Widefield Photos

Widefields

‘Widefield’ photography is hard to define precisely.  A good working definition is that you’re generally trying to capture stuff over a large part of the sky;  you might see planets or the moon, but you’re not aiming to get close in to them.

Some really nice shots can be obtained using really simple equipment.  The easiest way to get a nice effect is to put a camera on a tripod, using a ‘bulb’ setting to keep the exposure running for several minutes, and capture some pictures.

None of these photos involved a telescope (although some were taken with the camera screwed to the telescope mount, to avoid trailing),

Here the camera is pointed roughly at the Pole Star, and left open for a few minutes.

I didn’t record exactly how long, as I was on holiday in Crete with my partner and we’d just had a nice meal and a couple of bottles of local wine on the beach…

Polaris looks like a point star;  the other stars ‘trail’ round it as the earth turns.

This was a ‘grab’ shot I spotted as I was setting up the telescope.  People think of rainbows as being beautiful phenomenae;  they’re actually quite rare. There are lots of other, similar effects like sundogs, solar pillars, coronae…

A lunar corona (the sun creates them too) like this works on the same principles, except it’s ice crystals rather than raindops that refract the light.

Getting the Pleiades next to the moon in the same frame was a nice bonus.

Here is a single frame of the Hyades (the bright star is Aldeberan, the eye of the bull;  the ‘V’ shape to the right and back above represents the Bull’s head).

The original image was a little out of focus, I’ve tried to reduce it a bit but you can still see the stars are a little ‘fat’ and not perfectly round.

Here’s a really good example of the problem of, and partial solution to, light pollution.

This is a single 30s shot of the Seven Sisters. (Canon DSLR at about 200mm zoom and approx F5.6, ISO 1600.)

There’s a little bit of trailing, so I should have probably gone for shorter exposure.  But notice the horrible pink/brown background to everything.  With exposures of more than even a few seconds, this creeps into every frame.

Welcome to London astronomy 

Is all lost?  No – not quite.

This is the result of stacking 6 x 30s frames like the one above in Registax.  This increases the signal to noise ratio a bit;  with some judicious tweaking of levels, colour balance, and contrast in Photoshop we’ve lost the horrible haze and brought out lots of hidden detail.

I actually think this is the most aesthetically pleasing version of the shot.  However, I can’t tell the difference between the nebulosity in M45 and the background hazy cloud!

This is a further processed version of the same frame.  We’ve lost the cloud and we can see genuine nebulosity around the main stars in M45;  but as a photo I think it’s been pushed too far.

Here’s a point worth making:  decide what your ultimate goal is.  If you want to do accurate scientific work – say, measuring variable stars – you need to adopt a different approach than if youmainly intend to produce pleasing images.

This image comes closest to what I would expect the Pleiades to look like, with these frames, and I pushed the processing to get there. But as I say above, I actually think the previous is a much nicer picture.

There isn’t a “perfect” shot.  It’s easy to get carried away with clever software; sometimes it’s harder to just stop!