Louis D

I searched around the internet and the best diagrams of 3 element doublet-singlet eyepieces were on Telescope-Optics.net. I cropped and combined together four Kellner or "Reversed Kellner"-like designs below for easy comparison: There was no mention of a true Reversed Kellner design on that site.

I still see some used electronic setups relying on RS-232 connectors in the classifieds. I think to myself, how would I rig up a way to talk to it? Some sort of USB dongle? What about drivers?

Same here. I'm thinking a harmonic mount would be terrific. My biggest gripe with regular GEMs is that they require counterbalance weights. Really? It's been how many years since harmonic drives became common place in manufacturing robots (with no counterweights), and they're only now making it into astro mounts?

Yep.

Bumping for today.

I'm jealous. It would probably take a Carrington level event for me to ever see the Northern Lights from Texas.

Sure you can observe through glass. Can you observe well through ordinary window glass, no. Generally, you can still pick out the high contrast details like the positions of Jupiter's moons and the features along the moon's terminator. If you go to the trouble of replacing your glass with optical glass polished flat to within 1/10th wave or better and coat it with anti-reflective multicoatings, you'd stand a much better chance of being able to do critical observing of low contrast objects. Consider this. I don't know of a single observatory, professional or otherwise, that observes through glass of any type. The scope is always open to the elements.

Maybe Apple is keeping Canada behind the technology curve and they've only released up to 12 there. 😉

I guess it comes down to optical pickiness versus budget. The TV NT6 13mm would seem to tick all the boxes except for price. At that focal length in 1.25", I really like my APM Hi-FW 12.5mm. However, it's probably too large and heavy for your intended use case(s).

What's wrong with the Speers Waler 13.4mm in your signature?

Also good for flocking the rear baffle tube of Maks and SCTs.

I've had this problem with brass compression rings becoming distorted on undercuts and then coming up and out of their groove and jamming the eyepiece in the holder when trying to pull it up and out. It took a lot of coaxing to get the ring to drop back down in the groove so the eyepiece would release.

Okay, then the ability to overtighten is a design flaw that needs fixed in a future release. They could design it to use a torque sensing release that just clicks and rotates once it reaches the proper tension. The gas caps on my cars have worked this way for years without any problems.

I'm guessing much lower violent crime rates in the UK allow the police to investigate laser violations there. We had a case here where it took police 2.5 hours to respond to a DUI/DWI vehicular accident involving injuries because they prioritize homicide investigations much more highly.

I've heard of that as well. Older eyes tend to filter violet light. From a quick internet search on the topic: Apparently, age 70 is about the starting point. The eye's lens starts to yellow, filtering violet and some blue light. It can also mess up distinguishing green from yellow-green. Cataract surgery that replaces the natural lens can fix this issue as a side benefit.

Be conscious of the weight of 2" 82 degree eyepieces. The 30mm ES-82 and 31mm Nagler T5 are both quite heavy in particular.

Agreed. They're basically the same as the Green X1 filter just with higher transmission which doesn't really matter on bright stars, planets, the moon, and the sun: Bessel V curve: Or Johnson-Cousins V curve (the green one): Hoya (Rokunar) Green X1: I looked for an affordable V filter, but couldn't find one. I'm happy with the X1 for now.

By one account on that other forum, they're pretty close with the NZ being better across the zoom range, especially at the short end. Despite having the means to purchase a NZ, I could never justify the cost and limited use cases for my preferred styles of observing. The price/performance ratio of the SZ is such that I had no issues picking one up for my travel kit. I've been quite happy with it.

Perhaps for BV usage. Eddgie, the BV guru over on that other forum, has been gushing over his recently acquired pair for BV usage.

Sounds like there needs to be a buck-boost constant output voltage regulator between the battery and the device.

This thread got me interested in revisiting fast achromats a bit more, so I recently picked up a used Astro Telescopes 6" f5.9 first generation KUO achromat for a good price. It's basically the same optically as the current Starwave 152mm F5.9 V3 and TS-Optics RFT 6" f/5.9. My first impression is how much heavier it is than a 6" f/5 GSO Newt (about 10 pounds heavier). I mounted the two on either side of my DSV-2B mount. Surprisingly, it didn't have any motion issues with the two once well balanced. Going back and forth, I would have to recommend the Newt as the better all around scope for most folks. It's lighter, cheaper, color free, and the eyepiece is in an easier to view from position (at least for me being a Dob guy). That being said, it's pretty special viewing bright objects with no spider diffraction spikes in the achro frac. However, you have to filter the view in the frac to get a sharp view which brings this post back to the subject of this thread. I also picked up a Baader Semi APO filter for a good price recently. All I can say is, it cuts maybe 50% of visible violet fringing while trying to maintain a neutral color balance by cutting yellow and orange spectrum using Neodymium glass. It cuts violet by using violet reflective coatings instead of yellow glass. As such, this filter is probably more appropriate for daytime use where such things matter more. I'm just glad I didn't pay full price for it. Pairing it with either the Hirsch Yellow #12A or Rokunar Yellow K2 eliminated all residual violet fringing at the cost of a bit more yellow cast. Much more cost effective are my two recent purchases detailed in my previous post: the Rokunar Yellow K2/#8 and Rokunar Green X1/#11. Both are high quality Japanese made photography filters in 48mm mounts, so they can be used as 2" astro filters. On bright objects (above magnitude 2), the Yellow K2 cut all violet while introducing just a slight yellow cast and adding very little to no additional scatter. Sirius looked more pleasing without spikes in the achro than it did with spikes in the Newt. I did not attempt to see the Pup in either, though. However, there was residual red fringing which made Sirius sort of orange depending on how I refocused with the filter. Thus, in went the Rokunar Green X1 filter. All violet and red fringing was gone with just a slight green cast added to the star. It yielded a distinctly sharper view. Basically as sharp as the Newt, but with less scatter because of a lack of central obstruction and spider vanes in the frac. The 50% transmission of this filter was not an issue on such a bright object. If anything, it made it easier to view. Overall, I'm very pleased with these two vintage photography filters. I'd love for GSO to bring them back in 1.25" size. Right now, their Yellow #8 is more like a Wratten Yellow #3/#4 and their Yellow-Green #11 is more like a Hoya Green X0 which has no Wratten equivalent that I can find: The Hoya Green X0 (GSO #11) passes way too much orange and red to be useful at blocking residual red fringing once violet fringing has been blocked. That, and it's not quite aggressive enough at blocking violet fringing. It's very similar to my Hirsch Light Green #11, which I've found to be ineffective at completely blocking either violet or red fringing on bright objects. The Rokunar Green X1 was definitely sharper and caused less scatter than my home-brew R89 Moss Green film mounted in a 1.25" Meade #8 Yellow filter or 2" Skylight 1A filter. I'm glad I was able to locate an optical glass equivalent to the R89 film. The Rokunar Yellow K2 was just slightly more aggressive than my Hirsch Yellow #12A at cutting violet/blue wavelengths. I would consider either acceptable for cutting violet fringing on bright objects. Both are way better than either a modern GSO Yellow #8 (too weak) or GSO Yellow #12 (too strong). The cheap Chinese made Yellow filters come closest, but with more scatter. The biggest surprise of the night was that violet fringing was all but invisible at magnitude 2 and dimmer. Thus, the Orion belt stars and Collinder 70 looked just as good in the frac as in the Newt. The same goes for the Orion nebula and nearby open clusters. It's hard to say if they looked better in the frac to justify the weight, cost, and color fringing issues on brighter objects. I just enjoyed discovering that large, fast KUO achromats are almost indistinguishable at moderate powers from a Newtonian. I'll keep the 6" f/5.9 achro for a while to see if it grows on me.

I discovered another plus for the laser sight last night. I had both my 6" Newt and 6" frac on either side of my alt-az mount. The two sides aren't quite perfectly aligned. So, I put the laser on the Newt (and aligned it) and the RACI on the frac. I would find a dim object scanning the sky with the Newt (shorter focal length makes it easier) and observe it for a bit. Then, to center it in the frac for comparison purposes, I would light up the laser while looking through the RACI which was aligned with the frac. I would note where it was pointing on the sky in the RACI FOV, quench the laser, and move the RACI crosshairs to where the laser had just been pointing. BOOM! The frac is centered on the same object in seconds. It's much quicker, easier, and more accurate than jumping between two RDFs on two scopes to do the same. Yes, I need to work on getting the two sides of the mount aligned better, but this was a great workaround.

Having owned some Tele Vue eyepieces, I can attest that they are not perfect and can be improved upon. I retired my 27mm Panoptic in favor of my 30mm APM UFF, my 12mm NT4 for my 12.5mm APM Hi-FW and 12mm ES-92, and my 17mm NT4 for my 17mm ES-92. I'm on the hunt for a 22mm NT4 replacement with greater eye relief and/or AFOV while being at least as sharp across the field with less SAEP. The 23mm Pentax XW 85° might be that eyepiece. I'm just not willing to drop $500 on one until I know for certain it is comfortable to use with eyeglasses (at least 17mm of usable eye relief in my case). It seems to tick the other criteria (greater AFOV, sharp across the field, and less SAEP).

Read up on SkEye DSC star alignment. The key is to mount the phone to the scope and then use one of two alignment options: 1) select an alignment object in Indirect mode and slew to it and confirm or 2) point to a well known object and then drag the screen to the object and confirm it when centered. I generally use the second method.

Although I wonder how much effect observing locale or clientele has on the optical properties of a widely available eyepiece. I could see where power supply impressions might vary greatly between US/UK given the power grid differences.