12mm BST Starguider for binoviewing? + eyepiece diameter request.

[Davesellars]

I have the OVL //Skywatcher style binoviewers and have been getting on really well with the 18mm BCOs and using a 2x barlow element on the BV nose (gives me effectively 3x) and therefore 119x with the 102ED.   This is a great combination and produced outstanding results so far on Jupiter!

I'd like a bit more magnification particularly for lunar observation as well as Saturn and Jupiter to get to around 170-180x.   So I've been looking at a few options already including 12.5mm orthos however, the BST Starguiders seem to get really good reviews with 60 degrees and proper eyecups would likely to be more comfortable for longer sessions.  Does anyone have experience with these in BVs?

Also, could someone check the diameter at the widest point of the eyepiece?  Just to ensure that two EPs are going to fit OK.  I have an IPD of 63mm.

Many thanks in advance!

Edited August 29, 2022 by Davesellars

[Louis D]

You could try a quick experiment with your existing gear.  Try the Barlow element on the front of the diagonal in the frac, assuming it's a 1.25".  That would add at least 60mm of extension, so your magnification might go up to between 4.5x and 5x.  That would boost you to somewhere around 180x with the 18mm BCOs.

I would get a pair of lower cost zooms so you can dial in your maximum magnification based on the seeing conditions.  At 3x and f/21, they'd perform excellently.

[Davesellars]

Thanks for the reply, however the BV nose won't fit directly in my 1.25" diagonal as the nose is very slightly oversized.  I currently fit it into a TV 2" to 1.25" adapter and then into a 2" diagonal with a Celestron Omni 2x barlow element fixed on the the BV nose (thus giving 3x).  This is really secure as well and so I don't really want to change this arrangement.

I'm not really interested in zooms - half decent ones would be around £150 each.  Basically, I've got it down to either the 12.5mm orthos or the 12mm BST Starguiders (the mount is untracked so perhaps the BST would be more suitable).  I needed to check what these are actually like for lunar observing and sharpness for planetary observation.

Edited August 29, 2022 by Davesellars

[Second Time Around]

Svbony 7-21mm zooms should work well at f/21 and cost only about £50 each.  They certainly punch above their weight.  They're also very slim and light so especially suitable for binoviewers.

[Ricochet]

I've got a pair of 25s, but the width of the 12 is the same. At the widest point, which is the rubber below the top coloured band, they measure 49mm. With an IPD of 63 that will leave you 14mm between eyepieces. At the widest point of the eyecup they are 47.5mm so a gap of 15.5mm. In comparison the 18mm BCOs are 35mm in diameter which gives you a 28mm gap. My IPD is about the same (not sure of the exact measurement) and I always found the Starguiders very comfortable to use. They are not quite as good optically as the BCOs but due to the increased comfort level I often found myself using the 25s with a 3x barlow over the 18s with a 2x. 

Lastly some comparison photos with the BV set to an IPD of 63mm. 

[Don Pensack]

My IPD is 63.5mm and I have no problem at all with these eyepieces in a binoviewer.

I've even used eyepieces 54mm and 58mm in a binoviewer with no issues.

The larger one had a very long eye relief so my nose was nowhere near.

But these?  No problem.

[Davesellars]

@Ricochet That's awesome for the complete information and photo!  many thanks.  & @Don Pensack - Many thanks too.  Good to know these will work OK.

 

@Second Time Around  Many thanks for zoom recommendation - It had me thinking and doing some research.  I'm not sure about the SVBony ones as reviews suggest they rather lose out in contrast which is of critical importance for planetary observation, however the OVL Hyperflex seems to be much better so I'm considering that as the price is not too bad at £89 each.  To be honest though as I've already got 119x covered with the 18mm BCOs I don't really need any other focal length until perhaps 15mm and below to perhaps max 10mm.  Still, could be useful to have that range from 10 - 16mm!

A concern with the zooms though would be getting them both at the same focal length setting with the binoviewer (since there's no click setting).

I think the Starguiders are still "leading".  The 12mm focal length also seems to have some good reviews and the comfort level is there (I don't wear glasses so I don't need massive eye relief) - I really like the idea of the 60 degree FOV over going for an ortho at 42 degrees I'll need to nudge much more constantly even if it may be a little sharper...

 

[Louis D]

36 minutes ago, Davesellars said:

A concern with the zooms though would be getting them both at the same focal length setting with the binoviewer (since there's no click setting).

I zoom the eyepieces simultaneously until the image size seems best.  I then fine tune one against the other until the images snap together at the same image scale.  It's really pretty easy to find that sweet spot because nothing quite matches up radially until then.

[Zermelo]

Someone asking very similar question here:

https://stargazerslounge.com/topic/393287-binoviewer-eyepiece-options-12-15mm-range

 

and if you do have trouble making room for the Starguiders, you can slim them down quite a bit by "decloaking":

https://stargazerslounge.com/topic/397380-decloaking-bst-starguiders

 

[Davesellars]

In the end I decided to go for the 12.5mm KK Fuyijama orthos.  These are purely for planetary / lunar observation so decided this was most likely the best for the job although rather more expensive.  After a bit of experimentation with sizing as well, the bridge of my nose rather interferes with anything larger (and not wanting to mess about de-cloaking).