Louis D

Like this?

In this case, it might be the expense of making a specialized triplet that limits the design from being mass produced.

Indeed, my 2011 vintage Delos 10mm arrived with the traditional dual sided cap.

I always go by lowest power (25x to 40x), mid power (65x to 90x), and highest power (150x to 220x) and then do the math for the particular telescope to figure out what eyepieces make sense. Certainly, there is plenty of room to fill in the blanks at the higher end of the power range when poking at the limits of seeing.

I suppose if you're far enough north it is, but not from here. It is technically visible all day from here, but good luck seeing it through a blue sky.

Never had that issue in Texas, not even on my 127 Mak. Perhaps because I don't observe in the mornings when the air temperature is closer to the dewpoint. I've never felt the slightest need for dew strips or shields.

Did you mean entrance pupil of the eye?

In digital design, slew rate is the speed at which a device transitions from 0 to 1 or 1 to 0. There's no pivoting involved at all, so explain that one.

With or without eyeglasses? I've had trouble using them with eyeglasses at star parties, so I haven't bought one myself.

I just avoid going out on nights with significant particulate matter in the air, like on night of the 4th of July (fireworks residue), when my neighbors are burning logs in their fireplaces, backyard grilling, or are running their smokers overnight. The rest of the time, the level of airborne particulates hasn't been much of an issue for me.

I cool mine straight up and down like a chimney. I don't know what advantage tilting it would provide.

I've used a cheap M&SG filter to cut sunset haze a little bit to detect other horizon hugging comets in the past.

Yep, you're even further south than I am here in Texas. You can relate to air you can wear. 💦

I would avoid Kellners in favor of Plossls. There were a few Japanese made (Nikon and Pentax) long Kellners that are highly sought after, but beyond that, they're generally not that great.

If you get a custom Dob with a hand figured mirror, it will show planetary detail better than any Mak or SCT of equal aperture as well as showing DSOs very well in my experience. Take the money to buy one really good scope with excellent resale value rather than two mediocre commercial scopes. Not knowing where you live, I can't really make any recommendations, new or used, to look for.

Here's an interesting read including a direct comparison between the 95mm Baader Travel Companion and the 92mm AP Stowaway.

Sounds good. Are the rest of the books on that list also aimed at more advanced photographers and are not usually recommended on here for that reason? I know what you mean about books going out of date. I have Michael Covington's Astrophotography for the Amateur from the late 90s. It focuses on film photography since digital photography was in its infancy when published.

If you're under about age 45, you probably won't notice any field curvature because you still have visual accommodation. In other words, you don't have presbyopia yet (needing to wear bifocals). My 14mm Pentax XL also has field curvature. I never noticed it until I got presbyopia. I then replaced it with the 14mm Morpheus, which also has some, but it is less severe and further out. That, and being over 10 degrees wider is quite noticeable.

Any idea what focal length(s) you're leaning toward?

The 22mm Omegon Redline and its other-branded bretheren are flat of field, unlike the 20mm XW, and sharp out to about the last 10% at f/6, and even then, the astigmatism is only minor. I finally retired mine only after doing multiple comparisons to the 22mm NT4 (which I finally found used for under $280). The Nagler is sharper beyond the 30 degrees off-axis point, but it's more difficult to take in the entire 82 degree field with eyeglasses. The discontinued 22mm Vixen LVW might be worth looking into on the used market as well if you want to stick to 1.25" eyepieces.

The spot diagrams show a star image at best focus (I think it ignores curved focal planes) in an f/5 system. The black is simply a green wavelength since it's in the middle and our eyes are most sensitive to green. The red/blue plots show chromatic effects on the image. Horizontally, you are moving from center (axis) to edge. The degree increments vary by actual field width. The ExP numbers refer to exit pupil separation at midfield and edge. The greater the difference, the greater the SAEP (kidney beaning). Normally a circle of known size is drawn around each plot for scale so you can judge whether or not the aberrations would be visible to the eye. However, they are missing from those plots and is only shown at the top. Here's another set of plots from the webpage previous to the linked image with more discs shown: In these, the center color is explicitly shown as green instead of black. The plots are also shown for f/10 and f/5 systems so you can compare the performance as the scope places more stress on the design.

Yes, I have 2.0 diopters of astigmatism in my observing eye, so eyeglasses are a must down to about 1mm exit pupil. It's also helpful in that I don't need to clean my eye lenses very often nor do they fog up very easily thanks to having the eyeglasses as a barrier.

Both are fine with eyeglasses. No crowding or exit pupil issues. The APM UFF 24mm is also decent with eyeglasses as are the 22mm 70 degree eyepieces like the Omegon Redline SW. The 40mm Meade 5000 SWA is excellent as well if you can locate one. There's also the ES-92s, Delos, Delite, and XWs. The Vixen LVWs were a little tight on eye relief with eyeglasses, so I went with the XLs. The NT4s are also tight on eye relief with eyeglasses.

Holy !#$@. There are three versions of this eyepiece at least: Original Japanese version: Original Chinese version: Current Chinese version:

I had always thought the ETX scopes were originally made in the US. I didn't realize they were getting them from JOC all along.