Louis D

I tried out the same filters as in the April 12th posting above in the Astro Telescopes 6" f5.9 Sunday night on Venus and the moon. Violet fringing is clearly stronger than in the ST80 while orange-red flaring is weaker. This matches up well considering KUO tweaked the usual Fraunhofer doublet formula to favor red over blue as seen below: Notice that KUO keeps the 546nm through 633nm lines very tight (under 0.5mm variation) center to edge versus 0.75mm in the Fraunhofer. The down side is they allowed the blue (486nm/F) line to rapidly lose focus moving from center to edge (from 0.4mm to 1.1mm) while the Fraunhofer keeps it tight (about 0.5mm variation). This is quite noticeable at the eyepiece. Even with the Yellow #12A filter, blue fringing was quite obvious. This filter was sufficient in the ST80 to cut violet-blue fringing, but not in the A-T 6". However, the Yellow K2 perfectly cuts off all blue fringing. At the other end, orange-red flaring was much less pronounced on Venus than in the ST80. Filtering it out with the Cyan BG39 was not as impactful as with the ST80, especially on the moon where most folks would probably be content with the Yellow K2 by itself. I tried the Baader Semi APO, and I can see why some folks like it on the moon with these scopes. It suppresses violet fringing to a fairly tolerable level without greatly imparting a yellow color cast to the moon. However, it was useless on Venus and left a lot of image sharpness on the table with the moon by allowing so much residual violet washing over dark features. For maximum sharpness, I still couldn't beat the Meade Green interference filter. However, the Green X1 and Yellow K2-Cyan BG39 combination both yielded nearly identical, less overwhelmingly green, images without violet, blue, or red fringing visible to my eye. Thus, I felt that having a slightly less restrictive yellow-green filter is acceptable for best sharpness. With this scope, it might be possible to allow more orange and red through than with the ST80 and still maintain a sharp image. I know I struggled to see a significant improvement over using the Yellow K2 alone when stacking the Cyan BG39 with it on the moon. The red fringing had very little detrimental effect on fine lunar details. It was needed for Venus, but much less so with the moon. I then tried the Meade red and blue interference filters on Venus. I could get a sharp image focused with the red, but not with the blue. Violet-blue fringing was quite obviously washing out the image sharpness. KUO really destroyed just about all blue spectrum sharpness with their design choice. I came away with a better understanding of achromatic doublet variations. It was clear to me that fringe filtering needs tailored to each achromatic design for best results.

I tried Radians in an astro shop in 1998 when the first came out. They had terrible SAEP (kidneybeaning) in daytime usage. The Vixen LVs and Pentax XLs did not and had equivalent correction, so I went with a 9mm LV and 5.2mm/14mm XLs. I'm glad I did because strong SAEP limits using these types of eyepieces from being used for solar or lunar observing in my experience with other eyepieces with strong SAEP like the TV NT4 line. If you back off and lose some field, then they become usable again on bright targets that cause your eye's pupil to constrict.

I didn't have the patience to wade through 1.5 hours of video, but does the device kick out the finished image in real time or does it require significant post-processing work? That, and did all the software used come with it with full online support for beginners?

Are several of you confusing oversampling with over-sharpening?

BVs on Mars at opposition were transformative for me. Mars went from being an overexposed orange-red blob to having a wealth of detail. I suppose I could have tried a moon filter on it for monovision, but none was necessary for BV usage. I was seeing detail in my Dob rivaling photographs. In particular, one night, Mars looked very similar to the upper left image below: I was able to easily discern the light/dark/light row of fine detail near the center of the image (Xanthe Terra region, I believe). The best I've done in monoviewing has been to discern Syrtis Major in the lower right image, but only as a featureless dark marking. That, and the polar caps are fairly easy, but featureless.

Try the new Svbony 3-8mm zoom if eye relief isn't an issue for you. I did a write-up on it here on SGL and have read lots of very positive reports both here and on CN. It punches well above its price. It's excellent from 5-8mm, and still pretty darn good from 3-4mm. Add a quality 2x Barlow, and you'll have quite a range of high powers to choose from.

Back on the original subject and OP, I would have started thinking about what to bring months in advance. I was planning for months about what to bring to Nebraska for the 2017 eclipse. At this point, you'll probably have to make do with whatever you've already got.

My point was that the AZ5 mount head isn't all that heavy if you can mount it on a lightweight tripod. I'm guessing it's sold with steel legs because that's the cheapest solid material to make legs from. I've never heard of photography tripods made from steel, just aluminum and carbon fiber. Wood used to be popular for photography and motion picture tripods. I mention them because weight is generally an issue for location photography and filming, so these would make for good travel astronomy tripods as well. If you need weight for stability, you can always hang weight from the center of the tripod. It could be a gear bag, a trash bag filled with locally sourced rocks or sand, or anything else that can hung from a tripod.

How much is the mount head alone? You might be able to save considerable weight with an alternate tripod made from aluminum, wood, or carbon fiber.

With tripod. The head is only 5 pounds. The tripod is 12.3 pounds. I generally think of them separately since most high end alt-az mounts don't come with tripods.

So, has anyone compared the APM SZ doubled with a Barlow to roughly 4mm to 8mm against the Svbony 3-8mm? I have the latter and find it very nice except for the tight eye relief. The doubled APM SZ might be a nice alternative, but it would rival my 5-8mm Speers-Waler for length.

Same here. The Panoptic might have a hair's breadth tighter stars on axis, but that's about it to recommend it over the APM.

I can't speak for the 31mm Nagler or 35mm Panoptic, but my 30mm ES-82 is flatter than my 27mm Panoptic. I can't detect any defocus due to field curvature in the former, while there is a bit in the latter. The 30mm APM UFF is flat of field as well. My big issue with the 30mm ES-82 is severe chromatic aberration of the exit pupil (CAEP) at the edges. The visual effect is to split Jupiter into slightly separated red and blue copies in the last 10% of the field. The whole point to having an 82 degree eyepiece for me is to allow more drift time to observe an object in an undriven scope, and this optic aberration ruins the usefulness of the extra field over the 30mm APM UFF which has perfect spectral alignment at the edge. If you look straight at the center and keep the edge in peripheral vision, you won't notice the CAEP in the 30mm ES-82, so it may not matter depending your viewing style. You can see the CAEP manifesting itself as a rainbow circle in the AFOV image of the 30mm ES-82 below:

I use the nosepiece from a vintage 1990s Meade Series 4000 140 APO 2x Barlow to reach focus with my Arcturus BVs in my Dob. It only has 25mm of in-travel from primary focus, so this solution would probably work for any Dob. The Barlow element operates at 3x when screwed into the filter threads of the BV's nosepiece. As long as you stay above 15mm on eyepieces, you shouldn't have any issues merging images. Just watch out for eyepieces tipping in their holders when you tighten them down. I push them hard into the holder while tightening to prevent tipping. I'm too lazy to fill the undercuts. I can get it back down to 1.0x magnification by putting a 0.5x focal reducer between the Barlow element and the BV with 45mm of spacer tube distance between the Barlow and FR. Of course, there's severe field curvature due to the cheap FR, so TANSTAAFL.

The trick to getting decent night shots is to prevent the camera from trying to render black (or near black) as 18% gray (the logarithmic midpoint between white and black). To do this, go into the exposure compensation settings of the phone and dial back the exposure into the negative side (under exposure). Try several settings to see which works best for your camera and sky conditions.

My only concern about traveling with any SCT is the probability of the thin corrector plate cracking during handling. The thick meniscus corrector of a Mak has no such issues. Click on the following posting showing lots of shattered SCT corrector plates: By was of comparison, here's a damaged, but not shattered, Mak corrector: Mask off that damaged area with tape, and you're good to go observing again.

The only concern I might have with photographic filters is when using them for solar observing. Some photographic line filters strongly leak in the IR wavelengths. This is not an issue photographically because they are usually paired with a UV/IR blocking filter when imaging in the visual spectrum because test images will clearly reveal this leakage. However, the human eye can't perceive this leakage beyond a mild discomfort while viewing. Thus, be careful and knowledgeable when using photographic filters for solar observing and take appropriate safety measures.

One problem I've had with Chinese made OIII filters in the past is that they tend to have poorer quality control. I'm not saying that is the case any longer, but it really falls to the branding company to ensure the quality of what they offer under their name. Note below how my decade old Zhumell OIII filter (Chinese made) is right shifted. It actually made for a excellent comet filter on Comet ZTF to make it stand out better from my light polluted skies. I'm actually quite happy with the $10 I paid for it now that I know it makes for a good comet filter. By way of comparison, my Lumicon OIII filters basically masked it completely. My new Svbony UHC is actually quite decent compared to my 25 year old Lumicon UHC, especially considering I paid $22 for it. The slight blue-violet bleed isn't visually noticeable by my older eyes. The view of the Orion Nebula looked remarkably similar through both.

I will say that while people are briefly interested in viewing imagers displaying DSOs being built-up on laptop screens at outreach events using high quality imaging rigs, they quickly lose interest and gravitate toward the visual-only scopes on the field despite having to wait in lines for a quick view.

Would it be easier and cheaper to simply swap the entire diagonal for monoviewing? I do that with my rig. I have a 1.25" WO dielectric diagonal for my Arcturus BV to limit in-travel requirements, and a 2" GSO dielectric diagonal for monoviewing. It's pretty quick to loosen the 2" receiver on the scope to take out the adapter/1.25 diagonal/BV/eyepieces combo and swap in the 2" diagonal and eyepiece and then retighten the receiver.

Complete nonparfocality as in my Speers Waler 5-8mm zoom is a huge pain. It's impossible to dial in the best magnification in real time because you have to zoom, focus, zoom, focus, etc. I've tried zooming while focusing simultaneously without much success. It would have been nice if Glenn had invested more effort in the mechanicals to include some cams to maintain focus while zooming as with camera zoom lenses.

Not that I've ever heard of. You could try taking it to a local machinist to have the threads measured and have one made for you. Alternatively, look for a vintage Meade series 4000 140 APO barlow. Its optical nosepiece has standard filter threads. It normally operates at 2.4x, not 2x as advertised. In my Arcturus BV, it operates at 3x. Optically, I've compared the Meade to my TV 2x Barlow, and I can't see any difference between them. Both are Japanese made. I've got 3 copies that I use for various purposes, and have never paid more than $50 for one.

As long as the bandpass(es) are within the range of human vision (photopic or scotopic, depending on the viewing conditions), photographic filters should work fine. An example of one that would not work visually would be a Ca-K filter which operates at 393nm, or far violet, which is basically not perceivable by our eyes. I use a Meade Green interference filter visually which was sold as part of a photographic set for LRGB photography. It's probably my best green filter by far. It has high transmission and very sharp cutoffs at the blue and red ends. Note how tight, bright, and pure the Meade Green is compared to my other green filters: The other two Meade interference color filters work well as blue and red filters as seen below:

I have the 3.5mm Pentax XW, and it is aberration free across the field as near as I can tell under close scrutiny. It also has very good contrast and stray light control. It might not be quite at TOE or HR levels, but it is very good for us eyeglass wearers. It does not have any SAEP issues, so holding the exit pupil is a breeze. However, I use it so rarely due to seeing conditions and floaters at that tiny exit pupil that I sometimes wonder why I bought one. I highly recommend extending(?) some longer focal length eyepieces in your collection with your 2x ES Focal Extender first before buying a 3.5mm XW as recommended above. You may find it to not be a very useful view. I've found that observing with a larger aperture scope of longer focal length works much better for higher power views at larger exit pupils than trying to squeeze out the last bit of magnification at smaller apertures.