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This is a subject rarely discussed in AB although very often mentioned, especially in advices to newcomers. But before delving into the subject matter a bit of backstory. I finally managed to take the family to the long promised holiday in Greece, which, for one reason or another (read: pandemic and urgent family matters) has been postponed for few years now. The location was the bay of Navarino in what we call Morea (although in Greek it would be something different so apologies for that). A quick check revealed a pretty good Bortle scale for the camping site we were heading for, at around 4. Given that the last time I spent any amount of time under semi-pristine skies like these has been lost to memory this was a massive step-up in sky quality. On the flip side of the coin there was more than a fair chance that imaging would have been practically impossible because of tree/sun shade cover, noisy and nosy neighbors and viciously bright lights all over the place so I wasn't to pack even the lightest EQ mount and any bulky scope so I elected to go for the rarely used star tracker, the Fornax LightTrack II and a number of lens doing double duty (daylight/night-time). And while I was at it I also packed 4 cameras (DSLR/Mirrorless), 2 modded and 2 standard, just in case... Eventually I also packed the equatorial bar, all the counterweights, a large number of cables, a 12V battery, its charges, power-cables / extensions, a guide-scope with relevant guide-camera and attendant cables, a polar scope, a variety of adapters/plates and bolts/nuts (just in case) under the principle that that is better to carry everything than forgetting something critical. Yeah, right... And mission creep too. So everything was eventually packed in the car (barely) and kids and wife too we drove the odd 1,700 miles to the place. Which proved to be what I feared: the tent plot was under cover of an extensive sunshade with trees all around and rather packed too. Still, an off chance might be offered if the the beach was suitable. It turned out that the beach was "potentially" suitable if not for the massive floodlights at each entry/exit point. Still, the sky was indeed excellent with the full display of the MW tapering down on the sea. Or rather, it would if not for Pyros, the main local town at the other end of the bay which seen from the vantage point of the camping site was just due south. Fantastic... After few days spent acclimatizing to the local conditions I was ready to give it a go with either a wide-field lens or the 105mm. Took the bag with all the components (other than the tracking head) and it suddenly dawned on me that I forgot a key element: the bloody wedge was left at home! Murphy's Law strikes again. After few days digesting the sour feeling this crushing news left me with I made peace with it and decided to try a thing that I haven't done in a decade or more; non-tracking astro-photography. Which brings in how to calculate the maximum exposure for any camera/lens combo. I had worked out an excel spreadsheet to carry out the task and decided to stick to either the Canon 7Dii (modded) or the Nikon D610 (FF). In alll case I alaso made the "play safe" decision to keep the f/ratio at 4 and no less to contain aberrations with one of either the 35mm (24mm mistaken for a 50mm was left at home, again!) or the widefield workhorse, the Nikon 50mm f/1.8 "pancake". In the end I decided to go for the 50mm with the either the Canon or the Nikon. Inserting these numbers and the pixel size for both cameras yield the following results:  I also decided upfront to limit trailing error to a maximum of 2 pixels, which is probably a bit on the conservative side but better safe than sorry I said to myself. Given that the Canon is modded and the D610 isn't I played it safe and went for the Canon to try to pick up the major emission lines nebulae in the Southern sky as seen from Navarino, as well as giving me a bit more oomph factor in terms of image scale. I was going to image the MW from the Scutum to as far South as was safe to go considering the Pylos massive LP (and never mind the strobing lasers from the night-clubs) . So on the night I made to the outer edge of the beach and as far as I was able to avoid the security lights and started taking the 3 sets of un-tracked shots to cover the 0 to -40 Dec range (with some significant overlap). Note that I was pointing by dead reckoning base purely on the presumed locations of the main objects I wanted to cover and with a simple pan head to support the camera. All the shots were taken with the internal camera intervalometer set a taking a 2.5s shot every 3 seconds. In the end, with a number of mishaps on the way I manged roughly 270 shots. (around 50 for the lowest pane, around 100 for the second, middle pane and around 120 for the upper one. Then sea haze started rolling in and this brought the thing to a close. I still haven't got though to process the mosaic properly with the right projection (beware of upgrading to PI 1.8.9-2) so the following is the best I manged to coax for these shots.  The LP halo form Pylos is visible in the lower part of the frame (despite my best attempt to get rid of ). Also the banding and other artifacts are entirely due to my hasty processing and the issues with the method used in PI to stitch the shots together (then subsequently cropped and rotated). In the end the image goes from M11 (the Wild Duck Cluster) in the upper left end to M7 (the Ptolemy Cluster) to the lower right end and comprises a number of what are typically dubbed "eye candies" such as M8, and M20 as well M17 and M16 further up. M22 is the brightest GC in the image but others are also visible to the trained eye. |
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Hi Andrea, Very nice vacation with the family! Thanks for the enjoyable read and sharing you beautiful image! Jim |
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| This is why untracked rocks. |
