Louis D

My concern would be, will the Nirvana 7mm be any sharper on axis than the BST Starguider 8mm that disappointed you? Has anyone done a comparison between these two?

I must be the metal tubes causing the issues. My Dob's tube is Sonotube and has no such issues. It also has no dewing issues, either. It also never gets cold to the touch in winter.

If FLO paid extra to get them branded BST Starguider, I hope they got a discount back from their supplier for their mistake.

Not sure which question you're referring to, but since you live on the coast, you probably have very good seeing, as long as you're not behind a coastal range. As such, 150x to 200x with your scope should be quite doable. However, I've often found that 100x to 125x yields better views of planets. Pushing toward the higher powers is usually more useful on planetary nebula and globular clusters. Highest powers above that can be used to split tight doubles.

No experience with the Orion, but the HD-60 is very good at f/6. It has a wider apparent field of view than the Orion based on specs. Ultimate resolving power? Probably quite similar. Here's a collage of test images I've taken through my eyepieces around the same focal length using a field flattened 72ED f/6 refractor. It hangs right in there with the better eyepiece on edge of field correction. I haven't tried to nail down how good it is at stray light control and contrast around bright objects. It's probably not as good as the Pentax XW, but it's not terribly far behind, either.

And a diagonal unless you only plan on using it terrestrially as a spotting scope.

It might be useful. In photography, one use is for panoramic stitching. You need to pivot directly below the focal plane to avoid stitching issues with near/far objects. For eyepieces, such a marking would need to be at the virtual field stop for eyepieces with lens elements between the objective and the physical field stop because those lenses generally move the focus position relative to the physical field stop just as a Barlow or focal reducer would. For example, most positive-negative eyepiece designs have the physical field stop located above the focal plane (virtual field stop). Another issue would be that it would have to be marked on the insertion barrel for eyepieces with a focal plane below the "reference surface". A stamped marking on chrome or printing on Morpheus style kerfs might be difficult to read.

Back to the original question, I wouldn't go below an 8mm eyepiece. I have a couple of 127mm Maks, and the power builds rapidly with a 1500mm focal length. That, and you're only working with about 118mm of actual clear aperture due to the undersized primary mirror. Thus, the exit pupil gets really tiny really quickly. An 8mm eyepiece is only yielding a 0.63mm exit pupil, which is reaching the limit for extended objects. The 8mm BST Starguider is quite good in that scope with very comfortable eye relief and a very usable 60 degree field. I would also get the 12mm BST Starguider because ~190x is a bit high for Jupiter's low contrast details. ~125x with the 12mm is usually much more usable.

So, a rough initial alignment on two widely spaced stars as Don suggests should be good enough as a starting point.

How about "Insertion Barrel Termination Plane"? Or "The point or plane of the eyepiece where the part you stick in the focuser suddenly gets wider and stops the eyepiece from going any further in" to be totally long-winded? 🤪

LA skies must have cleared up a bunch thanks to emission controls. When I lived in the Mid-Hudson Valley in upstate New York 30 years ago, I could see the moon and 4 brightest planets, but almost no alignment stars thanks to the heavy smog layer. There were clear days when I couldn't even see the sun due to the thick, gray smog. I could only figure out where it was because it hurt my eyes when I was looking straight at it, so I figure either IR or UV light was making it through. On some better days, the sun was a dull red orb. If I drove 2 hours out into the nearby mountains to gain some altitude and lose some light pollution, the night sky was amazingly better. The Hudson River acted like a super-highway channeling low altitude smog from the NYC metro area up to us. I didn't take up astronomy until I moved to Texas 26 years ago.

Does it have "realign on current object"? My Sky Commander DSC has such a feature to refine the alignment in each new section of the sky. I find it helps quite a bit to realign on each object after I center it.

They're decent, but probably no better than the Astro Essentials Super Plossls or the Revelation Plossls. Some are made in China, some in Taiwan, but in the end, all the lenses may be sourced from the same supplier.

These all get high ratings: 1.6x 1.25" Nikon EIC Barlow 3.0x 1.25" Televue Barlow 2.4x 2.0" Vernonscope Dakin Barlow 2.0x 2.0" AP BARCON (BARADV) Barlow 2.5x 2.0" Siebert Telecentric 2.0x 1.25" Carl Zeiss Abbe Barlow

You can just pull the rubber eyecup straight off. Perhaps then the adapter would work:

Sorry about that. How about we hold a contest for a more intuitive name for the "reference surface" than either that or "the shoulder"? Neither is very good I'll admit.

You could check with Martin Pond over on CN. He loves to take apart vintage binocular eyepieces and create new, home-brew eyepieces from the lenses.

Agreed, most Pentax, Morpheus, and ES (JOC) eyepieces focus very close to the shoulder. All Tele Vue eyepieces focus further in or out relative to the shoulder except for the 17mm NT4 which also focuses right at the shoulder. I really notice swapping in my 10mm Delos because I have to rack it 1/4" out to reach focus. The 12mm NT4 was so annoying at being 20mm below the shoulder that I added five 4mm thick O-rings and a 20mm 2" extension ring to the bottom to nearly parfocalize it.

The 8mm, 12mm, and 18mm BST Starguiders would work well in your scope without breaking the bank.

Yep, you'll need to invest in a Tele Vue In-Travel Adapter which will run you about another £43 or so to parfocalize it somewhat.

The best option without doubt would be the Paracorr T2 at 495 GBP. However, if your pockets aren't that deep, the GSO/Revelation CC is quite good for 65 GPB. I use it in my Dob to good effect. It does need a 25mm spacer tube between the optical section and the eyepiece holder. As long as all your eyepieces focus within 5mm of their shoulder, coma will be corrected to within about 95% or better of optimal. I only had to parfocalize one eyepiece, my 12mm Nagler T4 because it focuses 20mm from its shoulder, so coma was noticeable with it without parfocalization. I've found it to be plenty good enough that I've never felt the need to upgrade to a Paracorr. It does need removed for highest power work because it contributes a bit of spherical aberration visible only under those conditions. It's my understanding the Paracorr T2 does not, so there is that. The GSO/Revelation requires 11mm of in-focus, which is similar to the Paracorr. The ES HRCC requires 31mm, IIRC, which is a lot more and beyond what I have available.

Definitely M17 and M22 are easy in light polluted skies (at least this far south they are). I just enjoy sweeping the Milky Way to see what I see from time to time. There are plenty of random open clusters and star associations and asterisms along it to marvel at.

If you have a coma corrector that also flattens the field, it is possible to see that the 14mm Morpheus has a very slightly curved field in the last 15% of the field. I also confirmed this in a field flattened ED refractor. By comparison, the 17mm ES-92 is dead flat to the edge in the same scopes despite being significantly wider. You can confirm this for yourself by moving a bright star from best focus in the center to the edge and seeing if it needs refocused there. However, if you don't have a flat field scope, you won't be able to be certain where the field curvature originates from. The 14mm Morpheus also has slight astigmatism at the edge (unlike the 17mm ES-92). Again, put a bright star at the edge and rack it through focus from inside to outside of best focus. If the star changes from a radial to a tangential line (flattened oval) on either side of focus, that's what astigmatism looks like. It's likely, though, that coma could be what you're seeing a the edge, especially if you're not using a coma corrector in a Newt. It will make a bright star look like a pointed tear drop with the point aimed at the center.

I would cross import the 35mm Aero ED from FLO rather than getting the two low power ES-70 eyepieces. It is both cheaper and better performing. There's no VAT, sales tax, or import tariffs, just shipping charges. The difference between 58x and 68x does not justify two eyepieces. A 56mm Plossl would be a better option to get a larger exit pupil for using an OIII filter on nebula. The true field won't be any larger than with the 35mm Aero ED, though.

The Veil nebula is all but invisible in my skies, but easily visible with an OIII filter. It's simply a matter of increasing the contrast by eliminating non-nebula emitted light from light pollution. With the Orion nebula, which is quite bright, it simply allows a greater extent of the faint filaments to be seen.