Louis D

Remember, in North America, you need to add sales tax or VAT to the advertised price. Only excise taxes on tobacco and alcohol products along with fuel taxes are hidden in the advertised price here. With thousands of taxing jurisdictions, it's just not feasible to include the taxes in online prices. Sales taxes are collected at the local levels of government, not at the national level as in Europe. It helps to ease property and local income taxes somewhat.

Since the 31mm Nagler has less usable eye relief than the original ES-82 30mm and its brand brethren, I'm in no hurry to plunk down $500+ for one. That, and being the same basic design (ES copied it in large part), it still suffers from CAEP. I much prefer my 29mm ES-92 (a surplused 12mm ES-92 missing it's Smyth group of lenses) to the 30mm ES-82. It has much better usable eye relief, no noticeable CAEP or SAEP, a truly immersive field of view (93 degrees), and a 48.4mm measured optical field stop (52mm physically) yielding a 96 degree eAFOV. Sure, it has progressively worse chromatic aberration outside the inner 30 degrees or so, but it's not noticeable if you look only on axis. Sweeping rich star fields with it is an amazing experience. It's what the old Kasai Super WideView 90° should have been, and more. If ES could work out how to tame the chromatic aberrations without losing usable field, it would be the complete package.

A laser collimator (with or without the 45 degree window port) is also useful for getting the primary on a truss Dob back in the general vicinity of where it should be if it has shifted on its support pads and sling during transport. You just crouch at the back of the scope and adjust bolts until the return spot coincides with the outbound spot on the face of the secondary mirror.

I believe the Luminos line was designed by the same folks who did the Meade MWA line. Both suffer from loads of SAEP that limit the easily usable FOV. Resale value isn't particularly good for either line should you buy new and decide to move it along later, so make sure to buy used to avoid being the one who takes the hit to the wallet.

It is in the US if you stole it from a highway post. College kids love to do this with signs with evocative messages and put them in their dorm, fraternity, or apartment as decorations. Heck, I remember some college kids driving down a street after high winds blew down some stoplights. They picked up one of them, tossed in the back of their pickup, took it back to their home, refurbished it with electronic controls, and now it cycles through its red/yellow/green lights in a corner of their basement bar.

Actually, I would vote for neither and recommend the APM UFF 30mm. It has a measured 73 degree AFOV, a 69 degree eAFOV, and a 36.4mm diameter field stop. It is sharp from edge to edge and flat of field with plenty of eye relief for eyeglass wearers. It has basically no SAEP or CAEP. My mushroom top ES-82 30mm isn't as sharp in the central part of the field and has loads of CAEP in the outer 10% of the field, rendering that area unsuitable for allowing planets to drift edge to edge. Planets get split into distinct red and blue images in that region. Thus, that extra 10 degrees of AFOV/eAFOV and 42.4mm diameter field stop don't really buy you that much extra usable field of view. It's only pleasing to use by keeping your gaze on axis and allowing the CAEP to disappear in your peripheral vision. For that use case, the space walk experience is definitely better than that of the UFF. It really depends on what you want to use it for. The original version I own is just barely useable with eyeglasses. The current version is not. If you don't wear eyeglasses, the 100 degree APM XWA 20mm might be a better choice for an even more immersive experience. It is sold under multiple brands including Astro-Tech XWA and Stellarview Optimus. You'll also get a darker background for better contrast.

I just look at the shadow of the scope on the ground and minimize the size of its shadow in both the up-down and left-right directions. Once minimized, the sun is generally visible in a low power eyepiece. However, I did finally bling out my white light solar observing setup as seen below: It is much more accurate than the the shadow method.

I don't know exactly what's going on with those formulas. I double checked, and it looks like I typed them correctly. Try doing some online research on film astrophotography and reciprocity failure. Perhaps there are better formulas out there.

The Canon AE-1 Program could only meter down to EV1 which is 1 second at f/1.4. My Olympus OM-4T could meter timed exposures down to about 4 minutes or about -EV7 because it used real-time integrated readings taken off the film during exposure using a photocell aimed at the film. I have no idea if it took reciprocity into account, though. I never found it all that accurate for astrophotography, though; so I just used Bulb with a stopwatch to time exposures. I'd put a black felt hat over the end to start and end exposures coordinated with the camera shutter release to avoid camera shake at the start or end.

I checked an old astrophotography film exposure reference, and the exposure formulas were as follows: Standard Exposure Formula: t (seconds) = f**2 / (A * where f is the f-ratio, A is the ISO film speed, and B is the relative brightness of the object. B would generally come from astrophotography tables. The exposure time then needs corrected for the film's reciprocity failure as follows: t (corrected) = [(t + 1) ** (1/p)] - 1 where p is the Schwarzschild exponent. 0.7 is a typical value for non-hypersensitized fillm.

Those star tails look like line scanner artifacts.

I've only tried it during good seeing. It seems like it might increase the contrast of low contrast details on Jupiter and Mars, but using a binoviewer is far more effective. During the last Mars opposition, I tried it with binoviewing, and it seemed to increase contrast a tiny bit more. However, the psychedelic effects are pretty hard to ignore immediately surrounding the object. Overall, I wouldn't recommend taking the time and effort to make one. It's not particularly hard or expensive to make, but it seems like a waste of time and storage space. Here's the mask itself made from two sheets of crafting foam board, three offset layers of black window screen spray painted flat black, and some short screws (not visible) around the perimeter holding the layers together and in place: The taped nubs are the heads of two long bolts threaded through the board that the mask hangs off of while on the front end of the telescope tube.

“Tis better to have loved and lost Than never to have loved at all.” ― Alfred Lord Tennyson

Try it with some yellow (#8 or #12), yellow-green (#11), or light green (#56) filters to see if narrowing the pass band sharpens things up a bit on high contrast objects like Venus and the moon.

Here is @Geoff Lister's 127 Mak backpack setup: I setup my daughter with a similar rig for her camping trips. I don't know about Sweden's secondary market for telescopes, but 127 Maks come up for sale at around $300 here in the States all the time. When I bought hers in 2018, they were going for $200 apiece. Inflation has crept into the secondary market, apparently. I have a 127 Mak myself. You can use it at lower powers just fine while you wait for it to acclimate. It never needs collimation. I love that there is no focuser flex. I also love the short lever arm on a manual alt-az mount.

@Jiggy 67 What's the advantage of the EQ6-R-Pro over the ZWO AM5 for visual observing? For about the same money, the latter is far lighter, and can be used without a counterweight for lighter loads, something I don't think the EQ6-R-Pro is capable of doing. I'm thinking about getting an AM5 with a ZWO TC40 carbon fiber tripod to use visually in alt-az mode instead of using a similar capacity manual alt-az mount like an AZ-100 similarly equipped with encoders.

Might look similar to my apodizing mask:

@Peter Drew are you sure about that? Isn't the secondary cutting an elliptical conic-section from the light cone, and aren't all ellipses symmetrical across both axes? I assume secondaries are diagonally cut from cylinders and are also ellipses. Shouldn't it be possible to get the major and minor axes to match that needed to match that of the cone's ellipse?

Texas alone has SpaceX, Blue Origin, and Firefly Aerospace off the top of my head. Then there's NASA's Mission Control in Houston. As far as aerospace, Lockheed Martin, Boeing, Raytheon, Sikorsky, BAE Systems, L3Harris, and many others have operations here as well. And that is just one state in the US.

I'm picturing US customs confiscating it from Japanese tourists upon arrival at US ports of entry. If they get them developed back in Japan, there shouldn't be much, if any contamination issues in the US. The EU bans plenty of stuff the US considers safe enough like titanium dioxide which can be used to make candy coatings more vibrantly colored.

See this recent thread you started:

If there are no electronics, I would mainly worry about plastic, rubber, and glued parts. All will become brittle and crack/crumble more quickly when exposed to high heat in my experience. If there are any press-board components, the glue holding them together might be compromised at some point by heat. I know I have trouble with press-board absorbing moisture and swelling in non-climate controlled storage areas. I would think metal and glass parts would be completely unaffected by temperature. Sure, they'd take longer to reach thermal equilibrium when you take them out to observe, but they wouldn't be damaged or degraded like plastic, rubber, and glue. However, high humidity could quickly lead to fungal growth on them. I keep my equipment stored in my climate controlled house to avoid these issues with our Gulf humidity. My Dobs' mirrors look terrific for being 25+ years old. I have no idea if your 10" Dob has any non-metal, non-glass parts or uses any glue.

As far as binocular astronomy, I have alternated between my 8x42 and 15x70 binoculars for decades now. The former works well for wider angle views of chunks of constellations while the latter works best on cluster rich regions or large star clusters.

I recall hypering Tech Pan film used to be quite popular back in the days of film. Tech Pan hasn't been made since 2006, though. I doubt you could find hypering equipment today, either.

Yes, Lytro's plenoptic cameras never found a market niche. They were mostly useful for macro photography. However, computer controlled focusing of camera lenses allows for rapid fire captures of multiple images at different focus points. These can then be combined in post using dedicated image processing software (just like astrophotography has its own dedicated post SW) into an image with much larger depth of focus. This seems to be the direction macro photography has headed over the past decade or more.