Celestron C5 telescope eyepieces.

[Guest]

I have a Celestron C5. I am considering ways to improve it. I have several wide field 1 1/4 inch eyepieces, the longest focal length being a 16 mm 82 degree. 

I was wondering how a wide field 20 or 24mm Eyepiece would work with it. There ie also a 32 mm Plossl. 

[Moonshane]

Hi Martin 

How do you wish to improve it? The widest true field assuming a 1.25" rear aperture would be a 24mm 68 degree eyepiece and this would gain you about a third of a degree of true field more than your current 16mm.

[Ben the Ignorant]

My C5 has a 24mm 68° Explore permanently in its diagonal. 1.3°, maximal field for that scope. Some curvature of field shows but it's from the scope, not the eyepiece. Because its field lens has the same diameter as the inside of the focuser, the 24/68 displays the maximal field for any 1.25" focuser scope.

The curved field is typical of Schmidt-Cassegrains, the image is flatter in my f/6 and f/7 apos. However, I cheated; I bought it during a temporary price cut for 99€ instead of 159€. Maybe the sale will be repeated because it already took place a couple of times, it's worth watching for it. Or try to find a second hand one.

After comparing the Explore 24/68 with the Hyperion 24/68 for sharpness, I gave away the Hyperion to my brother who is only an occasional observer, that's how sharper the Explore is.

[Ben the Ignorant]

9 minutes ago, Moonshane said:

The widest true field assuming a 1.25" rear aperture would be a 24mm 68 degree eyepiece and this would gain you about a third of a degree of true field more than your current 16mm.

True, but 1° 18' versus 52' helps when viewing open clusters or star-hopping. 

[Moonshane]

I think we are agreeing ?. I am just not sure what Martin means by improve.

[Ben the Ignorant]

10 minutes ago, Moonshane said:

I am just not sure what Martin means by improve.

Indeed. I painted the inner baffle matte black, it took forever to dry for lack of ventilation but grazing reflections are done with. Same for the diagonal and the secondary housing, inside and outside. A much lengthier job was the placement of seven baffles in the main tube. Now even a flashlight at close range has a tough time causing glare.

I was about to forget, but a 20cm long homemade dewshield garnished with the same black paint is needed to get that efficiency. I went as far as adding two baffles near the dewshield's nose cause that's a sensitive place for parasitic reflections. Urban stargazing turned me into a hardcore glare killer.

[Guest]

11 hours ago, Moonshane said:

I think we are agreeing ?. I am just not sure what Martin means by improve.

Hi Moonshine. I like to use the C5 to take to darker skies near where I live. The C5 being f10 does not lend itself to wider field viewing. I somehow got it into my mind that any eyepiece above around 16mm would distort the image horribly. But encouraging to know that reasonable views can be got with 24 mm 1 1/4 inch eyepieces.