Louis D

They've become quite popular with American astronomers, especially those who can't crank their head around any more to use an RDF. I have yet to hear or read of a single astronomer being approached, let alone arrested, by a police officer for using one.

My bad. I didn't realize it didn't have a vixen style finder shoe. You can always add one quite easily: I just swapped in this one for the single screw one that came with my Orion 127 Mak. It holds dovetails much more securely with its two screws. Of course, you'd have to either add a dovetail foot to your RDF or order one with the dovetail foot.

I would get one of these and mount both the RDF and a (better quality, RACI?) finder scope at the same time. I got one for my refractors to mount a finder scope, a laser sight, and a QuikFinder/RDF simultaneously. It also helps get them farther away from the eyepiece so I tend to bump them less often.

If it's one of the ones that originated for rifles and pistols, they're really simple. Once locked into the finder shoe, just center a star in the main scope, turn on the RDF to its lowest brightness, and then adjust the windage and elevation knobs like azimuth and altitude adjustments to place the red dot in the viewing window on the star. They're actually simpler than the Telrad and QuikFinder adjustments that have three knobs and require a bit fiddling to fine tune.

Multiplying barlow magnifications together might not work precisely if the barlows won't seat all the way into each other, as would be the case with older, long barlows. You might not be able to reach focus in that case, either.

Sorry, the only google hits I got in the US for Skywatcher 90mm were like the following: Searching deeper, I finally found the Skywatcher Evostar 90 AZ3 Telescope in the UK and Australia, but none in the US: I don't think it's imported to the US because Orion USA, Meade, Celestron, Rokinon, and Levenhuk all import a similar telescope.

I didn't think Herschel wedges could be used with Mak-Casses like the Skywatcher 90mm. I would think the baffles or secondary spot could be damaged by the heat buildup.

You'd probably have to realign/recollimate the focuser (it appears to have collimation screws), but that would be about it. It appears to have a symmetric base. Just double check that the focus tube is dead center between the mounting screws in both the X and Y directions.

It also matters if you have severe astigmatism in your observing eye. By severe, I'd say 1.25 cylinder diopters or more (check your prescription for CYL or cylinder). If so, you may want to observe with eyeglasses at lower powers that create larger exit pupils. Larger exit pupils reveal more of the eye's astigmatism. The BST Starguiders are just usable with eyeglasses, except for the 25mm version which is fine with glasses. FLO (our sponsor) has a nice discount that increases with increasing number of Starguiders bought at once. You'll probably also want a widest field 30mm to 40mm eyepiece for locating objects before centering them and for viewing larger objects like the Pleiades. I'd recommend the 35mm Aero ED. It's not perfect, but it's relatively light, compact, is just usable with eyeglasses, and does fairly well at f/6.

Large Dobs with well figured mirrors not only excel at DSOs, they're terrific on planets. In a 12" to 16" Dob, you can start to clearly see barges and festoons within the belts of Jupiter that simply don't resolve in smaller scopes. The larger exit pupils at the same magnification as smaller scopes make for a more relaxed view since you don't have to dodge floaters in your eye. The biggest downsides to them are weight, size, and cost. Setup time is surprising quick with a truss tube. When I was regularly using my 15", I could be up and running in about 10 to 15 minutes. The weight of mine got me after a severe back injury, so there is that. 😥

I went back looking for this lateral color, and it is there but very slight. It's a bit of a purple smear pointing toward the center. The 5mm XL showed it as well, but to a lesser extent. I guess it's not as big a deal as I remember from when I first got the eyepiece. I also compared them to the 4.5mm and 6.5mm Meade HD-60s and 5mm and 8mm AstroTech Paradigms, and there wasn't much to choose between them. These budget eyepieces are basically flat of field and sharp to the edge with lateral color no worse than the Pentaxes. The eye relief with eyeglasses was just a bit challenging on the Paradigms and the 4.5mm HD-60 to a lesser extent. The 6.5mm was nearly as nice as the 7mm Pentax XW in all respects except apparent field size. The 25mm HD-60 was indeed better than the 25mm Paradigm from 50% out to 75% out, but both were left in the dust by the 24mm APM UFF. All were similarly easy to use with eyeglasses. I compared them against the moon, Pleiades, and various Orion targets in my 90mm TS Triplet APO with and without the TSFLAT2 using a couple of GSO dielectric 2" diagonals (quartz and non-quartz).

Possibly you're seeing vignetting, though the sensor is only 27mm in diameter, the same as the clear aperture for a 1.25" adapter. Take an image of the blank sky to see if there is light falloff toward the corners. Colors will be washed out because your SCT has a large central obstruction. That reduces contrast causing the washed out effect you're seeing. This is apparently not an issue at night, though. I tried using mirror telephoto lenses for daytime photography and quickly switched to refractor style ones because the contrast on the latter ones are so much better. That, and out of focus highlights are donuts instead of round blurs. Again, not an issue at night because everything is in focus at infinity. As far as images being dark, try switching to manual mode and experimenting with different shutter speeds and ISOs to see if you can get lighter exposures. As for focus, try live view on you camera LCD screen and increase the magnification to 5x or 10x to try to get better daytime focus. Look for high contrast transitions to focus on. At night, you can use a Bahtinov mask while focusing on a star to get good focus.

@Barry-W-Fenner: Why don't you start a new thread on this subject (and which 30mm to 40mm 2-inch eyepiece to get) in the eyepieces forum? I think it's a good subject, but this thread is about eyepiece cases, and I don't want to continue dragging it off-topic with my thoughts on the matter. 😉

Since these scopes cost $50 new here in the States, and maybe $20 used, it's unreasonable to expect mechanical perfection from this class of scope. Thankfully, the main achromatic doublet is usually pretty good, so good images are possible if you can fix up the mechanical deficiencies. For the finder, see if you can loosen the screws attaching the stalk to the tube and make it align with the added degree of freedom. Retighten the screws and perform final alignment with the finder's alignment screws. For the focuser, you'll have to shim it with thin plastic or teflon strips on the side opposite the rack to take out the play as has been suggested by @Carbon Brush. There's not a lot to be done for those alt-az mounts to tighten them up to take out play in them. If you have a photographic tripod with a fluid video head for videography, they work way better. It would then just be a matter of mating the scope to the tripod head via a mounting block of some sort. As for targets, try panning along the Milky Way to see what randomly pops up in the field of view. Starting with a pair of binoculars to find denser star fields can help with this. If your son really likes astronomy, he'll be the one taking the lead on modifying the scope. Hopefully, this scope doesn't turn him off to the joys of stargazing. Find a local astronomy club and attend one of their public star parties to see what is possible with properly designed equipment. Like any hobby, you can drop thousands of dollars into it when you get serious with it.

For the tripod legs, try putting blinking red LEDs at their feet. For leaning, try using a kitchen step stool with a nice handle they can lean against instead of the telescope:

A bit facetiously, but I can't resist, Earth is the easiest planet to see with or without a telescope. At star parties, we always count it in when telling people how many planets they can see that night. IMHO, it's still the most beautiful planet. As others have mentioned, a public star party thrown by a local astronomy club is a great way to see the planets and learn more about amateur astronomy.

You also need to be balanced along the tube axis. Any asymmetry along the tube, such as finder or guide scopes, will cause an imbalance as well and you'll need to add counterweights on the other side of the tube to compensate. You might be balanced when the tube is horizontal, but aim it at the zenith, and it may tip right on backward if it is top heavy. I have this issue with my alt-az mounts.

Interesting scope. It's an achromatic Petzval design at 127mm. I don't think I've ever seen that implemented before. It's sort of an achromatic take on the Tele Vue NP127is for about 6% of the price. The biggest issue with it will be the false color. It should be flat field if it was designed and implemented correctly. If you shoot narrow band images, the false color shouldn't be an issue. The single speed focuser might become an issue at f/4.9 when trying to achieve best focus.

If all else fails, remove with the eyepiece, point the scope at a tree (there appear to be a bunch out that window) in the daytime, and look down the focuser tube from about a foot away. You should be able to see an inverted image of the tree in there. You may need to move your head in closer or farther, but you should be able to see the tree reflected off the secondary mirror below the focuser tube. If you can't see that, your collimation is way off. If that is the case, look down the tube from about a foot away from the end to see if your face is reflected in the primary. Your face should be centered. If it is skewed to the side, your primary collimation is also off. Let us know what you see. You could even snap a couple of images with your phone's camera and post them here for diagnosis.

That might just be the lens cap sitting askew on the top of the eyepiece.

Absolutely. I remember paying $240 each for my Pentax XLs back in 1998. The XWs are barely more expensive than that today. On the other hand, custom made, American Dobs have scaled with inflation, and then some.

I just realized I paid $90+tax for my 9mm LV back in 1997. It's remarkable that they're back down to that price range 23 years later, at least in the UK minus VAT. Americans are always saying "+tax" because sales tax is added on at the end of the sale. It's not included in the advertised price like VAT. Gasoline/diesel (petrol?) is advertised at the pump with all excise taxes included, so that is the same as the EU.

They're $169+tax in the US, and many retailers still show limited stock of them. By comparison, they're only $80 to $90 shipped from FLO to the US, less if more than one is bought at a time. Since I'd have to buy over $800 of them to get hit with the 8% tariff, that leaves only 8.25% sales tax for me to remit. Something is going on, but what?

Thanks! That lends credence to the school of thought that the sub-9mm SLVs are the same in AFOV as their LV and NLV counterparts. Perhaps the sub-9mm LVs used more Lanthanum elements than the rest? Perhaps some other rare earth glass causes the cofffee tone that only the sub-9mm versions used? I hope you didn't sell that 7mm LV. They're hard to find nowadays. It's worth holding onto just for collectability sake.

Thanks. Better tell Optics Planet they're misinformed on both counts. 😁