Jan 312013
 

I recently bought a new 130mm f/7 APO Refractor and have already posted one or two images from this new bit of kit. However, one of the reasons I wanted it was because it comes with a nice focal-reducer/field-flattener that brings the f-ratio down to about f/5. This gives a slightly wider field of view and is optically ‘faster’. In fact it is nearly twice as fast because the speed is related to the squares of the f-numbers being considered. So (7×7) / (5×5) = 49/25 = 1.96.

I’ve had the kit since November 2012, but, I was unable to achieve focus with the reducer in place! To cut a long story short, the reducer went back and it was discovered that the lenses had been assembled wrongly!

Anyway, here is my ‘First-light’ image of the Horse-Head Nebula in Orion. It is an H-alpha image (because the Moon was about) and consists of 11 exposures each of 20 minutes.

 

 Posted by at 4:55 pm

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