It's so tempting to find new objects every night that I am with the scope, but after changes are made, I prefer shooting objects that I have done already, so I know if I have indeed improved anything. So, sorry if M51 is getting a little worn out here. If you don't like it, get your own scope. Better yet, get a scope whether you like this or not!
With the great seeing the last few nights, I thought it would be a good test of the changes i have made to the scope itself, rather than the mount. All of the screws and such used to line up all the mirrors were replaced with much larger hardware, with finer adjustments control, and the difference was staggering.
This alignment (called collimation) has some effect on the shape of stars and focus away from the center of the field, but it actually has an even bigger impact on contrast. That is why the last two nights, I've been picking objects visually that I never have gotten the faintest glimpse of from here.
And yes, it turns out it does have a large impact on the photos, too. This is only about 70 minutes worth of subs, far less than I would really want for a quality photo. In fact, it's very noisy and grainy in the fainter parts of the galaxy-that is strictly a sign that more photons need to be rounded up; you might remember how my pics of M81 took a huge leap forward in quality once I was stacking several hours of data, not tens of minutes. There's no point combining this with any earlier M51 sets, so I'll just use this as a new base to build on. Compare this to this picture, which was previously my best M51 shot.
I had a college astronomy prof who had worked on the Palomar All Sky Survey. He would show slides in class and whine and moan about the colors-his view was that the best way to find the proper color balance is to look at the colors of stars in the field, then match that. He would complain that pictures that purported to be a visual image should match reality, not just take advantage of whatever the more sensitive films showed. Hard to argue with that view, but it is not the standard way faint objects are photographed. (All that lovely bright red in so many pictures is simply wrong, for example; it should be lavender. That started with the Palomar survey; the filters they used in the RGB composites failed to allow a large part of the blue spectrum to pass into any of the images.) It's another matter when the purpose of the photograph is to show wavelengths we cannot see; those are called false-color photographs so that it's well-understood what you are seeing. Go Google some Spitzer Space Telescope pictures to see what false-color photography can uncover. If you've seen many images from that survey, you'd see that his opinion did not win out.
Anyway, getting long here-I have reached a milestone where my raw data is getting good enough that not only do my stars actually have color, I can use that as a reference in post-processing. See kids; sometimes you learn something in school that you end up caring about eventually!
I've also determined what had re-introduced the periodic bobble I mentioned earlier. Rather than rely on the fix I used last time, I'm waiting for my brain to stumble upon something a bit cleverer that will allow finer adjustment of gear angles and lash in the RA drive. I tend to get those ideas when I'm trying to think of something else, so I may spend the next few nights trying to clean the garage or something.
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