Louis D

Not bad looking for a first effort. It might also work well in a Mak with a 2" visual back to get to a large exit pupil for use with a nebula line filter.

Please post a pic of what you came up with. I'm curious now.

There's a person over on CN, Martin Pond, that at least used to post quite a bit about his tinkerings with various home brew eyepiece designs made mainly from surplus binocular optics. There are several more folks tinkering and sharing ideas there as well. They also mention a Facebook group as well for homemade eyepieces. Hunt around a bit, you might find some fellow eyepiece builders out there to share ideas with. It's a subject that indeed comes up rarely on SGL, but a search here might be worthwhile as well.

To add to the excellent suggestions already: The phases of Venus over time The double-double in Lyra (i.e., Epsilon Lyrae) Trying to pick out Mercury near the horizon naked eye is always rewarding Collinder 70 (Orion's Belt) in binoculars The star cluster rich area near the Double Cluster and Perseus (sorry, don't exactly know the name, but it is beautiful to scan around) The summer Milky Way from Sagittarius to at least Cygnus. It's loaded with bright nebula and star clusters. Again, scanning along it is rewarding. Galilean moon transits/occultations of/by Jupiter and their shadows on Jupiter are fun to watch in real time With a fast achromatic refractor such as yours, you may need to sometimes add some filtration to see fine planetary detail through the violet/red fringing.

Yep, T-thread/mount for camera adapters. It's M42x0.75. Not to be confused with the M42 mount which is M42x1mm and was also used for camera lenses.

Actually, its the distance to the focal plane of the eyepiece that matters, not the location of the lower lens. This is particularly true for eyepieces with internal field stops due to the use of a Smyth lens group.

Check my recent post to the TS 152 thread: I've been chasing the same goal of getting rid of spurious color in fast achromats. I've come to the conclusion I'd rather live with a bit of yellow-green tint and give up H-alpha for non-nebula observing. As such, a nice high transmission, sharp cut-off 470nm long pass filter gets rid of all the violet fringing while leaving almost all blue. This is fine for DSO observing. However, for solar system observing, adding a high transmission, sharp cut-off 625nm short pass is a must to cut red fringing. The color cast goes a bit more yellow-cyan than yellow-green with it. It's certainly possible to then stack whatever nebula, pollution, or Neodymium filters suit your tastes. Can you post the XLCR-1 curve as a point of reference?

The reviewer totally missed that the residual false color with the minus-violet filter was coming from the red end of the spectrum. That was what was causing some issues with planetary observing. Literally no commercial false color filters include far red filtering for unknown reasons. Sure, it's not obvious with no filtering, but once the violet fringing is minimized with a minus-violet filter, it is blatantly obvious as a bright red rim around every bright to dark edge on bright objects. It's not very obvious with scotopic vision due to the response curve of the rods in our eyes, so DSO observing is generally not impacted all that much by it. In my experience, it's the red light above 625nm that really contributes to red flaring in achromats, and scotopic vision pretty much doesn't pick up anything above 600nm as shown below: Thus, little to no red flaring on dim objects once dark adapted. However, photopic vision really picks up on red above 600nm on bright objects like planets and the moon, so some sort of short pass filtering is needed for fast achromats when observing such objects. Weirdly enough, no astro vendors sell such a useful, even necessary, filter. I've had to retask industrial and photographic filters for astronomy use as a result. The closest astro filter is the long out of production Hirsch Light Blue #82B which is really a light cyan with a gradual short pass cutoff around 625nm and fairly high transmission. I happened to find one on ebay last year. I'd never heard of it until then.

Not sure who you're addressing, but I also have a 6" f/5 GSO Newtonian that makes for a fine, sharp wide field scope with no false color, cool down, or dewing issues. I think I picked up my lightly used copy with the GSO Linear Focuser, GSO coma corrector, 8x50 finder, and laser collimator for about $300 shipped. At 13 pounds, it's also considerably lighter than the KUO 152 refractor. The spider vane diffraction spikes don't bother me at all. I also like having the eyepiece up nice and high so I don't have to extend the tripod's legs, leading to a more stable mount. While the Schmidt-Newt and Mak-Newt sound interesting, I'll stick with the simplicity of a pure Newt for now.

One more update on the KUO 152 and filtering. Santa brought me high transmissivity SP625, SP650, and LP470 filters, where SP means Short Pass (cyan in this case) and LP means Long Pass (yellow in this case). The LP470 exactly removes all violet fringing, unlike my Hirsch Light Yellow #12A which has roughly the same cutoff frequency, but trails off a bit, allowing some dim violet to get through. The SP650 helps some with cutting unfocused red light while causing very little color shift. The SP625 almost completely eliminates unfocused red without causing a drastic cyan color like my SP600. So, I spent some time last night on Jupiter, the Orion Nebula, and Orion's Belt (Collinder 70) with the LP470 ahead of the diagonal and swapping in the SP625 and SP650. For dim objects, the SP650 combination was good enough, but for bright objects, the SP625 was noticeably better. With the LP470/SP625 combination, I could sharply see Io approaching Jupiter and then merging with it. I still couldn't make out that it was in front of it, though. Without the filter combo, Io was lost in the unfocused light flares. I then added the Zhumell Urban Sky (Moon & Skyglow) filter (roughly the same as the Baader Neodymium), but I didn't see any appreciable new details, although it did slightly dim Jupiter making it a bit easier to view. Before coming in for the night, I removed the LP470 from the diagonal and moved it in and out of the FOV above the eyepiece. Even combined with the SP filters, there was no appreciable dimming of the Orion Nebula with the filters thanks to their 95%+ transmission each. However, the Trapezium was easier to resolve at low powers with the filters than without again because of their suppression of unfocused light flares. I even compared the various LP/SP/M&SG combinations to the Baader SemiAPO filter. It was no contest. The BSAPO was doing almost nothing to sharpen up the image compared to the various LP/SP combinations. Adding the M&SG to mimic the BSAPO frequency notches due to its Neodymium substrate didn't really add anything to the LP/SP combinations. I think Baader did that just to remove some excess yellow to compensate for the violet suppression. If Baader were actually serious about their BSAPO mimicking an ED scope, they need to suppress unfocused red light along with the unfocused violet light, but they don't. For the LP470/SP650 combination, the M&SG does result in a more neutral color for Jupiter. However, with the LP470/SP625 combination, it simply shifted the color more cyan than the yellow-green it already was. I preferred the yellow-green cast to the cyan cast. Overall, with the LP470 and SP625 in place, the KUO 152 was much more satisfying to use than without. The light yellow-green color cast was hardly noticeable after a while. I actually began to enjoy sweeping the star rich regions of the Orion constellation with it. Once the moon is back in evening skies, I'll have to try out the new filters on it as well.

I recollect it came from Telescope Warehouse originally. The owner, Bill Vorce, seems to get a lot of surplussed ES equipment. This particular eyepiece (the 12mm ES-92) has no Smyth lens group, only the upper, positive section. I'm guessing it was an abused return. Without the lower section, it has a 28.5mm focal length with an exposed field stop below the lenses. I removed the lower section's empty tube and added two step rings to adapt the original 2" nosepiece directly to the upper section. This reduced the required in-focus from 40mm to 21mm. It's third from the left in the group shot below. In the second image, you can see it has such a wide true field of view that I had to add a second yardstick to measure it. The slightly dark line near the left edge of the ES-92 29mm "full view" is where they push against each other. None of my other eyepieces, even my 40mm Pentax XW, are this wide in TFOV. If ES could reign in the extreme chromatic aberrations with a compensating prismatic, but zero power, lower element, it would make an awesome eyepiece. Even as it is, I love scanning rich star fields with it. It is what the Kasai Super Wide View 30mm 90° should have been.

The only Panoptic I have is the 27mm, and I've never noticed any SAEP with it. I just can't stand its tight eye relief while wearing eyeglasses. The 12mm and 17mm Nagler T4s are loaded with SAEP. It's so bad, I can't hold the entire FOV once the field stop becomes visible as I move closer to the eye lens. I tried the original Radians side-by-side with the Pentax XLs in the daytime at a shop back in the late 90s. I couldn't hold the FOV in the Radians at all, but had no problems with the XLs, so I ended up going with the XLs. I didn't notice any "coffee" tone in the Radian. My lone Vixen, a 9mm LV, views darker than my other 9mm eyepieces. I can't say that it doesn't go as deep as a result, but it sure seems dim by comparison. I wonder if it is due to the Lanthanum element introducing a coffee tone that suppresses blue hues to some extent? I don't see a coffee tone in the daytime with it, though. Perhaps I should try a fixed color balance photo through it to find out.

I recall seeing one of the Celestron long FL lineup in a photography store glass case back in the mid-90s. It was impressively large for the day, and expensive.

Absolutely loved the scenery and the people when the wife and I vacationed there 30 years ago. Hopefully, nothing has changed for the worse.

Sure they do when they're above the shoulder. There's some vignetting and lots of in-focus is required, but it does work. I've got the bare upper section of a 12mm ES-92 with a 51mm physical field stop that actually measures in use to be 48.4mm, probably due to cutoff from the internal shoulder step. Chromatic aberration is so bad toward the edge that I've never noticed vignetting.

Or a great month to take a holiday somewhere else with better weather. I usually vacation in the Mountain West during the heat of summer here.

We do get a lot of blue skies in this part of Texas. In fact, it was clear here for the entirety between Christmas and New Years. It's cloudy and drizzling right now, though. We need the rain. We were over 10 inches behind average (32 to 34 inches around here) for 2023. Of course, the further west you go in Texas, the more clear days you get because it gets more and more arid moving away from the Gulf of Mexico and toward the Desert Southwest. This map of average annual rainfall pretty closely tracks clear sky days. Less rainfall equals more sunshine: Moving from east to west across Texas, you go from Cypress swamps to high desert. I don't know of any European country that can say that. Australia is most similar to Texas in this and many other respects, though.

It's probably the whole change to making the international seller collect VAT instead of the courier/buyer collecting/paying VAT. It creates a huge amount of paperwork to collect it for each and every possible taxing jurisdiction and then remit it. I think that's what Don P. ran into with his recently shuttered store. He only had to collect sales tax for California sales because he didn't exceed $500,000 in sales to any other state. That really simplifies paperwork. I also know Gary is 80 miles from the nearest post office from which to get the proper export paperwork to fill out and file, so he doesn't want to deal with that headache. The US market is large enough that most sole proprietorships don't feel like they're giving up much in sales to stick with US-only sales.

They are highly sought after in the US, show up infrequently, and command high prices for what is a basically a Plossl. I think Gary Russell or Harry Siebert could cobble together something similar if asked.

Sounds like my neighbor who put in 2 foot high metal edging along the fence on their side. This effectively created a dam and violated Texas law about blocking the natural flow of water and causing it to flood neighboring properties. Rather than take them to court, I waited until they moved out and listed the home for sale. When no one was around, I went over to their yard and ripped out all the metal edging to allow water to flow naturally again. That was 20 years ago, and no new owners have ever tried blocking the flow again.

Our part of Texas is quite particular about limiting runoff from impervious cover. Developers have to build large catch basins with elevated outlets to retain most of the runoff and allow it to soak into the ground rather than run off into a stream, creek, or river. This also limits the spread of pollutants from oil spills on pavement. Here's one near my house with a little bit of water still in it just behind the spillway to the far right: That whole open area can fill with water after a rainstorm like a temporary pond. If it rains more than it can hold, the excess goes over the spillway.

A shorty Barlow tends to be any Barlow that seats all the way into a diagonal. They have deeper curves in the lens group to diverge the light rays in a shorter distance to get to the same magnification factor that traditional long Barlows get to over a longer distance. Here are some images I found illustrating the difference. Shorty Barlows next to a PowerMate: Long Barlows next to a PowerMate:

IIRC, it happens with simple positive-only eyepieces like Plossls and shorty Barlows with rapidly diverging light cones. I think it's what is causing SAEP in the 6mm and 9mm 66 degree "UWA" eyepieces as well. Eyepieces with a well designed Smyth lens group tend to tame down the incoming diverging light rays pretty well.

Unless you're using a super slow scope like an f/15 Mak and want a large exit pupil for narrow band nebula filters, I can't think of a particularly good reason to have a long focal length Plossl.

I've found Barlows can also create SAEP (kidney-beaning) where none existed before.