Eyepieces for binoviewers.

[Kronos831]

Hello, I am most likely buying a binoviewer for my 8” f/6 Skywatcher Dobsonian,I have most of the magnifications covered, however I don’t have any eyepieces pair for wide field observation. I was wondering, could my scope and binoviewers take two Vixen 40mm eyepieces successfully? (Of course with a Barlow to reach focus) .If not so, which paid can I use that won’t cost me more than 100€?

thanks

-Kronos

[Stu]

Bear in mind that a 40mm 1.25" eyepiece has no wider a field of view than a 32mm due to the field stop limitation. I have used 40mm ones in my binoviewer for Ha solar observing in order to get lower magnification when using a Barlow, but for normal observing I think the 32mm would be the better option.

I have used Celestron Omni Plossls to good effect and they are a very reasonable price.

[Geoff Lister]

I have several 10mm & 25mm EPs that came with my various Celestron/Skywatcher setups, and a pair of 25s and a x2 Barlow work well with most OTAs. The Maks have an extended focal range, and so the Barlow is optional. The helical focus adjustments on each EP act as effective verniers in conjunction with the OTA's main focus knob. 

I have also used a pair of cheap 7-21mm zooms. With care, these can be set to the same value, and the brain seems to be more forgiving of their imperfections, when both eyes are active.

At my advanced age, I have "floaters" in my eyes, and a binocular view seems to filter out their effects on non-pinpoint targets.

Geoff

 

[Kronos831]

Thanks for the information guys,but I read somewhere that

binoviewers have clear apertures at 20mm eyepieces and that higher focla lengths eyepices , will suffer from vintaging. Is that true? What is vintaging and how can it affect my views?

[Stu]

23 minutes ago, Kronos831 said:

Thanks for the information guys,but I read somewhere that

binoviewers have clear apertures at 20mm eyepieces and that higher focla lengths eyepices , will suffer from vintaging. Is that true? What is vintaging and how can it affect my views?

The clear apertures vary, normally around 21 to 23mm I think. The issue you describe is vignetting which is where the outer field is not fully illuminated ie it looks darker around the edges. This is not particularly noticeable in 32mm plossls, your eye is not particularly sensitive to it and also with binoviewers you tend to look on axis rather than pan your eyes around the field.

[Louis D]

6 hours ago, Kronos831 said:

Thanks for the information guys,but I read somewhere that

binoviewers have clear apertures at 20mm eyepieces and that higher focla lengths eyepices , will suffer from vintaging. Is that true? What is vintaging and how can it affect my views?

Yes, there will be some vignetting in the 32mm Plossls.  I've seen it in my Arcturus binoviewers.  25mm or 26mm Plossls also work well and avoid the vignetting issue.  Since I use a 2x Barlow nosepiece operating at 3x to reach focus in my f/6 Dob with the binoviewers, I actually prefer the cheap Svbony/Vite/noname 23mm 62 degree aspheric eyepieces available on ebay and elsewhere.  They provide pretty close to a max, unvignetted field in my binoviewers and have sufficient eye relief to use comfortably with eyeglasses once the rubber eyeguard is removed.  At f/18, they are fairly well corrected across most of the field.  They are also super light and tiny, making them easy to balance and to get a large nose between them.

Below, you can see them at f/6 in my AT72ED refractor.  There are a few other binoviewer max field options shown in the same image.