07-01-16 - M42, Horsey and Flame at 200mm focal length

[Jonk]

As we had really good skies last Thursday, I wanted to get set up and practice what I've spent the last month or so reading about.

I'm still playing with a modded Canon 1100D, Clip filter and 70-200mm lens in the back garden (so subject to local streetlights lighting up the air, but it's not too bad), but hope to be upgrading soon to ccd and apo.

I chose 3 targets to play with, M31, M42 and Comet Catalina.

Here's the result of about 1hr15mins (25 x 3mins) with 10 x 5 seconds for the M42 core.

There are problems I can see already.

1. Halos round the brightest stars, probably due to the lens not really being perfect for astro (hence the need to invest in a good apo!).

2. Banding, probably a result of me pushing the levels a bit high.

Anything else jump out to the experts?

All in all, I'm very pleased, as it definitely shows improvement.

Here's the Orion region result, others may follow once I process them.

[Uranium235]

Dont worry, its a good image. The halos are nothing to worry about either as you would still get those in an APO too. The banding can be easily dealt with by using Noels actions in Ps (vertical banding filter) - the actions are worth getting... cheap as chips and you will use them a lot (in fact, on every image!).

[Jonk]

Firstly thanks! It's probably my best attempt so far with the lens.

Why would the halos not be aligned with the stars, presumably something in the optical train is not perfectly square?

They appear to be on the left of the stars on the left of the image, and right of the stars on the other side.

The lens was stopped down to f4 from f2.8, and the image is cropped so I suppose I'm at the limit of what it can do.

I can't imagine any multi-lens system would be perfect, it wouldn't be 'manufacturable'.

[Uranium235]

If you think about it, the halos towards the edge of the field are slightly off axis becuase you are imaging through a curved surface (the lens) onto a flat surface (the chip). If you moved the bright star to the centre of the image, you would then find the halo to be on-axis.

[Jonk]

Hmmm...makes sense.

PS... I did think about it!

[laudropb]

Still a vert nice image.