GazOC

I'd go for the ST102 for the reasons mentioned above, it would be the perfect compliment to the 127 Mak. The ED80 is undoubtedly optically superior to the ST102 (as it should be given the relative prices) there's no beating the extra aperture for DSO observing.

The reason I've read is that, while in an ideal world there's no reason a Mak/Cass should outperform a SCT, it's easier to accurately mass produce the Mak corrector than it is the SCT corrector so the customer is more likely to get better quality optics. (Disclaimer: I am not a telescope manufacturer)

@John I tried to find one but couldn't but if you can locate a similar diagram for an ED doublet or an achromat it may show the idea more clearly Depending on how the designer has chosen to set up scope the focus point for the wavelength at the blue end of spectrum will be further apart from the on the vertical scale from where the red/ green wavelengths come to focus than it is the example above. This is the CA you see at the eyepiece

It's sounds like you're sold on the refractor and planets despite the pros and cons probably weighing in favour of the Cass being the more versatile scope overall? If that's the case then go with the 'frac

I've used a HEQ5 for lunar/ planetary imaging with a 180mm Mak and it's more than capable.

I like the look of that, John

Ouch! It's worth 3 times more than the scope

Does anyone make a 1.25" only Crayford or R&P focuser? I'm guessing not but it could be an option for people who wanted to move away from the stock focuser without wanting the extra weight of a 2" focuser on the back of the scope?

I'm very sceptical of the baffle tube being the problem, it's very carefully tapered in width from top to bottom That's not to say it can't be wrong, just that the designers have given that part a fair bit of time and effort

Are the gold 150mm Maks not full aperture but have oversized mirrors in the later black diamond models? I only ask as this was supposed to be the case with the 180mm model and, from the model I measured, the gold model also had an oversized primary the same size as the black diamond version

@Mr Spock Has anyone measured a Skywatcher 150mm primary or effective aperture? They don't seem to get mentioned as much as the 127 or 180 for some reason

I've taken the corrector out my blue Mak and made a couple of *very quick* measurements. The clear aperture of the front of the corrector seems to be 127mm, the back of the corrector is harder to measure but the ID of the cell is 133-134mm with a ~3mm lip all around near the corrector so somewhere very near 127mm. I wish I'd have measured the primary when I had the thing stripped a few weeks ago as that is often given as the reason for the restricted aperture but haven't got the stomach to attempt that job again

Or a "Skymax Pro 190" and chucked an extra 50 quid on the price

The mirror is oversized and there's lot of space in between the mirror and the tube so I can't see that being the problem To me, that leaves the baffle coming out of the primary (realistically the secondary baffle isn't going to knock off 10mm from the effective aperture) as the only possible culprit but whoever designed that part has made sure it tapers in as it gets closer to the secondary. Just MHO but I'd be surprised if Skywatcher redesigned the scope to give it an extra 10mm aperture and then said nothing about it ?

That'll be me The mirror is 200mm. It could be that that baffle coming out of the primary is cutting out light but it looks very carefully graduated in width as it approaches the primary Someone has put a lot of thought into the width of the baffle at any given point. That's not to say they've not just got it wrong but they've not just stuck a tube on and hoped it's correct