Louis D

A couple of quick questions: What is the pixel resolution on each axis of the imaging chip? Any idea what's going on with all of the scatter in the solar image? Do you think it is due to the solar filter, objective, or lack of internal stray light control?

Sounds like what happened to my boxes of crayons left in the car on summer family road-trips when I was still into coloring books. Thankfully, since I observe from around my house, melting filter wallets hasn't been an issue for me, but I see your point.

If you were nearby here in Texas, I'd definitely let you borrow my 127 Mak for as long as you wanted. I can't remember exactly when the last time was that I used it. It was probably when I took some recent SAEP/CAEP images through some new to me eyepieces. Its slow f-ratio really brings out the worst in eyepieces relative to SAEP/CAEP.

Yep, there even appears to be a cross-section of the optical section labelled Barlow Element that might help with the original question:

I use photographic filter wallets to hold my filters. Typically I can fit two to four 1.25" filters or two 2" filters into a single pocket, depending on how big the filters were it was originally intended to hold.

If you're just popping out for 10 or 15 minutes to grab a quick peek at a planet, the 127 Mak is a terrible choice. It shows all sorts of chromatic aberrations at high power on bright objects while trying to cool down. By comparison, I see no such issues with a similarly sized Newtonian. My 90mm triplet shows spikes around bright objects while trying to cool down, so also not a good quick peek choice. My 72ED doublet is pretty much ready to go immediately, though. It really depends on your intended use case which telescope will provide the best images.

That's kind of what I observed at a recent public star party where the unwashed masses stood around for a few minutes watching a nebula's image grow brighter and more detailed on a large monitor in a similar setup, but with a 10" reflector. However, well before 10 minutes had passed, they had moved on to see what other scopes were aimed at. Perhaps if it were the only scope available, they'd have stuck around.

Also, the shorter the Barlow tube (shorter focal length) or the longer the diagonal's optical path length (2" diagonal is longer than 1.25" diagonal), the larger the multiplier effect of putting the Barlow before the diagonal will be. Looking at the above equation, it should be obvious why these two points are true.

Here's the only diagram I know of for a 3 element Barlow: As far as dust and dirt, random specs of dust have practically no effect, so leave them be. A deposited film of atmospheric grime can lead to decreased contrast. Scratches near the center can be very detrimental, but there's really nothing you can do about them. Simply moving a bright object like a star around the field until the spiking disappears or is minimized can mitigate the effects. Microscratches across an entire lens from overzealous cleaning can also decrease contrast by scattering light. Again, nothing can be done about them.

How about a view showing how you attached it? I'm curious.

Did you mean Barlow rather than zoom?

Again, using the blinking technique with stray ambient light blocked by a hood, and using a long eye relief eyepiece to fit the filter between your eye and the eyepiece, makes confirmation of faint comets (or bright comets in murky skies) easier. The comet coma will be the only thing not dimming with the filter. Interestingly enough, I find the comet disappears as I keep staring through the filter at it and have to blink it again to get it back.

Possibly, but it seems most folks jump from 70mm or 80mm to 100mm for their second scope if staying within ED scopes. Not many make the jump to 90mm without expecting a massive improvement in optical quality to compliment the subtle increase in aperture. That's what I was doing when I went from a 72ED to a 90mm FPL-53 triplet. You're right, it's a great grab and go or travel sized scope.

I've heard that about its 150 big brother, but not about the 127.

Agreed. I bought used Synta 127 Maks for myself and my grown daughter for $200 each pre-pandemic. Even now, they still trade well below their new prices due to how many of them compete for the same secondary buyers. Both still have perfect collimation. Remember, the 127 is really about 118mm of clear aperture because Synta used 127mm primary mirrors, when in fact they need to be slightly larger to capture the meniscus's slightly diverging rays. The JOC (ES/Bresser) version doesn't have this issue, but has a longer focal length.

What do you like viewing with them most?

For the out-travel case, I generally just don't insert the Barlow all the into the focuser. I just insert it until the eyepiece pops back into focus and tighten it down.

Here's a post of mine from a similar thread 2+ years ago covering various lens cleaning formulations:

Thousands Oaks also sells a few varieties of solar film that render the sun yellow-orange. Another problem noted with the Chinese made solar filters is that they mount the film in a stressed manner leading to loss of resolution. Wrinkles don't matter, but stretching tightly does. It looks nice and flat, but that's actually detrimental for films. Another unknown with the Chinese made solar filters is how well they filter out of visual band light (UV and IR). I haven't seen any independent spectrographs of any of them, but have seen plenty of them for Baader, Thousand Oaks, and Solar Skreen (example below).

Another alternative is a Lunt, Hercules, or other brand of 1.25" Herschel wedge. Their back focus requirement is much less.

There are various 33mm diameter 0.5mm thread pitch step rings out there. You might be able to jobber several step rings together to get to a usable thread size for an adapter. However, it may add too much distance to be of any use for pupil matching as Don has pointed out.

No, the dude I bought it off of actually works for an aerospace company that makes CF tubing. Being the head tube maker, he was able to make an appropriately sized tube to replace the original aluminum tube off hours. It's not hyperbole that he made it to the same spec as the stuff going to various aerospace contractors.

Or a 1.25" Tele Vue Paracorr. But they're so rare, I didn't think it worth mentioning. All this assumes 1.25"-only.

My frac's CF tube is military grade (from a US company that makes them for the aerospace industry). No blemishing from the rings on it.

You can identify a Barlow lens by it having an eyepiece holder at one end with a setscrew and a lens at the other end that inserts in the focuser.