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What eyepiece makes it look like looking through a tiny tunnel?


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I went to a star party a few months ago and had a look through a SW 10" dob, this was before I purchased my own. I was looking at Mars and thought, it was quite small (which obviously it is, except I didn't know this back then), so I asked if I could see it closer. So the chap put a different eyepiece in and when I looked through it it was like looking through a tiny hole with hardly any sky around it, like a very tight tunnel. I have no idea what eyepiece this was, I'm guessing a high powered plossl but I might be wrong. Anyway I didn't really like it and don't want to make the mistake of buying one like it, so does anyone know what it might be so I can avoid it, or are all high powered eyepieces like this? I quite like the look of the BST's but worried they might be like this too, if all high powered EP's are then I guess I just have to live with it.

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You may have been looking through an orthopedic lens which is very small and gives a small field of view....BUT they have less glass in them than some eyepieces and this can provide enhanced contrast and hence show features other eyepieces miss...but as you say not the most comfortable view..

There are many mid range high power eyepieces out there with a 55deg + FOV with big eyepiece lenses and reasonable eye relief which are more pleasant to look through. The BST, or TMB style ones are a good bet and there are many others from Celestron, Meade etc which are just as good.

If you want 80-100 deg FOV then you are talking more money but an even wider view experience..

Mark

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If you wish to avoid the tunnel vision that some eyepieces can give, the basic specs should tell you what you need to know.

Look for 'apparent field'. 40 - 45 degrees apparent field is narrow, and is probably what you didn't like with that Mars view, orthoscopics are an example of this type.

50 deg is normal, Plossls are usually that spec.

60 - 70 deg is wide field, 80 - 100 deg is super wide. The price rises steeply as the field gets wider.

But what different people prefer varies a lot. If you can get to another starparty, ask around, most folk in this hobby are happy to let you see their eyepieces, and you can look through them in day light and see the apparent field as a circle of light.

Regards, Ed.

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High mag plossls and orthoscopics are very narrow like that, but as you learn to look through a scope and pick out tiny details, you appreciate that those types of eyepiece give much better views due to less glass and less manipulation of the light.

Personally, i prefer slightly wider views, since i use an undriven dob, so the wider fields mean less "nudging".

BSTs are 60 degree, and i find them very comfortable to use, with very acceptable image quality. For low power stuff i have an aspheric 31mm, which is by far my favourite eyepiece.

That said, i wouldnt mind having the option at high mags to stick an ortho in when the seeing is good, just to get those crystal clear details.

If you dont like narrow, i'd say go for anything with 55 degree apparent field of view, any less and it feels a bit tight.

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Thanks all. I didn't know anything about ortho's so its interesting to hear about them being better for picking out detail. I think as a dob user i too would favour wider views to aid less nudging and I like the feeling of having more room to look around too. Good to hear not all HP EP's have tunnel vision though. Not sure I can wait till the next star party before I buy the EP's though I'm far too addicted to this hobby already lol.

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I would definitely recommend that you wait until you can attend another star party so that you can get a good feel for what you prefer. It can save you from making painful mistakes. However, if you treat the eyepieces with respect, the second hand value should be pretty high, especially on the BST explorers that come highly recommended for their price. Also, buying second hand can save you a lot of money and reselling s/h eyepieces should only cost you the postage, ideally.

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