Louis D

I got "lucky" I guess because my eyes are fixed focus at about 8 inches, so I can generally read notes by simply looking under my specs. My wife is like you in that she had to get bifocal computer glasses for work so she can read her monitors at 2+ feet and documents at around one foot. My astigmatism doesn't bother me too much when reading for brief periods of time, as at a telescope.

The Mak is the much better deal of the two. The Newtonian seller wants new pricing for used equipment while the Mak seller is applying a proper discount against the new price. The Mak will also have much better resale value down the road. Those cheap Newts don't hold their value at all.

They probably ran out their existing stock and decided that it wouldn't be economical to start another run given past sales performance. They would also probably have to raise the price as well to cover new, higher manufacturing costs to such a point it probably wouldn't be at all competitive.

Mostly you'll see spiky stars instead of round stars no matter how much you try to bring it to best focus. The spikes also rotate with your head if you pivot it around the axis of the eyepiece. This same effect also blurs low contrast details on planets and makes resolving globular clusters difficult. To see the effect for yourself, try looking through an eyepiece at a well focused, bright star with either eye without glasses (may need refocusing between eyes), and then repeat the experiment after refocusing while wearing your eyeglasses. At 3.25 diopters of cylinder, you should see a dramatic improvement in the appearance of stars with eyeglasses. For us astigmatism sufferers, I recommend sticking with longer eye relief eyepieces and buying a dedicated pair of distance-only eyeglasses with low index plastic lenses (to reduce off axis chromatism) for astronomy. Daily wear glasses get thousands of tiny scratches in the lenses that manifest themselves when viewing stars in my experience. Keeping a dedicated, low-scratches pair around is really helpful. When viewing with ultrawide field eyepieces, single vision lenses are also superior to bifocal or multifocal lenses because all parts of the field are in focus at the same time. In the US, I've had very good luck with EyeBuyDirect buying low cost, online, single vision eyeglasses. I'm sure there's a reputable UK equivalent.

I would recommend the 35mm Aero ED for a widest field eyepiece in that scope. I believe TS-Optics has it in stock as the UFL based on a recent post here on SGL.

It's based on exit pupil which is the eyepiece focal length divided by the telescope's focal ratio, and diopters of cylinder correction on your prescription. Tele Vue's Dioptrx page has a nice diagram for estimating when you'll need correction based on exit pupil and number of diopters of cylinder (astigmatism) correction that I've repeated below: The upshot is that if you have mild (0.5 diopters or less) astigmatism, you probably won't notice it except at the largest exit pupils when working at low powers with smaller f-ratio scopes. If you have strong astigmatism (2 diopters or more like I do), you'll probably need to wear your eyeglasses or use a Dioptrx at all but the very smallest exit pupils when working at very high powers.

It's fully described in my original images thread in two posts.

All are optically the same internally with different barrel designs outside. I've also read that some of the heavier versions (e.g., Altair) use a stainless steel barrel instead of aluminum like the APM.

That's my situation since my trees matured. I have a sliver of sky about 20 degrees wide to the south and overhead that are clear. The rest is either partially or completely obscured. Two star aligning my DSCs is a real chore because of this. I'm lucky if I can see one bright star at any given time. That's why I really like SkEye since it requires no initial alignment. I then refine alignment on objects that are visible. It's been helpful in getting my bearings when I can't see an entire constellation or group of them.

As far as 1.25" eyepieces in that range, I have the 24mm APM UFF, 25mm Meade HD-60, 25mm BST Starguider (Paradigm), 23mm Aspheric 62°, etc. I'm assuming you're wanting to stay within 1.25" eyepieces. The 24mm ES-68 is also well thought of as is the 24mm Panoptic, but neither have enough eye relief for me. Do you need long eye relief for astigmatism in your observing eye? What is your budget? Below are some of my eyepieces in that range imaged through an AT72ED similar to yours: The Meade MWA is really a 25mm, so it fits your criterion if 2" is okay and you can find one. They've been discontinued along with the HD-60 series.

So, if you're way north in the summer, you can forget about this technology working during the "night".

For what purpose? Surely she has expressed an interest in using it either visually or photographically. Any idea which way she leans on usage? Hopefully not just as a piece of interior decor.

Maybe I'll pick one up sometime to try. Does it have enough eye relief for eyeglass wearers?

As far as defocusing goes, use whichever side yields better Fresnel rings. My APO has near textbook rings on one side and near mush on the other:

Become the resident expert on the equipment and the sky so you can quickly get your dad up to speed upon his return.

When pondering maximum magnification, I calculate the resultant exit pupil. Given your scope is an f/10, and 0.6mm is about the limit for small exit pupils before floaters become an issue for many folks, I'd say a 0.6mm*10=6mm eyepiece would be the absolute shortest usable focal length in your scope on most nights. This would yield 1500/6=250x. Rather than buy a 6mm and a 7mm eyepiece to search out your maximum usable power on any given night, I'd just buy a quality 2x Barlow for the BHZ to yield 4mm to 12mm, or there abouts. I'll let other make currently available shorty Barlow recommendations since I don't own any. If you come across a vintage Japanese made Celestron Ultima 2x, Parks Gold Series (GS) 2x, or Baader Triplet 2x Barlow, I can verify they are exceptional shorty Barlows. Mars is receding away from us and is getting smaller by the day. It was at opposition in October 2020 and won't be again until December 2022. Other than for a few weeks on either side of opposition, Mars isn't all that great of a telescopic target. Try defocusing a mag 2 star like Polaris once it is centered and highly magnified (the BHZ will be handy to determine the best magnification for this). The Airy disk should show nicely concentric, smooth, round Fresnel rings on either side of best focus. If the image shows poor collimation as on the right, you'll need to investigate SCT collimation further. Since I don't own one and have never collimated one, I can't offer any further insights. Just make sure the star is dead center. Moving it off axis will make it look uncollimated. You can defocus the star until its bloated image nears the field stop to better center it.

In what scopes? How is center to edge sharpness and flatness of image?

If you're careful and push the cutout against two sides, that will maximize the leftover filter material in the opposite corner for a finder filter or small refractor filter. I'd recommend getting a SVBONY IR/UV cut filter to put on your eyepiece. I'm not convinced the filter material is doing a good job of blocking nonvisible wavelengths. After some time observing, I get a fatigued feeling in my observing eye as if it is being cooked without the filter. A variable polarizing filter may also come in handy to knock down the brightness a bit further if you find ND5 too bright. I know I find it a bit too bright.

That still requires a dead lift of 46 pounds to a height of about 2 feet. I can just manage that, but it leaves me with a backache. I don't know about the OP's back situation. Hopefully, he'll chime in with a more specific weight limit.

Sorry to have taken the images out of context where I explained that. The "Full View" are taken with a 5 MP ultrawide angle cell phone camera so I can capture the entire 70+ degree view in one image. The regular images are taken with an 8 MP wide angle cell phone camera limited to about 70 degrees on the diagonal. I then scale up the resolution of the 5MP image to match the linear scale at the center of the 8MP camera. Due to magnification differences across each camera's field of view, they may not match at each point. I capture the 8MP edge views by pointing the camera at the field stop so I have a higher resolution view out there for comparison with the center resolution image. To summarize, there just isn't as much resolution when using a 5MP imager producing a shrunken image. I'd love to get my hands on an affordable 24MP or more cell phone camera covering at least 110 degrees on the diagonal.

I wouldn't exactly call $55 cheap as chips. If it were in the $25 range, I'd agree. This eyepiece is sold under many other brands such as Apertura and Omegon, so hunt around to see if you can find any feedback or reviews of them. Regardless, it will probably perform admirably well in an f/12 or slower Mak. At f/8, expect some astigmatism and possibly field curvature in the outer 25% of the field. At f/5 or slower, it will probably be a mess beyond 50%. I have an Orion SWA Centering 20mm, 70 degree eyepiece. Here's how it looks in an f/6, field flattened ED refractor for reference: Not very pretty in the outer 25%, is it? Think of it as a 20mm Plossl with more, but blurrier, outer field for context. It will look slightly better at f/8.

A 127 Mak on an alt-az mount is a good beginner's setup that isn't extraordinarily heavy and yet is quite capable of delivering rewarding views of most solar system objects and the brighter DSOs. I'd definitely recommend getting a 9x50 RACI finder to go with it because the Mak's long focal length yields such a narrow field of view. The problem right now is lack of stock. Are you looking to buy from within the UK, US, or elsewhere?

That's kind of what I figured. They're also the two weakest focal lengths in that lineup because they are positive-only designs, IIRC. I'd probably steer people toward the BST Starguider 15mm and 18mm offerings instead.

It's my understanding the hoisting a C9.25 onto a mount is right at the limit for many folks with good backs, and the OP has stated he has back issues, so I would probably steer him toward a lighter solution. I know I had to take a pass on a used 127 Mak/EQ combo from Orion because the OTA was bolted directly to the mount without a dovetail and clamp. Along with the counterweights, it was just too punishing on my back to lift as a unit. I didn't feel like adding and removing the weights each time I wanted to move it around the yard, so I went with an alt-az mount with the 127 Mak. It's much easier to pick up and move as a unit to dodge trees, houses, and bushes.

It gets me within 4 or 5 degrees of objects generally after aligning on some easy object(s) like bright planet and stars. Sloppy by traditional DSC standards, but because it's showing me the star pattern on the screen around the object, I find it fairly simple to use either a Telrad/QuikFinder or GLP to fine tune the pointing enough to get the object within my widest field eyepiece in the main scope. This presumes you can see stars down to about magnitude 3 or so. Once it's centered, I realign SkEye on the object, and pointing in that region improves quite a bit. During centering, I zoom in on the SkEye screen view to match what I'm seeing in the eyepiece. I'm still getting familiar with it, but I've found it fairly handy so far. It's not for the inexperienced for sure, but if you're experienced and are looking for new or difficult objects with a scope on a mount with no traditional DSCs, it's a huge help. It much faster and more convenient than referring to a paper star chart or non-linked planetarium software on a tablet or laptop.