Louis D

I spent some time last night observing Venus, Jupiter, and Orion and vicinity with my ST80 and various filters. Here are my observations: The IR filter did nothing to remove red fringing or sharpen the image. It must have been the significant IR from the sun being filtered that sharpened my white light solar observing earlier in the day. The sharpest views of Jupiter's bands and of Venus were with the Meade Green inteference filter. The Cheap Green filter was a bit behind because of light attenuation, but was a good, less expensive option. Both gave bright stars and star clusters a strong green color cast while allowing for pinpoint focus. Both made the Orion Nebula invisible. The #12 Yellow gave a sharper view of Jupiter's bands than the light #12A Light Yellow. Both cut out all violet fringing. The red fringing was more pronounced than with the #12A Light Yellow, perhaps because there was no blue left in the #12 to counteract it. The #12A Light Yellow didn't really cause any noticeable color cast while cutting out all violet. However, significant red fringing remained that ruined sharp focus. The Cheap Yellow filter gave nearly identical results to the #12A except with a bit more scatter on Venus. The #11 Light Green (Yellow-Green) filter didn't do a whole lot to block violet or red fringing. On the violet end, it was similar to a #8 Yellow or Minus Violet filter. On the red end, it did help to attenuate the red fringes a bit, but not completely. Combining the #12A Light Yellow and #11 Light Green creates a near perfect way to cut violet and diminish red fringing on dimmer objects without introducing much of a color cast or losing much light. When used on Orion, the nebula stood out a bit better and stars were more pinpoint with almost no color cast. Venus and Jupiter still had way too much red fringing to be a useful combination on them. The R89 Moss Green filter completely eliminated all violet and red fringing while maintaining a brighter image than the Cheap Green filter, but it was dimmer than the Meade Green interference filter. Contrast on Jupiter was lower making the bands more difficult to make out for some reason. Venus showed as a sharp disk. I'll have to pair it with a variable polarizer to see if Jupiter was simply too bright. The Orion Nebula stood out better with the Moss Green filter than with the #12A-#11 combination by darkening the sky more by attenuating some yellow and orange-red light and cutting all red light without cutting H-B or O-III bands. The view was actually similar to the Svbony UHC but more pleasing because more stars were visible and more natural looking giving a better context. The green cast was barely perceptible. Star clusters around Orion were much more sharply focused by eliminating the unfocused violet and red light. Bright stars were nearly pinpoint while having only a slight yellow-green cast. The narrowband filters were really only useful on the Orion Nebula. They didn't really do much useful for Jupiter or Venus. The M&SG filter improved the visibility of the Orion Nebula slightly by cutting yellow and orange-red light which darkened the sky background of some light pollution. It wasn't very useful on Venus or Jupiter without adding the #12A or #12 filters to cut violet fringing. There was still plenty of red fringing ruining best focus.

Once again they are haunted by that bad design (hybrid skirts) from way back when. The screw-on/off 2" adapter paradigm works much better. It's a shame Al didn't go with that approach when he was starting out.

0.25 diopters of astigmatism might cause some of the sparkle you saw on axis. Try looking at stars naked eye and see if they also sparkle similarly. Overall, that is a very low level of astigmatism. I use distance-only single vision glasses when observing. That keeps the focus plane close to the eyepiece design focus plane so the field stop should be sharp. It also makes looking up to the sky for object acquisition easier. I could see using readers if you were referencing a detailed star chart when trying to locate Pluto or an asteroid, though. That way, you could go back and forth quickly without any fussing putting glasses on and taking them off again.

I just got in from trying various filters for white light solar observing with my ST80 and Baader Solar Film. My ST80 would not come to focus with my 1.25" Hercules solar wedge, so I had to use the BSF. First, just adding an interference type IR blocking filter ahead of the diagonal helped sharpen up the image by filtering out unfocused far red light. I kept it in place for all testing since it didn't shift color at all. This effect would probably not be very noticeable at night with scotopic vision, but I might try it with Venus and the moon. The best filters for getting sharp images in roughly the order of best to just so-so improvement: Meade Green interference Cheap Green Meade Red interference #12 Yellow Svbony UHC Zhumell OIII (that is right shifted to cover C2 lines from comets) R89 Moss Green #12A Light Yellow Cheap Yellow It became apparent that you want a narrowed (but not necessarily narrowest) passband so best focus can be more easily achieved by filtering unfocused spectrum. The worst was a cheap magenta that made matters worse by cutting out the well focused green spectrum in the middle leaving the hard to simultaneously focus blue and red ends. I could not bring the image to a combined best focus. The orange, red, and blue cheap filters didn't help much either. They didn't make matters worse, though. My Lumicon OIII didn't help much despite the Zhumell OIII showing good results. My collection of narrowband Optica b/c interference colored filters didn't deliver like I'd hoped. The images were generally sharp in them, but it was quite difficult to hold the eye positioning because getting ever so slightly off axis caused blackouts. Thus, it was difficult to draw any conclusions about them. I thought the wider passband of the Meade filters showed details more easily and with the same sharpness. Based on this, I'm not likely to buy a Baader Solar Continuum filter. The Meade Blue was poor. I think this is because it passed all unfocused violet. Lighter filters like my #12A Light Yellow, Cheap Yellow, #11 Light Green, and R86 Pea Green didn't help much because they passed too much unfocused spectrum at either end. On the other hand, the #12 Yellow was showing really good detail. I wondered if pushing to the Cheap Orange would show further improvement; but no, it was actually worse for unknown reasons. Apparently, there's a Goldilocks region for low pass filters right around the #12's cutoff which is very close to 490nm. The Zhumell Urban Sky (Moon & Skyglow) filter failed to improve the image to any significant degree, even when combined with the #12A to block unfocused violet. I didn't think to try it with the #12 Yellow because it was working so well by itself. The R89 Moss Green caused barely any color shift to yellow-green while noticeably improving sharpness. I should try combining it with the variable polarizer to cut some of the glare because it is such a light filter. However, narrowing the passband to purely green with either the Meade or cheap green filters sharpened up the image further. Overall, a cheap green or #56 Green would probably make for a good filter when white light solar observing in an achromat without a lot of cash outlay. A #12 Yellow is another good, inexpensive option.

At large exit pupils, make sure you're not seeing eye astigmatism on axis and assigning it to the eyepiece. With a star on axis, rotate your whole head around to make sure the lines of sparkle don't follow your eye's orientation. The increase in distortion center to edge can safely be 100% assigned to the eyepiece, though. What you're describing sounds a lot like a traditional Erfle eyepiece. It's appalling Baader charges so much for these BHA eyepieces. To confirm eyepiece astigmatism, rack focus inside and outside of best focus. The lines should swap between radial and tangential forming a small cross at best focus. If there is a fan pointing away from the cross toward the edge, that is coma and/or chromatic aberration depending on whether it is gray or rainbow colored.

I have never seen a Meade Super Plossl that looked like that. Perhaps it was specific to a particular scope or collector's edition?

I have no idea if the Taiwanese ones are inferior. I know my Sirius Plossls from 1990s Taiwan are inferior to my GSO Plossl from 2010s Taiwan. I'm guessing optical prowess improved in the intervening two decades. Likewise, I would infer early 2000s Chinese made would be inferior to 2020s Chinese made. They have noticeably improved optical and mechanical quality in the last 20 years across many product categories.

As long as JAPAN is stamped on the upper black barrel, they had 5 elements. The last year or so of production added eye cups. The revised 4 element design has JAPAN stamped on the lower chrome barrel. They are still very good thanks to superior polish and coatings. Production first moved to Taiwan in the mid-90s prior to production moving to China. All were 4 element designs. I doubt Taiwan was stamped on the bodies. I have Sirius Plossls from that mid/late 90s era where the boxes say Taiwan, but the eyepiece barrels themselves are blank.

Before investing in exotic glass like Tak TOEs, I would look into getting an entry level binoviewer and a good quality Barlow to boost power when using 15mm to 25mm eyepiece pairs. I find I can see far more detail on planets using two eyes instead of one. It also cuts down on glare because both eyes see the same brightness. I compared the view of Mars at opposition through my Pentax XW 3.5mm and Pentax XL 5.2mm against my Arcturus BV loaded with a Meade 140 2x Barlow element and 2 Svbony UWA 20mm eyepieces. It was no contest. The BV was showing loads of detail while both Pentaxes showed a featureless and overexposed orange disk.

Couldn't they have simply designed the tunable top to have more travel range upward by 16.5mm and gone with a flush 1.25" adapter? That would also negate the need for the High Hat adapter. It might require a more clever extension design, but I have 1970s/1980s manual camera lenses and macro lenses that can extend 6 inches on internal helicals and maintain optical alignment, so I know it can be done. Some even do it via nesting tubes to maintain compactness. The only issue would be getting it low enough to not need the In Travel adapter for any eyepieces. Again, a more clever barrel extension design might have been workable here as well. The Paracorr 2 costs over $500, so it's not like it's a budget device that couldn't afford to have better mechanicals. All these adapters seem to scream that this was not a well thought out extension device.

Is it one of the old Kowa made 5 element ones? Those are exceptional if you can find them.

Perhaps the TV eye lens is recessed a bit much? My Orion Sirius Plossl 32mm has the eye lens recessed so much that I can only just use it with eyeglasses. The 26mm version is recessed a similar amount, making it impossible to use with eyeglasses due to Plossl eye relief scaling with focal length.

I agree that the GSO 32mm Plossl is quite good. Some folks rave about the Vixen NPL 30mm, but at the end of the day, it's still a Plossl at twice the price, and that will show as astigmatism at f/5 at the edge of the field.

I would get the Nirvana-ES UWA-82º 7mm and 10mm instead of the Luminos 7mm and 10mm. Performance-wise, they're very similar, but the Nirvana eyepieces are much less expensive.

I keep mine in a large, vintage Tamrac camcorder case I had lying around underutilized. It was intended to hold 1980s sized camcorders, so it swallows up the 127 Mak with ease. 😆 My daughter keeps hers in a gym duffle bag with the OTA wrapped in bubble wrap for protection. The pockets are handy for storing accessories like spare batteries.

Did you flock the interior of each baffle tube as well? That's where I'm getting most of my internal reflections in my 127 Mak.

I found this In-Travel adapter diagram showing the adapter differences graphically: So, if like me, you are already using a low profile 1.25" to 2" adapter like the one that comes with GSO diagonals, the In-Travel adapter won't buy you anything outside of a Paracorr. If there was a notch in the Paracorr tunable top for the 1.25" locking thumbscrew, you could probably use the GSO adapter in it. My Dob's focuser also has this 2" insertion barrel notch to allow 1.25" and 2" eyepieces to be parfocal if both focus at the shoulder, which most of mine do. I wonder why the Paracorr tunable top does not? I can understand why folks would despise switching between 2" and 1.25" eyepieces if they are forced to be non-parfocal due to the construction of the 2" insertion barrel and 1.25" adapter combination as in the Paracorr. It's already bad enough that my 10mm Delos focuses 0.25" below the shoulder forcing me to rack my focuser outward 0.25" relative to most of my other eyepieces. I suppose I should just invest in 0.25"-worth of 1.25" inner diameter O-rings for it to parfocalize it. I'm guessing TV thinks all 1.25" eyepieces should focus 0.25" below their shoulder, thus the 10.5mm height of their adapter. Even that doesn't quite compute because 0.25" equals ~6mm. What's with the extra ~4mm?

Reflectors did have a lot of problems back then. Long focal ratio mirrors led to long, unwieldy OTAs and massive EQ mounts. The ideas for Dobsonian mounts and EQ platforms hadn't yet dawned on anyone. I'm not sure why short f-ratio mirrors took so long to be adopted even after the Dob mount and EQ platforms became popular. Perhaps the eyepieces of the day looked terrible in them? I don't think any new mirror grinding or testing methodologies have been invented for a long time.

You'll need about 75mm of space between the back of the CC optics section and the DSLR's imaging plane. If you're using a T-ring, that alone gets you to 55mm spacing. Thus, you'll need approximately 20mm of additional spacing. I would think an M42 to M48 adapter would also be necessary plus some spacer ring(s) to get your to that 20mm. I would invest in a spacer ring kit to fine tune the separation. These kits say M42, but mine came as an M48 kit.

I recently picked up a used Hirsch Light Green #11 which is more teal and less yellow than the Wratten standard. I ran it through my spectrograph and found it passes a lot of violet and red. I confirmed this on Venus, Jupiter, and Sirius tonight in my f/5 ST80 while imparting very little green color cast. It helped a bit, but it was not a complete solution. I then paired it with Hirsch Yellow #12A which lies midway between Yellow #8 and Yellow #12, and is very similar to a cheap yellow filter from China, just with a sharper cutoff and less attenuation as I showed in an earlier spectrogram post. This cut out the majority of the residual violet as my spectrograph tests predicted while imparting a noticeable yellow cast. However, spurious red remained. I next tried my Meade Green interference filter and my cheap green filter from China. Both snuffed out all the spurious violet and red, but with a strong green cast. According to the spectrograph testing, much or all blue and yellow/orange/orange-red also gets cut. Finally, I ran all the Roscolux green, yellow-green, and blue-green filters through the spectrograph and chose the ones with the best cutoffs at each end to test tonight. Those three were R86 Pea Green, R89 Moss Green, and R389 Chroma Green. Of the three, the R89 Moss Green had the highest transmission and passed the most spectrum. All three cutoff all visible spurious violet and red, so I declared R89 Most Green the winner based on providing the lightest touch. I won't lie, the R89 Moss Green image is green to yellow-green, but it is much less intensely green than either the cheap green or Meade green filters while still cutting out all spurious violet and red. I feel vindicated that it would be possible to create a yellow-green interference filter passing all the light from about 470nm (dark teal blue) to about 610nm (orange-red) to cut out all visible spurious violet and red in fast achromats. For now, the R89 Moss Green filter works well enough because having about a 50% transmission in the central passband is not an issue on these super bright objects that show loads of spurious violet and red in fast achromats. With all three super bright objects, clarity was greatly improved by cutting out unfocused light at both ends of the spectrum. An interference filter with ~95% transmission in this central passband would open up the list of viewable objects to dimmer ones. Splitting tight doubles would become easier as well. I composited the spectrograph results for the various filters and filter combinations described earlier: A filter with this passband would agree well with the spectral frequencies that are well focused by achromats (the dotted green line) below. From just below 500nm to just above 600nm is about ideal.

As an example, globular clusters in particular simply will not resolve at all in my 90mm APO FPL-53 triplet but resolve nicely in my 8" Dob.

I composited together the 24mm APM UFF (which has about the same TFOV and correction level as the 24mm ES-68) with the 30mm APM UFF to show the difference in TFOV, AFOV, and magnification: You get a nice 33.3% increase in linear field of view with the 30mm over the 24mm APM UFF with much better edge correction and a wider AFOV.

Long focal length eyepieces, especially 2" ones, don't do well in traditional Barlows. The outer field will have a hard cutoff rather than soft vignetting due to the diverging outers rays caused by the Barlow not being captured at all by the eyepiece field lens. This is why Tele Vue introduced the Panoptic Barlow Interface (PBI) for its 2" Big Barlow years ago. It reconverges the light rays as in a telecentric magnifier like a TV Powermate. As such, there is no vignetting or hard cutoff around the edges. I use a PBI in a GSO ED 2x 2" Barlow as a poor man's 2" 2x Powermate because the GSO has nearly the same focal length as the TV Big Barlow. However, you're getting a mighty long stack sticking out of your focuser. This isn't much of a problem in a Dob with a sturdy focuser, but it would be a nightmare in an alt-az mounted small refractor to keep balanced.

The ED 35mm is going to be slightly better than the BHA 36mm, but not head and shoulders better. Here are Ernests tests of the BHA 36mm, ED 35mm, and Panoptic 35mm for comparison. Here are the entries from his index of tests below: FL AFOV F4 F4 F4 F10 F10 F10 rest Eyepiece mm °/deg. axis zone edge axis zone edge aberrations Baader, Hyperion Aspheric 36 70 3 30 60 3 15 25 Ast.,FC +3% Levenhuk Ra, ED 35 70 >5 >20 >35 4 12 20 Ast.,FC TeleVue, Panoptic 35 67 <2 8.5 13 <2 3 6 Ast. +15% As you can see, the ED is slightly better than the BHA at the edge, but not hugely better and certainly not at Panoptic level correction.