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Question For RC6 Owners

iOptron Photron 6 inch Ritchey-Chretien (RC6) Focuser Troubleshooting
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Kerry Werry avatar
Kerry Werry avatar
So I'm a refractor guy who wanted more reach so I bought a used iOptron RC6 with an upgraded Moonlight manual focuser. I've just got it and am trying to reach focus and failing miserably … I've tried every combination of the main extensions with no joy. Trying with a ASI 533 camera with the standard 55mm rings…. Could it be THAT FAR out of collimation. I'd rather not start playing with the collimation if I don't have to.. 

Am I missing something stupid? I've been trying this during the day on far targets and not even getting close to focus..

Is there something else I should be looking at since the scope was shipped cross country (no damage to box or packing)..

Thanks for the help!!

Kerry
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Stephan Linhart avatar
Stephan Linhart avatar
Hi Kerry

You need the three M90 spacers that should have been included with the scope. Then you need another maybe 20mm. This depends on your focuser.
The three spacers have a total length of 100mm,

Regards,

Stephan
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Nicolas Godingen avatar
Nicolas Godingen avatar
Before playing with focus you need to check this, with the original focusser from the 2" connection you need to have 159mm to achieve the backfocus …. so if you stack the extensions you deduct the distance you stacked to this 159mm, then you should be able to achieve focus.
Kerry Werry avatar
Kerry Werry avatar
Just to close the loop on this I did find focus at about 263mm and had a quick first light under poor conditions, but it went well and I did also manage to do a star test for collimation and it was spot on which was great since the scope was just shipped to me across Canada via regular post. So now I just need to get some good conditions and get out imaging as I have a pretty good list of targets I want to try with this scope.  Thanks for the help!
wizzlebippi avatar
wizzlebippi avatar
Take a sub against a dense star field and plate solve it.  I suspect you're well off the nominal 1370mm.  

To adjust this, use the knurled ring behind the secondary mirror to adjust the spacing.  Outward/forward is shorter focal length and inward/backward is longer.  The ratio is about 10:1, meaning you change focal length roughly 10mm for each 1mm of secondary mirror travel.  Hold the secondary mirror housing and loosen the knurled locking ring.  Then spin the secondary mirror in the appropriate direction.  Rinse and repeat until you're within 10mm of 1370mm.  

You should only have to dial this adjustment in once.  This may throw off your collimation, but that's fixable as well.
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