Louis D

Once the exit pupil gets small enough, weak astigmatism in your observing eye may become unobtrusive without correction. Here's Tele Vue's chart for their Dioptrx line: You can calculate the exit pupil by simply dividing the eyepiece focal length by the scope's f-ratio. For instance, your 6.3mm Plossl in your f/5.9 scope yields a 6.3mm/5.9=1.1mm exit pupil. According to the chart, you might to want use astigmatism correction if your cylinder prescription is 2.0 diopters or more. I have 2.0 diopters of cylinder correction and can verify I can see sharpness improvement at a 1mm exit pupil when wearing eyeglasses. For a low power eyepiece, I would probably recommend the 30mm APM UFF or its other brandings ( Meade UHD, Celestron Ultima Edge, Altair Ultra Flat Field, Tecnosky Ultra Flat, and Orion (US) Ultra Flat). It is perfectly corrected edge to edge at f/6 and has plenty of eye relief for eyeglass wearers. With a 5.1mm exit pupil in your scope, you would need well less than 0.5 diopter of cylinder correction to avoid wearing eyeglasses, so this eyepiece is a good choice if you have more than that amount of correction. There are plenty of lower cost eyepieces with decent eye relief and wide field at or near this focal length, but they don't perform nearly as well at f/6 as this eyepiece. For high power, if your astigmatism is low (1.0 diopter or less), you could get away with not wearing eyeglasses and use eyepieces with less eye relief. Personally, I use a mix of Pentax XL and XW eyepieces with long eye relief at high powers because it's more comfortable, relaxing, and I almost never need to clean the eye lens of these eyepieces because my eyeglasses form a barrier to prevent eyelash gunk from getting on them. The Morpheus line might also be a good choice at a somewhat lower price point.

- Insufficient eye relief for eyeglass wearers. I can just barely see the entire field of the original 30mm ES-82 mushroom top (same JOC made eyepieces as the Celestron Axiom LX and the original Meade 5000 UWA) wearing eyeglasses. Being a scaled design, the 23mm would put the FOV just out of reach. At least for the 30mm version, it has strong ring of fire and some very minor edge astigmatism in the last 10% of the FOV at f/6. Stars are also not as pinpoint in the central 50% as the 27mm Panoptic or even the 30mm APM UFF. Stars remain a bit bloated in comparison at best focus. It's why I keep all of them. Each has its strengths. Have you compared the 23mm to a 24mm Panoptic or similar for central sharpness? It does have a perfectly flat field even to my presbyoptic eyes. I assume the 23mm is the same way.

I'm guessing it's a Bird-Jones/Jones-Bird telescope based on the fact that the main tube does not look to be a meter long as the 1000mm focal length would imply and is a relatively fat tube for an f/8.8 scope. As such, make sure there's an optical element toward the bottom of the focuser. It would look like a glass lens. It acts like a permanently attached 2x Barlow element to help correct the spherical aberration of the primary mirror.

That's a loaded question. Over the same ~60° field of view, I would expect the Nirvana to be better since that's still within the 75% inner area of Nirvana. Over the entire field of view, I would expect the X-Cel LX to be better since 60° is easier to correct than 80° while on a budget. There's a lot more at play here, though. At 60° and a lower power, you'll be more easily able to appreciate the view in one glance. The eye relief will be much longer, making the view more relaxing. However, the background sky will be brighter making nebula and globular clusters less contrasty. At 80° and higher power, you'll have to move your gaze around the field to take it all in in more detail. This will be made harder by the shorter eye relief as you have to move your head to maintain exit/entrance pupil alignment. On the plus side, the background sky will be darker, improving contrast on fuzzy objects. I would get the XCel LX if it's available for a good price at the current time. Just ask about black flecks in the field of view. There have been multiple reports of blackening paint flaking off onto interior lenses, messing up the view of the moon and the sun (observed with a proper solar filter, of course).

Time to go down the 2" eyepiece rabbit hole. 😁

If the 25mm X-Cel LX is the same as the 25mm Meade HD-60 which I do have, it should be a decent eyepiece. It's better corrected at f/6 than the 25mm BST Starguider, but it has a slightly smaller true field of view.

Sure you didn't. We believe you. 😉

How many diopters of astigmatism do you have in your observing eye? If it is low, you can probably get away with not wearing eyeglasses at mid to high powers. I have 2.0 diopters of astigmatism, so I can see an improvement wearing them at all but the very highest powers. The relationship actually revolves around exit pupil size rather than magnification, but the two are in inverse proportion to each other. In your situation, I would probably get a 32mm Plossl for 20x, a 12mm BST Starguider for 55x, and an 8mm BST Starguider for 83x. Since your scope is an achromat at f7.3, it's going to show a lot of false color even with the 8mm eyepiece. All of these eyepieces will have enough eye relief to be usable with eyeglasses. I don't find myself using in-between powers very often. I generally go for lowest/widest power, move up to mid-power for most observing, and then jump to highest power if conditions and the object warrant it. Technically, both the 8mm and 12mm yield mid to mid-low powers, but your scope isn't really suited to reaching for high powers above 100x due to aperture and false color. If you mask off false violet/blue and orange/red colors with a light green filter, you could push your power up to 130x with a 5mm BST Starguider on bright objects like the planets and luna and get a rewardingly sharp image. Even in my 8" Dob, I generally observe planets at around 100x to 125x on most nights because I get the best contrast on planetary details in that range. The moon and globular clusters are where I push to 200x or more. Your scope simply doesn't have enough aperture to ever resolve globulars, so they will always look like fuzzy blobs. That said, open clusters and bright planetary nebula should make for interesting observing in your scope.

D=Diameter of the primary mirror, the big one at the bottom of the main tube. FL=Focal Length: If you were to measure the distance from the primary mirror to the secondary mirror and the distance from the secondary mirror to the top of the focuser, it would be about 1200mm.

Having bright streetlights can be counterproductive when people forget to turn on their headlights because the roads are so bright. Sure, they can see the road just fine, but other drivers can't see that car nearly as easily as if their headlights and taillights were on. I'll flash my high beams at them when I pass them, but they always remain oblivious. Following them, I notice that they only turn them on once they enter an area without streetlighting. This doesn't apply to GM and other cars that have sensors to automatically turn on the car's lights at twilight and during wiper usage. It surprises me this feature hasn't been mandated for all cars by now.

If you go out to SearchLight Spectra Viewer and select the Astronomik and TV Bandmate II OIII filters, you'll see they're basically the same. Add in some other OIII filters, and you'll see that these and the Chroma are a cut above the rest. The Lumicons are as good in the OIII band, but bleed red. I can vouch for this. My 1990s Lumicon OIII shows OIII emission lines really well (no rust, thankfully), but bright stars have a weird green/red duality that I find distracting. I wonder if my cheapie Zhumell OIII is like the StarGuy OIII and passes C2 comet bands as well. The SG OIII is nearly identical to the Lumicon comet filter. That would be neat to have gotten a comet filter for $16 because it makes for a pretty poor OIII filter. 🤨

Another diagnostic tip is to defocus the star and observe the undulations on a larger scale. Put your hand in front of the objective and you should see heat waves emanating from it. Remember, we're looking up through many miles of thick atmosphere that has all sorts of currents and bubbles in it. It's one of the reasons professional observatories are placed high up on mountaintops that have fairly laminar airflow over them year-round.

And the AZ-GTi has a Point and Track mode that doesn't require prior alignment if goto is not needed (as for bright solar system and DSO objects) and the mount is well leveled. That alone sounds very useful for high power observing. Alignment of my Dob's DSCs can be an issue for me due to the narrow swath of sky I can see from my backyard. I use the app SkEye to get me in the ballpark of dim objects since it relies solely on internal sensors. It gets me close enough to know if the object is even visible at that time for me.

It's pretty simple. Just pause the video at the beginning of the section you want to highlight, right mouse click over the video, select the third option down (Copy video URL at current time), and paste that URL. You could even edit your post above to fix this by clicking on the three dots at the far right of the gray bar with your user ID and post timestamp, selecting Edit at the bottom of the list of options, delete the original video inserted and paste in the corrected URL, and then fix up the text since you now know how to do all this. 😀

You'll definitely want a side mounted alt-az for visual use, as long as you don't mind manual tracking. I've tried using a fluid head on a photographic tripod for astronomy with an ST80, but beyond a certain point vertically, the telescope tips back uncontrollably.

From my understanding of their offerings, the UHC-E is a bit cheaper because it has a wider passband around the H-β and O-III lines than the UHC. The general rule in passband filters is, the narrower the passband, the more expensive the filter, all other variables being equal. The UHC-E also seems to pass a bit less of the H-β and O-III lines, but you'd be hard pressed to see this difference visually. Astronomik also recommends the UHC-E for 5" and below telescopes and the UHC for larger scopes; although if you have both, I would get the UHC. In use, having a narrower passband will eliminate more light pollution and sky glow. This will in turn increase contrast making nebula features easier to see. At a dark sky site, this would be of less importance. UHC-E: UHC: Astronomik points out that the UHC-E filter passes at least one of the C2 carbon lines at 511nm and 514nm associated with comet filters like the Lumicon Swan Band Comet filter. Thus, it might serve double duty. I'm kind of surprised they didn't include them in the UHC-E passband image above for positive marketing purposes. Lumicon Swan Band Comet Filter:

Famous last words:

Absolutely correct. I just don't know the details involved in other industries as intimately as I do semiconductors.

Stacking an OIII with a UHC will just pass the OIII lines if the UHC was designed correctly. Of course, if the UHC passes OIII less efficiently than the OIII, the OIII lines will be dimmer. If the UHC doesn't pass OIII (they all should, but some are off a bit), then you'll see basically nothing. Short answer, don't stack nebula filters. You can stack other filters types like the moon & skyglow filters with a yellow filter to more strongly cut unfocused violet light when using an achromatic refractor. The combination can improve sharpness a bit in that usage case at the cost of some blue light.

The Technosky is Long Perng made, I believe, and many reports are claiming better quality control, consistency, and spherical aberration correction than the Sharpstar. Long Perng is Taiwanese while Sharpstar is Chinese if that matters to you. Even then, it's likely Long Perng sources some parts from China. I have the older TS-Optics Photoline 90mm APO FPL-53 triplet for visual use, and the rear end of it looks almost identical to the 94EDPH. They use really beefy thumbscrews that seem to be solid steel or brass instead of pot metal. The machining and fit of everything is first rate as well. I really like the camera angle adjuster for aiming my diagonal off to the side without loosening the retention screws or rotating the focuser. I haven't tried removing the rear tube section to use binoviewers natively yet, though I'm sure it works fine. Now my peeves with it: It annoys me a bit that it shows spherical aberration on one side of focus. I get a nice Airy pattern on only one side of focus. The other is just an even blur. I guess we'll leave it to AP, Tak, TMB, TEC, and LZOS to nail that detail. The focuser is a bit mushy under heavy loads as well. I have to overshoot best focus a bit near zenith with a 3+ pound load in the focuser because the fine focus knob tends to counter rotate a fraction of a turn once let go of. This might not be an astrophotography issue with a motorized focuser, though. I don't know if it would be up to the task of demanding AP. It also shows pinched optics while acclimating (spiky stars). This can take 30 minutes or more to settle down. Again, I find this annoying in a smallish refractor. False color seems well controlled in focus even on bright objects. However, it shows green tinge on one side of focus and red tinge on the other, so it's no reflector. Otherwise, it's been a decent enough visual-only scope, but it's far from what I would consider perfect for visual use. Would it be good enough for AP? I can't say. For what I paid used for it, I can't complain too much. It was way cheaper than an AP Stowaway.

I use a 6" long bolt of the same thread as a threaded hole on my DSV-2B mount with about a pound of washers I had laying around hanging off the end of it. It swings up to horizontal when the mount is at zenith to partially counteract the effect of the eyepiece in the diagonal.

If you don't have strong astigmatism in your eyes, you don't really need to wear eyeglasses with binoculars. Sure, leaving them on can speed up looking at the sky naked eye, and then quickly switching to binoculars without having to take off your eyeglasses first. To diagnose your issue, take off your eyeglasses and then start by focusing the binoculars by closing the eye with the diopter adjustment and focusing through the other eye. Next, close the first eye and use only the diopter adjustment to focus for the other eye. Now open both eyes. You should see two equally sharp images. If you have astigmatism, you'll see a slightly blurry image in the daytime or spiky stars at night. Now, close alternating eyes and see if the image jumps between two positions or remains stable regardless of which eye is viewing. If you see the image jumping about, your binoculars need collimation. Put your eyeglasses back on and repeat the above steps. Do you see any differences? There is a very slight possibility that your eyeglasses have prism correction which allows you to merge misaligned images naked eye. However, you'd probably be well aware of it since it is usually diagnosed at a young age. That, and you'd see double images without eyeglasses or binoculars.

What's your budget? What do you like to observe? Do you have strong astigmatism in your observing eye? What eyepieces do you already have? Your question is a bit too open ended to make any specific recommendations beyond getting low, mid, and high power eyepieces to cover a broad range of objects.

Having worked in the semiconductor industry for 35 years, I can explain a few things about chip costs and manufacturing. Chips were cheap when they were small and contained relatively few transistors. Practically any company could afford to make them. However, you could forget about portability or battery power for all but the smallest of chips. People demanded more functionality in smaller and more power efficient packages. This necessitated more transistors and larger chips. This also necessitated shrinking transistor sizes. This increased manufacturing costs and startup costs. Chips being more complex required more and more process steps to complete them, requiring longer and longer manufacturing times. If you cancel an order today, it can take 9 to 12 months or longer to get back in the queue during good times. Automakers and others foolishly cancelled chip orders early on in the pandemic due to a panic reaction, not fully realizing the consequences of their actions. Foundries simply filled those manufacturing slots with orders from further in the future that were going to wait for the automaker orders to complete. PC, laptop, and tablet sales and semiconductor orders skyrocketed, more than making up for the lost automaker orders. Future slots filled up fast. The automakers and many others were shutout in the near term. Fast forward to today, and it costs 7 to 10 billion dollars to build a cutting edge semiconductor foundry to manufacture chips. Even mighty Intel is struggling to keep up with Samsung and TSMC (the two largest leading edge contract chip houses or foundries). All the other leading edge legacy chip design houses have sold their legacy foundries and have gone fabless (outsourced their chip manufacturing). Most legacy fabs in the US are owned by Global Foundries. These legacy foundries make "good enough" chips for many purposes, but at an elevated price per part at yesterday's performance and power levels. The US military is one of their biggest customers since they try to source as much from within the US as possible. One problem for the US military is that there are no microprocessors made in the US anymore. Unless governments such as China and the US are willing to subsidize new foundries in their own countries, it's unlikely this consolidation of semiconductor manufacturing will change. You have to be able to sell billions of chips per year to recoup your foundry investment costs. This requires taking in orders from outside of your own company even for companies like Samsung that sell hundreds of millions of consumer products a year. Even building a small custom chip requires a $10,000,000 up front cost for manufacturing setup and reservations. Thus, a lot of companies are moving toward FPGAs for low volume (less than 10,000 units or so) production. These chips are programmable but cost more per unit on a gate level functionality basis. It might cost $100 to $2000 for a single FPGA that a custom ASIC in full production volume might cost $5 to $100. However, if you amortize in the setup costs, they come out cheaper for low volume production. FPGAs are also larger, hotter, and draw more power than their ASIC equivalents, so they're not a drop-in replacement for all applications. Also, no FPGA can hold an entire cutting edge microprocessor's worth of gates or run at their elevated clock speeds. Thus, FPGAs are best for smaller designs and/or coprocessors to offload compute intensive operations from the microprocessor.

Well, I find the jump from 1 degree to 1.7 degrees with a 40mm SWA 2" eyepiece quite nice in my 127 Mak. It's not widefield like a 72ED frac, but it does help with getting targets centered and for showing better context since it reveals 2.9 times as much sky by area and 70% more by linear measure. Since I already have all the required bits, it seems silly not to use them just to remain a 1.25" purist. That, and I can use my ES-92 eyepieces which are 2" only.