Trying to develop astrophotos is no easy task. The professionals all probably do it themselves with trays of chemicals, clothes pegs and
light bulbs covered in red tissue paper.

For those who have no access to a proper developer's studio, we are left with popping a 35mm film cartridge off to Boots. I usually take mine to Tesco's, in Binley, Coventry, since it's about fifteen minutes from my front door. I have, however, had experience with many different organizations, and they are, without exception, all the same.

The actual developing bit is all okay… A negative is a negative is a negative, pretty much. However, then comes the printing process, the bit that actually make the photographs, the part of the process that actually remotely useful to the end user.

These days, the printing is done inside a large grey box, and is controlled by computer. The hapless store assistant takes the strip of negatives and feeds them through one end of the machine. She then presses a large, round red button marked 'Go' and then wanders off to do a five minutes stint at the tobacconists kiosk.

The computer that controls the machine is a fantastic example of software engineering, and can cope infallibly with any film that is presented to it. When it receives an image, it first checks it and adjusts for brightness. It also checks to see whether it can see any actual image in the frame. If not, if the photographer has decided to stop at, say, frame 3, wind the film on inside the camera and continue at 17, the computer will simply discard the frame and not print anything. 

This process is all well and good, but poses several problems.

Trying to brighten a picture of the blackness of the infinite of space doesn't work to well. Space is black, and trying to brighten it simply leads to a reduction in image quality. To be fair, the loss isn't that much, but photos still look significantly less than exiting when they're with a grey background as opposed to pure, crisp noir.

The second problem is that stars are quite small. Not in actual terms; the sun for example is well over 1300000
km in diameter at its equator. However, if set to a distance of 4 ly, the distance
of Proxima Centauri, it will appear just 1 hundredth of an arc second across. This means that
stars only appear as small pinpricks of light. The resolution of the camera on the computer that decides whether there is an image underneath it is significantly lower than that of the actual film. This means that the computer does not see stars, or, if it does, interprets them as noise. This means that most frames are, therefore, discarded even though they are perfectly respectable images.

Long-exposure images (10 minutes, etc) of the night sky may be okay, because
there's enough in the frame for the computer to pick up. Exposure of 10 seconds
or less, which yield crisp star points, are hardly even picked up.

There are several ways around this. One is to incorporate a section of hill,
or hedge, or wall into the photo which will show up quite bright on the frame
and ensure that it will be printed. The other is for a photography company to
design control software that doesn't try and decide what constitutes a good shot
on the photographers behalf...