Twilight Venus

[josefk]

Well what a relief to be out again after what has felt like weeks of cloud. Totally rubbish sketches but hey oh. (In my defence i am waiting for some new glasses to be made up).

This is an observation in NE Northamptonshire in twilight (20:55 to something like 21:40 BST). I was set up quite a bit earlier but could not for the life of me find Venus in the bright blue sky on this occasion and failed on a single star align on the sun because it beat me into the tree line. TBF the sky was very pale, graduating from hazy white near the horizon to pale china blue higher up. When i have found Venus before in the daylight it has been against a clearer and truer blue sky.

Seeing wasn't great - there was the odd shimmy and 'jump' in the view. Really it it barely supported the x200 i was trying to use but x125 was too small to observe well and i don't have an in-between without faffing with a powermate which i wasn't in the mood for:

1st the 'real' sketch - nothing to see except a lovely phase and brighter poles (if they're not optical artefacts). I don't think the brighter poles are illusory as they stood out in several filters. The #82A light blue filter used here was superb. Extremely naturalistic in the blue sky.

This next card is not really a sketch - just an aide memoir. The right hand side view is why i bought a refractor (again)! Trying (bright) planetary again with the Cassegrain brought a satisfied smile to my face (honestly the ADC was visible in the refractor unfiltered but the horrible diffraction 'beams' and glare were not!). 🙂

The filters were not stacked BTW - but red and dark yellow behaved similarly to brighten the poles (red particularly) and dark blue and violet behaved similarly to shrink the apparent size of Venus and to a considerable degree. Neither dark blue nor violet revealed further variation in brightness. #82A was king this night.

[RobertI]

Lovely report, interesting results with the filters, I’ll give it a go. What is ADC btw?

[josefk]

Thanks at @RobertI Actually you've pulled my up on an an error of description there that i systematically make in my notes - ADC is Atmospheric Dispersion Corrector. What i really mean is the actual atmospheric dispersion itself (red and blue on Venus) which is the prismatic splitting of red and blue in our atmosphere.