28 july 2025

July has been a very poor observing month.  The whole summer has been unusually cool, with the marine layer blowing in each evening.  Good for comfort, bad for backyard astronomy.  This night was clear, but with poor transparency and average seeing.  Nonetheless there were two observations I needed to make, in response to posts I had seen on CN.

HU 575 AB: 508, 564x: A short period pair I've been following in my movement pair list.  This night it was suspected double at lower power but easily split with higher powers.  Unequal light orange stars.  When I compare this sketch to one made in May 2020, I notice considerable change in the PA, and that I needed far less magnification to split it (0.336" PA 71.4 in 2020, and 0.482" 25.4 in 2025).  

Next was the Cygnus Egg, RAFGL 2688, which someone raved how night vision had transformed the view.  Using my 20-inch, I observed it visually and with NV.  

Visually, the nebula appears like two small, faint elongated elliptical galaxies end to end with a small gap between, with the points nearest each other a little brighter.  The "wings" were narrow lines and faded at the opposing ends.  I needed 282x to darken the background sky for the "best view."  Adding a single polarizer, and spinning the eyepiece, helped marginally to bring out more glow.

Using the PVS-14 afocally with the 67mm Plossl+ (38x) and a 685 longpass filter did have a dramatic effect.  It was now a high surface brightness object and appeared like two comets with fan-shaped tails facing each other.  The brighter one appeared slightly larger and seemed to have a star at its inside tip; the other was fainter, with a shorter tail, its inside tip was brighter.  I did not notice any detail; the image scale was small.  I had a similar view unfiltered, but the background sky was brighter, and I preferred the filtered view.

I then used the PVS-14 in prime focus mode -- having removed the 1x objective and using threaded adapters to a 2-inch nosepiece and adding a 2x barlow to reach focus (195x).  Still with the 685 longpass, I had a similar view as afocal but at much larger image scale.  This time, I could see subtle, turbulent dark mottling inside both "wings," but I did not see it as a distinct "X" shape or as concentric rippling (as in the Hubble photos).  I did, however, have the sense of a extremely faint roundish, puffy cloud of nebula, some 3x the diameter of the wings and surrounding them -- but this could have just been background nebulous atmosphere.  Maybe this would show better at a dark site.