After yesterday's success with a flat, I decided to go back out and try to make new flats for 0.55x FR (30 mm spacer) and 0.65x FR (15 mm spacer). Unfortunately things did not go well.
- At 0.55x and 0.65x, the flat has a very pronounced disk of light. When stacking with them, the outside gets too bright (a sort of reverse vignetting effect).
- I also noticed that the disk of light in the flat moves around as I move the flashlight. So the dispersion by the cloth is not as good as I thought and I should probably use some kind of flat panel covering the whole aperture instead.
- Also, with greater FR, the coma is quite noticeable as you look away from the center.
To make matters worse, tracking was not as good today (time to replace the anti-slip tape again maybe?) and it got breezy.
I briefly tried to stack M42 with low gain but still using the high gain flat and that produced a bad result. I should have created a flat at low gain.
Observations:
- M42 Great Orion Nebula, M43 de Mairan's Nebula and NGC 1975 Running Man Nebula
- NGC 2024 Flame Nebula and IC 434 Horsehead Nebula
- M45 Pleiades - Taurus
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| M42, M43 and NGC 1975 - 0.55x FR |
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| NGC 2024 and IC 434 - 0.55x FR |
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| M45 - 0.55x FR |
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| M42 and M43 - 0.65x FR |
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| M45 - 0.65x FR |
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| M42 and M43 - 0.75x FR |