Louis D

I have two diopters of cylinder (astigmatism) correction in my observing eye. I also have presbyopia, so I normally wear bifocals. The problem is that bifocals prevent viewing the entire field of wide angle eyepieces without a line through it and all at the same focus point. My solution has been to only buy eyepieces with long enough eye relief to use while wearing eyeglasses. In addition, I bought a pair of single vision, distance-only eyeglasses with low index plastic lenses to reduce edge chromatism and to show the entire field in focus at once. Also, they're cheap enough I don't worry about scratching them on eyepieces if I push in too hard on an eyepiece with an exposed metal edge like the 27mm Panoptic while trying to take in the entire field. They are always perfectly aligned for optimal astigmatism correction because they're attached to my head, not the eyepiece like a Dioptrx. I can also instantly go from looking at the sky to the eyepiece without having to deal with taking my glasses off. Being a devoted star hopper, this is very important to me. As for reading charts, I can always look under my glasses and deal with my astigmatism since my eyes are fixed focus at about 10 inches which is perfect for reading.

It can still be an issue for solar and lunar observing due to the brightness of the object causing one's iris to constrict.

I just remembered reading that thread and looked it up for your sake (along with a UK source). While undercuts annoy me, I have yet to reach the point of feeling the necessity to fill them it. I can only remember once when a focuser's brass compression band came out of its track and got wedged against the eyepiece as I lifted it out. I was cussing pretty hard trying to get it to release. I'd be most likely to fill them in on my binoviewer pairs where the undercuts lead to eyepiece tipping in the collets which causes insurmountable misalignment.

Check out this CN'ers solution. You'll want 1/4" or 6mm wide pinstripe tape.

It was daytime blackouts due to massive SAEP. I compared them side-by-side with Pentax XLs in an astro shop when they first came out in 1998. I could not find any position to avoid kidney-beaning with the Radians, but no issues at all for the XLs. I bought the 14mm and 5.2mm XLs and have never regretted that decision. I gave Al another chance with the Delos line 13 years later, and with Paul D.'s help, he got long eye relief right that time, so I own a 10mm version now.

Dobs are great with kids because they are practically impervious to damage in use or transport. You may need a step stool for shorter kids to get them up to the level of the eyepiece for viewing objects near zenith. Pick up a collimation cap at the very least to check primary mirror alignment each time it is setup. It also makes a nice dust plug during storage while allowing for a tiny amount of fresh air to reach the inside of the tube (assuming the main tube's ends are capped).

No, stacking narrowband filter won't work as others above have pointed out. However, OPT is selling Radian Triad tri and quad band filters that simultaneously transmit H-alpha, H-Beta, and Oxygen III or H-alpha, H-beta, OIII, and SII respectively. They would achieve what you want to do. Keep in mind that you would need to use a color camera to retain color data. A monochrome camera would show all bands as various shades of gray in a single image that would be immune to post processing into a color image.

While using my TSFLAT2 field flattener visually in my AT72ED, I do not see any evidence of coma in the refractor's image at the edge. However, with it removed, the defocused stars at the edge due to the severe field curvature of such a short focal length refractor masquerade as coma-aberrated. Stars at the edge need to be refocused to see if they come to a better focus before declaring coma in a refractor. With true coma, refocusing does not improve the tightness of the image.

How do your Televue eyepieces feel about the two Myriad eyepieces? Do they play nice with them, or do they gang up together to bully them for not having green lettering? 😉

From what I understand, these Chinese eyepiece factories will crank up production on whatever you want and label it however your want so long as you meet their prepaid minimum order standard which seems to be somewhere between 100 and 300 units. So, until some vendor like FLO, TS, or Astronomics decides to place an order, there won't be any more produced.

It boggles the mind that the 40mm Aero ED/Sky Rover is sold out everywhere and the Chinese factory isn't churning out any new ones. Clearly there's a demand for it worldwide.

I tend to prefer my Meade 5000 SWA 40mm (same as the Maxvision) to my 35mm OVL Aero ED and 30mm ES-82 for scanning wide swaths of the sky. I also really like my Baader Scopos Extreme 35mm due to it being super sharp in the center 60% of the field (better than any of my other wide fields). The downside is it only has a 39mm field stop compared to the 46mm Meade, 44mm Aero, and 42mm ES. The 30mm Wide Scan clones (Agena UWA 80 below) are great in the center 50% and then have severe field curvature out to their 44mm field stop. If your eye has loads of focus accommodation like a camera lens, it might be a cheap option bought used. Here's my composite of wide field eyepieces I posted elsewhere:

With each doubling in power, surface brightness is quartered (squared rule). This isn't such a big deal for stars because they are not extended objects, so star clusters end up taking power quite well. This is why you can really crank up the power to split tight doubles. Since you went up roughly 4x in power going from 26mm to 6.1mm, surface brightness went down by 16x, which is quite noticeable as you discovered. To avoid this darkening, just increase your aperture by 4x in diameter to 300mm (12 inches or 1 foot) by buying a larger telescope. 😉

There's a pinned topic on Cloudy Nights with lots of input on just this subject.

@parallaxerrThat's a mighty slippery slope you're heading down. You better watch your wallet carefully. I've got thousands of dollars tied up in eyepieces, and I'm no where close to done. 😁

One thing I noticed about my 127mm Mak is that if you defocus a star, there's a black hole in the center of the light disk due to the central obstruction. As I bring the star into focus, the hole gets smaller and smaller, but at best focus, it seems to be preventing all of the light energy from being focused to a pinpoint. The star just won't collapse into a perfect pinpoint. In fact, the focused star seems to twinkle, possibly due to thermal acclimation issues. It reminds me of the black hole trying to push out all the light crowding in on it. I'd swear I can still see glimpses of a tiny black pinpoint in the center of the star at best focus. I then tried the same experiment with my co-mounted AT72ED. A star defocuses to a perfect disk all the way to the center. Then, as the star is brought to focus, it just goes down to a tiny pinpoint without any fuss. There is no twinkle, either. Perhaps due to better thermal acclimation.

As a matter of fact, Mike Clements in Utah did buy such a spare blemished spy mirror and built this. Apparently, it has a permanent home now. Does this make you wish the UK had a constellation of spy satellites with lots of spare mirrors?

As far as getting another eyepiece, I'd get a mid-power, work-horse in the 16mm to 20mm range to achieve a good, general magnification of 75x to 100x. There are so many choices in this space. Because you don't need to wear eyeglasses, you can save money, weight, and bulk by buying eyepieces with shorter eye relief.

I would get a GSO/Revelation coma corrector before I'd get a barlow. The CC will help flatten the field as well as correct coma. I added a 25mm M48 spacer ring to mine to achieve very good correction for eyepieces focusing within 5mm of their shoulder. It is also useful for achieving focus with only a 10% increase in magnification. I used it to take the following Mercury transit image with my 8" Dob:

I would get an FPL-53 doublet over an FPL-51 triplet. The correction is nearly indistinguishable and the doublet cools down quicker, is less front heavy, and tends to have fewer collimation issues.

Have you considered using an off-axis mask on your 16" Dob to make it a 6" to 7" unobstructed system? It would also help with punching through seeing conditions.

Any scope with a central obstruction will have poorer double star performance aperture for aperture. It's a simple matter of optical physics. Stars are much more pinpoint in my little AT72ED than in my 127 Mak or 8" Dob. For instance, the E component is much more apparent in the Trapezium with the 72ED than with either obstructed scope. The main four stars bloat too much in the obstructed systems to see the E component.

Here's a review by Bill Paolini of the first three Vixen HRs released. I apologize if you've already read it. The Takahashi TOE eyepieces are also considered another good alternative in this space.

You don't know the power of the Green & Black side: Resistance is futile:

Dang, move to west Texas or New Mexico and multiply that by at least 10. That, and you'll be quite a bit further south with much darker and drier skies.