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🤣 I haven't received any formal complain or so sofar, but sure they must be nervous every time I deploy the big gun 😁 Seriously I do most of my observations from the rooftop, but sometimes I am bit lazy and try to catch up some doubles and the planets behind the buildings from my tiny balcony. Then you see all neighbours shutting their windows up at once 🤷‍♂️🤣 Enjoy your new scope, a double star cracker!

... ut one you go long you get hooked, here my Japan made Carton F13 before restoration.. 😁 same tripod and mount

Wow that's exactly my same scope/tripod combination. Only my alt az is a Giro Ercole. Great taste Solar B!

Thanks Don, too much to learn and digest from your posts. I just bought myself the HRCC and am waiting for a clear night to test It.

Will do, and I will keep on going trying to improve my collimation skills, etc. I am pretty new to Newtonians. Perhaps an autocollimator will do? any experiences? I was looking at one of these https://www.firstlightoptics.com/catseye-collimation-tools/catseye-infinity-xlkp-autocollimator.html Are those better than the typical Cheshire/SightTube than I am currently using?

I see what you mean but still I am surprised that all these factors put together can defeat an advantage of 27% more aperture in the reflector. This is 62% more light grasp, and the smaller 4" scope still not only matches the larger but defeat it. I am surprise that nobody else seem to be surprised by this observation.

Well It seems that the large CO (35%) of the 130mm is enough to impact the image as to obviously show less stars in a similar FOV, magnification and exit pupil than a 102 mm refractor despite of the 3cm of more aperture of the former. Lesson learnt.

That would mean that a 6" F8 refractor and 6"F8 Newtonian are expected to perform around the same, I guess. To pickup just an example of the top of my head..

I see this in the practice indeed but how's that from the theoretical point of view? What about the "aperture is King" tenet in astronomy then? "Aperture is King" for "seeing finer detail", but also for "seeing deeper". This is what is repeated ad nauseam in every astro forum since I know of.

For an 8" @ F5 to have a fully illuminated field one is looking more to 30-32% of CO, i.e a secondary of 60-63mm.

So all that said I can confirm that a reflector to be able to compete with a refractor, the former has to be at least 27-30% larger in apertura. The myth becomes truth.

As the title says. My 102mm F11 achromat is showing fainter stars at 46.7X than my new 130mm F5 Newtonian does at 40.6X. I' m aware the effect magnification has on seing fantier point light sources, but according my math 6X more should not overcome 3cm of larger apertura of the reflector. On the contrary, my math tell me that the reflector should see around 0.1 magnitude deeper than the frac does... I have check mi collimation to the best of my current abilities. Clear skies C

That's right, estimates down to .1 mag are expected. And yes, field of view should be fully illuminated or at least symmetrically illuminated.

You guys think it makes not sense because maybe not worthy to buy a coma corrector costing more than twice than the Chinese scope needed to be corrected? I have seen some folks with eyepiece collections costing many times more than the scopes they are used on. But again, I am not sure that this would be like buying the latest generation low noise cold camera to shot mag 14 carbon stars with your ShortTube 80. On the other hand, I have heard this 130PDS is used by some guys here for AP, and I guess some of them plug a CC into this scope for this application.. why wouldn't one plug a CC for visual then? I'm not interested now in obtaining an larger/more worthy Newtonian for the kind of observation I pursue at the moment (visual observation of brighter variable stars ). Probably some day I will get something like am 8" but I don't think that would happen any time soon. Maybe I should consider a fast refractor, but I would be struggling with CA instead of coma (not enough money for an APO). However I m not sure what would be worst (or less bad) for visual variables, coma of the fast reflector or false color (and field curvature) of a fast refractor.

Great info here Don, thanks. I have the SW 130PDS which has a 2" focuser. Which ES and TV eypieces you would recommend then at F5? As you say, probably I wouldn't need perfect astigmatism correction right at the edge! I am happy with the level of correction my Fujinons 10x50 provides (or my F11 refractor for that matter). Also, in the practice what does offer the Paracorr over the ES HRCC? Thanks, C

Looking at Bartels' web got me thinking that he uses himself some not so large and very fast Newtonians (F3.3!) which would have (proportionally) huge secondary mirrors. Ergo the contrast in these instruments should suffer for visual. However Mr. Bartels use them happily (I guess with Paracorr and Ethos) for visual rich-field astronomy. So there's something I'm missing or maybe the role of CO on contrast is not that great as common knowledge implies?

Gerry thank you for pointing me to this!

John, I use at the moment an ES68 16 and an ES68 24. But I was thinking in getting some from the 82 series for my wide-field endeavors after reading about them for years and hoping they are any good..

It seems, or at least I think I remember reading something along these lines, that in the reflector world the size of secondary mirrors scale inversely proportional to the focal length, which is independently of the focal ratio , meaning that, for instance a 5" F6 would need a proportionally larger secondary than a 10"F6 scope (?). I have seen from a popular brand a 6"F6 with a 46mm secondary (~30% of the primary), and from the same manufacturer an 8" F6 with a 50mm secondary (25% of the primary). Both, they claim , optimized for visual.. If that's true then for a wide-field Newtonian with good contrast (i.e. proportionally smaller secondary) one necessarily hits a trade-off region, as the larger the scope so it can have a proportionally smaller CO, the larger the focal distance that negates wide fields... would that be a sound reasoning? Maybe my best bet is to go the fast achromat refractor route?

I though that Paracorrs even when designed with TVs Ethos and Naglers in mind, would work fine for whichever wide AFOV eyepieces reasonably well corrected for off-axis astigmatism and other aberrations at the eyepiece's border. And I heard that ES are reasonably good eyepieces (good value) for not having the green lettering on them.. The ES eyepieces do work flawlessly over the whole field of view in my F11 and F13 refractors!

This is the question. I have probably been spoiled by the very well corrected fields of both my long refractors and my 10x50 Fujinons that I seemingly cannot take the coma showing at the edges of my new 130PDS Newtonian at F5. I bought this as an entry level reflector to learn collimation and especially to team up with my binoculars as a wide field telescope for estimating magnitudes of bright variables. As you may know, very often you need to compare your variable star with stars of known magnitudes (called comparison stars) in the same field of view. So one wishes to have an instrument able to provide wide fields (such as small refractor or reflector), but obviously with a well corrected field for both curvature (especially in fast refractors) and/or coma (especially in fast reflectors). My 5.1" Newt is showing its ugly coma in my ES eyepieces (but less in my TV Plössls). I also think that, because of coma I am not detecting faint magnitude stars due to a low perceived contrast. Should I invest in a Paracorr for such an instrument? i.e. the Paracorr would cost more than twice the small reflector! would the corrector "clean" the image enough and provide more contrast as to show me stars close to the theoretically limit magnitude for its aperture? or the CO in the design (secondary is allegedly 46mm) is too much? (I heard this small Newtonian is optimized for AP and not too much for visual). I am aware that if I purchase a Paracorr/coma corrector I would be able to plug it in other larger fast reflectors I may have in the future but at the moment this little guy is the only Newtonian I have living among two long focus refractors.... Many thanks and your opinions and insights are very welcome C

My Fujinon 10x50 together with my Carton 100 F13 are my two most valuable and loved pieces of astrogear.