Louis D

Do you mean that by having more closely spaced, finer grooves, you will have stronger spikes? If so, that sort of makes sense. However, don't you reach a point where they are so fine they just look gray to the incoming light?

If you don't need the eye relief, you might want to check out the 20mm APM XWA HDC. It will show a larger patch of the sky and probably be as sharp as that portion which overlaps the 22mm Nagler.

Try loading Skeye on your phone and then strapping it to a non-ferrous part of it or put a large block of foam in between and use it in DSC, push-to mode. You can align on Mars and go from there. Buy long eye relief eyepieces and wear eyeglasses at the eyepiece. I've been doing this for 20+ years and have never had an eyepiece fog up. The eyeglasses act as a vapor barrier to prevent body moisture from fogging the eye lens.

What about being made from clear acrylic? Would there still be enough diffraction at the edges to work?

I tend to avoid Barlows because they're a pain to keep putting in and pulling out of the focuser. Once in, I tend to leave them in. That said, if you can locate a quality Barlow, they're fine. I tend to buy vintage, Japanese made Barlows myself. Chinese made stuff tends to be all over the place quality-wise. A Barlow would not be useful with the 5mm because 2.5mm would be much too high a power for that scope on most nights. That, and a 0.5mm exit pupil is verging on being a pain to use due to eye floaters. The Barlow would make the 12mm a 6mm effectively, which is quite close to the 5mm. So, again, not a big gain. I would probably spend the money on the 8mm BST SG to split the difference in power. Thus, you'd have 28mm, 12mm, 8mm, and 5mm eyepieces for 23x, 54x, 81x, and 130x respectively. That scope's short focal length doesn't lend itself well to high powers. In my experience, 30x per inch is usually doable with fast reflectors which equates to ~150x for your scope. This would equate to a 4mm to 4.5mm eyepiece, but it would not be that big of a jump over 130x visually. You can see below in my comparison image of AT Paradigm (BST Starguider) and Meade HD-60 apparent fields of view how the image scale changes at different focal lengths:

Scammers are getting smarter because they actually send you something (not all what was advertised), which makes it harder to claim fraud than if they sent nothing at all. They also steal in smaller amounts than in the past. Governmental authorities tend not to investigate petty theft like this. According to one of the OP's links, they'll actually send you a 25mm monocular instead of a 12" Dob, for which $20 isn't such a bad price (should be about $10). Thus, it's not even petty theft.

Try swapping out the WO OCS/GPC with a high quality Barlow nose piece. The two OCSs/GPCs that came with my Arcturus BV were both garbage. They added a weird coma effect to all stars across the entire field, as if there was a tilted element in there somewhere. I generally use the nose piece from a vintage Meade 140 2x Barlow. The views are super sharp. I also recently tried a Parks Gold Series 2x (same as Celestron Ultima and Orion Shorty Plus) Barlow, and it was equally sharp.

To nicely frame the moon, you'll want somewhere around a 1 degree true field of view eyepiece since the moon is 1/2 degree across. I would probably recommend a BST Starguider for your rather demanding on eyepieces f/5 reflector. Since these eyepieces are 60 degrees apparent field of view, this equates to needing 60x in power (60degrees/60x=1 degree). Given your scope's 650mm focal length, this would equate to 650mm/60x=10.8mm. The closest available focal length would be 12mm for 650mm/12mm=54x. This would also be a useful power for looking at many open clusters and larger nebula as well as for solar viewing with a full aperture solar filter. Now, to get better, close-up views, I would recommend jumping up to the 5mm Starguider for 650mm/5mm=130x. You would still have a very reasonable 1mm exit pupil (eyepiece focal length/scope focal ratio=exit pupil). Exit pupil is how big a circle of light is coming out of the eyepiece and into your eye. Below about 0.7mm and floaters can start to be an issue. This power would also be useful for looking at brighter nebula, planetary nebula, and planets themselves.

From Agena Astro's Sky-Watcher 6" Dob webpage: OTA length: 44.5" OTA width: 7.125" OTA weight (with accessories): 15 lbs Base weight: 25 lbs Base dimensions: 29 x 20.5" Zenith eyepiece height: 44.5" Since the focuser is at least 6" from the end of the tube, figure it sits about 50 inches tall or slightly more. Remember, though, it could be stored in two parts to save a bit of height or with the tube at an angle to save some height. You could also store it to the side toward the front of the closet but just back a bit with the coats up against it since it's less than 8 inches wide. That's how I store my 8" Dob in our other downstairs closet. Literally no one ever notices it in there. I also store a bunch of astro gear in our under-stairs closet at the back where it's too low for hanging coats. It's really surprising how much space there is back there.

I taped some rulers and yardsticks together on their back sides with packing tape and then wedged them under the edge of one of my kitchen cabinets, but hanging off to the side. I always align the 17 inch yardstick mark with the edge of the door for consistency. I turn on every light in the kitchen/dinette area and open all the blinds to maximize the available light. I put my AstroTech 72ED telescope on its leveled alt-az mount at the other end of our rather open plan house, about 35 feet away and close to level with the yardstick and close to perpendicular with it. I put a 2" GSO dielectric diagonal in the focuser with a TSFLAT2 field flattener spaced 15mm in front of the diagonal body on the scope side. This pretty effectively flattens the otherwise severely curved focal plane of the scope. Luckily, I don't need to add any extension tubes to reach focus, unlike when I try this with a 127mm Synta Mak. I put each eyepiece in the diagonal and focus the image with my eyeglasses on so the afocal image is focused close to infinity for the camera. This allows the field stop to be at its sharpest if it was correctly positioned during assembly and allows the camera to focus at infinity. I then center the yardstick in the field of view and lock the altitude clutch. Next, I nudge the mount left/right to put the edge of the ruler at the edge of the visible field stop, or at least the edge of the field for those without field stops. This can be a judgement call for eyepieces that use the barrel for the field edge as the edge will fuzz out. Also, you can move your eye off center and see more of the field with them by peeking "around the corner" of them, so to speak. That's why some don't show the edge when the camera is centered. I'll sometimes take an image with the camera way off to the edge looking at the other edge at an angle to get a clearer image of this effect, just like your eye would be doing in this situation. I use the high resolution, normal wide angle rear facing cell phone camera for most of my images. In my case, a Galaxy S7. I cup my thumb and forefinger around the top of the eyepiece to make a landing pad for the phone. I start well away from the eyepiece and move the camera in toward the afocal image using the screen to guide my movements. It's important to keep the camera level and centered. That's where your thumb and forefinger come into play. With practice, you can get it down to a fraction of a millimeter. You can roll your fingers get fine height adjustment. I've tried using adjustable height eye cups on eyepieces that have them to do this, but I couldn't get them to work very well. Now, you have to move the camera phone in and out until the edge of field or field stop just pops into view. You're at the correct exit pupil distance for that camera at that point. Any further out, and you miss some of the field. Any closer, and you start to get blackouts. If there is spherical aberration of the exit pupil (SAEP or kidney-beaning), you're going to be fighting a dark shadow all around the field. If you are perfectly centered, you will get a dark circle with a bright center and a bright edge ring. This cannot be helped as it a defect of the eyepiece and not the camera or scope. In this situation, you may need to turn down exposure to -1.5 to -2 to avoid the autoexposure circuit trying to make the shadow 18% gray while blowing out the bright areas. Make sure to use the camera's diagonal to get the widest image possible for super wide angle and wider eyepieces. You'll have to rotate the image in image processing software later. I then proceed to take a series of 3 to 5 images to later pick out the best of the bunch on a large computer screen. I've found that it's impossible to critically judge these images on the phone's screen. I then take an angled image of the edge for super wide angle or wider eyepieces since the edge of field of even the best camera lenses is not as well corrected as the center. It may also be cropped off for ultra wide field and wider eyepieces, so this is a necessity for them. If your phone has an ultra wide angle camera, use it to take all-at-once images of ultra wide field and wider eyepieces. I bought a second hand LG G5 phone for $25 off ebay just for its ultra wide angle camera since my S7 doesn't have one. That's what I use to take my "full view" images. I scale them up to match the scale in the center 20% of the S7 images. Differences in angular magnification across each camera's field of view accounts for the slight width difference in the final images when using the same eyepiece. Unfortunately, the G5's a 5 megapixel camera compared to the 12 megapixel S7 camera. When combined with the smaller image scale, these "full view" images are pretty low resolution by comparison. I'd love to acquire a 24 megapixel or higher ultra wide camera for this purpose. Anyone know of used ones that sell for cheap on ebay? In post-processing, I do not do any exposure adjustments or sharpening. I just rotate and flip them to be more readable. I also crop and composite them for comparison images. Hopefully, that answers your question. If I missed something, let me know.

Notice I said solar charged and not solar powered. I had originally typed powered and realized how stupid that sounds.

I wouldn't doubt it with the advances in low dispersion glass and improved Chinese lens polishing. The question then arises, are their lens cells as well designed to hold collimation as temperatures drop for astrophotography?

I found this AP 130 EDF scope resold twice in the last two years on CN classifieds: https://www.cloudynights.com/classifieds/item/146793-astro-physics-130-edf/ https://www.cloudynights.com/classifieds/item/165492-astro-physics-130-edf/ First, for $5000 in 2018 and then $5150 in 2019. In 2020, I would guess it would fetch $5300 or more. There's a wanted ad for one, so there's still demand for them. The ad you linked to has it listed for £4195 which would be about $5400 at today's exchange rates. As such, there really isn't much of a price difference between the UK and the US vis-à-vis A-P scopes based on this one data point.

Luckily, my neighbors are using low wattage solar charged lights only in their front yard that are fairly innocuous. They were shining into our master bedroom window until I asked them to redirect them. Even low wattage was annoying in our darkened bedroom. Our houses block that light from being a problem in the backyard where I observe.

And DSLRs are extremely difficult to use for afocal projection. Generally, the entrance pupil of most DSLR lenses lie deep within them, making it difficult to get it to coincide with the exit pupil of the eyepiece unless it has very long eye relief. Zoom lenses just compound the problem by burying it even deeper than with prime lenses.

@Ruud Your next animation should be to explain chromatic aberration of the exit pupil, and how it causes the ring of fire in the 31mm Nagler and 30mm ES-82.

I rarely use either of my 14mm XL or Morpheus eyepieces in favor of my 12mm and 17mm ES-92s. The exception would be in 1.25"-only usages. That, or where a light weight eyepiece is necessary. I know, many folks don't consider 12 to 13 ounces light weight, but it is in comparison to the ES-92s.

You may have to flip the eye cup down to be able to get the camera close enough to properly couple with the eyepiece's exit pupil. The eye cup being up may help block stray light, though. You'll just have to experiment and see what works best. Having taken all of those afocal images of my eyepiece apparent fields of view in this thread, I've found it is possible to couple cell phone cameras into eyepieces with as little as 3mm usable eye relief. Here's a new one I haven't previously released. It's of a generic 6mm Huygens I got with a $25 70mm x 300mm refractor off of ebay with just 3mm of usable eye relief: This was with the AT72ED and a Galaxy S7 rear facing camera. It is actually not that bad of an eyepiece at f/6. It shows that with skill, it is possible to use eyepieces with very little eye relief. I was hand holding the camera using my finger edges to maintain alignment with the eyepiece. It's an acquired skill.

Collinder 70 (Belt of Orion open cluster) is another large favorite of mine at low power. 15x70 binos show both it and the Pleiades rather well.

I remember at another star party that an imager was stacking deep space object (DSO) images in real time on his laptop using a dedicated astro camera in the focuser. In about 10 minutes, faint nebulosity that was invisible to the human eye was readily apparent. I can't say that it was a very exciting experience. You might as well download professional images off the internet if you're going to stare at a laptop screen at a dark sky site. I much prefer gathering ancient photons with my eyes.

For that kind of money, you can get into some seriously heavy rigs. How much weight are you willing to lift? How much space do you have in your vehicle to haul a scope and mount? How much storage space do you have at home? As far as my recommendation, I'll relate a recent experience I had. There was a newbie at a star party here in Texas with a brand new Celestron NexStar Evolution 8" EdgeHD. He was happily, wirelessly controlling it with a tablet running planetarium software. With a 10mm Delos, it was providing an excellent image of Jupiter and other targets that night. It was super easy to select targets within the planetarium software on the tablet. Once selected, the mount quickly slewed to the new target and kept it perfectly centered. The Starsense made alignment a cinch as well. This rig would be easy to store, setup, transport, and use. It would also leave plenty of money from your budget for eyepieces and other accessories. 8" is a sweet spot for astronomy. Big enough to provide good views of most objects and yet not so big as to put off using it due to inconvenience.

I figured you mentioned it somewhere, but I wasn't looking in the thread title, just your posts. It's not the first time I've missed pertinent info mentioned only in the thread title. 🙄 It will definitely work in your C8, but it will requiring moving your mirror forward which will increase the focal length a few hundred millimeters I believe. It will also induce a bit of spherical aberration by moving the mirror well away from the optimal design position. It might be visible at high powers or it might not. Some people are sensitive to it while others are not. The longer the Barlow is originally, the less effect lengthening the working distance in BV usage has on the magnification. The Meade is a "mid-length" Barlow like the 2x Tele Vue 1.25" Barlow. Your Baader Q-Barlow would be classified as a "shorty" Barlow. I do have a "long" Barlow (6 inches or so), but it does not have a removable optics section. If it did, it would be terrific for BV work. I'll have to see if I can swap the optics into a spare Meade 140 nose piece I have someday. It will all depend on lens diameters and the combined spacer/lens depth of each.

Which of your many telescopes were you using the BVs in? I get 3.0x magnification with the optical nose piece of a vintage Meade 140 2x Barlow screwed onto the front of my Arcturus (similar to OVL) binoviewers. I have no trouble reaching focus in my limited in-focus Dob with this combo.

I have the 22mm Nagler T4 now. Does the 31mm Nagler have the same usable eye relief as the 22mm NT4? I'm using the 30mm ES-82 mushroom top right now because the eye lens is basically flush with the top and I can just take in the full FOV with eyeglasses. I've wondered over the years if it is worth upgrading to the 31mm NT5 for its better correction. Although I wouldn't do it if it doesn't have at least as much usable eye relief as the ES. My TV gear includes all the NT4s, 27mm Panoptic, 10mm Delos, 2x 1.25" Barlow, and PBI. They're all fantastic. Adding @Don Pensack re: 31mm vs 22mm Nagler usable eye relief question.

There's also the possibility of a rubber lens hood with the lens-end inner diameter similar to the widest part of the ES-17's upper barrel. That would allow it to be slid up or down somewhat to adjust the height. Once fitted, it could be cut down to custom fit the hood to the user's facial shape including wing shaped.