best eye piece for galaxy viewing?

[rpmiller78]

which size? do you want a low power or high power? i bought a set that has a 40, 17, 10, 7.5, and 6.3mm eye pieces, plus the 25mm that came with my orion xt8. i am a noob at this.

[gurneyfan67]

You would want to use a low power e/p for galaxies so that you get a wide field of view. The 40 or 25mm would be the ticket. High power for planets and globular clusters.

[John]

Low power eyepieces are very useful to find them but many galaxies are quite small so it's worth increasing the magnification to darken the background sky and bring out the contrast of these faint objects a little. You could find even the 10mm eyepiece being useful for a closer view.

[newman]

Low power eyepieces are very useful to find them but many galaxies are quite small so it's worth increasing the magnification to darken the background sky and bring out the contrast of these faint objects a little. You could find even the 10mm eyepiece being useful for a closer view.

Indeed. People often go by the rule "low power for DSOs, high for planets" but tend to forget contrast in that equation. Even though galaxies should look brighter in my 17mm Ethos, they seem brighter in the 10mm one, when the target allows 100x magnification that is. This is because I get increased contrast due to a darker backround with the 10mm, making the galaxy "pop". You want a low power / wide field to find them, but you'll often want to crank up the power on these once you've got them in the eyepiece.

[cs1cjc]

Typically an exit pupil of between 2mm and 4mm is best so you are looking at focal lengths between about 12mm and 24mm for your f/6 XT8. 17mm from your set might be a good place to start. There is a nice article by David Knisely here:

http://www.cloudynights.com/item.php?item_id=547