|
Forum: Pentax Camera and Field Accessories
10-04-2015, 11:25 AM
|
| |
my recommendation is to use it with lenses 50mm or longer. Disregard the 5 minute maximum -- I find two minutes (or less) is more like it, especially true with longer lenses. As such, you need to get behind the idea that this technology "fills the gap" between what you can do with super-wide-angle lenses + high ISO and what you can do with dedicated motorized tracking. The sweet spot seems to be between 50-200mm.
Michael
|
|
Forum: Pentax Camera and Field Accessories
03-16-2014, 11:04 AM
|
| |
well the key thing is "near" -- I wasn't directly pointing to Polaris, probably off by 5 degrees or so. With the 400mm I would have expected a "little" drop in max time as reported by Astrotracer. Apparently not. The key thing is to see if others can corroborate these findings then the next step would be to see if the suggested times for all lenses actually have a basis in reality.
Michael
|
|
Forum: Pentax Camera and Field Accessories
03-16-2014, 09:30 AM
|
| |
So for kicks I wanted to get a glimpse into the algorithms behind the "Maximum Recommended Exposure Times" that Astrotracer is suggesting. I used a tripod set up to rotate around the horizon and oriented the stop points at approximately true north/east/south/west. Then repeated the results with the camera angled 45° from the horizon at each norht/east/south/west stop point. As I am near Boston MA my latitude is approx 42.0° N Here are my results.
NOTE: It would be great if others could replicate this to verify my observations.
For recording the data for different focal lengths (and given that I didn't own all the lenses I wanted to document), I simply used a generic manual lens attached to the body and each time I turned on the camera I specified a different focal length. i.e. I started with 50mm, then doubled that to 100mm, then 200mm, and finally 400mm. It is interesting to note that no matter WHERE I pointed the 50mm in the sky, the recommended max exposure time was a consistent 5'00". It is also interesting to observe that even fairly long lenses pointed near the North Celetial Pole still allowed long exposure times -- something that has been suggested elsewhere on this forum.
Michael
|
