Sunday night on Mount BaldyNovember 3, 2015
Sunday night I went up Mount Baldy for a solo session. I was rolling with the C80ED, which has become my default grab-n-go rig.
One of my goals was to test a couple of new eyepieces. Several astro retailers had a big sale on Meade wide-angle eyepieces last month. I was torn between the 20mm and the 5mm Series 5000 Mega-Wide 100-degree EPs (man, is that a mouthful or what?). The 20mm would have been a great low-power, widefield scanner, which is something I’ve gotten progressively more interested in this fall. But for a long time I had been without an EP shorter than my 6mm Expanse, which is not without its problems, so I sprung for the 5mm instead.
In the meantime, thanks to this thread on Cloudy Nights I had become aware of the VITE eyepieces. These odd little birds come in only 3 focal lengths (at least so far): 23mm, 10mm, and 4mm. They are three-element EPs with one aspheric plastic element and plastic bodies. They’re about $17 apiece on Amazon, or $9 apiece on eBay. I ventured my nine bucks and got the 4mm from eBay, thinking it would make an interesting comparison with the 5mm Meade 100-degree. I had done a quick comparo late Saturday night from my driveway on the moon and the Orion Nebula – more about that in a bit.
Sunday evening on mount Baldy I cruised through the highlights in Lyra, Cygnus, and Sagitta. I did a quick, rough sketch in my notebook of the open cluster NGC 6823. It has a curl of stars wrapping up around it like a fiddlehead fern.
After that a couple of high school kids and their little brother drove up nearby, and I spent about an hour showing them around the sky – the Dumbbell Nebula (M27), the Double Cluster, Pleiades, Andromeda galaxy, Polaris, M15, 61 Cygni (aka Piazzi’s Flying Star), and finally the Messier open clusters in Auriga – M37, M36, and M38.
The kids left about 10:30. Since I was in the area I had a look at M1, and then cruised down to Orion. The constellation was slowly crawling over the ridgeline to the east, so I started visiting the bright stars, and in some cases splitting them. First up was Meissa, which was elongated at 68x and cleanly split at 120x in the 5mm MWA and 150x in the 4mm VITE.
Mintaka was an easy wide split at only 25x. Seeing was not good, but Eta Orionis appeared to be elongated east-west at 120x and 150x. The view in the VITE was kind of a mess, so I spent a few minutes just cruising around Orion’s belt and sword with the 5mm MWA. Alnitak and its dim companion were widely split. I turned south to Sigma Orionis. I’ll have to check my notes, but I don’t believe I’d ever split this star before. It’s pretty great, with a group of three fairly bright stars and a second group of three much dimmer ones. I backed down to 68x and all six stars were still nicely split, and frankly looked a bit sharper, although that might have been down to bad seeing.
So, here are my thoughts and observations on the 6mm Expanse, 5mm MWA, and 4mm VITE. These don’t count as an actual review, as I didn’t have equivalent focal lengths to compare, and I’ve only spent a couple of nights with the two newer eyepieces, observing only a handful of objects. Still, I tried them on a variety of things – the moon, globular and open clusters, the Orion Nebula, double stars – and the strengths and weaknesses were consistent. All of these observations are with the C80ED, so the chromatic aberration (CA) with certain EPs is particularly interesting.
6mm Expanse – Has a small but noticeable amount of CA on bright stars. Eye placement is a bit tricky – I get some kidney-bean and full-aperture blackouts until I get my eye placed just so. Comfortable enough once I get my eye in the zone, though. Halos on some bright objects.
5mm MWA – Sharp from edge to edge. No detectable CA, but the edge of the field does look blue until I get my eye centered. No detectable field curvature. Eye relief is pretty tight – when I move in close enough to see the entire field, my eyelashes brush the lens about half the time (I do have long lashes, but still). I have to move my head around to focus on objects in different parts of the field. Very immersive – I feel like I could climb through the eye lens and into space. The rubber eyecup is annoyingly loose – it frequently comes off with the dust cap.
4mm VITE – Can’t focus the whole field at once. Center of the field is sharp enough, but objects start getting blurry halfway to the edge of the field and are entirely defocused at the edges. ‘Sweet spot’ is pretty small. Considerable CA – makes an ED refractor perform like a short fast achromat! Strong internal reflections from bright objects on the edge of the field, or just out of the field. Almost impossible to focus on the lunar terminator if it’s centered – a big bright glow from the lit side of the moon fills the center of the field. Eye relief is tight – eyelashes scrape most of the time.
Verdict – The 5mm MWA is a keeper. The eye relief is short but tolerable, and totally worth it for the huge, flat, well-corrected field. As for the VITE, I’m glad I didn’t spend more than $9. I’ve read that these perform better in longer focal ratio instruments, but at f/7.5, the C80ED isn’t exactly fast. So how long does the light cone have to be for the VITE to perform well – f/10? f/15? At those focal ratios, it would take an exceptionally still night for a 4mm EP to be useful. I will try the thing in my Mak and probably in my C102 but I am not expecting much. People on CN seem pretty happy with the 23mm, so maybe there’s some variation within the line.
Back to the observing report. By midnight I was tired and my feet were cold. I had just resolved to pack up and head home when I saw that the hillside behind me was lit up by moonlight. The moon was coming up behind the ridgeline to the east. It had been a long time since I’d had a chance to shoot the moon rising behind trees, so I quickly set up the camera adapter and got to work. My best still shot is at the top of this post. And here’s a video:
I went for the sideways aspect ratio this time, but I didn’t quite get the camera square on to the view. Guess I’ll just have to try again next month.