Replacement

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Replacement

Postby Xalp » Mon Jul 06, 2015 11:04 pm

Recently bought a 2nd hand Skywatcher 90 1250 Cassegrain (IIRC!). I knew the red dot finder didn't work - the former keeper tried changing batteries to no avail. Should I try a direct replacement (if yes any recommendations?) or should I consider something like a Seben 5x24 FS1?
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Re: Replacement

Postby Gfamily2 » Wed Jul 08, 2015 12:50 pm

Xalp wrote:Recently bought a 2nd hand Skywatcher 90 1250 Cassegrain (IIRC!). I knew the red dot finder didn't work - the former keeper tried changing batteries to no avail. Should I try a direct replacement (if yes any recommendations?) or should I consider something like a Seben 5x24 FS1?


Before you replace it, check that the adjustment screws haven't been turned so far that the red dot is not emerging from the hole.
I had this problem with the RDF on my Meade scope and assumed that it was broken. However, once I'd taken it off the scope I found that it was a problem with the adjustment screws being too far in one direction.

I've no idea which screw you need to adjust, but I'd suggest you take it off the scope, switch it on (maybe replacing the battery if the former keeper left it switched 'on'), then sit and twiddle the knobs from one extreme to the other to see if the red dot appears.

It worked for me, and saved me getting a replacement - though I'm not so sure that a RDF is what I want, I might prefer a RACI - (note to self - must get to my astro soc to see what others are using).
Scopes: Meade 8" SCT, Skywatcher 127mm Mak, Raffle winner of SW ST80
For imaging: Pentax K5, Asda webcam, Star Adventurer (new toy)
For companionship: Mid Cheshire Astronomical Group.
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Re: Replacement

Postby Xalp » Wed Jul 08, 2015 7:53 pm

Thanks I'll try that.
What's a RACI?!
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Re: Replacement

Postby Gfamily2 » Wed Jul 08, 2015 11:14 pm

Xalp wrote:Thanks I'll try that.
What's a RACI?!

Right Angled Correct Image - it's basically a finder that gives a non-inverted view, so you can more easily compare your 'naked eye' view with the 'finder view' before you swap to the actual eyepiece.

If you google "RACI finder scope" you should see examples and reviews

To be honest, I only found out what it meant yesterday myself :)
Scopes: Meade 8" SCT, Skywatcher 127mm Mak, Raffle winner of SW ST80
For imaging: Pentax K5, Asda webcam, Star Adventurer (new toy)
For companionship: Mid Cheshire Astronomical Group.
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Re: Replacement

Postby dave.b » Thu Jul 09, 2015 9:27 am

If you have a goto mount then a red dot finder will be easier to use to set the mount up. If you have a manual mount then there may be benefit from a magnifying finder as you will be able to see fainter stars through it at the expense of a narrower field of view.

If you need to get a new RDF then have a look at the Baader Sky Surfer Mk3, which will be in the £25 price bracket. It comes with a number of mounting options and has a reasonably wide viewing window.

Dave B.
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Re: Replacement

Postby david48 » Thu Jul 09, 2015 11:33 pm

As dave.b says, have a look at the telescope. and its price. Don't bother with the stars, planets etc.
Who wants to look at them? Just fondle your telescope, and look at it. The equipment is the most important thing.

What you can see through it, doesn't matter. The question is this - have you got impressive equipment?
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Re: Replacement

Postby The Man with the Corrugated Iron Roof » Mon Jul 20, 2015 7:50 pm

I had one but I much prefer a 9x50 right angle finder. One of my better buys.
How can I be one with the universe when we don't know what 96% of it is.

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