Another ST80 session. I was set up by midnight, the ST80 reaches equilibrium incredibly quickly, but already the conditions were changing. It wasn’t cold but there was a dampness and humidity which wasn’t helping the transparency.



First target was M44, easy to find near the Gemini Twins and essentially a naked eye object. I had to catch it quickly before it got too low. I’d only taken four eyepieces (and three Barlows) out with me: BST 25mm StarGuider, 9mm Orion Expanse, 6.4mm Meade Plossl and a 6mm Vixen NPL. I spent some time in Gemini, Cancer and Cassiopeia. The transparency was not with me and getting worse. The overall seeing wasn’t bad though, it’s just that the water content in the air wasn’t allowing enough transparency. Jupiter should be really bright this near to opposition, but it was a little hazy.



I originally bought the StarGuider for my 102mm SkyMax but I’ve discovered that I can use it in the ST80 without an extension tube, which greatly simplifies things for me.



I’ve also discovered that its 60° FOV isn’t sharp completely to the edge of field and actually requires refocusing to see sharply. I’ve read about this but assumed it only applied to fast Newtonians. It probably won’t stop me using it though as I’m still probably getting over 55° FOV. I find the StarGuider ergonomically easy and pleasant to use with a relaxed eye position. I normally automatically take a 19mm TeleVue Panoptic out with the ST80, but the lower magnification of the BST gives me more TFOV, and I don’t have to keep jacking around with an extension tube. Even if I’m getting less actual well defined field, I’m still almost getting three and a half arc degrees (possibly slightly over) than the 19mm Panoptic’s just under three and a quarter arc degrees of truly sharp to the edge TFOV. ‘Swings and Roundabouts’ as we say in my country.



I decided not to wait for a rising Saturn (or Moon and Mars for that matter), primarily as my RACI had dewed over and I was getting tired. So I concentrated on Jupiter up to transit.



I tried for 150x with the 6mm Vixen and a Baader Q-Turret Barlow. I did discover that I could swap the #8/UHC1 stack for the Baader Fringe Killer, and then that stacked that with a Baader Neodymium. I even tried an #11 Yellow-Green. Jupiter just wasn’t bright enough for this though. There is a new and often repeated opinion that you can use any aggressive filter with the smallest of scopes, and all that rhetoric about not being able to use certain filters (often ultra high contrast) with scopes under 80mm is wrong. And you can use any filter with any scope at any time wearing any trousers. It’s not true though. The GSO AD058 #11 Yellow-Green Filter has a 78% transmission rate. It was too aggressive to use on Jupiter at transit for me last night. On a good night, due to location, I can get a sharp 167x on Jupiter with an ST80. This was not one of those nights. And I was wearing cargo trousers. I did get a quite sharp 111x with the 9mm Orion Expanse combined with a 2.5x Barlow though, and much sharper than the recent last session. So that was some consolation. Not a bad night really.