Louis D

I see some boxes marked FRAGILE (Fra-gee-lay). They must be Italian. 😉

Here's a thread on CN from two years ago on this very subject.

The older focal lengths all seem to be about 78 degrees, but most reports peg the newer 17.5mm at 74 degrees. Since I already have a 17mm ES-92, 17mm NT4, and 17mm AT AF70, I just don't feel a compelling need to add a 17.5mm Morpheus to see if that number is true and if it bests those. Perhaps someone on here with one could perform a flashlight/torch test on it to determine the AFOV.

Go out and do some ATM reading on mirrors, I just did myself. Each glass type has its pros and cons. I'm not sure there's a one best answer to which glass type is best for commercial grade mirrors. For high end mirrors, fused silica (quartz) is probably the way to go.

If you just want to show her the moon's craters, Jupiter's main bands and Galilean moons, Saturn's rings, Venus's phases, the Orion nebula, and showcase open clusters, just about any budget scope will work in my experience. It comes down to the quality of the view, the ease of finding objects, and the ease of tracking once found. Moving up the price scale improves each bullet point.

I figure my 127 Mak is operating at about 1800mm instead of 1500mm with the additional path length causing the mirror to be moved so much. Thus, the 20mm eyepieces would be operating at about 16.7mm. With two eyes, the combined image appears larger than with a single eye, so you may be experiencing this phenomenon.

Since Pyrex changed from using borosilicate glass (looks colorless edge-on) to tempered soda lime glass (ordinary glass that looks green edge-on) with the 1998 divestiture of Corning's consumer division to World Kitchen LLC, I'm not sure it makes any difference. Borosilicate glass is known for thermal shock stability, not necessarily gradual thermal stability. Borosilicate glass's coefficient of thermal expansion is 6 times that of fused silica (quartz) glass, so it is more of a marketing ploy than anything else. Besides, they can now use soda lime glass and call it Pyrex, so you don't really know what they're actually using. By the way, if you are shopping for vintage Pyrex and want to make sure it is borosilicate glass, look for it to be colorless edge-on and for the brand to be PYREX all in upper case. The newer soda lime glass versions are green edge-on and say pyrex all in lower case.

Yes, not everyone's bank is the same. I put $500 toward my daughter's first telescope 3 years ago at Christmas, and all of it was used equipment to stretch the budget. She was 24 at the time, and it was a bit of a late college graduation present as well, but still a gift to my daughter nonetheless. The age of your daughter will also play into the recommendation. Even though my daughter was 24 and a working electrical engineer experienced in electronic hardware, she was still overwhelmed and taking notes from my walk-through of how to use it properly.

Did the 127 Mak come with a 1.25" or 2" visual back? The current US version has a 2" visual back.

You're going to want to attach the dovetail foot to a longer dovetail bar to achieve balance. The R&P focuser should be a nice upgrade from my AT72ED. Its focuser slips under heavier loads at high altitude pointings despite increasing the tension on the focuser set screw.

Looks like a slightly bigger version of my Astro-Tech 72ED. I use mine for all of my indoor eyepiece testing, so you've probably already seen plenty of those images. 😁 Even with my new Planetary II 2.5mm eyepiece, red/green fringing on the planets was very muted. I was able to discern low contrast details, and high contrast images like the moon and Saturn's rings looked fantastic and color free. Since your scope will be faster and larger in aperture, the color correction will be slightly worse. I would hope the lens figure is just as spot on as mine is.

Now that I think about, my favorite eyepiece is whichever one is yielding the best view of an object at any given time. 😉

Wrong. Ever since the Supreme Court's South Dakota v. Wayfair decision in 2018, most states are requiring retailers anywhere in the US to collect and remit sales tax. Retailers outside the US seem unaffected, however. I believe this is mostly due to a lack of state enforcement power on international sales.

Rigel Systems makes a series of astro flashlights. One of them might meet your needs.

We're not talking about exit pupils which are dependent on the eyepiece/telescope combo. We're talking about the entrance pupil which is dependent on the diameter of the human eye's pupil. Certainly, the limiting factor is the smaller of the two. That is, even your pupil is fully dilated, a tiny exit exit pupil from the eyepiece determines the size of the system's combined pupil. Since the human pupil won't contract much smaller than 2mm, an exit pupil of 2mm or less is never going to exhibit SAEP as long as the observer remains centered over the exit pupil. If the eye drifts off center, there is a chance SAEP could be seen. Drop down to a 0.5mm exit pupil, and the chances of seeing SAEP would become nil.

I'll bet UK/Euro prices for Chinese sourced eyepieces are significantly less than ours thanks to an extra 25% tariff applied by the US government only to them. Regular import tariffs on optical gear is maybe 8%, IIRC. Tele Vue gear is Taiwan or Japan sourced, so it is not affected.

@TheLookingGlass could be seeing subtle SAEP with the smaller entrance pupil. I believe SAEP becomes harder to detect with larger entrance pupils. Notice that the smaller the entrance pupil, the more easily mid-field rays will be cutoff.

That's why I measure each independently via photographing the AFOV and TFOV simultaneously with the rulers.

You would need to shorten the tube to accommodate the added optical path length of the Amici prism. It's probably simpler and cheaper to sell the straight through finder on the classifieds and buy a new or used RACI.

Have you ever written up your experiences with the Antares? It didn't do too well at f/5.2 in this report on CN.

The original mushroom top version is just usable with eyeglasses. It was also sold as the Celestron Axiom LX 31mm and Meade 5000 UWA 30mm. The conical top version is the same optically, but has a recessed eye lens making it impossible to use with eyeglasses and a bit more difficult without. It's not as sharp in the center as a 27mm Panoptic or 30m APM UFF. Stars remain a bit bloated at best focus in comparison. Without a reference eyepiece, it might go unnoticed. It is absolutely flat of field as far as I can tell. The edge has pronounced chromatic aberration of the exit pupil (CAEP) leading to an orange ring of fire inside the field stop on bright objects like the moon or during daytime use. I've noticed that planets split into red and blue copies of themselves near the edge slightly separated from each other. I only keep mine for the immersiveness of the view where I only look on-axis and the edge issues are strictly in peripheral vision. It's not so good for tracking objects drifting from edge to edge on an undriven alt-az mount for the above reasons.

I noticed that FS=FL relationship, but I couldn't quite put my finger on the reason. I simply plug my measurements into my spreadsheet that has linear curve fitting derived coefficients from my 70+ measurements.

It might be possible to limit image forming lens growth if a focal reducer first stage as with the 30mm APM UFF were employed in the design. In the diagram below, the first group acts as a focal reducer while I believe the second group acts as a traditional Smyth lens. The upper 3 groups are the traditional Panoptic style image forming section where rays are first spread out and then reconverged.

Good timing. I think you sold it near the peak of the real estate market. With rising interest rates, a forced march back to the office, and inflation raging, vacation homes aren't moving at all here in the US.

Quick test report on the Aquila (TMB) Planetary II SW 2.5mm: Measured actual apparent FOV (AFOV): 58° by flashlight method, 57.2° photographically Measured fieldstop via photography: 2.5mm Calculated effective AFOV (eAFOV) based on above measurements: 57.5° Measured usable eye relief: 13mm Eye lens diameter: 20mm Measured axial focal length via photography: 2.5mm Measured radial edge focal length via photography: 2.2mm Edge magnification distortion: 13.9% Weight: 162g (5.7oz) With eyecup folded down and fully screwed down: 92mm long x 45mm wide Overall, it lives up to its posted specifications very well. The image appears sharp across the field without noticeable vignetting. Eye relief is a bit tight for eyeglass wearers, but you can still see a good portion (~90%) of the FOV without pressing in too much. The field stop is nice and sharp. However, due to extreme magnification, you can tell the edge is bit ragged due to machining limitations. I'm really reaching the resolving limit of my 72ED scope. However, the image held up fairly well. I've posted an updated 2.5mm to 6mm eyepiece AFOV photo collection including this eyepiece in the following thread: