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Souped-up Skywatcher?


FLO
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Inspired by Marks 'Rubber Band Engineering' post... I got to thinking:

The Skywatcher range of achromat refractors are affordable when new and an absolute bargain second-hand.

Do you think there is any mileage in stripping one down and rebuilding it to enhance its performance? Perhaps tighten up the focus, replace the sticky Chinese grease, fit a small aperture-mask to reduce false-colour and blacken any shiny bits to improve contrast.

It could be an interesting project.

Perhaps someone has already tried it?

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I have one of these, any "pimp my 'scope" tips?

I'm going along the lines of Accufocus to get rid of the focusser worries, but the rest, well who knows what can be done? How APOish would it be with a mask over the front taking it to f/20 for example? How does the test work, if there is one?

The blackening bit intrigues me, are there shiny bits inside? I'm sure there aren't any outside on mine.

Captain Chaos

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Which refractor do you have CC?

An aperture mask - even a modest one - should improve contrast, acutence and reduce CA.

As for shiny bits: If you look inside the scope from the front, you will see the silver ring that is the end of the focus tube. Beneath that and attached to it, you will probably see the front of the focus rack winking it you. Anything shiny can scatter light and reduce contrast.

I guess you could also remove the lens cell and blacken its edges with paint or a marker pen...?

James. Didn't you do something similar with a refractor a while back?

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I like it, "Pimp my Scope" :D

I've got a 102 f5 that I've put the Crayford off a ED80 on. Does that count?

As for stopping down a refractor..... :nono: You shoulda just bought a different scope :D

The Chinese grease swap is something that needs doing as a matter of course. Esp. in the winter.. :D

CC,

As a rule to be "Apo-ish" an Achro refractor needs to have a f number 5 times its aperture in inches. So a 3 inch needs to be f15, a 5 inch needs to be f25. The scopes get pretty big (and quickly) as you move up in aperture and is the reason why they had big f# refractors in days gone by.

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I have found that on the moon and jupiter, where you have plenty of light to play with, that just using the aperature stop in the cover works wonders, the CA virtually disappears.

as for the grease, yes replace that. My 120 f5 has shiny bits inside on the end of the focus tube, which I blame for the loss of contrast. Keep promising to strip it down and painting it, should make a big difference.

naz

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The 120mm is one I was thinking of 'souping up’.

If the above improvements (particularly the blackening of shiny bits/lens edges and an internal aperture mask fitted to one of the baffles) were applied, I think it would be noticeably better!

Probably ought to put a disclaimer somewhere in this thread: I think it’s a good idea but … I might be wrong!

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There have been a number things kicking around the net with regard to a re-grease and blacking out the inner tube!. The only thing I will say is, the Sentinel semi-ED has just had another small drop in price and is giving SKywatcher gear a run for its money. I have owned a ST102 and the Sentinel wipes the floor with it... and its under £200

Rob

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