Louis D

I agree that using binoviewers is your best option. Remember, the full moon is only as bright as asphalt at noon on a sunny day, so your eyes should have no issues with its brightness if you use both at the same time. I find viewing the full moon with binoviewers to give very rewarding, highly detailed, non-blinding views.

@Don Pensack, how can you instantly get a feel for the amount of stretching or compression at the edge from AFOV and FS diameter without further calculations? I happen to like comparing AFOV to eAFOV because I instantly get a feeling for which kind of distortion the eyepiece has and how much of it. When the AFOV is greater than the eAFOV, I know the edge will appear stretched. When the AFOV is smaller than the eAFOV, I know the edge will appear compressed. When they equal, there is little to no noticeable stretching or compression. The relative difference between the two gives me an indication of how strong the effect will appear. I'm at a loss to understand this relationship from merely looking at the AFOV and the FS diameter without further calculations. Please describe how these two values describe the edge distortion present in an eyepiece without further calculation. Perhaps I'm missing something obvious.

I would skip the 3.2mm BST Starguider in favor of Barlowing a longer focal length eyepiece based on reports from Jon Isaacs on CN about the 3.2mm being not that sharp past 60% of the inner field in f/7 scopes. I have all the Paradigms/Starguiders except for the 3.2mm for this reason.

OMG, it allows you to use bogus online tools like Astronomy Tools field comparator more accurately. That's certainly one valuable usage I would think. Too many newbies take the AFOV as gospel when it comes to calculating TFOV. They end up passing over eyepieces with smaller AFOVs and lower distortion in favor of eyepieces with larger AFOVs and higher distortion thinking they're getting more TFOV. I'm thinking specifically of the 24mm ES-68 vs 24mm APM UFF. Why don't you go out and write a corrected ATFC webpage that uses field stop instead of AFOV for TFOV comparisons? Until then eAFOV is very useful, at least for that webpage. I also find eAFOV valuable when comparing eyepieces of like focal length. Sure, I know the field stop values, but how does that translate at a particular focal length? eAFOV has a much more intuitive feel to it than field stop diameter when comparing eyepieces at a particular focal length to better understand what will actually be seen if distortion was nonexistent. I do use field stop values to compare eyepieces of different focal lengths' TFOVs, if that makes you feel any better.

I bought a second SVBONY 68° Ultra Wide Angle 20mm when they went on sale for $20 shipped via ebay. I finally had the chance to try them out as a pair in my Arcturus binoviewer with a Meade 140 2x Barlow nosepiece to reach focus. In my f/6 Dob without CC, the 3x equivalent equates to about an f/18 operating focal ratio. They work insanely well together. Merging and holding the two images was a piece of cake. There were no blackouts that had to be fought off. Eye relief was sufficient to comfortably take in the view with eyeglasses while just touching the flipped down eye cups. Stray light was well controlled as was scatter around the planets. The sky background was nice and dark. Sharpness was excellent to the edge (remember, f/18). The pair was easily as good or better than my vintage wide field microscope eyepieces that had been my mainstays. The 23.7mm field stop plays very nicely with the 22/23mm clear aperture of the binos. I saw no vignetting near the sharp field stop. The only downside was their barrel undercut. I had to spin the collets quite a few turns to tighten them down. I will definitely be hunting down silver metal pinstriping tape to fill them. The pair were resolving brighter stars across the core of M22. The Cassini division and a band on Saturn were easily visible. Multiple bands on Jupiter were seen despite the magnification being a bit high for the seeing conditions tonight. Star fields were sharp across the field with no visible edge of field brightening (EOFB). Overall, they were a delight to use together as I had suspected based on monoviewing. Having paid about $50 for the pair with sales tax, I'm very happy with them. They have kicked my 19mm Konig binocular eyepiece pair out of my bino case. The SVBONYs were far and away better. They are highly recommended if you binoview at long focal ratios with eyeglasses.

With my astigmatism, I'm lucky to split Mizar/Alcor naked eye (many moons ago, haven't tried recently). The DD just looks like a single star to me naked eye. I've found going up in aperture helps extract more detail than trying to buy exotic eyepieces. Going from 4" to 8" to 15" makes a huge difference in what can be resolved.

I had battery corrosion ruin my original. Replacement battery holder didn't help. I'm guessing battery out-gassing corroded something in the rest of the unit.

It would be nice if it included a filter wheel or slide of ultra-narrow band emission line filters so it could stack nebula images in real time.

Good luck in your observing adventures. Give both cyclops and binoviewing a try on all object types to find out what works best for you. We haven't even discussed EEVA preferences. Many folks with deep enough pockets do most of their nebula observing with high end night vision gear nowadays. I have seen the difference it makes at a star party, and it is dramatic.

Remember, the field stop diameter actually determines the TFOV visible, not the angular size of the AFOV. There can be, and generally is, quite a bit of edge distortion that decreases the TFOV from what an AFOV calculation would predict. Thus, I'm sure the actual AFOV of the BHZ is actually around 40° to 42°, but due to distortion, the effective AFOV (eAFOV) is actually 38° as you found. The AFOV of 68° at 8mm may actually translate to an eAFOV of 66° due to distortion. Only detailed measurements can resolve this issue. The 24mm ES-68 has quite a bit of distortion, being modeled after the Panoptic line. My 27mm Panoptic has 68° to 69° of AFOV, but has an eAFOV of only 65° to 66° due to distortion. Thus, using AFOV figures to calculate TFOV is fraught with error unless you know the eAFOV based on field stop measurements.

It seems like a natural move for more mounts to integrate smartphones as Celestron has done with their StarSense system. Between cameras for plate solving and various sensors and cell tower triagulation, it should be straight forward to figure out where you're pointing, where you are on earth, know the exact time of day, and show you star charts and object info. As such, it would help to keep down the cost of a computerized mount by not having to duplicate all of these things that you already have in your pocket.

I looked at getting a used 127 Mak on a EQ3 mount. The moment I tried to pick up the fully rigged mount to move it, I realized it was not for me. Way too top heavy and awkward to move fully assembled. I ended up going alt-az to avoid counterweights which greatly reduced the overall weight.

Good luck with it and keep us updated about your experiences using it.

No need to. Just raid the retirement account. 😉

Why didn't you just get an 8" Dob in the first place? I've been hauling mine out in one go for 20+ years. I'm up and going in under 2 minutes. If I need to dodge a tree or bush, I just pick up the whole thing and move it in one go again. I've never missed tracking.

You definitely don't want to jump up and down on the ground anywhere near a telescope coupled to the ground when being used at high powers. I did an experiment with my daughter once where I focused on a planet or star (I can't remember which) and had her walk away up to about 50 feet and jump up and down at each distance. The amplitude of the vibrations definitely went down as distance increased, but I could still see the impact it had on the image. It's wild just how well the ground transmits impulses of energy.

If you're within 5mm either way of the best correction distance with the GSO, it's hard to perceive any improvement by tweaking the distance, so I wouldn't sweat the last 2.5mm for the 17.5mm Morph. However, being 21mm off is quite noticeable as with my 12mm NT4 that I had to parfocalize to get decent correction. It's the only eyepiece in my collection that is that far off from focusing within ~5mm of its shoulder. That's why I felt I had to point this out to @Barry-W-Fenner, so he wouldn't be disappointed under the stars by the poor correction in that configuration.

Considering that the reference plane is the shoulder between the 1.25" and 2" barrels, and the depth of the 2" barrel is 21mm, you'll need an additional 21mm of separation in 2" mode to get back to the optimal working distance of 75mm even with the spacer ring you already have. Alternatively, put a 2" to 1.25" adapter in the CC and use the Morpheus in 1.25" mode. Then, you might be a bit farther away than 75mm, but not by as much as being 21mm too close as in 2" mode.

A very good upgrade, but it still can't correct for field curvature of the primary, so check that first by refocusing for the edge. In my tests of the Meade 5000 HD-60, generally considered optically similar to the Celestron X-Cel LX, the 18mm does have some edge astigmatism at f/6 in my field flattened 72ED refractor as revealed by blurriness below: However, it's pretty minor compared to a Konig or even the Paradigm/Starguider BST. The Delite should be at least as sharp to the edge as the Nagler T4.

Many modern quintuplets are triplets up front with a doublet corrector somewhere between it and the focal plane.

If the dew point is well below the ambient temperature, dew formation is highly unlikely. If they are close, dew formation is likely. Just check the relative humidity. In my experience, anything above 70% can be suspect. Above 90%, dew is almost guaranteed.

Exactly my thought as well. Everyone with deep pockets? I'm wondering who is funding these guys. Do they really have enough sales to be profitable?

Is this another Celestron Xcell eyepiece giving you problems or the same one you posted about below: If so, why the duplicate post? Why not continue the original thread with your current question?

Have you tried refocusing the edge to see if field curvature is the main culprit? At 600mm focal length, I have to use a TSFLAT2 with my 90mm f6.7 APO to ensure stars are sharp to the edge. Since your refractor is the same FL, I would think you need to use one as well.

I really like binoviewers for planets and the full (or near full) moon. It evens out the brightness between my eyes allowing me to make out fine details easier. It also helps reduce the visibility of my floaters. These are non-issues for DSOs, and I enjoy the much wider fields of view available in mono-viewing for star field sweeping; so I don't binoview them. I find I can see much more planetary detail in my 8" Dob than in my 90mm triplet APO, so I tend to use the latter for wide star fields. The stars appear as much tighter pinpoints than in the Dob which is aesthetically pleasing to me.