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Go Back   IceInSpace > Beginners Start Here > Beginners Equipment Discussions

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  #21  
Old 03-01-2018, 12:35 PM
bigjoe (Joe)
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Good review of APMs UFF 30MM over at Cloudy Nights.
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  #22  
Old 03-01-2018, 03:20 PM
bigjoe (Joe)
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Originally Posted by Wavytone View Post
Oh they aren't crap, that's for sure.

The big question is how the APM UFF 10 and 15 compare against say Vixen LVW 8 and 13, the Vixen SSW10 and 14, or the TV Nagler/Radian/Delos/Delite/Panoptic.

I'm thinking of ordering the 30mm and maybe the 18.

Here's another thought for you too... someone has recently revisited Dollond eyepieces (a cemented achro doublet) and concluded the image quality really is excellent if you can live with a 30 degree field of view. In particular the clarity and contrast are quite striking, and concluded that centuries ago refractor users really were able to push their scopes to the limits. It has had me scrabbling around tonight to find some optics I can cannibalise to make a Dollond, just to try. I either have to dismantle a 10mm LV (hmm...Kunama wants one) or a camera lens...
This sounds like the old adage that less elements is more in optical terms. An old Japanese 12.5 Kellner I had from Unitron had the sharpest and clearest image Ive ever seen on axis !
bigjoe

Last edited by bigjoe; 03-01-2018 at 03:22 PM. Reason: Add
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  #23  
Old 03-01-2018, 07:49 PM
Wavytone (Nick)
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Originally Posted by bigjoe View Post
An old Japanese 12.5 Kellner I had from Unitron had the sharpest and clearest image Ive ever seen on axis !
bigjoe
Joe there's even better - take the Kellner apart and use the doublet alone, plano side towards the telescope. The clarity and contrast will astound you, though the useful field of view is typically around 30 degrees.

An achromatic doublet used this way is actually a Dollond eyepiece and just goes to show that 18th century observers really did not lack good eyepieces. You want a really, really, fast doublet - say f/2 - and 12mm and 6mm focal lengths could be a bit hard to find.

I can safely say that a doublet used this way is better than the original Steinheil monocentric, and the contrast is almost as good as you would get from a spherical eyeiece (single element being a glass ball, with extremely limited field of view and virtually impossible to apply multilayer coatings). The bonus is the 30 degree FoV which, in its era, was first class. You can see why the RAS types swore by this eyepiece at the time, if they had one from a competent optician. No wonder the Steinheil was controversial in its day.

Last edited by Wavytone; 03-01-2018 at 08:42 PM.
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  #24  
Old 03-01-2018, 08:36 PM
bigjoe (Joe)
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Originally Posted by Wavytone View Post
Joe there's even better - take the Kellner apart and use the doublet alone, plano side towards the telescope. The clarity and contrast will astound you, though the useful field of view is typically around 30 degrees.

An achromatic doublet used this way is actually a Dollond eyepiece and just goes to show that 18th century observers really did not lack good eyepieces. You want a really, really, fast doublet - say f/2 - and 12mm and 6mm focal lengths could be a bit hard to find.
Sounds good will do..who cares about the field..were all obsessed with that aspect..Clarity first I say!
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  #25  
Old 04-01-2018, 07:37 PM
Finski
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Originally Posted by Wavytone View Post
Given your scope is f/7.8 a useful range is from about 6mm (200X, high power) to a 25mm eyepiece (low power). It has a 1.25" focuser which rules out the larger 2" ones like the APM 30mm or Prostar 38mm 70-degree UWA.
It comes with the 2" adapter, can/should I look at some 2" EPs also?
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  #26  
Old 04-01-2018, 09:43 PM
Wavytone (Nick)
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It comes with the 2" adapter, can/should I look at some 2" EPs also?
Sure, as per my previous post. But the maximum aperture inside the focuser will limit the useful field of view in low-power eyepieces. It will be a "bottleneck", in the literal sense, like sticking the narrow end of a coke-bottle into the focuser then trying to look through the bottom, as these big low power beasties have field stops in excess of 45mm - which is rather wider than your puny focuser.

Alternatively at some point you may decide to replace the focuser you have with a proper 2" one. Thus begins the slippery slope of upgrades, and at some point you will realise there is more merit in upgrading to a better scope rather than tinkering with what you have.

But IMHO resist the urge to upgrade bit-by-bit, it is ultimately futile when you are using consumer-grade gear. Best to live with what you have and its limitations, for a year or two. Learn the sky, and what there is to be seen. You will know when you are ready to upgrade and when that time arrives, flog the lot and buy a better scope - if you dare.

The only exception to that rule is when you have a scope that is quite special and you will keep for many, many years, possibly forever. My Santel MK91 is one such scope and deserves to be modernised carefully. The other scope to aspire to is a Questar, if you are lucky enough to have one these are treasures for life despite being vintage 1954 mechanically.

Last edited by Wavytone; 04-01-2018 at 10:01 PM.
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  #27  
Old 05-01-2018, 02:47 AM
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But IMHO resist the urge to upgrade bit-by-bit, it is ultimately futile when you are using consumer-grade gear. Best to live with what you have and its limitations, for a year or two. Learn the sky, and what there is to be seen. You will know when you are ready to upgrade and when that time arrives, flog the lot and buy a better scope - if you dare.
I think that there is merit in this advice...It is easy and tempting to buy “upgrades” early in the hobby. Patience is a virtue and good gear (if taken care of) will last a lifetime. Take your time learn what you like by attending viewing nights and looking through other folks gear, then and only then (in my opinion) look to upgrade
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