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Junming-jm
- Posts: 78
- Joined: Sun Oct 03, 2010 2:54 pm
- Location: On your optical lens and mirror
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cloud_cover
- Posts: 1170
- Joined: Mon Jul 12, 2010 6:08 pm
- Favourite scope: 94.5", f/24 Ritchey-Chretien Reflector
- Location: Restaurant At the End of the Universe
Ken - so sorry, I fired that last response in between MRT stations - had only 1 station to go!
I was assuming prime focus photography.
Do read up on the various means of photography; prime focus is only 1 of them. There's also afocal, eyepiece projection and barlowed prime focus.
In terms of power for EPs, generally I find myself using about 60-100x power for most objects. To find your power, divide the focal length (which is aperture, in mm, time f ratio) by the focal length of the EP. Jupiter is viewable at 60x although going between 100-200 on a decent night is fine. The Seeing locally seldom allows views well in excess of 200x however, which you shouldn't be exceeding anyway since that would be about the max practical mag for your scope (4.5 x50, minus a fudge factor to allow for the fact an Orion mirror is not "premium")
For nebulae, you want something with good light transmission. While less glass elements mean less material between your eyes and the target object, theoretically decreasing the transmission loss of light, I find my Naglers to excel above generic plossls (Antares); nebulae are distinctly better seen in the Naglers compared to Antares Plossls. Orthos are reputed to let through the most light since they use the least glass elements. Do read up on the many, many, many, many (you get the idea) reviews online
When getting an EP, other than power, consider field of view. A smaller FOV will mean the same object need to be smaller (less magnified) to fit the viewing circle of your eyepiece compared to a larger FOV eyepiece. A larger FOV eyepiece will also have darker backgrounds, a definite plus. There's also the fringe benefit of not feeling like you're looking through a soda straw with larger FOV EPs. I've used Orthos, Plossls and the Naglers. And I always go back to the Nagler. I suggest a 68deg FOV as a good price-budget point (i.e. Hyperions, among others. I had good deals on my Naglers which was why I bought them and also why I'm not buying Ethoses). If you're feeling like spluring then the Televue EPs are hard to beat. (I'm sure I've just ignited a debate...)
Do be careful of the low-cost ultra-wides. They are unable to deal with the light cone of faster (lower f numbers) telescopes and result in blurred images away from the center of view. Use them if you have an f/10 and above scope. I have one, its a 30mm Agena Astro 82deg FOV (I couldn't bear to pony up for a Nagler 31) and in my f/9.75 scope it shows abberations about 2/3 way out. Since I use it as a finder EP, that's less of an issue.
Hope it helps When buying EPs, do remember that while you will probably change your telescope in future (looking at the recent trends, probably sooner rather than later), you can still use the same EPs decades into the future. Also, when buying second hand, if you're unable to inspect the item, generally owners of expensive eyepieces are more likely to take good care of them compared to cheaper items (isnt that true of all things? )
I was assuming prime focus photography.
Do read up on the various means of photography; prime focus is only 1 of them. There's also afocal, eyepiece projection and barlowed prime focus.
In terms of power for EPs, generally I find myself using about 60-100x power for most objects. To find your power, divide the focal length (which is aperture, in mm, time f ratio) by the focal length of the EP. Jupiter is viewable at 60x although going between 100-200 on a decent night is fine. The Seeing locally seldom allows views well in excess of 200x however, which you shouldn't be exceeding anyway since that would be about the max practical mag for your scope (4.5 x50, minus a fudge factor to allow for the fact an Orion mirror is not "premium")
For nebulae, you want something with good light transmission. While less glass elements mean less material between your eyes and the target object, theoretically decreasing the transmission loss of light, I find my Naglers to excel above generic plossls (Antares); nebulae are distinctly better seen in the Naglers compared to Antares Plossls. Orthos are reputed to let through the most light since they use the least glass elements. Do read up on the many, many, many, many (you get the idea) reviews online
When getting an EP, other than power, consider field of view. A smaller FOV will mean the same object need to be smaller (less magnified) to fit the viewing circle of your eyepiece compared to a larger FOV eyepiece. A larger FOV eyepiece will also have darker backgrounds, a definite plus. There's also the fringe benefit of not feeling like you're looking through a soda straw with larger FOV EPs. I've used Orthos, Plossls and the Naglers. And I always go back to the Nagler. I suggest a 68deg FOV as a good price-budget point (i.e. Hyperions, among others. I had good deals on my Naglers which was why I bought them and also why I'm not buying Ethoses). If you're feeling like spluring then the Televue EPs are hard to beat. (I'm sure I've just ignited a debate...)
Do be careful of the low-cost ultra-wides. They are unable to deal with the light cone of faster (lower f numbers) telescopes and result in blurred images away from the center of view. Use them if you have an f/10 and above scope. I have one, its a 30mm Agena Astro 82deg FOV (I couldn't bear to pony up for a Nagler 31) and in my f/9.75 scope it shows abberations about 2/3 way out. Since I use it as a finder EP, that's less of an issue.
Hope it helps
When buying EPs, do remember that while you will probably change your telescope in future (looking at the recent trends, probably sooner rather than later), you can still use the same EPs decades into the future. Also, when buying second hand, if you're unable to inspect the item, generally owners of expensive eyepieces are more likely to take good care of them compared to cheaper items (isnt that true of all things? )DON'T PANIC
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cloud_cover
- Posts: 1170
- Joined: Mon Jul 12, 2010 6:08 pm
- Favourite scope: 94.5", f/24 Ritchey-Chretien Reflector
- Location: Restaurant At the End of the Universe