Further improving my astrophotography

Question

So, I've built a barn door tracker:

and I was astonished that pictures just got better:

That's Alcor and Mizar, and in the top right part, the fuzzy thing is the Pinwheel Galaxy (M101). It's a single exposure (30 s, +1.5 EV --> ISO 6400), shot with my Sony Alpha 6000 and a Varexon 135 mm f=2.8 lens.

Though I'm now able to reduce motion blur, the pictures still look... interesting. I made the pictures on a parking lot though, with some street lamps some 150 ft away.

And here are three exposures stacked (same 30 s, same ISO 6400), with a very interesting motion blur.

Are there any suggestions for my next steps? Is there a way to further improve the sharpness of the images? (I guess I have to weigh down the tripod a bit more, even when I'm careful not to shake the contraption.)

My other lenses are:

• Speedmaster 35 mm f=0.95 (truly great but gets blurry at the edges at wide apertures)
• Minolta 50 mm f=1.7
• Osawa MC 28 mm f=2.8
• a 500 mirror lens, f=8 (talk about dark images...)

Answer 1

Also to reduce blur further dont take images in the wind and use a remote shutter release preferably a wireless one and one other point is if you dont have mirror lock then get a black card place over the lens open the shutter and count to 5 slowly then take the card away. It compensates for the camera movement.

Answer 2

We can see that the shift between the exposures is only visible at the very left side and in the top right corner, while the rest seems to be ok. This might indicate that something with the alignment of the images before the stacking went wrong and that it probably is not motion blur:

With this setup of a barn door tracker you can probably improve the tracking within a single exposure but not across multiple exposures (such that the same star hits the very same pixel of your sensor in every exposure), so I assume there was a slight shift between the exposures. This means that the distortion due to the wide angle lens was slightly shifted across the exposures.

So my guess is that you did not do any (or not a good enough) correction of the lens distortion before stacking. This is especially important for wide angle lenses as their distortion (usually) varies more across the image.

This is just my guess from my (limited) experience, so maybe it is something else. But in any case, keep trying:)

Answer 3

The answer is find a way to a make a lot of money. No, it does not seem very helpful right now. But clearly I can see that one day you will look back on this and find that was really this best answer.

Your photos are fantastic for what you have made. The Earth is spinning. The sky is moving fast. The more you zoom in, the faster it is moving relative to the pixels of your sensor.

Your barndoor tracker is negating some of the motion of the stars. But the axis has to be aligned to the Earth's axis and has to move the camera at the same speed the stars are moving. Any error will leave some star motion.

There are two things you can do to get rid of blur. Your choices are better tracking or shorter exposures. (To a lesser extent a wider field of view will also hide the motion blur too.)

Shorter exposures mean less data, more noise. The goal is usually the longest exposures you can get. That leaves you with better tracking on a better mount. There are a lot of star trackers you can easily look up. But those lead to better photos which leads to bigger heaver telescopes which leads to german equatorial mounts which leads to... needing a bigger income!