shutter release is depressed.

When set on manual, the lens will be at the working aperture all the time, the screen will be darker, but depth of field can be roughly judged. On cameras with no automatic diaphragm mechanism (no plate at the bottom of the mirror box to activate the mechanism) the manual setting can be used.

AS I recall, Super Takumar and later M42 lenses mostly have automatic diaphragms (there will be excpetions).

Lateral thinking: how about buying a low cost second hand manual camera body for the astronomical work? The MX, for example, allows the shutter to be locked open for as long as you like and without any battery expenditure. Electronic cameras use up power to keep the shutter open, and 8 hours on B is as much as you might expect from a new set. Any maual body can be equally well locked open with a locking cable release. If you are going to be taking large numbers of astronomical pictures this route might cost less than the toll of replacement batteries.