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CPC 800 wedge?

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Psychobilly

Psychobilly

Posted
Posted

Orbit is the Canines Danglies... I designed made my own for the obs - a combined pier and wedge and was lucky to have it made FOC... it has and adjustment range of +/-1 degree around my latitude and I adjusted it with a wixey before shimming the scope base for the fine adjustment...

If your having to setup / strip down a lot though then you really need the more sophisticated wedges if you want to make accurate PA an relatively straight forward process...

Peter...

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brantuk

brantuk

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I have the Celestron wedge and it only just does the job. It needs a small mod to make it "not break" which involves filing a flat on the az bolt so the locking grub screw actually locks and doesn't strip the thread when you turn it. And there's not a lot of throw in az.

For the price I'm totally unimpressed with the general quality of it - I expect much better engineering when forking out nearly £500. And I wouldn't put anything heavier than the CPC-800 on it. It really doesn't need to be more than £250 including the upgrade kit (which incidentally is essential).

Trouble is - they have you by the short 'n' curlies cos the next best thing is over £700 - the all singing all dancing Orbit of course. You might get the Celestron wedge for around £300 s/h if you're lucky. :)

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ollypenrice

ollypenrice

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How come you can pick up a Meade wedge for an 8" for less than £200, can they really be that different?

Yes, they are in all honesty the most obnoxious pieces of junk I have ever come across in astronomy. When you try to align them you loosen the retaining bolts a little, crank the adjusters and the wedge goes wherever it likes. You tighten the lock bolts and ditto. Adjusting altitude changes azimuth and vice versa. The whole thing is cast then not machined so it is held together by friction and nothing stops it changing alignment as any bolt is tightened. The bit against which the adjuster pushes is a piece of tat pushed off vertical by about 15 degrees. An alignment takes all night. (BTW, this is the 'superwedge' I'm describing.)

And after all this you are depending on getting a mass produced fork mount to track accurately at some prodigious focal length. Many people never succeed in this, though some do, I admit. But more don't in my experience. I know an awful lot of folks who have de-forked SCTs for deep sky. I'm one.

I feel that the publicity blurbs surrounding fork SCTs for deep sky imaging should be subject to litigation, something I very rarely say.

Of course, fork SCTs are brilliant for planetary imaging and competent in visual use. But in visual the alt az fork is a real treat of convenience.

Olly

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brantuk

brantuk

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"I take it you want the wedge so you can do astrophotography?"

Hi Paul - the usual reason for turning a fork mount into an equatorial (with a wedge) is to achieve the style of tracking required to facilitate deep sky photography.

(or put another way - Yes!) :)

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paul11

paul11

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I was faced with a similar problem with my 10” lx90, I looked at the wedges and decided the best thing to do was to buy an EQ6 and de-fork the Meade. The great thing with this is I can now put my newt or my lx90 on it or anything else I buy. £700 for a wedge or £900 for an EQ6 and never look back.

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Questions

Questions

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I was faced with a similar problem with my 10” lx90, I looked at the wedges and decided the best thing to do was to buy an EQ6 and de-fork the Meade. The great thing with this is I can now put my newt or my lx90 on it or anything else I buy. £700 for a wedge or £900 for an EQ6 and never look back.

I think deforking a cpc is a one way thing unfortunately

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ollypenrice

ollypenrice

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Sorry to sound like a grumpy old man (oh dear oh dear!!) but that darned wedge of mine had me fuming.

I agree that the cost of a decent wedge and the cost of an EQ6 are utterly disproportionate. But I would stress again that for DS imaging at SCT focal lengths you need very accurate guiding and that will not be guaranteed on an EQ6 either. I tend to feel that the EQ6 is hunky dory out to a metre and after that you have a fair bit of work to do to get everything shipshape for longer focal lengths. Not saying it's impossible, just that it may be tricky and you are likely to have cussed spells. At about 500mm my EQ sixes never fail (famous last words.)

If you splash out on a wedge and find you can't get the fork to deliver good enough tracking you really will be fed up. I certainly was. And this month alone I have had two guests who have given up on imaging attempts with wedge-and-fork sytems just as I did.

Olly

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Psychobilly

Psychobilly

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How easy were they to make and do you know of any plans that are in the public domain, may be a cheaper option.

I designed and made the ally one myself using scrap plate that i happened to have lying around.. the angle can be adjusted +/- 1 degree but its essentially preset before the scope gets mounted I am lucky in so much that have the machines at home..

The Steel Pier Wedge again designed myself has the same

+/- 1 degree adjustment.

Luckily my mates (2 Brothers) own a Sheet metal fabrication company so they could take my CAD drawings and use them to Laser cut the parts from 6mm steel plate... I let one of their welders do the welding ... He let me have it FOC as I sometimes do machining jobs for him...

The PA is within 2 arcmins in both axes and i find this is fine when I auto-guide. Most of my imaging is through a Megrez72 FF III setup attached to the CPC OTA but I have imaged at f10, and f20 through the SCT...although mostly I tend use it at f6.3...

Unfortunately I haven't got the CAD drawings anymore...I tried to find them last year for someone...

Peter...

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Coco

Coco

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All the adjustable wedges I have ever come across have a 'bed' & 'tilt' plate. no matter what you do when you tighten up the bed plate the polar alignment has changed as has the azimuth... frustrating. The Mitty and Milburn also have the same issue with this regard although much much more robust than the offerings from the big telescope making brand names..

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