Ha scans with Sol'Ex- 28 July 2023

[NM_mike]

Finally the monsoon season has set in and a pattern change with the weather. Mornings are often still very good for a quick set of scans.

This morning I switched out the USB cord for a "premium" cable and found that I could run the 178MM much faster. Perhaps this was the issue- sometimes these things seem to calm down only to show up again later. I set a new record with the Atlas Az/EQ pro mount- 20X scans. Out of 60 I tossed 8 and I think it was more related to camera glitches based on the hardware discussion in Doug's recent thread.

With SolEx I find that to achieve best focus across the whole disc involves a tradeoff. In this image there is noticeable blurring at the poles. This morning I didn't spend that much time optimizing focus.

Quite a bit of activity before the M4 flare ~ 1700UTC.

10 RA scans @ 20X sidereal, Atlas Pro Az/Eq
AT72EDII / ( 2" Baader ND 0.9 / Astronomik ir/uv type 1) / SolEx /ASI178MM
exp 1.9ms /Gain 135 / ~375fps
theSmiths v. 4.0/ ImPPG/Gimp

[thesmiths]

That's a really good result. I'm still puzzled by the fuzziness at the bottom, though. I really suspect there is a tilt somewhere. Maybe at the telescope focuser? If everything were square, then the top and bottom should be equally out of focus if the centre is in focus (due to normal field curvature issues).

[marktownley]

Excellent result!

[Montana]

This is a remarkable image it is only the south pole that suffers, what happens if you turn the camera upside down?

Alexandra

[rsfoto]

Very good

[highfnum]

lovely

[thesmiths]

With SolEx I find that to achieve best focus across the whole disc involves a trade-off. In this image there is noticeable blurring at the poles.

I realised recently that it is difficult to differentiate between tilt in the internal optical components and an off-centre slit. For the Solex, the collimating lens is so short (80mm focal length, 25mm diameter -- f/3.2 !) that you have a limited image circle. So the slit really needs to be quite precisely centred (also since the slit length is quite short, you don't have room to move around to find the optical centre of the lens).

[NM_mike]

Douglas and Alexandra's replies started a few ideas over the past few days... I have had SolEx apart and back together. I have also tried several different configurations with similar results- blurring at the image bottom. I think I have improved things slightly. I had shimmed the grating wheel earlier. ( Christian does this in the assembly video and I needed a shim in the same spot) I reduced the number of foil shims and it seems that the blurring is somewhat reduced.

Here is this morning's scan under decent conditions.

9 scans @ 20X sidereal, RA /Atlas Pro Az/Eq
AT72EDII / ( 2" Baader ND 0.9 / Astronomik ir/uv type 1) / SolEx /ASI178MM
exp 1.9ms /Gain 135 / ~425fps
theSmiths v. 4.0/ ImPPG/Gimp

[thesmiths]

I had shimmed the grating wheel earlier. I reduced the number of foil shims and it seems that the blurring is somewhat reduced.

Following up on my previous post, if things improved by reducing the grating tilt, it likely means the slit is positioned too high or too low. Try taking out all the shims and centre the slit on the camera sensor by moving the slit up and down rather than tilting the grating.