Louis D

@Alan64I thought Bresser is the European marketer of JOC products as Explore Scientific is in the US while Ningbo Sunny out-right owns Meade.

From my own experiences at f/6 or so: 30mm APM UFF: Very good, easy to use with eyeglasses 22mm Nagler T4: Very good, a bit tight with eyeglasses but still usable 17mm ES-92: Very good, easy to use with eyeglasses, very heavy 14mm Morpheus: A bit of field curvature and astigmatism in the out 15% of the field, but nothing too distracting, easy to use with eyeglasses 14mm Pentax XL: Quite a bit of field curvature, no edge astigmatism once refocused, easy to use with eyeglasses, only found used (discontinued since 2003) 12mm ES-92: A very tiny step down from the 17mm ES-92 in terms of edge correction, ease of use, and eye relief; slightly lighter as well 9mm Morpheus: Very good, easy to use with eyeglasses, fits in well with Delos (I have the 10mm) 9mm Vixen LV: Very good, easy to use with eyeglasses, claustrophobic after using 65 to 80 degree class eyepieces 7mm Pentax XW: Very good, slight chromatic aberration in the outer 10%, easy to use with eyeglasses 5.2mm Pentax XL: Very good, no aberrations, easy to use with eyeglasses, only found used (discontinued since 2003) 3.5mm Pentax XW: Very good, no aberrations, easy to use with eyeglasses. All of the Delos except perhaps the 17.3mm are considered very good with no edge correction or eyeglass issues.

Not the original mushroom top version that I have. It was also marketed as the 30mm Meade 5000 SWA and 31mm Celestron Axiom. Decloaked, far right (I never took a picture of it with the outer part still attached): The 30mm diameter eye lens is basically flush with the top of the housing. Measured, I get 16mm of usable eye relief, which is right at the limit of eyeglass usability. It views similarly to the NT4s which also have 30mm eye lenses and 82 degree AFOVs.

Yes, position angle is not a big deal with Dioptrx, but I was pointing out that you need to buy a new Dioptrx if your astigmatism diopter changes too much. Sure it's slow, but mine has crept up from 0.5 to 2.0 diopters over 40 years. I used to need mostly distance correction (0.75 diopters), but that has also crept up to 1.75 diopters. I just wanted to point out that a Dioptrx might not be a once in a lifetime purchase for everyone. Maybe once every 10 to 20 years or so, depending on your age. Based on my own experience, I would hold off buying one around your mid-40s as that is when my prescription was noticeably changing year by year in both distance and astigmatism as presbyopia was also setting in.

Here's a thread about building a Dob mount for a bare Newtonian tube: https://stargazerslounge.com/topic/356587-diy-sw-explorer-200p-dobsonian-convertion/ As far as eyepieces, you could add a Barlow to maintain eye relief or a short focal length Plossl to keep costs low at the expense of eye relief. The 8mm or 5mm BST Starguider or one of the Sky-Watcher UWA Planetaries would make good choices to maintain eye relief and keep costs on the low side.

It also depends on how savage the light pollution is that they're embedded in. I'll have to try them out at a dark sky site someday to see if indeed the UHC performs better than the OIII under those conditions. Perhaps if ordinary UHC filters were more like the OPT Triad Quad-Band Ultra filter with the intermediate wavelengths excluded, it would be more usable in light polluted skies: Hydrogen-beta Oxygen III Hydrogen-alpha Sulfur II FWHM 5 nm 4 nm 4 nm 4 nm Peak Transmission 79% 97% 87% 90%

H = Huygens, SR = Symmetric Ramsden. The difference between a Ramsden and a symmetric Ramsden is the former uses two different lens elements while the latter uses two of the same element. Note the various eyepiece designs in the diagram below: The above Ramsden is pretty close to symmetric as opposed to the one in the following diagram where one lens is clearly larger than the other: Symmetrics, whether Ramsden or Achromat Pair, are cheaper to make than asymmetrical designs (such as true Plossls) because you only need to make half as many unique lenses or lens pairs.

In 20+ years of observing and having both Lumicon UHC and OIII filters, I find I rarely use the UHC. Adding H-ß to the O-III lines just does not overcome the loss of contrast due to the wider passband.

Except that astigmatism correction tends to change with age. That, and Dioptrx won't fit on many eyepieces and still requires about 15mm of eye relief.

Here in the States, we liken it to being in the movie Groundhog Day.

If you can reach focus without moving the mirror by sliding the Barlow in and out until reaches focus with the eyepiece, then any magnification change is entirely due to the Barlow. This assumes the Barlow requires out-focus and not in-focus. This is generally true for longer Barlows while the opposite tends to happen for shorty type Barlows.

Here's Tele Vue's table to help figure out if you need to wear eyeglasses at a particular eyepiece: Exit pupil is simply the eyepiece focal length divided by the telescope's focal ratio while the astigmatism value can be read from your eyeglass prescription's CYL or cylinder correction value. Basically, the more astigmatism you have, the smaller the exit pupil (higher power) you'll detect it in. With my 2.0 diopters in my observing eye, I can easily see aberrated stars down to 1.0 to 1.5mm or so. Below that, I find improved resolution wearing eyeglasses, but stars look okay.

You may have trouble locating "Making every photon count" in the US. I see Amazon has a used copy for $120. You could cross import a new edition from FLO in the UK for much less than that. In the US, The Deep-Sky Imaging Primer by Charles Bracken might be a good alternative as well.

If the OP already has a 2" diagonal, all he needs to add is a Mak to SCT thread adapter and a 2" visual back to use it with his 127 Mak, and then he can use 2" eyepieces with it. I've found the vignetting to be minimal to the eye as I discussed in the following thread:

Repeating myself from this thread: The equation for Barlow magnification is M = 1 - L / fb where L is the distance from the Barlow lens to the eyepiece's field stop and fb is the Barlow focal length (always a negative number for magnifying Barlows). Regardless of the Barlow focal length, which is never reported by any Barlow makers to my knowledge, it is clear that increasing the working distance between the Barlow lens and the eyepiece is going to increase the magnification. That's why using Barlow elements in front of a binoviewer generally yields more magnification than when the Barlow is used as designed. This assumes that the Barlow had a shorter working distance as designed than the optical path length of the binoviewer. There are vintage long Barlows for which this might not be the case, but they didn't generally have removable lens cells. BTW, I find most Barlows yield around 3x to 4x when used with binoviewers. I find I prefer eyepieces in the 16mm to 25mm range because they can be wider in field (than 32mm Plossls) and still not vignette when used with 22mm clear aperture binoviewers like the one I own while maintaining good eye relief and ease of merging. I can then go from widest field at 25mm up to a slightly higher power at 16mm with an eyepiece swap, or I can change Barlows for a higher magnification range if the seeing permits. Zooms can also be particularly well suited to binoviewers as well. They're just narrower at the lower powers.

Unless your flat roof is covered in sod, heat from the day radiating off of it during the night will ruin your seeing conditions. Most folks build their observatories well away from buildings for this and other reasons.

You don't state the f-ratio of your scope. Multiply 7 by your f-ratio to determine the typically longest focal length eyepiece you would want to use with your scope. This is because you don't want to go much above a 7mm exit pupil because that about the biggest your eye's iris will dilate during dark adaptation. That, and the skies get really washed out making it difficult to pick out DSOs. Let's say you have an f/6 scope, 7*6=42mm would be the longest you'd probably want to go. For an f/10 SCT, theoretically, you could go to 7*10=70mm, but the view would be like looking through a straw due to the limits of a 2" visual back. For an f/4 Dob, it would only be 7*4=28mm, thus the popularity of the 21mm Ethos or 25mm ES-100.

And yet the original NT2 eyepieces and their NT5/NT6 equivalents have similar eye reliefs around 10mm to 12mm despite the NT2s being much larger than their NT5/NT6 nearest equivalents. Sometimes it is possible to reduce size and weight while maintaining eye relief through improved designs.

As the scope gets faster (lower f-ratio), the Panoptic line pulls away from the ES-68 line. If your scope is f/8 or slower, the difference would be minimal. Around f/5 to f/6 differences start to appear, and by f/4.5 or faster, Panoptics generally have a significant edge. The downside to this improved edge performance is increased pincushion distortion. The moon gets stretched into an egg shape and stars appear to move across a globe during panning. This also happens in the ES-68 line, but not to the same degree.

It should be fine at f/5. I've used my 1990s vintage 27mm Panoptic in my 15" f/5 Dob to good effect. @Connor brad Why didn't you start a new thread instead of resurrecting this 7 year old thread?

I was out last night with my Dob and binoviewer. I was able to verify that using a Meade 140 Barlow nosepiece as the reference distance that a Celestron Ultima type shorty barlow required about another 1/2" of in-focus while the above Orion long barlow required about 1" of additional out-focus. This was also true with just an eyepiece. The shorty Barlow required in-focus while the long Barlow required about double that out-focus.

I had this issue with my 127 Maks, so I swapped sides on my DSV-1 and DSV-2B alt-az mounts, rotating everything including the handle 180 degrees. I don't know if the AZ-5 mount is as flexible to allow this.

The OP might want to try the new Svbony 8-24mm SV171 zoom available on ebay, amazon, aliexpress, and Svbony's website. It's been getting quite a bit of good chatter by early adopters on Cloudy Nights.

The 27mm Panoptic is a fine eyepiece, but only has 14mm of usable eye relief. I've scratched at least one eyeglass lens on the exposed eye lens retaining ring by trying to push in enough to see the entire field. It took nearly 20 years, but I've finally found a worthy replacement that is easy and safe to use with eyeglasses, the 30mm APM UFF.

Curious that the same thing happens to the 4.5mm and 6.5mm Meade HD-60s. They are a few millimeters tighter on eye relief than the 9mm and above, but still usable with eyeglasses. The shorter FL Pentax XLs and XWs don't do this. @Don PensackWhat about the shorter FL Delos and Delites? I've only got the 10mm Delos, so no experience there.