Louis D

It's the same as my Agena 20mm/30mm 80° UWA in the following comparison image. Notice how much better it is than the MPL (6 element Erfle) and Kasai eyepieces. It is terrible as a 20mm, so bad I didn't even do a test photo through it. The barlow element vignettes the field of view and adds distortions. It really needs a TV PBI type element in between to realign the diverging rays as in a Powermate. It barlows quite well in such an arrangement, but the barlow element is much further removed yielding a 15mm eyepiece. It has really comfortable eye relief thanks to that giant eye lens. There are no blackouts, either. As a 30mm, it isn't bad in the central 50% at all. In fact, it's sharper than the 30mm ES-82 there. The biggest problem with it is extreme field curvature. I once over corrected the field correction in my AT72ED with my TSFLAT2 just to flatten its field, and it only shows minor astigmatism in the outer field once the field is flattened. If your eyes are younger and have large amounts of focus accommodation, it is quite usable, at least until you get presbyopia in your mid-40s. 😉 If you can pick one up used or new for around $60 to $70, it's totally usable until you can afford a 30mm APM UFF.

Unless I'm missing something or google maps is amiss, it's only 60 miles from Dorset to Chippenham. I've driven 250 miles one way to pick up Dobs. 60 miles is about what my spouse used to commute each day each way. Do you lack a car? Ask if the seller would be willing to meet half-way. Perhaps the seller would be willing to make the 120 mile round trip if you paid for gas money and treated them to dinner.

Another option is the GSO/Revelation Deluxe 8"/200p Dobsonian. I couldn't locate a UK dealer, but there are some within the EU.

I'm thinking that getting its optical axis aligned with the main OTA might prove challenging without tube rings of any sort. That, and it's weight would making mounting it extra difficult.

Since you originally mentioned the Baader Hyperion-Aspheric eyepieces, and because I just remembered there being a decent comparison article, I'll add the following translation link for you to read up on them and their Aero ED SWA counterparts.

I would go with the 30mm APM UFF. It has replaced my 27mm Panoptic in that range. Better flatness of field, better edge correction of lateral color, much wider true field of view, and much better eye relief. It might be a tiny bit less sharp in the center, but the 10% difference in magnification makes it a difficult comparison. See below for some comparison photos of eyepieces around 30mm.

I used to use a 60mm f/4 binocular half with a 32mm Plossl and 90° Amici prism as a wide field finder when first starting out. I found the weight (with the finder's tube rings) threw off the balance of my 8" Dob no matter where I put it, so I stored it away for nearly 20 years (being a pack-rat). It added some field to the Dob, but at the cost of light gathering. I found a Telrad or QuikFinder to be good enough for star hopping, especially once I added DSCs. I dug it back out for use with my daughter's 127mm Mak. This time, I put a 24mm APM UFF in it and mounted it close to the altitude axis's centerline. The 127mm Mak and the 60mm finder make for a very complementary pair now.

I bought my single vision distance glasses from EyeBuyDirect after finding a frame of about the same dimensions and style as one I liked from the optometrist's store. I think I paid under $20 for them, and they are of a surprisingly good quality. The frame is actually much nicer than my wife's Ray-Ban frames. You seem to pay for the name in the case of Ray-Ban. They stay in a case in my astro toolbox along with my miscellaneous astro gear.

The only eyepieces I have that issue with are my ES-92s. The left and right edges are fine, but the top and bottom fall outside the corrected area. However, it's pretty rare that I look up or down rather than left or right. I can't use the Ethos or non-T4 Naglers with glasses because the eye relief is too short. It's my understanding that you still need about 15mm of usable eye relief to use the Dioptrx successfully; so, for example, the 16mm Nagler T5 wouldn't be compatible with them. My other thought is that my long eyelashes would probably grease up the Dioptrx corrector lens on shorter eye relief eyepieces whenever I blink.

Would you be willing to compare the view through single vision eyeglasses versus the Dioptrx sometime? I found the biggest problem with eyeglasses was that older pairs have microscratches all over them, so I bought a brand new dedicated astronomy pair to remedy that. As stars passed over those microscratches, they would suddenly have diffraction spikes, ruining all that work to perfect the eyepiece image with correctors, collimation, and premium eyepieces.

I use a laser sight to get the scope on target because I can't twist my head around very well anymore. Just be sure to check the skies before lighting it up and be aware of local laws and regulations (Australia in particular).

I've order some Baader items from Microglobe that were shipped to the US in the past. There were some initial ordering hiccups with CC payment and removing VAT, but they came through in the end. The Celestron f/6.3 Reducer Corrector Lens is available for $113 shipped and sales tax free to most states in the US from both Agena Astro and B&H Photo. It would be a few dollars more shipped to the US from the UK once VAT is removed, especially since the GBP has recovered a bit off of its August lows relative to the USD.

The 9mm Morpheus is just about the equal of the 10mm Delos at f/6 in my AT72ED refractor. The difference is quite minimal. The 14mm has some edge astigmatism and field curvature, but is otherwise quite similar to the 14mm Pentax XL. Neither suffers from any sort of SAEP (kidney beaning). They're a great set of lenses by all the reports and reviews I've read. Here are two comparison shots I composed through the AT72E of my 13mm-15mm and 9mm/10mm eyepieces I did a few weeks back that include the two Morpheus I own. I don't have the 17.5mm version, but I do have the 17mm ES-92 which is a fantastic eyepiece if you can stand the weight, price, and bulk and have a 2-inch focuser. See below for those comparison shots.

I haven't tried a Paracorr in my Dobs, but I notice right away when I forget to put the GSO CC in the focuser and start observing. My first thought is, why are my premium eyepieces showing so much aberration at the edges? Then a moment later I realize I had forgotten the CC. I slip it in, and all is right with the world again. It does so well, I never feel the need to upgrade it. Just remember to remove it for high power viewing (below about 1mm exit pupil). I find the views sharper without it, but YMMV.

If you are having to deal with light polluted skies, I suggest getting a UHC or OIII filter to make seeing nebula easier. Galaxies are going to be all but impossible to see except possibly for their cores (M31 comes to mind). Higher powers will make globular clusters stand out better from the background as @Mr Spock suggests.

Yes, the 28mm would probably be close enough for starters. It's only a 3mm difference, and would only affect eyepieces focusing significantly above their shoulder. There was an interesting thread on the GSO CC on CN recently and how screwing the optical nosepiece onto the bottom of the Baader 2" ClickLock with 2" CL Extension 47mm gives exactly the desired separation and you have a much nicer eyepiece holder to boot.

It is definitely a more lightly built 2" diagonal than the GSO equivalent. Optically, I didn't notice any major differences, but I also haven't done a critical back to back test of the two. I'll add it to the list of things to do in my copious free time. 😉 I was just looking for a low cost 2" diagonal for my daughter to take with her camping observing kit, but was unprepared for such a design oversight.

I finally found the discount dielectric diagonal I was referring to above. It is still listed on Amazon for $49.99. What's deceptive is that you can't see the position of the 2" thumbscrew or compression ring from the photos relative to the top of the eyepiece holder. They are very near to the end and work terribly with undercut 2" eyepieces as described above. Otherwise, it's a fine diagonal. It's a shame it's marred by poor design. It is somewhat usable if you slip a parfocalizing ring or rubber O-ring on each 2" eyepiece prior to putting them in the eyepiece holder to lift them slightly out of the holder to allow the compression ring to align with the undercut.

Sounds similar to the GSO/Revelation CC in this regard. Only my 12mm NT4 shows coma because it focuses about 19mm from the shoulder which is well beyond the 10mm on either side of the best correction zone which I've centered on shoulder focusing eyepieces. The rest of my well corrected eyepieces focus within that 20mm band of best correction. I've noticed a color tint when swapping the GSO/Revelation CC in and out of the focuser.

Still using it. The only quibble I have with it is that one of the thumbscrews stripped in the eyepiece holder because they're made of pot metal instead of brass or steel. Luckily, there's a second one. Don't over tighten the screws.

Unless that glass is increasing the magnification, and assuming that glass is properly multicoated, the light lost to additional glass elements in the path is minimal and below the threshold of human perception. In fact, if that added glass is a focal reducer, it actually increases the amount of light on a per area basis.

One thing to be wary of with the cheap dielectric diagonals. The locking screw or compression ring is often very close to the lip which causes many eyepieces with undercuts to be pushed up and out at an angle.

You might look into a unit power finder such as a Telrad or QuikFinder. Their bases can just be stuck on the tube with double sided foam tape if you don't want to drill additional holes. They do require cranking your head around, but it's manageable for the young and young at heart. These finders make star hopping to your target much easier than trying to sight along the tube. Once in the general vicinity, a RACI (Right Angle Correct Image) finder will be much easier to use. I find trying to use a RACI by itself to put the scope in the general vicinity problematic because you're looking at the tube, not the sky, as you line it up. I like to think of RACI's as low power refractors; and as such, most useful for picking out objects invisible to the naked eye but just detectable with it for centering.

Remember, coma does not decrease with increasing power. As long as the AFOV remains the same, coma at the edge will remain the same apparent size. Coma increases linearly center to edge, so it is more noticeable in ultrawide field eyepieces. Going to a shorter focal length will double the magnification at the edge, bringing the apparent size of the coma right back to where it was at the lower power's edge of field. That said, I have noticed that eyepieces with built in Smyth lenses (a matched Barlow in essence) tend to decrease the visible coma. For instance, I see no difference in visible coma with my 10mm Delos in an f/6 Newt with or without my GSO coma corrector (that is to say, none is visible either way). The difference with and without is quite noticeable in my 9mm Kellner, which has no Smyth component, despite its much narrower AFOV. No problem. I've never heard of parfocalness having any effect good or bad with respect to barlows. Conjecturing here, it might reduce pushing the eye relief outward, and as a result, not introduce any added SAEP. I did not know that the Celestron Ultima Barlow (the Japanese made shorty, I presume) was parfocal with the Ultima eyepieces. You're saying that little to no refocusing is necessary when adding that Barlow to the optical chain? That would be very useful for refractors in particular.

If funds are an issue, I'd do what I did and get the GSO/Revelation CC with a 25mm spacer tube. It has a 65mm to 85mm separation distance where correction is quite good, so there isn't much need to find tune the separation visually. I'd say for most eyepieces that focus within 5mm of the shoulder, I get about 95% or more reduction in coma, which is plenty good for visual usage for me. I need somewhere between 10mm and 15mm of inward travel, so not bad at all there.