I am new to the hobby and looking to build out a 2 or 3 eyepiece collection for my Maksutov scope. (More equipment details and intended use details are at the bottom of the post).
I have noticed that eyepieces come in a wide range of AFOV angles from 40' in entry-level zooms to 110' super wide. And based on my reading, it seems like wide AFOV eyepieces show more context at a given magnification and provide an immersive space-walk like experience.
It seems too good to be true, so I wanted to ask:
- Are there any downsides to wide AFOV eyepieces (besides cost / weight)?
- Does stretching the view over a wider AFOV make the view dimmer compared to a narrow AFOV piece?
- How does a focal reducer / barlow affect AFOV and brightness / contrast?
- Wide AFOV eyepieces are expensive. Should I get one high-end eyepiece and use it with a barlow + focal reducer to have 3 usable magnifications? Or are there better strategies for covering a range of magnifications?
I am using an Orion Maksutov scope with 127mm aperture, 1540mm focal length (f/12.1). 1.25" Focuser. No electronics.
- I use my scope to see the moon, Jupiter, and Saturn from home since they are not affected much by light pollution and are visible on most nights.
- I hope to take my scope along on camping trips and start exploring deep space objects from national parks and dark sites.
We each have our own opinion and approach to our eyepiece set.
I have one eyepiece that maxes out my field of view for each scope. For a scope with a 1.25" focuser that would be a 32 mm Plossl. Plossls are excellent eyepieces and are quite inexpensive so you don't give up anything with a 32 mm Plossl in a 1.25" focuser.
In my F15 Mak I tend to use a 32 mm Plossl and an 8-24 zoom for most observing sessions. As you can see in my signature I have many other eyepieces to choose from, but this is my preferred observing set.
Understanding Telescope Eyepieces- There are recommendations, based on budget,
but the meat of the article is about understanding the considerations and specifications
to know when selecting eyepieces.
As you go up in magnification, a wider AFOV will provide more drift time when using a manual mount. A tracking mount takes care of this so not as much of a consideration.
A wider AFOV will give you better context, especially for larger DSOs. And some DSOs are quite large. The Pleiades are about 2 degrees wide. The Andromeda galaxy about 3 degrees and the North America nebula about 4 degrees. This is why many of us have multiple scopes, one with a shorter focal length to enable wide field of view and, perhaps, one with longer focal length which are more optimized toward the Moon, planets and those smaller, high mag DSOs. Your Mak would be of the latter type.
In an F12 scope like yours, having a good image across the entire field of view is easier for the eyepiece as compared to using it in an F5 scope. This has to do with the angle of the light rays as they enter the eyepiece.
I have several scopes ranging from F15 to F4. An eyepiece used in the F15 scope may give me an excellent image right to the edge of the field of view. That same eyepiece used in the F4 scope may show distortions as you get closer and closer to the outer edge of the field of view but is likely to be just fine in the center 60 to 70 percent of the field of view.
The wider you go in AFOV the harder it is for the eyepiece designer to handle these outer areas in low focal ratio scopes. This is where the more expensive eyepieces will have a performance advantage over the cheaper eyepieces. Some people don't mind this outer edge fall off in quality, others are very sensitive to it.
If you plan to have that one scope for a long time, this will be less of a concern as you buy eyepieces. If you have plans to add a scope that is less than F8, this will be more of a consideration. Below F6, the loss of edge quality is more apparent.
For my single FL eyepieces I have standardized on Explore Scientific and Meade 82 degree eyepieces. And I am a very active user of Zoom eyepieces. My Baader Hyperion 8-24 is my most used eyepiece.
I hope that helps.
Edited by aeajr, 25 September 2021 - 07:35 AM.