New Apo on the block

[paulastro]

That's interesting Olly.  Over the years I have heard of a couple of refractors when it was claimed  that they were not the aperture they should be.   I had always assumed that they were probably rumours originated with one person and were then passed on from one person to another as being true.   I didn't realise that anyone had ever done this deliberately, how trusting I am.  I hope it doesn't apply to any of my two current refractors or any other well know instrument that is still available! 

 

[Ben the Ignorant]

Clipping is not done in any modern quality refractor. I've seen it in a 60mm f/13.3 cheapo that had a mini baffle inside the focuser, reducing the light to less than 40% of the total, which was not much to begin with. I removed the baffle which was stupidly superglued, and skewed, to boot, and the scope became what it should have been since the getgo: a fine achromat.

Of course normal eyepieces, Plössl and up (I'm not even claiming quality eyepieces) performed very well, and even a white mercury lamp wouldn't cause appreciable fringing. The clipping must have been done to hide the horrendous aberrations of the two-element, plastic-lens Huygens oculars in dotation. I'm sure Kellners would have done well, too, but I don't own any three-lens eyepiece any more.

The main tube had a poorly placed baffle that didn't kill the enormous amount of light the focuser baffle did, I simply moved it, and added a few more not clipping the light cone.

Anyway, this kind of cheating is not done in a newly-issued 1.500€ apo!

[John]

I've heard of aperture clipping occurring through poorly placed light baffles, usually at the focuser end of the scope and rumours of scopes not operating at full specced aperture but usually the latter turn out not to be the case. It's not too difficult to see what the real operating aperture of your scope is:

https://www.cloudynights.com/topic/431279-the-flashlight-test-for-aperture-illustrated/

[F15Rules]

On 20/11/2017 at 22:18, Moonshane said:

I've often wondered if I should combine my SW 120mm ED and my Astrotech 102mm  ED plus possibly my 150mm f11 newt to get a single higher quality scope but cannot really afford a 128mm Tak and there seem to be few options about the £1500 mark without needing a bigger mount than my eq5. Maybe this could be a contender.

Shane, I wouldn't make that trade, to be honest. I think you have 3 good scopes there, covering 4" to 6" aperture with varying focal lengths..I would imagine that F11 Newtonian must deliver wonderful contrast?

As Simon says, (pardon the pun!), an extra 5mm over your ED 120 is unlikely to be that noticeable, and to get that I don't think a trade of your current fleet of 3 fine scopes would be worth it☺.

Dave

[Moonshane]

Cheers Dave

I think you are probably right if course. I'll be doing more thinking as reviews come out. 

My logic is probably faulty in that if the 125mm is expected to be as good as the 120ed then I could therefore just sell the others and keep the 120ed. 

Maybe that would be a good strategy as if another 128mm Tak were to surface I'd have to raise less funds