Louis D

Here's an Ed Ting comparison between a reflector, a refractor, and a Maskutov to see which yielded the best images.

Let us know your thoughts on it once you've had a chance to use it. The discontinued 35mm Aero ED would have been a viable alternative a few years ago. At f/6, it's good out to about 75% before astigmatism sets in. At f/5-5.4, I'm sure it would degrade faster, but I have no way to test that.

Think of a focal reducer as an image circle compressor. It takes that 46mm image circle and compresses it down to 29mm as Don says above. It also flatten the field a bit. Depending on the design, it might also correct some of the aberrations inherent in an SCT. Thus, the amount of light per area is increased leading to a brighter image using the same eyepiece. The trade-off is less magnification and image scale. To get back to the same image scale and magnification would require a shorter focal length eyepiece. However, image fidelity will suffer at some point because focal reducers tend to introduce some spherical aberration into the image at higher magnifications, much like Newtonian coma correctors and refractor field flatteners. As such, removing the FR for critical planetary observing would probably be recommended.

In that case, I would suggest putting a longer dovetail on the tube so you can move the pivot axis back toward the focuser. You would then need to put ankle weights or similar around the back of the scope to bring it back into balance. That way, the eyepiece end would swing through a smaller range and would also be less likely to hit the tripod legs. Notice below how I have a 14" long dovetail plate on my 90mm APO because, despite being a triplet, it's still massively back heavy thanks to the 2.5" focuser, finders, 2" diagonal, and my use of heavy 2" eyepieces. As a result, the eyepiece swings through a fairly modest range of heights. With heavier eyepieces like my ES-92s, I move the clamp even further back toward the eyepiece than shown, practically next to the focuser housing. Moving the tube rings backward isn't as much of an option because they only fit in one position back into the fitted case, and I don't feel like moving them each time.

What telescope are you using that swings through such a wide variety of eyepiece heights? A giant Dob? If so, Starmaster used to make an observing chair/stool that you could probably duplicate with a bit of woodworking and pipe cutting skills.

But imagine the surprise of an Ark ship arriving at a planet that has been fully colonized for centuries by folks who arrived via faster drive technologies. That, and they're tech knowledge is centuries or millennia out of date. Perhaps they would have appreciated being "hailed" centuries earlier now that they have no place in the modern world except perhaps to make period dramas. Imagine a 1600s cross-Atlantic ship full of colonialists just now arriving in the Americas. Awkward!!!

See this CN thread on Orion USA discussing their (literal) trials and tribulations.

I put together a 127 Synta Mak on an alt-az tirpod mount for my daughter to take camping. It takes up a relatively small amount of space in the back of her Chevy Equinox, which is small by US SUV standards. It wouldn't be good for AP, but it is decent enough for camping. That, and its collimation takes the trip to the campsite very well.

The alt-az mount is a DSV-2b on a Manfrotto 058B tripod.

I cobbled it together from parts I had lying around from previous projects. The Synta/Vixen finder foot, mini ball head, and cellphone mount all came from ebay back when supply chains were good and prices and shipping from China were quick and cheap. I couldn't find the exact same phone mount I bought. The new ones are all plastic, which is probably best for SkEye usage. I removed the central thumb screw from the mount, discarded the eyepiece clamp part, and screwed it directly onto the ball head where a camera would normally sit. Luckily, the mount used a standard tripod thread of 1/4"-20. I can't guarantee the mount I linked to would as well. Next, I threaded a 1/4"-20 hex socket head cap screw up through the finder foot into the base of the ball head. I don't recall the exact length since I again had some sitting around, but it was probably about 1/2" to 3/4" or thereabouts.

The Hyperflex zoom has a narrow field of view even by zoom standards as seen in this post of mine:

In my experience, SkEye gets me within a few degrees of the target each time running on an old Galaxy S7. Once centered, I then realign and it's a bit better for the next target in that region. Once in the general vicinity, I'm usually good to go finding it in a widest field eyepieces or a RACI. I can zoom the screen view to see what the immediate neighborhood looks like and match it to the eyepiece view. I have an aluminum phone holder on a cheap ball mount that doesn't seem to interfere with it:

My Surplus Shed zoom version has 33° AFOV @ 20.6mm (a bit short of 21.5mm) and 11mm of eye relief and 51° AFOV @ 7.4mm (again, a bit short of 7.2mm) and 10mm of eye relief. Eye relief bottoms out at 9mm around the 12mm focal length. If it weren't so stiff to zoom, I could probably live with it. Since I only paid about $35 for it on sale, I'm not complaining too loudly. It is pretty sharp, but being sharp over such a small AFOV isn't all that hard to achieve design-wise.

Well, it only took a couple of years, but Lacerta ordered a batch of the 40mm EDs (along with the 30mm EDs). I picked up one before this batch sells out. It competes very well with the 40mm Pentax XW while being lighter and slimmer, although a bit taller. That, and it's quite a bit cheaper, too.

The new APM SuperZoom is supposed to be easily usable with eyeglasses. If they're back in stock for Christmas Eve delivery, I'll be asking Santa for one.

I zoom the eyepieces simultaneously until the image size seems best. I then fine tune one against the other until the images snap together at the same image scale. It's really pretty easy to find that sweet spot because nothing quite matches up radially until then.

I remember reading a sci-fi novel about 40+ years ago where no one on a multi-generational interstellar ark had any idea they were even on a spaceship. There was no "crew" on the bridge, and it was only a nosy teenager who went exploring and discovered that they were nearing their destination after reaching the bridge and looking out the windows to see an approaching sun. I can't recall the details, but no one would believe his story or theory of their existence. In the end, I think he figured out how to take a shuttle launch by himself down to the planet they were supposed to colonize while the ark sailed on past the planet into oblivion.

It would be right at the limit of what your scope can do. You might want to explore the Barlowed zoom route to better explore the magnification limits of your scope and the seeing limits of your skies.

You could try a quick experiment with your existing gear. Try the Barlow element on the front of the diagonal in the frac, assuming it's a 1.25". That would add at least 60mm of extension, so your magnification might go up to between 4.5x and 5x. That would boost you to somewhere around 180x with the 18mm BCOs. I would get a pair of lower cost zooms so you can dial in your maximum magnification based on the seeing conditions. At 3x and f/21, they'd perform excellently.

The difference in magnification between the 12mm and 15mm is only 15x (75x-60x) and 10x between the 15mm and 18mm (60x-50x) for your scope. Both would be negligible differences. I usually recommend the 12mm and 18mm for a 75x-50x=25x difference which is noticeable, but you've already got the 15mm, so we'll work with that. I would get a 32mm Plossl for widest field at 28x and a 5mm BST for 180x. That would give you 28x, 36x, 60x, 113x, and 180x with exit pupils of 4.6mm, 3.6mm, 2.2mm, 1.2mm, and 0.72mm, which is a nice progression. You might want to hunt down a 6.5mm or 7mm for 139x or 129x for nights that won't support jumping to 180x. A barlowed zoom might fill this role:

I was just trying to understand how similar it's out of balance load capacity would be to a harmonic drive.

According to the SearchLight data Don pointed to, The Astronomik UHC-E (the blue line) passes both Carbon lines (olive green) quite well along with a particular Orion SkyGlow from Japan (olive green) and one from Korea (magenta). However, other SkyGlow versions don't, so it's pretty hit or miss on Carbon lines for them.

Glad you had such a memorable night out! However, for future reference, I believe you were using a red dot finder (RDF for short around here), and not a true laser finder (typically green and often referred to as a green laser pointer or GLP).

Notice that the StarGuy O-III is nearly identical to the Lumicon Comet. Might not be a bad deal if used for comets. I wonder if it is the same as my Zhumell O-III I picked up in 2014 for $10. It's more of a blue-green filter than an O-III filter. My 25 year old Lumicon O-III totally trounces it.

Interesting. I wonder what the maximum amount of out of balance it can deal with.