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80mm ED and 120mm ED or single 100mm APO?


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On 3/1/2016 at 21:33, John said:

Would it be correct to say that the Tak FC 100 can resolve to the Dawes Limit for 100mm of (I think) 1.16 arc seconds or can the Tak do a little better than that even ?

 

A few years ago while using a friends Vixen 102 F6.5 ED we both felt certain wed managed to split a 0.9" star close to Procyon. In moments of steady seeing the kissing binary really did appear as two distinct stellar points. Splitting close doubles was his thing, but it was never really mine.

For me, planetary offers a far more telling method of  determining a telescopes resolving power. For example, the width of some of the finest linear features visible on Saturn's rings are well beyond the resolution of a good 4" or 5" refractor, and yet there they are, as easily seen as the finest grooves on an record. If the features were point sources they would not be visible, but because of their linear nature they become evident. Their width is unresolvable but their length is not! Because of this, sharp optics and steady seeing are essential. When Saturn was high in the sky and the rings fully open, my FS 128 would readily show the Enke gap just inside the outer edge of the A ring, not the Enke minima, but the gap itself. 

Many planetary features push the resolution limits of telescopes over the edge, showing that good scopes of any design, are far more capable than the stated resolution limit dictates. Mars is another great test subject for testing the resolution of a scope. With patience, it soon becomes evident that some of the linear features visible can have their width divided into the disc size in arc seconds, many more times than the theoretical resolution would allow. Ambrosia, a fine linear feature in Solis Lacus, and Indus, a linear feature linking Acidalia with Margaritifer are such features to look for. I feel that stellar point sources against a black background only tell part of the story.

Mike 

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On 3/1/2016 at 20:21, cotterless45 said:

Jump into my pond ! The wonderful world of achros. I'll be bringing the C6r and the 102 to SGL. I have never thought of getting anything exotic as I'm visual with a bit of sketching.I'm quite taken with this talk of exotica !

Study the reviews of Neil English well.

 You're very welcome to pop around to the pre-unloved and rescued fracs.

under those clear skies !

Nick.

Very infectious. I love the idea of running a 'achro sanctuary'. I'd like to think that if and when I emerge from my grab-and-go phase wanting to branch out...who knows?

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On 3/24/2016 at 14:09, John said:

Not many snobs or self appointed experts on this forum thank goodness. Just friendly folks who like to share their experiences :icon_biggrin:

 

Indeed. Sorry for the necropost but I felt compelled to apologise to all for the tone of my post, on rereading it came out harsher than was really intended, especially considering I was quoting MikeDnight, who is a very knowledgeable and friendly person and draws a mean planetary sketch, and is the reason why I am here. In comparison my sketches are like a child being let loose with a box of crayons in art class. :happy10: LOL.

 

Tony.

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On 01/03/2016 at 08:13, swamp thing said:

;) 

Sadly I cannot afford one Stu :( 
TBH if I had that sort of money I'd buy a Nikon 300mm f2.8 prime lens instead. Now that is an APO I'd buy tomorrow.
 

The ai ed if 300mm f2.8 and 400mm f3.5 Ed if are reasonable.  I haven't yet tried them on a gem.  The exterior on mine are worn but the glass is good.

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