Louis D

12 minutes ago, Don Pensack said:

All those eyepieces are discontinued except the ES.

And your point is what?  I never claimed they were.  Besides, the AF70 is available under other brands in Europe.  The B&L eyepieces were long since discontinued when I bought them off ebay 15 years ago, so the point is moot with them.  They're probably 1960s or 1970s vintage.  The 17mm NT4 was just discontinued and is still listed as in stock a few places.

I tried that approach with my 12mm NT4's 2" skirt with extension, but where the parfocalization ring needed to go was right on the lower taper, so it wanted to slide into the taper as I tightened it.  I ended up going with rubber O-rings instead:

35 minutes ago, jetstream said:

You know, I think that if the undercut saved a , well, lets say a 21E when the diag/eyepiece spun around from leverage that many might be worshipping the machinist who cut, it avoiding broken glass on the ground?

I had something similar happen when a diagonal tried to unthread itself in a similar manner.  All I could do was grouse that this would never happen with a Dob that has it's focuser angled upward.

I was just about to suggest it, but then realized many premium eyepieces have lenses in the lower barrel, so this would only work with an interchangeable 2" skirt on 1.25" eyepieces or on 2" eyepieces that don't need the entire ~46mm inner diameter for lenses.  It would be a simple solution for eyepieces that have no lenses in the lower barrel, though.

16 hours ago, HoneyBadger-231 said:

I'm just south of the mackinaw bridge

Ahh, that makes you a Troll (under the bridge dweller), at least according to Yoopers (upper peninsula, above the bridge, dwellers).  I'm married to a "Troll" from the Detroit area myself.

My favorites are a pair of vintage 15x wide field B&L microscope eyepieces I originally bought for my AO Series 10 microscope.  At f/18 with the 3x Barlow nosepiece on the binos, they are super comfy and sharp.

46 minutes ago, PigzMightFly said:

Do you prefer the Skywatcher scopes over the Celestron for any particular reason?

Since Synta owns both, there's not much to choose between the two on quality.  I guess it comes down to features.  If you are going with a computerized telescope, I would make sure it maintains alignment even when manually moved without using the motors.  That way, it can be used as a push-to as well as a go-to scope.

My basic Arcturus binos' collets tend to tip eyepieces with undercuts.  I have to really mash them down in the holders while tightening them to avoid this.  However, once tightened, they're solidly in there.

However, since there is no way to lock the diopter setting except to snug it all the way up or down, I have to sometimes fight with it while zooming stiff zoom eyepieces.

1 hour ago, Nugs said:

Newbie looking for first EP’s I can use on 130-PDS newt and WO ZS71.

Having an f/ratio of f5 and f/6, respectively, you'll want a 5mm as your highest power eyepiece for most nights.  From there, I would add the 8mm, 12mm, and 25mm Starguider focal lengths.  This would give you a nice range of powers in each scope.

17 minutes ago, jetstream said:

Yeah, I dont crank the screws down on the holder really distorting the band- I just snug them. I wonder if some give a "robust" turn of the screw(s)?

You kind of have to with stiff zooming zoom eyepieces, or you have to grab the lower part of the eyepiece to zoom, which is a pain in binoviewers with two of them to zoom.

On a whim, I picked up a 25mm Edscorp Ortho which looks to be the same as other Tani made volcano tops.  While sharp in the center at f/6 and flat of field with very little distortion, it is blurry at the edge at f/6 in my field flattened AT72ED.  I went so far as to disassemble it and try all 4 orientations of the two groups (singlet and triplet groups) with respect to being possibly flipped by a previous owner, and the original orientation was still best, so it's a design issue with this ortho at f/6.

However, at f/12 in my 127mm Mak, all is well for the ortho as well as for the rest of my 25mm 3 or 4 element eyepieces.  A similar improvement can be had using a 2x Barlow with an f/6 scope, though I didn't take any photos of that combo yet.

I had one eyepiece holder/eyepiece undercut mismatch so bad that I almost couldn't retrieve the eyepiece from the holder because the brass compression ring got snagged and pulled up out of its groove where it jammed against the eyepiece above its normal position.  I was pretty panicked.  I'm not sure how I eventually got it freed (it's been years), but I'm more careful now.  If there's any snagging, I don't try to brute force the eyepiece out of the holder.

The real issue is that compression rings and narrow collet bands don't interact well with eyepiece undercuts.  Either by themselves don't generally cause issues.

5 hours ago, PeterC65 said:

OK, so the area of sky I can observe depends as much on the FOV of the EP as it does on its focal length. According to Baader their Zoom EP has a 48° FOV at 24mm, and others have said that at 24mm it is similar to a Plossl (the Baader Plossl is 50°) so the difference in FOV may be quite small. Using the figures from Baader, I get 0.77° for the Zoom at 24mm and 1.07° for the (Baader) 32mm Plossl. The Zoom at 8mm gives 0.36°, so a 2.1 : 1 ratio with the Zoom at 24mm, whereas the ratio between the 32mm Plossl and the Zoom at 24mm is only 1.4 : 1. I’m not sure how much of a benefit that would be.

When I’ve observed M31 so far, I’ve only been able to see the centre as the galaxy, and then only as a grey blob. It may be that if I could observe the whole of M31 I could then make out its edges and so see it differently but I don’t think that will be possible with the Skymax 127.

Interesting that the Skymax 127 is available in the USA with a 2” visual back. I’ve noticed that on larger Mak’s here in the UK. Mine has a 2” SCT thread on the visual back but the aperture diameter within this is only 28mm. Because of this, and because the Baader Zoom is 1.25”, I’ve stuck with a 1.25” optical pathway.

Actually I have on order a 2” SCT adapter and 2” nosepiece to fit between the scope and a 32mm diagonal, but that’s mainly to provide mechanical strength and easier slewing of the EP (the adapter is a Baader ClickLock).

How did you convert your scope to a 2” visual back? Doing that to mine looks like it would involve major surgery to the scope itself!

So I think I’m limited to a maximum 32mm EP which will make it impossible to see the whole of M31 with the Skymax 127.

I was going by the measured AFOV of 44° to 45° as measured by multiple CN users.  I can't recall anyone on SGL measuring theirs.  I also can't recall anyone accurately measuring the field stop at each focal length.  That's what really determines TFOV.

As far as converting goes, I just added a step-up ring to bring the native Mak thread up to an SCT thread so I could add a 2" visual back.  It's still a 28mm rear aperture, thus the vignetting.  Because it is so far ahead of the eyepiece's field stop, the falloff is subtle.  If the 28mm opening was at the end of the eyepiece's insertion tube, it would be a hard vignette and would be rather unusable.

15 minutes ago, Voyager 3 said:

T0 ? 😎

The original 13mm Nagler prototype?

Look on these webpages for images of the T1's predecessor (I can't link the images because they're not https).

On 24/08/2021 at 01:18, Alan64 said:

If the finder-scope is placed directly over the fulcrum, then there might be no balancing issues whatsoever.

Ideally, wouldn't you want the finder scope directly opposite the altitude pivot point (the side facing the camera)?  Where it is in the image will make it turn turtle once the altitude gets high enough, unless you crank down on the friction knob.

2 hours ago, Mr Spock said:

lol, typo - a T6 7mm 

I know, but still, we can dream someone got a hold of a T7 prototype (or the mythical T3).

4 hours ago, PeterC65 said:

According to the FOV calculator, a 32mm plossl looks like it would only gives me a little more coverage than the Baader Zoom I have on order (24mm). What do people think? Is it worth having 32mm as well as 24mm?

The BHZ has a 44° AFOV at 24mm while a 32mm Plossl generally has a 52° AFOV.  Assuming minimal magnification distortion, you're going from about 0.7° to 1.1° TFOV on the sky in your 127 Mak.  That may not seem like a lot, but it is a 2.5x increase in area on the sky seen in the image circle.

In the States, Synta is shipping these 127 Maks with 2" visual backs and 2" diagonals.  I did the same upgrade to mine before this became standard here.  With a 40mm, 68° AFOV eyepiece, it increases the view seen on the sky from 1.1° to 1.8° (or 1.0° to 1.7° using field stop measurements).  That's another 2.7x (or 2.9x by FS) increase in area on the sky seen in the eyepiece.  Relative to the BHZ at 24mm, that's a whopping 6.6x increase in area on the sky seen in the eyepiece.  Yes, there is about a 40% decrease in illumination in the outer field of view, but it's hardly noticeable when looking in the center.  The difference in what can be seen in the eyepiece is enormous, especially for rich star fields.

Below is the difference demonstrated by photographing a ruler through both a 24mm widest field eyepiece (roughly the same field stop size as the 32mm Plossl) and a 40mm widest field eyepiece.  You can see how it gets dimmer toward the edge.

And here's how it looks in the focuser from two different angles:

I know I'm not going to mess with the near perfect factory collimation of my 127 Mak for BV usage.  It works well enough as-is for my purposes.

1 hour ago, globular said:

I'd love to hear from anyone with one.... whatever scope they use it in.
@Knighty2112 have you had first light with yours yet?

You could start by reading this mini-review of the Orion equivalent by Tom Dey (a retired optical designer) on CN.

3 minutes ago, Zermelo said:

yes, or ones that accept Dioptrix (=more £)

But that requires one on each eyepiece if you don't like moving them between eyepieces.  Also, they don't do well if you tip your head to look at the edge of ultra to hyperwide eyepieces.  The cylinder corrector needs to be perpendicular to your eyeball, not the eyepiece, so correction is best only when looking at the dead center of the view.  Lastly, you still need to put your glasses back on to look up at the sky if you're in the object hunting phase.  For all these reasons, I stick with a dedicated pair of distance corrected eyeglasses with the lowest index material possible to minimize CA.  I'd get them made in glass if I could locate a place still willing to do it.

It also depends on how fast your scope is.  Orthos tend to have poor edge correction below about f/8.  If you have an f/5 or faster Dob, you'd really notice how poor the edge correction is.  You'd have to be constantly trying to keep the object centered, and by the time the scope settled, you'd have to do it all over again!  Of course, if your scope/mount tracks, this isn't an issue.

Also, if you have really strong astigmatism in your observing eye, you can see it in views at 1mm and below sometimes, necessitating wearing eyeglasses to get the sharpest image possible.  This isn't going to happen with an ortho below 25mm.

Maybe I missed it above, but do you have significant astigmatism (above 1 diopter CYL) in your observing eye?  If so, you'll probably want long eye relief in your lower power eyepieces so you can wear your eyeglasses at the eyepiece.

Yes, moving your mirror forward to reach focus with binoviewers will add some spherical aberration to the image.  You'll probably never notice it at lower powers, but you might notice it at higher powers.  In that case, you might want to swap in a Barlow element to reach focus instead of moving the mirror forward.  It has the added benefit of allowing you to use your lower power eyepieces at higher power.  That, and it can be difficult to merge high power eyepiece views due to slight collimation issues in the binoviewer not visible with lower power eyepieces.

Hooo Boy!  Ain't she purty! 🤠👍

8 hours ago, Mr Spock said:

I've had a few TV eyepieces - T4 and T7 Naglers

Better hold onto those never released T7 Naglers.  They've got to be worth a fortune due to their rarity. 😉