gaseous
12-05-2017, 02:24 PM
Last Friday saw the delivery of my new binoviewers from Telescopes & Astronomy in SA, and as is usual, the clouds/rain decided to roll in. Needless to say there was a week of high dudgeon as I waited for this insolent weather to cease and desist, so I didn't get to bust them out for their maiden voyage until last night. They're a pretty standard OEM binoviewer which come with some fairly rudimentary looking 30mm eyepieces, and two 1.25" barlows: 1.85x and 3x.
They appear well made, and adjust smoothly, with a twistable eyepiece locking mechanism and adjustable focuser for each each. The moon last night was 100% full, so I was mainly interested to check out Jupiter, the Moon, and maybe a few other objects to get a feel for them.
Firstly, the small barlows are essential to reach focus in an 8" dob. No chance otherwise. I honed in on Jupiter with the 30mm ep's and the 1.85x barlow, and was pleasantly surprised - the view was very sharp and showed nice banding on the planet even at a fairly low power 74x mag. I then popped in the 3x barlow for 120x mag and the views were still very good. For a comparison, I swapped over to an ES 11mm 82° eyepiece for a monocular view at about 109x, and the binoviewers didn't appear to lose much, if anything, over the single "quality" eyepiece. Seeing wasn't great, but there were sufficient moments of calm to appreciate that there wasn't an appreciable difference between them. I then popped the BV with the 3x barlow into the back of my 2" 2x barlow for 240x mag, and while the upper air turbulence was obviously more pronounced, the views were still great and better than I'd expected with what appear to be some very low-tech eyepieces. There is a lot of talk about BV's reducing the amount of light coming through, and while this is true it didn't appear particularly noticeable on Jupiter, and probably even helped bring out some of the detail given it's natural brightness.
I then focused on the Jewel Box cluster NGC4755. I wasn't anticipating spectacular viewing (given the previous comment about light reduction), but overall the views weren't too bad. The stars probably weren't as crisp as you'd expect from single-eyepiece observing, but that may come down to inexperience on my part - the BV's have individually adjustable focussing for each eye, so coupling that with getting the correct IPD is a bit of an art I'll need to master. The bv adjusts very smoothly, so altering the IPD can sometimes alter the focus of each eye, and vice versa. Again, there wasn't a lot of difference in the light coming through compared to a single EP, although the background was considerably darker.
Not expecting much joy, given the natural light pollution coupled with a full moon (my admittedly dodgy SQM app gave a reading of 18.08) and the fact that nebulae aren't really the standard target for BV's, I swung over to Eta Carina with a DGM NPB filter. I must say I was quite surprised at the level of detail achievable, and when I popped in a single eyepiece for a comparison, again the alleged light loss through the BV wasn't as extreme as I anticipated. I tried a pair of standard 25mm plossls (the type you get with a new scope), and they were quite loose in the BV due to the recess in the barrel - I'm hoping it's for this reason that there was absolutely breathtaking coma across 90% of the FOV. Back with the budget 30mm ep's and all was well again. I could reasonably expect that under a dark sky, the BV's on brighter nebulae may be quite enjoyable despite the relatively high magnification.
Last target was the moon. I wouldn't say the effect was "3D", but it was certainly interesting and more immersive than single ep observing. With the moon being so bright and taking up so much of the view, it highlighted the need for getting the correct interpupillary distance as close as possible otherwise there are minor "blackouts" (I'm sure there's a technical term for this). I think the moon at quarter phase will be quite stunning.
Overall, I was very pleased with these low-range bv's, given the conditions and the eyepieces I was working with. The reported light loss was considerably less than I was expecting, and although noticeable, it was certainly not overly detrimental to viewing even targets not normally associated with BV's. I'll need to spend some time getting them properly adjusted for my eyes, as this was a fiddly process, but overall I think I'll be getting a lot of enjoyment from them. As a final note, I would say that the ease/comfort of using two eyes cannot be overstated, particularly if you're observing for extended periods of time.
They appear well made, and adjust smoothly, with a twistable eyepiece locking mechanism and adjustable focuser for each each. The moon last night was 100% full, so I was mainly interested to check out Jupiter, the Moon, and maybe a few other objects to get a feel for them.
Firstly, the small barlows are essential to reach focus in an 8" dob. No chance otherwise. I honed in on Jupiter with the 30mm ep's and the 1.85x barlow, and was pleasantly surprised - the view was very sharp and showed nice banding on the planet even at a fairly low power 74x mag. I then popped in the 3x barlow for 120x mag and the views were still very good. For a comparison, I swapped over to an ES 11mm 82° eyepiece for a monocular view at about 109x, and the binoviewers didn't appear to lose much, if anything, over the single "quality" eyepiece. Seeing wasn't great, but there were sufficient moments of calm to appreciate that there wasn't an appreciable difference between them. I then popped the BV with the 3x barlow into the back of my 2" 2x barlow for 240x mag, and while the upper air turbulence was obviously more pronounced, the views were still great and better than I'd expected with what appear to be some very low-tech eyepieces. There is a lot of talk about BV's reducing the amount of light coming through, and while this is true it didn't appear particularly noticeable on Jupiter, and probably even helped bring out some of the detail given it's natural brightness.
I then focused on the Jewel Box cluster NGC4755. I wasn't anticipating spectacular viewing (given the previous comment about light reduction), but overall the views weren't too bad. The stars probably weren't as crisp as you'd expect from single-eyepiece observing, but that may come down to inexperience on my part - the BV's have individually adjustable focussing for each eye, so coupling that with getting the correct IPD is a bit of an art I'll need to master. The bv adjusts very smoothly, so altering the IPD can sometimes alter the focus of each eye, and vice versa. Again, there wasn't a lot of difference in the light coming through compared to a single EP, although the background was considerably darker.
Not expecting much joy, given the natural light pollution coupled with a full moon (my admittedly dodgy SQM app gave a reading of 18.08) and the fact that nebulae aren't really the standard target for BV's, I swung over to Eta Carina with a DGM NPB filter. I must say I was quite surprised at the level of detail achievable, and when I popped in a single eyepiece for a comparison, again the alleged light loss through the BV wasn't as extreme as I anticipated. I tried a pair of standard 25mm plossls (the type you get with a new scope), and they were quite loose in the BV due to the recess in the barrel - I'm hoping it's for this reason that there was absolutely breathtaking coma across 90% of the FOV. Back with the budget 30mm ep's and all was well again. I could reasonably expect that under a dark sky, the BV's on brighter nebulae may be quite enjoyable despite the relatively high magnification.
Last target was the moon. I wouldn't say the effect was "3D", but it was certainly interesting and more immersive than single ep observing. With the moon being so bright and taking up so much of the view, it highlighted the need for getting the correct interpupillary distance as close as possible otherwise there are minor "blackouts" (I'm sure there's a technical term for this). I think the moon at quarter phase will be quite stunning.
Overall, I was very pleased with these low-range bv's, given the conditions and the eyepieces I was working with. The reported light loss was considerably less than I was expecting, and although noticeable, it was certainly not overly detrimental to viewing even targets not normally associated with BV's. I'll need to spend some time getting them properly adjusted for my eyes, as this was a fiddly process, but overall I think I'll be getting a lot of enjoyment from them. As a final note, I would say that the ease/comfort of using two eyes cannot be overstated, particularly if you're observing for extended periods of time.