Jump to content

Ok, Help me out here - Delos at F10 ??


Recommended Posts

I know that these are great at F4 - 5 (only reading the reviews on here) - just trying to evaluate the extra cost against my Hyperions - don't get me wrong - very nice at F10 - but at F4 - 5 whilst using a paracorr, do the Hyperions/ES 82 fail due to the actual quality of the EP, or the fact that at F4, all the mid priced EP's will fail (due to the fast focal system) - also does FOV play a part in the outcome - at what point do these ultra wides become - just "Plossl" like - (hope that you can understand that < or around 50 degree).

Paul.

Link to comment
Share on other sites

I'm no expert but I think the better eyepieces are better at coping with the steeper light cone in a fast scope. I presume it just costs more to produce the optics that are able to do this. It's not just the quality of the eyepiece components but also it's design. The failings of the lesser eyepieces don't show up so much in the slower scopes so the difference between the two is not so obvious. If you're asking at what point it becomes the same I don't know, it probably never does but just becomes less or barely noticeable.

That's my take on it. Im not sure I follow the FOV bit.

Link to comment
Share on other sites

Hi Richard - thanks a lot.  The FOV I refer to is that the scope at F10 is only going to show a very limited "expanse"- so will the 50 degree show just as much as the 82 degree and as much as the 100 degree or does the fact that the SCT's long focal length have a bearing on this - no matter how much the EP will show in degrees, will the limit of the SCT's FOV have a cut off point - I've been observing for years but  not really got to grips with the actual maths and not understand it fully - hope I've explained things ok.

Paul.

Link to comment
Share on other sites

Hi Paul,

An eyepiece with a wider AFOV than another eyepiece will show a wider TFOV in the same scope regardless of its f ratio. Both eyepieces would show a narrower TFOV in a slower scope. The calculation is a function of the focal length of the scope, an f10 scope is just longer than an f5 with the same size primary but it's longer for both eyepieces, so the one with the wider AFOV will still show a wider TFOV. Hope this makes sense.

Link to comment
Share on other sites

Hi again Richard and Robin - thanks very much - what I am trying to find out is that would the ES 82 (may struggle a little with these because of ER (I can get away without specs at the EP - just thinking ahead when I may have to wear them at the EP) and the Delos (fine with good ER) be a real leap for me at F10 - the mega wides and ultra wides, to me, seem to be of little importance due to the scopes I have and not really wanting anything at F4 - 5.

I think the Explores will be a little tight on Eye Relief for me thinking further down the line, but the Hyperions are about the same a the deloi regarding ER - I'm ok at the mo with taking my glasses off to observe, but can just as well leave them on at the scope - so no real problem.

Just thinking will these EP's be a major step up at F10 for me regarding contrast, depth of view, background sky colour (much darker I'm led to believe reading the endless reviews) - I have no way of trying before I buy, but was wondering if anyone out there can give a comparison of, say, the Hyperions Versus the ES 82's or the Deloi at F10.

Paul.

Link to comment
Share on other sites

I think there will be subtle improvements in the views given by the Delos and ES 82's over the Hyperions at F/10 but they will be subtle, not a major step. You won't see anything in the Delos and the ES 82's that the Hyperions would not show you.

If you were interested in using them in a scope faster than F/6 at some point then I'd steer away from the Hyperions.

Link to comment
Share on other sites

Hi John, Thanks very much - I think in an ideal world we could try before we buy - but this is never the case as with the loan of a £250 EP.  I have tried to surf the reviews regarding these better quality EP's but they all seem to say that they are really good at F4 - 5, but I can't seem to find anything for the longer focal length reviews, don't get me wrong I'm very happy with the Hyperion's and cause I only observe with long focal lengths, I have got used to the larger image scales they produce and the ease on the lower priced EP's, but I think if I was out under really dark skies instead of the light polluted Midlands, the outcome would be a little different.

Thanks again and Regards.

Paul.

Link to comment
Share on other sites

I don't have a lot of eyepieces and use them in an f6 and f10. the televue and pentax I use are better than the maxvision in both but not nearly £200 difference. I am sure that the delos will be better than the baader in an f10 scope  but  I doubt you will see enough difference to justify more than doubling the price you get a view that is a little brighter and a little sharper which gives an overall impression of nicer but not twice as good.

Link to comment
Share on other sites

I have an astigmatism so would need to wear glasses if I weren't using the Televue Dioptrx. I don't know whether one would fit the baaders but it might be an option that's worth pursuing, certainly cheaper than buying a few Delos.

It works well, but does reduce the effective eye relief slightly. With my Delos I have its eye-guard up and still get the full FOV but with the Nagler I have to have the eye-guard down to get the full FOV. I'd guess the eye relief would be fine with eyepieces with a narrower AFOV.

http://www.televue.com/engine/TV3b_page.asp?id=54#.VF_GfmIgGK0

Link to comment
Share on other sites

Hi John, Thanks very much - I think in an ideal world we could try before we buy - but this is never the case as with the loan of a £250 EP.  I have tried to surf the reviews regarding these better quality EP's but they all seem to say that they are really good at F4 - 5, but I can't seem to find anything for the longer focal length reviews, don't get me wrong I'm very happy with the Hyperion's and cause I only observe with long focal lengths, I have got used to the larger image scales they produce and the ease on the lower priced EP's, but I think if I was out under really dark skies instead of the light polluted Midlands, the outcome would be a little different.

Thanks again and Regards.

Paul.

To be honest, reviews of eyepieces conducted with slow scopes are of limited value becuase they really don't challenge the eyepiece much. I've very rarely read of any eyepiece performing badly in, say, an F/10 scope. When you get to F/5 optical issue make themselves much more apparent.

I used to have a Japanese 2" 30mm Widescan III eyepiece which gave a massive 84 degree field of view. It was a really excellent eyepiece in the F/10 SCT and refractor I had back then but really rather poor in the F/6.5 refractor I aquired a little later.

Tele Vue's are all designed and tested to work well down to F/4. I think it's safe to assume that they will handle F/10 without breaking sweat.

Link to comment
Share on other sites

When I started in astronomy many many years ago, the "standard" scope was a 6" f8....

I was told that at f10 or greater " even the bottom of a Coke bottle" would give good views

I never got round to testing that out ;-)

But I think the moral of the story is almost ANY eyepiece will perform well at f10.

You pay your money, you take your chance.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.