No Perseids but a nice consolation prize

Super image once again Anthony, you relly know how to turn them out!

Thanks Seanie!

How is the image so clear of light pollution though? When I tried my own star trais photo with Orion here , from what I thought was a good dark site for a 30 minute exposure put an orange wash over the image!

Two comments here ...

(1) I took this image from a mountain location with a limiting magnitude of at least 6.5. There is indeed a light gradient at the bottom of my image but it is nothing relative to real light pollution. The skies at this particular location are so good (dark) that even the slightest amount of light will appear disproportionately great.

(2) I used 6-min exposures on purpose so that the impact of light pollution, however small or great, is minimized. By using such an approach, the brightest six-minute exposure of the set effectively determines the brightness of the final photo.

If I am not being crystal clear with any of the above, please let me know!

Anthony.

No, you are perfectly clear. I guess that withmy old format of film photography, it just won't allow for a quality picture like that unless I have the extra money to be able to take different filtered exposures or multiple shots, and stacked the images or negatives...


...oh well...

I guess that withmy old format of film photography, it just won't allow for a quality picture like that unless I have the extra money to be able to take different filtered exposures or multiple shots, and stacked the images or negatives...

Seanie,

I am sure it is not as lost a cause as you may think. For example, take a roll of 36-exposures ... a six-hr total exposure is equivalent 360 minutes or 10 minutes per exposure for your 36-roll.

The trick is to minimize the impact of (any) light pollution by having a "short" exposure. With ten minutes per exposure, we do indeed minimize the impact of light pollution. Simply ask the lab to scan the roll onto CD rather than request for prints.

Since the tripod and camera are fixed during this six-hr exposure, there is no need to align etc. Simply stack one exposure on top of the other and use "Lighten" for the blending mode when layering the successive exposures. Since effectively the only difference between any two successive exposures is the extended star trail from one exposure to the other, you are literally capturing the incremental growth of the star trails while keeping the foreground light polution at the same level.

By using one single long exposure, yes, you are capturing the growing star trails with the passage of the six hours but you are also allowing the light pollution to simultaneously build up as well. Not so with the scenario above where light pollution has ten minutes to accumulate and no more.

Anthony.

Nicely explained Anthony, now I know where my old film shots went wrong. But, I didn't know anything about stacking then or even thought about it, I was just at the very early stages of astronomy interest.
Bill.

Hi Bill,

One of the really nice things about astrophotography is that it is a constant and incessant learning process no matter how little or much we know.

Anthony.

True, that is a good way to get a long exposure done Anthony, albeit not 'on film', but the technique using a film camera when a digital slr is not available, is a good one. Thanks for that tip Anthony!