Louis D

You have to be very careful with all laser pointers, especially the cheap green ones outputting at 432nm. They often output way more than the rated 1 mW to 5 mW in green. Even worse, they often output 100 mW or more in the infrared because the cheap ones omit the IR blocking filter. You won't even realize your retina is being fried if flashed by one. They are great for pointing out things in the sky, but you have to be really careful to scan for any aircraft in the area to avoid dazzling and temporarily blinding a pilot. If that happens, the authorities will definitely hunt you down. The biggest issue I have with them is that little kids try to jump up and grab it out of your hand because they want to wave it around to pretend it's a light saber. They pay no attention to what you're pointing to in the sky. It's a huge distraction for everyone involved. Now, let's say you're done pointing out things with it. Now you have to secure it away, so little hands won't grab it when you're not looking. Can you be 100% certain little hands can't access it? Some high end laser pointers come with keys to lock and unlock them to secure them properly. Removing and safely storing the battery or batteries is another option to safe them. They've been such an issue in Australia that you have to be a trained member of a recognized astronomy club to be allowed to point them to the sky at outreach events.

Well, I guess we'll just have to get someone to buy 10 XLs in each of the US and UK from various dealer stocks, and then run extensive tests on them to determine if the differences in viewing experiences are due to unit to unit variations. 😏

I just checked US online retailers today, and the Pentax XL zoom goes for ~$329 at most retailers. The Baader BHZIV goes for $309 at pretty much every retailer. I recall the XL costing that much 20 years ago. For comparison, the APM Super Zoom doesn't seem to have a US retailer since Don closed up shop. However, direct from China via AliExpress under the Sky Rover brand it is available for as little as $329. For the XL and BHZ, you'd more than likely need to add local sales tax. The SZ would be tax/tariff free when ordered via AE.

I came across the term didymium as relates to neodymium and think it might account for the difference between the Baader Neodymium and generic M&SG filters. It turns out that didymium is a mixture of neodymium and praseodymium which happen to be right next to each in the period table of elements. The two elements are almost always found together in nature. Didymium glass has been in use for years by glass blowers and some blacksmiths to cut down the glow from hot sodium to a bearable level visually. Neodymium accounts for most of the blocking, but praseodymium accounts for some as well. It's this cutting of sodium emission lines that accounts for it being a decent light pollution filter when sodium lamps are the dominant LP source. My supposition is that Baader uses pure neodymium glass while the Chinese made M&SG generic filters use the cheaper didymium glass. As such, the latter blocks a bit more light thanks to the contribution of praseodymium. I think didymium is probably cheaper because it takes extra processing steps to separate neodymium from praseodymium. The neodymium glass has higher overall transmission than the didymium (M&SG) glass, so it would be better for faint DSOs. However, for making a poor man's Contrast Booster in combination with a cheap yellow filter to use while observing planets, the extra sodium line absorption of didymium (M&SG) filters might actually be advantageous. It also turns out that photographers have been using didymium filters for photographing fall foliage to make it look more vibrant by cutting some of the orange/yellow part of the visible spectrum to create a band-gap to reduce a certain muddiness to the image. This is basically what the Contrast Booster is doing, but additionally it cuts violet light with a yellow filtration to further increase perceived contrast visually.

Yes, @John mentioned that possibility above. However, the glass disc must be plane flat and free of bubbles or other flaws. It must also be multicoated to avoid a fairly serious loss of light due to reflection. I would think centering has to be done at the factory as with catadioptrics. There are hybrid scopes such as Mak-Newts that use spherical curves for everything but the flat secondary to avoid figuring a parabolic primary. There's also a Schmidt-Newt, but I know very little about what's going on with it. I would also think that glass secondary mounts would be size limited at a certain point, just like refractor primaries, so probably not the best choice for giant Dobs.

It depends on the thickness of the spider vanes and their number. Curved vanes distribute the spike around the entire field of view, slightly decreasing contrast by increasing background brightness. The main time diffraction spikes can be a pain is if you're trying to find a faint companion to a bright star, and it happens to be right behind a diffraction spike. If the tube is rotatable, you can reorient the spikes to possibly reveal the faint companion by putting it between spikes. I would take diffraction spikes in a fast Newt any day over the unfocused light at either end of the spectrum in a fast achromatic refractor of similar aperture.

Not sure what your point is, but if it is that a particular channel needs a different focus to be sharp than the other channels, then so be it. However, it could also be that due to design choices, the blue channel is less well corrected and doesn't ever reach a sharp focus relative to the other channels.

Be aware that some well corrected eyepieces like Panoptics and ES-68s greatly distort the moon if it is allowed to drift to the edge. It's a trade-off for better to excellent edge correction. If kept on axis, you won't notice any distortion issues.

Generally, there's a threaded ring holding the lenses in from the front of the scope. Take a look down the dew shield end of things to see if you can make out a retaining ring of some sort.

We haven't had any measurable rain here in our part of Texas for a month. That doesn't mean it's been clear skies. We've had clouds at least half of that time just teasing us. 30 years ago, we had much more predictable rain patterns in our area.

Here are Ernest's tests of the four eyepieces in question: Levenhuk ED 40mm (Aero/Lacerta/Titan/TMB) Vixen LVW 42mm Pentax XW-R 40mm Maxvision 68° 40mm (Meade 5000 SWA, ES-68) His testing of the Maxvision/Meade/ES makes no sense to me. Mine is almost perfectly corrected at f/5, so I can't imagine how it did so bad at f/4 for him. According to his testing, it performs more similarly to the Meade 5000 Plossl 40mm than the others in the list, which is not true in my experience. Look at how bad the Meade Plossl did in my photos at f/6.

I don't know about the Vixen LVW 42mm, but the Pentax XW 40mm is slightly sharper to the edge with better eye relief. The JOC made Meade 5000 SWA 40mm is much sharper to the edge with lots more eye relief. The ES-68 40mm is supposed to be similar to the Meade, but with less eye relief due to the design of the eyepiece top. Weight for weight, though, you really can't beat the Aero ED 40mm. Here's my comparison image of 32mm to 42mm eyepieces. My Lacerta ED is the same as your Aero ED.

@mikeDnight I assume you are using an Icarus filter to observe DSOs in the daytime? 😏

I took a hard pass on a 127 Mak at a good price on an EQ mount with counterweights a decade ago. I could barely lift it one handed due to the weight and top-heaviness of it. I need to be able to pick up and move my mount and scope around the yard to dodge obstructions, so this weight and bulk issue was a non-starter for me.

I have both the 24mm and 30mm APM UFFs. The 30mm is the better of the two. The biggest issue I have with the 24mm is that the field stop is fuzzy and the last 3% or so of the field is also fuzzy and vignettes. Basically, the designer pushed the design just a little to far for largest possible true field of view. If I had a tracking mount, I might not notice the edges so much.

That, with a 40mm Pentax XW, 40mm ES-68, or 41mm Panoptic would probably work best. Heck, at f/10, you could get away with less well corrected ~40mm eyepieces or even a 56mm Plossl. Alternatively, you could get a 0.63x focal reducer to use a 32mm Plossl for maximum field of view. The problem with these is that you would want to remove them for high power viewing because they add spherical aberration that is only visible at high powers.

There used to be a 1.25" Crayford focuser available as well, but I think it's been discontinued. Fitting a 2" focuser on a 127 Mak would be tight for space up against the native focus knob. Either way, you'd need a Synta Mak thread to SCT thread adapter ring. You'll see your focal length grow from 1500m to about 1700mm. There may also be a bit of added spherical aberration due to the non-optimal mirror separation.

You could add a RACI finder, Rigel QuickFinder, and/or a green laser sight to make using the Dob easier. Here's one of my finder setups along these lines: They're mounted on a three way finder extension.

If the air outside is super dry (dewpoint at freezing and below), you can cap your eyepieces and equipment to trap the dry air to avoid moist air from immediately hitting the cold optics and condensing on it when you bring it inside. Once they warm up to room temperature after an hour or so, you can uncap them as a precaution. If the eyepieces are stored in an airtight Pelican style case that is sealed with dry outside air before bringing it inside, you don't need to open it up. The moist interior air won't get to the optics before they warm up. If you have moist outside air, then what you are doing is the best.

The one original LV I really want is the 50mm. It's supposed to be really special. That, and it looks awesome.

The only 12" Dob I've used was a 12.5" Mag-1 Portaball with a Zambuto primary and Feather Touch focuser on an Osypowski equatorial platform at a star party years ago. It gave superb views of Jupiter with lots of detail in the bands. The platform worked great to keep objects from drifting. Being a ball design, it lacked Dobson's hole near zenith. It was super easy to move from object to object. DSCs weren't an option, but it would probably work well with today's smartphone DSC apps once rebalanced for the additional secondary cage weight. I might have gotten one myself back in the day had I had about $7000 burning a hole in my pocket. 😁

Do you find that the 6, 5, 4, and 2.5 are all actually 45° like the original LVs instead of the claimed 50°? I've read many conflicting accounts.

Based on recent "Sold" CN classifieds, if this LX850 comes with a 10" ACF scope, figure about $4500 with the mount. If a 12" ACF, about $5500. The 14" package ranges more broadly from $6500 to $7500. This is in the US. If you're in Europe or elsewhere, the market price could be far different.

Here's my contribution on this topic last year:

Weird that Corning isn't mentioned. I'm pretty sure they still supply a lot of optical glass for various space and DoD projects.