Testing out the barn door tracker

Looking to test the newly improved ‘barn door’ tracker to its limit, I dusted off my old Sigma 75-200mm/f3.8 with 2x tele-converter. But with a hefty 600mm 35mm equivalent focal length, I was prepared for the worst.

barn door tracker image of M13 Globular ClusterAfter less than a minute of polar alignment, and unable to frame the shot through the viewfinder (due to an awkward angle), I pointed the camera vaguely in the direction of the Great Globular Cluster in Hercules, and opened the shutter for a 30 second shot. Without a watch to count the seconds, I manually moved the dial round, counting the seconds off in my head.

Checking the screen, to my amazement, there it was! Not only had I centred the cluster first time, but there were virtually no trails. I know the shot is pathetic compared to most, but for a home-made, hand guided barn door tracker, cobbled together for under £10, I was blown away by the result.

Shown here is a single 30 second exposure (iso 2000) without the didymium filter, giving it much more colour than the final stacked image.

Details: Nikon D7000, Sigma 75-200mm/f3.8 (at 400mm with 2x converter). 5 minute exposure (10 x 30 seconds) at iso 3200 with didymium filter. Stacked with Deep Sky Stacker and tracked with barn door tracker.



The current solar maximum is on track to become the weakest in over 100 years. That is pretty disappointing news (and slightly worrisome!) if you’re a fan of auroras, solar flares and sunspots. But despite the low activity, I have put the bargain £12 sigma and 2x tele-converter to use with some solar shots. Here are a couple which make use of the ND filter and the £3 Hoya 80B filter. The lens and converter combo is surprisingly sharp when stopped down to f8.


I had to wait patiently for a few days to get this shot of a passenger jet transiting the sun. It’s always been a mini aim of mine as it really adds some scale and drama to the shot.


DetailsNikon D7000Sigma 75-200mm/f3.8 (at 400mm with 2x converter) with Hoya ND400 filter. 1/8000’s at iso 100.

sunspots suns limb