25.07.2021 Resolution with bells on!

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Sunday 25th 65F, heavy overcast, gales and at least two days of rain forecast. Possible thunderstorms with cloudbursts.

Yesterday's late afternoon seeing improvements never happened. I was wasting my time watching clouds racing across a mushy sun. 

So I pointed the telescopes at a chimney 260 yards away instead. The ASI174MM mono camera went into a  T-S 1.25" diagonal in the Vixen 90mm f/11. Replacing the Lunt 1.25" solar wedge. I then captured my usual 500 frames and processed them through AS!3. 

Certainly an improvement on the detail visible on the monitor. There some slight wind movement of the telescopes and a light thermal agitation after a warm 78F day with sunny periods. ImPPG didn't seem to work on this subject matter. Instant graininess! 

Then I pulled all the H-alpha filtration off the 6" f/10 iStar H-a. A 2" no-name, dielectric, star diagonal held the same camera via the usual eyepiece adapter.

An instant upgrade in resolution and detail! If the Vixen had surprised with its remarkable clarity the bigger iStar totally eclipsed it. The image was much larger too.

How about the crosses in a pair of 8mm diameter, cross-head screws on the chimney flashing? These were clearly visible at that distance. 

I stared at what looked like a five legged Daddy-long-legs spread-eagled on the chimney. Or perhaps a spider? The texture of the sand in the cement pointing between the bricks was clearly visible. AS!3 made everything even crisper. 

The telescope images above have been borrowed from Google Photos "reduced quality." The originals are on the laptop. I ought to do a comparison with those on the high-res. monitor. Comparisons are far from odious if something can be learned from them.

It was an interest exercise to play with all the usual "astro" features. Like the DIY electric focuser and drives on a terrestrial subject. The focuser movement was far too fast and had to be dialled right down. What does that say about focusing on the sun? 

Presumably it is a matter of seeing conditions. In perfect seeing I would need a slower focuser movement. How the imaging software reacted was interesting too. SharpCap had options like frame size, Gain and exposure. I habitually capture in 8 bit AVI. I should be using 16 bit SER! The difference is noticeable on a chimney. 

In fact I felt I learned more in a few minutes using that chimney as a target. Than in all the time I had been solar imaging. Part of the problem with the sun is judging the scale. A typically small segment remains of unknown extent. I usually capture and process using much enlarged boxes on the 27" monitor screen. The final result is inevitably much smaller and sharper. The enlarged solar image is also subject to thermal movement, going in and out of focus and softening by the seeing conditions. The chimney was relatively untouched by these familiar problems.

This image is taken this morning from about ten yards away. Using my Lumix G9 and Leica 50-200mm lens. I have flipped the image horizontally, resized from 5k pixels down to 1k and converted it to B&W. The "spider" is a star-shaped crack in the brick. Dark plant material [liken?] has filled the crack. Making it appear more visible. Finer cracks extend to the corners of the brick.


Last night: Eventually I was called in for dinner but the light was going anyway. I quickly lifted the first shutter rib into place on the dome. Thankfully it was much too long. Rather than painfully too short. The GRP shutter covers have shrunk from being lifted up to the new radius. [Pi D] Though the length should still be fine.

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