Louis D

The 6mm and 9mm Red/Gold line Expanse clones are supposed to be pretty decent in faster scopes thanks to the integrated Smyth/Barlow lens slowing down the light cone. However, they are poorly matched to the upper positive section leading to strong SAEP (kidney-beaning).

I would lean toward a 7mm as well given your scope's focal length and typical UK seeing conditions.

I can't answer that question, but with the addition of a low cost #8 Yellow filter, you could cut out a lot of the purple fringing of the achromat and substantially sharpen up the image in the process.

Is the red Hα? You'll have to compare visually to see if it shows up at all to the human eye with the UHC filter.

I've measured the 30mm APM UFF's AFOV at 73°. Its eAFOV is 70° due to some edge distortion. If you're only going to be using it an f/10 SCT, I'd recommend the various 30mm WideScan III clones. The field curvature isn't so bad for younger eyes at slow focal ratios. It's very sharp in the central 50% even at f/6. Here's a comparison image taken through my f/12 Synta Mak for several 30mm wide field eyepieces: Notice how well behaved the 30mm (ignore the 20mm marking) Agena UWA 80° eyepiece is. There's no SAEP or CAEP, and 18mm of usable eye relief. It also shows significantly more TFOV than the 30mm APM UFF and about the same as the 30mm ES-82, but with significantly less edge distortion and no CAEP. It's sold under many brand names. Here's the APM Eyepiece UW 30 mm 80° version. Here it is from an ebay seller. I can highly recommend it for slower scopes. I passed mine along to my daughter for use in her Synta 127 Mak.

It's this one I'm sure.

Try reading the Cloudy Nights threads returned by this google search to see if they answer some of your questions and concerns.

For an unobstructed system, you should be able to use the 41mm Pan in faster scopes as long as you don't mind losing a few photons to your iris and dealing with a brighter sky background. Since the 30mm APM UFF's field lens is a bit over 40mm in diameter, it should be possible to scale the design upward a bit before it completely fills the inside diameter of a 2" (~46mm) barrel. Perhaps a 35mm might be a possibility?

Other than the Pretoria eyepiece, a couple of Brandon eyepieces, and an APM Barlow, eyepieces and Barlows don't correct the coma of the primary. You'll need to buy a coma corrector for the f/4.7 primary mirror. Coma will be quite strong in most wide field eyepieces in that scope without a CC. The 12mm and below Starguiders will still perform well with your scope in all likelihood. At 15mm and above, I'd be looking at other designs better suited to fast scopes.

I had to look up that reference. We don't have them much over here.

Have you done a Panoptic 41mm vs Lacerta 40mm comparison for grins? My 40mm Meade 5000 SWA (Maxvision SWA) is nearly perfect edge to edge compared to either the 40mm Pentax XW or 40mm Lacerta, but boy is it heavy and bulky.

That's Mak (as in Maksutov, the Russian designer or it). I thought of the Apple product at first for Mac. My next thought was, why the choice between a computer and a telescope for a 5 year old? Then I got it by your second sentence. I'm a bit slow. As far as Barlows, I'm a sucker for 1990s Japanese made Barlows only available used, so I can't really make any modern, off-the-shelf recommendations for them.

At least eye floaters shouldn't be an issue for a 5 year old at high powers and small exit pupils like it can be for us gray hairs.

What is the rear port diameter? In my 127 Mak, I get reflections off the rear baffle tube from bright stars when using 2" eyepieces because the rear port is only 27mm in diameter at best. I keep thinking I'll install flocking inside the rear tube someday to tame those reflections.

Had a quick peek at the moon this morning through the 127 Synta Mak with both the 40mm Lacerta ED and 40mm Pentax XW. Surprisingly, not much improvement over the views through faster scopes. The Lacerta still starts to blur at about 85% to the edge, the Pentax just a bit closer to the edge. Overall, I was very surprised that neither was sharp to the edge at f/12 and improved only slightly from f/6.6.

A very slippery slope indeed as I can attest. 🙄

Way to take one for the team!

Here's Ernest in Russia's review/test of the 16mm Levenhuk Ra version. He briefly mentions the 16mm NT5 and has a photo of them side-by-side.

Well, I am looking at having Santa drop off an APM SuperZoom for Christmas if they come back in stock before then. 😁 I've never been convinced that the Leica ASPH zoom would have enough eye relief for me and my massive astigmatism.

Nothing wrong with you wrt eyepieces. To each their own. I must be going now, or I'll be late for my EA (EyepieceAholics Anonymous) meeting: 😉

I'll never understand the recommendation of binoculars for astronomy. Unless you buy the expensive image stabilized ones or mount them on a tripod, the view through them at night is extremely disappointing because stars and objects dance around due to human unsteadiness. That, and 7x to 12x just doesn't cut it. You'd think that at least large objects like the North American nebula would pop out at low power, but they don't unless you're under very dark skies. I had binoculars for years, and they were fine for peeking at lunar eclipses, planetary conjunctions, etc. You can't really learn constellations through them because they're way too big to fit in the field of view. However, once I bought a Dob, I went wild learning the skies, so I could find Messier objects, observe Jovian moon (and their shadows) transits, resolve Cassini's Division, follow Venus's phases, explore the lunar surface, etc. I tried the binocular route for a few years before buying my first scope based on recommendations, but found it extremely disappointing. Did anyone on here find binocular astronomy anywhere near as exciting as telescope astronomy? Without excitement, passion quickly wanes and interests migrate elsewhere.

I bought my XLs in 1998. XWs didn't show up for another 5 years. I guess the last XL version lasted quite a while.

It appears to be the same as the Orion EON 110mm ED f/6.0 refractor which has been around for at least 8 years. Do a Google search on it to see what has been said about it. They should be equally applicable to the SM version. It should be a major step up from an ST 102 color correction wise. It won't be apochromatic at high powers, but it won't be horrible, either.

Here's some poor pictures of my various Pentax XF/XL/XW eyepieces. All have undercuts: