Which size eye pieces to start with?

[Rattler]

I'm after 3 BST Explorer eye pieces and a 2x barlow for use with a ES ED80. The max magnification is 160x. Which of the following 3 would you recommend at first?

                              X2 Barlow
25mm    x19           x38
18mm    x27           x54
15mm    x32           x64
12mm    x40           x80
8mm      x60           x120
5mm      x96           x192
3.2mm   x150        x300

Cheers.

[alanjgreen]

I'd say buy one and see if you like it. Then buy some more. Eyepieces are personal things and we all have different shaped faces, eye sockets etc. 

As far as magnification goes, then I would try to keep gaps of x40-x50 between them.

Personally, I would not use a Barlow. It's just extra glass and unless it's a top notch Barlow it will just spoil the joy of decent eyepieces  

According to the spec, the ES ED80 is f6. A 6mm eyepiece will give 1mm exit pupil, 12mm gives 2mm exit pupil, 18mm gives 3mm and 24mm gives 4mm.

Personally, I would start with a nice low power eyepiece, so the 25mm. At 4mm exit pupil will be great for nebulas. 

So, then the 8mm will give just over 1mm exit pupil. x60 gives a nice gap from x19.

I would look for something around x100, a 5mm.

The 3.5mm may be a bit small exit pupil and be uncomfortable eye strain with this short stubby scope, someone who owns one can comment? I would think twice before going under 5mm.

conclusion = 25, 8 and 5

In fact, with the money saved from not buying a Barlow, I would instead get a 1.25" Castell UHC filter (if you have not got a UHC already?) from 365astronomy to help make nebulas more visible.

[Ricochet]

I would start with 25-12-8. The 5 would make an ideal planetary eyepiece but given the planets are all early morning objects and low in the sky I would concentrate on those most useful for DSOs. 

[mikeDnight]

Many more complex and expensive eyepieces use integrated barlow lenses, and I would definitely advise you include a X2 barlow to your armoury of eyepieces. SkyWatcher Delux X2 barlow lenses are actually of very good quality. They deliver superb image quality and will double the effective focal length of your telescope or halving the fl of any eyepiece, multiplying your magnification range. 

I use a delux barlow in my binoviewer and also have a second for use for mono viewing, and both enable me to use high powers that still maintain superb image sharpens and contrast. Buy the Delux barlow and not the standard!

 

[laowhoo]

+1 on the quality Barlow. Of a decent quality you won't even know it's there, unless it helps to improve eye relief. Also opens you up to spend extra $$ on better EPs (speaking generically, not in your case--I don't know the EPs you're considering). That said, given your aperture you could also get by with only the 25mm/8mm/5mm according to useful magnification. There are two routes you can go with EPs, by exit pupil size and by magnification steps. Manufacturers offer their various series in roughly 1.5x steps, and this comports with long established research on threshold detections for various DSOs. Neither do I like to go by exit pupil for the simple reason that, in many instances, what you want is the best framing of an object/cluster, and here's where the Barlow/mag steps are helpful. Exit pupil is better relegated to max/min of what you can practically use magnification-wise, i,e., no greater than 7mm if you're young, and no less than 1mm generally. Between these is where the mag. progressions do their best work, whether teasing out detail on planets or framing the Double Cluster. Globs are my favorite DSOs and for these framing is everything. Magnification is also the response to seeing conditions--when it's good you can go higher--and exit pupil doesn't enter into it at all.

[25585]

Of the eps listed 25, 15, 5. Big AFOV as possible is always good, eye relief for you allowing.

[Louis D]

5 hours ago, Ricochet said:

I would start with 25-12-8. The 5 would make an ideal planetary eyepiece but given the planets are all early morning objects and low in the sky I would concentrate on those most useful for DSOs. 

I would second this line-up, especially since the OP's sig indicates an 8mm BST already.

[Trikeflyer]

2 hours ago, Louis D said:

I would second this line-up, especially since the OP's sig indicates an 8mm BST already.

I'd third this line up. I have the 25, 15, 12 and 8 and use them all regularly.