A new eyepiece for Christmas

[Ratlet]

I'm wondering if any of the seasoned observers could help me pick an eyepiece focal length so I can fill in some of my magnification gaps with my 130 PDS (650mm focal length, F5 Newtonian) as I'm finding some of the skips in magnification a little unwieldy.

At the moment I've got an 8mm and a 32mm that use for not planetary observing.  I can Barlow the 8mm but find the 32mm a struggle if barlowed.  Also got a svbony 8-24 zoom, but that is only used for planetary as I find the FOV too narrow for other things.

This gives me x20, x80 and x160 power.  I'd like to fill in the gap with some with with a 60ish degree fov.  But I'm not sure what would give me the best utility.

12mm BST would give me x54 and x108 barlowed

Or I could go for something like a 25mm and get x26 and x52 barlowed.  I'm not sure on the best eyepiece if this is the best bet.

Not particularly sure what the most useful focal length would be to provide the most utility.  I'm enjoying sketching immensely, I wear glasses but tend not to for observing.  Mostly working my way through the popular rookie targets and Turn Left at Orion.

I'm probably able to spend up to about £100 for a goodun.

[Second Time Around]

Which Barlow have you got?

With some the black bit at the bottom can be unscrewed.  This contains the optics.  If you screw this into the filter thread of an eyepiece this will give you an amplification of approx 1.5x.

So with your current eyepieces this will give you about 30x and 120x, the latter being useful for planetary obs.

 

[Louis D]

I would probably go for the 12mm BST for 54x or 108x and exit pupils of 2.4mm and 1.2mm.  Both of these are useful magnifications/exit pupils.  That, and the 12mm performs very well at f/5.  The 25mm struggles quite a bit f/5.  26x with the 25mm BST isn't particularly interesting when you've already got 20x with the 32mm Plossl.

[Ratlet]

I've got the BST 2x Barlow.  Just checked and unfortunately whilst it does unscrew from the Barlow the thread is slightly larger than a filter thread.  Although it does screw into my BST eyepiece which is interesting. 

The 8mm has optics in its barrel so I'm wondering now if I can swap barrels and optics about.  I wonder if the 8mm would function with a barrel without any glass.

I do like the BSTs I must say.  I find them very comfortable.  The 12mm seems highly regarded also which is why it was my first consideration.

I'll need to do another read up of exit pupil to make sure I understand it a bit better.

[Louis D]

The lower Smyth (Barlow-like) group is an integral part of the eyepiece design.  Removing it and using the upper group alone would result in really poor correction and a much longer focal length.  You might be able to swap barrels within the BSTs, and see if you get anything usable.

Edited November 15, 2022 by Louis D

[Ricochet]

The 12mm Starguider would be a good choice. My other suggestion would be the 13mm Nirvana, which is a bit more expensive with a wider field but less eye relief and probably not quite as comfortable as that is a real strength of the Starguiders. 

 

[Zermelo]

1 hour ago, Ratlet said:

I'll need to do another read up of exit pupil

https://stargazerslounge.com/topic/375282-eyepiece-selection-based-on-exit-pupil/

 

+1 for the 12mm Starguider if you want 60 degrees at F/5.  I don't think you'll do better without paying a fair bit more.

I think most of the Starguiders have that Smyth negative group in the base, which will prevent you screwing in a Barlow section properly. I don't have the BST Barlow, but the detachable part of my Baader x2.25 Barlow won't fit into the bottom of the Starguider 12mm.

 

[badhex]

I wouldn't swap barrels about on your EPs if they have optics in as the lens arrangements and groupings are specific to the EP.

Whats your budget? Between 32mm and 8mm is indeed a massive gap. FWIW, my main use EPs are 40mm, 24mm, 17.5mm, 10mm, 4.5mm and I find this works pretty well for a small selection. 

Edited November 15, 2022 by badhex

[badhex]

Haha whoops didn't refresh before replying so I didn't see all the other replies 😅

[Louis D]

The bigger reason I wouldn't swap barrels is because dust gets inside and onto the bottom surface of the lowest lens of the upper group when you open up an eyepiece.  That surface is generally very close to the internal field stop location, so any dust on it is nearly in focus and very annoying.  It can be really difficult to get that lens surface factory clean again.

[Louis D]

51 minutes ago, Zermelo said:

I think most of the Starguiders have that Smyth negative group in the base, which will prevent you screwing in a Barlow section properly. I don't have the BST Barlow, but the detachable part of my Baader x2.25 Barlow won't fit into the bottom of the Starguider 12mm.

I think the 18mm and 25mm lack elements in the lowest barrel, but I can't check for certain because I've loaned my set to my grown daughter to use.  Even if they lack those elements, the Baader still might hit the field stop diaphragm.

Most Barlow nosepieces don't have elements protruding above the threads like the Baader, so not an issue for most.

[Ratlet]

I'm going to stop taking the barrels of they eyepieces now.  Appreciate the information.

I think it'll be a safe bet with the 12mm.  I do like the eyecups with the bst as they fit nicely against my neanderthal brow without touching my protruding eyes lol.

[Kon]

A 15mm BST might sit nicer than the 12mm between your current EPs. Worth also looking for an EP in the 20-25mm (I would not recommend the BST, i had it and it was not sharp at the edges). I had the 15mm and it was great. these two ranges were my most used ones (mostly nebula observing). For your £100 budget you should be able to get the two eyepieces to fill the gaps. Stellalyra and Nirvana have good reviews.

It also depends what you enjoy viewing. If your 8mm is a BST it barlows well for higher planetary or moon magnification.

Try find the posts from @Louis D on eyepieces. You cannot go wrong with his suggestions.

[Padtwo]

I have just managed to get my hands on a 7mm nirvana and really appreciate the wider field of view., but you are looking for something inbetween 32mm and 8mm.  Maybe the nirvana range might be worth investigating, the 16mm is widely praised but with the 32mm and 8mm and a 2x barlow you would be doubling up on magnifications, so I would suggest the 13mm nirvana, or 12mm bst

[ScouseSpaceCadet]

I've owned a 12mm BST for approx 3 yrs that has saw action in several scopes from f5 130mm &150mm newtonians, a 120mm achro, an 8" dob, a couple of Maks and an f7 102ED refractor. For the money you can't go wrong and x2 barlowing for 108x with your scope should be fine too.

Edited November 16, 2022 by ScouseSpaceCadet

[Ratlet]

Thanks for the advice guys.  I've now ended up with a spreadsheet (and a better understanding of eyepieces).  I think the 12-ish mm is a pretty good place.

LouisD's reviews and yard stick is one of my favourite things to find when I look for eyepiece reviews.  So We've now got another contender in the ring with the Meade HD-60 which apparently some new-old stock has been found and is available through Ali-Express.  More than likely I'll still get the 12mm BST though as it's for Christmas and the wife will be buying it.

[F15Rules]

There's a Vixen 12mm SLV on the For Sale section of this forum right now.

Nothing to do with me but I know the seller and his equipment is extremely well looked after. It has 20mm eye relief and superb optics, at £65 posted it's great value.

HTH🙂

Dave

[Ratlet]

51 minutes ago, F15Rules said:

There's a Vixen 12mm SLV on the For Sale section of this forum right now.

Nothing to do with me but I know the seller and his equipment is extremely well looked after. It has 20mm eye relief and superb optics, at £65 posted it's great value.

HTH🙂

Dave

I'm starting to wish I was a triclops lol

[bosun21]

21 hours ago, F15Rules said:

There's a Vixen 12mm SLV on the For Sale section of this forum right now.

Nothing to do with me but I know the seller and his equipment is extremely well looked after. It has 20mm eye relief and superb optics, at £65 posted it's great value.

HTH🙂

Dave

I know, I just missed out on buying the 4mm🥲.