Louis D

Nope. Longer eye relief is better for astigmatic eyeglass wearers. If your son's prescription has little to no cylinder (CYL) correction, he doesn't need to wear eyeglasses at the eyepiece. You can just focus out the distance correction with the focuser. Larger exit pupil makes extended, diffuse objects like nebula and galaxies brighter by concentrating the total light flux into a smaller area. Thus, more photons per unit area increases the perceived brightness. It also makes the sky background brighter (for the same reason, it's an extended object), sometime negating any advantages (both get brighter at the same rate). An exception to this is when using line filters like OIII filters on nebula. The increased exit pupil makes the dim image easier to see because it blocks the light pollution of the background sky while letting through the OIII emission lines.

I just received an affordable 600nm Shortpass filter. It has a broad, high transmission passband for wavelengths shorter than 600nm and a sharp cutoff very close to 600nm. Visually, it cuts out practically all red without noticeably dimming the view. Below is the manufacturer provided transmission graph: I paired it with my Yellow #12A, Yellow #12, Cheap Yellow, and Yellow K2 (#8) filters when viewing Venus through both the ST80 and ST150. The best view was the combination with the Rokunar Yellow K2 cutting all violet/blue and orange/red fringing in both scopes. The color was a pale green without much blue or yellow secondary cast. The Meade Green was still showing the better image due to the narrower passband, but the intense green color was hard to get past. I'll have to try out the various combinations on DSOs as skies and time allows. I'd like to see if a high transmission combination (better than 80%) can be successfully used on brighter DSOs to sharpen star images without losing dimmer components at the same time. Below is an update to my spectrograph image comparison showing the clearly higher transmission of the 600nm Shortpass filter and its combinations as compared to the Cyan BG39 filter and its combinations. That, and the cutoff is tremendously sharper at orange-red than anything else I have. The 600nm Shortpass filter is a work in progress because it is a square piece of glass that I hope to be able to cut 27mm and 46mm circular disks from for 1.25" and 2" filter housings, respectively.

Pretty much the same for me except that I use an AstroSystems laser instead of a Glatter laser and a Rigel Aline for the primary collimation. For the big truss Dob, I use the laser while working at the back of the scope to get the primary return spot coincident with the outbound spot on the face of the secondary to get it pretty close before checking with the Aline. I don't have 6 foot long arms to adjust the primary while peering into the Aline at the secondary cage mounted focuser.

For GnG, I would get a 102mm or 127mm Mak. They are very sharp on solar system objects and good for DSOs under 1 degree in size. They are rugged, compact, lightweight for their aperture, and hold collimation very well even after being roughly transported multiple times. If you insist on a refractor for GnG, I would recommend a 70mm or 72mm ED. They are quite compact, and yet will show larger DSOs and solar system objects quite well. If you want the best high power performance, spring for an FPL-53 version. 90mm to 102mm achromatic short tube refractors are still going to be big and bulky, just somewhat lighter than their ED/APO counterparts due to lighter weight construction. However, the color on solar system objects and brighter DSOs will probably displease you since you've been using an ED refractor for some time. I've been tinkering with filters to subdue the false color, but you end up with a yellow or green image for brighter objects to get a sharp image. The unfiltered false color doesn't intrude much below about mag 2 to mag 4, depending on your sensitivity to violet light. Thus, if you're only into faint DSOs, it might not matter much to you. Another option might be a Heritage Newtonian in either the 130mm or 150mm size, but mounted on an alt-az setup using the dovetail. I don't have experience with them, but they seem to be well regarded here on SGL and elsewhere. Just be aware that the helical focuser can be a bit of a work in progress and doesn't play nice with zooms. I did buy a 6" f/5 GSO Newtonian with dual speed focuser, and I can say that they are hands down a far better all around performer than a 6" short tube KUO refractor which I also bought for comparison. That, and the Newt is about half the weight and is much easier to mount and use standing thanks to the eyepiece being at the top of the tube. I suppose if you dropped down to a smaller diameter Newtonian like the SW 130P-DS it might be compact enough for GnG without sacrificing the dual speed focuser.

Howdy from Texas!

There seem to be several GSO 2 speed focuser models. Mine has to be the worst. It does work once adjusted properly, but I have to remind myself not to touch the tension knob despite the tension being a bit on the high side for lighter eyepieces. It's set as low as I can go without having the focuser tube drop under the weight of heavy eyepieces (e.g., ES-92 17mm).

Since the moon is basically monochromatic, try using a #56 Green filter to cut the poorly focused violet/blue and red ends of the spectrum. It will dramatically sharpen up your views.

I have the GSO Linear Bearing focuser on my GSO 6" f/5 Newtonian. It barely works depending on the tension setting. Too little, and the focuser tube just drops into the focuser under heavy eyepiece loads. Too much, and the action is heavy and sluggish. It's difficult to find the Goldilocks setting in between. It shouldn't be that hard. There's a dedicated thread on CN detailing why this is so. It's clear it was designed to a meet a certain price point.

OMG, I can think of a lot of other uses for that laser cannon, none of which can be mentioned here due to TOA rules.

Same has happened with me over the past 30 years. There are now 10,000 new homes, two car dealerships, two tollways plus their interchange, a high school with football field (Friday Night Lights), and multiple giant shopping centers. I've gone from Bortle 4 skies to Bortle 6/7 skies during that time. All of it built on blackland prairie farmland. Since our neighborhood trees have matured, I've lost all but my south facing view from my backyard. Our ice storm this winter did take out a huge chunk of a neighbor's tree opening up more of my southerly view, though.

Generally in the US at least, if you consider yourself a cowboy, you're a rancher rather than a farmer. Ranchers are generally regarded as way hotter than farmers, BTW, thanks to the whole cowboy mystique (cowboy hats, boots, rodeos, rugged appearance, etc.).

At higher powers, I'm generally looking at smaller objects, and 70 to 78 degree AFOVs seem plenty wide enough for my non-tracking observing of such objects.

A lot of these cheap, variable voltage power supplies are not well regulated. Their voltage can vary while under load, not supply enough amperage, introduce electrical noise into the line by being a switched power supply, burn out prematurely due to cheap components, etc. You just need 2A at 12V, so find a quality 12V transformer type power supply rated for at least 2A with the proper connector, and you should be good to go.

I'd probably like a 22mm to 25mm Apollo to replace the 22mm NT4 which needs better eye relief and less SAEP. I'd pay up to $600 for one, possibly more, if absolutely perfectly corrected, flat of field, 18mm of usable eye relief, and no SAEP at all. I'm good with the ES-12 and ES-17, so no desires for Apollos there. I can always Barlow these two to easily get to 8.5mm and 6mm focal lengths. I've done this, but I have never felt like I wanted to use that amount of FOV at those focal lengths.

Don't be afraid to push up the magnification into the 75x to 100x range to see if smaller DSOs like M57 become easier to pick out. At 33x it's basically stellar in appearance.

I could see that being an issue. Over a couple of decades ago, I recall reading about some who had fresh prescription blanks cut and mounted into filter housings by his optician to attach to the bottom of eyepieces. The poster claimed they worked well to correct astigmatism in his eye, but optical designers claimed that it wouldn't work if they were used before the eyepiece rather than after.

And the TV Apollo 11mm would be a lot more popular if they had cut about $800 off the cost. I'm not sure how well it would have sold without the caché of being a limited edition eyepiece.

I vaguely recall Denis offering an astro version of a Zeiss microscope binoviewer that almost entirely uses mirrors, so it might not have the differential dimming effects of a prism based BV. It still uses a prism beamsplitter, so differential polarization may be unavoidable even with it.

Lucky you. My 2+ diopters of astigmatism renders bright stars as spikes and dim stars simply wink out of existence without my eyeglasses. It's not until I get down to about 1mm exit pupils that the astigmatism effects fade, but never quite disappear.

I would probably just buy a Tele Vue Dioptrx first, even if it doesn't fit every eyepiece I own.

You probably don't want to view through vintage glass, though. My daughter's house has many original 120 year old window panes. Even to the naked eye, they make the outside world look a bit like funhouse mirrors. Glass flows due to gravity and ends up with waviness over the decades.

I have a 3x Barlow that I've used maybe 2 or 3 times in the past 25 years. However, I have a multitude of 2x Barlows that I regularly use. I would definitely recommend a 2x over a 3x.

Correct. It is usable thanks to it's SAEP being the mildest of the line. No doubt. Eyepieces that appeal to non-eyeglass wearers don't generally appeal to eyeglass wearers and vice-versa. There are those with long eye relief and adjustable eye guards which seem to appeal to both. As an example of the first case, having looked through a 21mm Ethos at a star party while wearing eyeglasses, I was very much "Meh" about it. If I could see 70 degrees AFOV, I'd be surprised. I took my glasses off, put my eye socket against the eye cup, and was greeted with loads of astigmatism (at least with bright stars) across the 100 degree field. All of the faint stars disappeared thanks to my eye astigmatism. I was completely underwhelmed by it. I'm sure if I didn't have 2+ diopters of astigmatism, I'd have been more impressed by it. Perhaps if ES added an adjustable eye guard to the ES-92 line, it would have more general appeal.

I know you briefly had the 12mm ES-92. How did the engagement differ between it and the 13mm Ethos? I vaguely recall you had difficulty holding the exit pupil of the ES-92. Wearing glasses, the ES-92s feel to me like the Delos/XW/Morpheus/Hi-FW taken up a notch in engagement without losing any of the ease of taking in the entire view at once. There's no comparison to the 12mm/17mm NT4s which are both very difficult to hold the entire view while wearing eyeglasses.

The 12mm Delos should be fantastic if my 10mm Delos is any indication. A more appropriate comparison for the 12mm Delos would be against other long eye relief eyepieces in this range: 12.5mm Morpheus, 12.5mm Docter/Noblex, 12.5mm APM Hi-FW, 12mm Nagler T4 and 12mm ES-92 (did I miss any?). I have the last three, and really like the APM for 1.25" use in smaller scopes and the ES for 2" use in larger scopes. I can't afford the Docter/Noblex and consider the Morpheus too redundant with the APM and my 14mm Morpheus. I should pass along the NT4 sometime because I never use it anymore.