The plan was to view a rising twilight Jupiter with my ED72 Evostar, wait for Saturn to rise a bit as it got darker, then some rich field observing, and finally the rising Moon. I particularly wished to view the Petavius crater. This entailed starting off with an Omegon 1.25” Amici diagonal and a 5x Revelation (GSO) Barlow, then switching to a 2” Baader diagonal for larger rich field 2” eyepieces, finally swapping back to the Omegon for the Moon. The plan worked, more or less.
I set the Portal II/APP-TL130 to its maximum height as usual and slid the cute little ED72 into the dovetail. I couldn’t see Jupiter but the sky was a rich blue and I knew it would appear. Often just popping out as if by magic.
I was ready at 21:00 British Summer Time with an 18mm Astro Hutech orthoscopic and a Baader Neodymium filter. I’d rotated the diagonal/Barlow downwards so I could observe seated. Seeing seemed a decent Antoniadi II with slightly below average transparency. At around 21:40 I could see Jupiter with the naked eye and then at about 117x with the ortho’/Barlow combination. Equatorial detail was good and eventually I could see Io and Ganymede.
I switched to the Astro Essentials 17mm Plossl, first with the Baader Neodymium then a Baader Blue 470nm Bandpass. The Plossl gave me a bit more FOV than the AH ortho’ but displayed no vignetting at all.
Apart from the fact that the Abbe orthoscopic showed a tiny bit more contrast, there was very little difference between the two eyepieces. Definition, colour separation, brightness and overall clarity were easily comparable. I could discern no aberrations in the Plossl, although it was actually being used in a Barlow. Admittedly the build quality of the Astro Hutech is slightly superior, and it isn’t really a fair comparison, but I thought the Astro Essentials Plossl was well worth 20 quid.
I observed a rising Saturn for a bit with both eyepieces, now with a Lumicon #11 Yellow-Green filter. Again, there was little difference between them. I could see faint surface detail and the Cassini Division with both eyepieces. Before the rich field session I turned back to Jupiter (still with the #11) which was now past transit and rapidly heading for obscurity behind my house chimney. Callisto was now also easily visible. The best image of Jupiter that night just before it disappeared behind my house was with the Astro Essentials Plossl at 123.5x.
After the rich field session I turned to the rising Moon with two more eyepieces; a 15mm Vixen NPL and a 12.5mm Kokusai orthoscopic for 140x and 168x respectively. I was also now using a variable polarising filter. Naturally I started off with the 18mm AH rapidly followed by the 17mm AE Plossl. I was especially interested in observing the famous Rimae Petavius. Around a couple of days after a Full Moon the terminator highlights the rille really dramatically. I wasn’t disappointed and the Mare Crisium and its ‘wrinkle ridge’ were also quite spectacular. I raised the magnification to 140x then ended on 168x (60x x 2.8”). Due to the conditions though I’d say that the sharpest defined images were with the 18mm ortho’ and the 17mm Plossl.
Lunar map image by Moon Atlas