Firstlight for RC.. Shame it didn't last long..

[TrevorW]

No diagram and I've emailed GSO but haven't had a response maybe someone could ask Lee A to contact and get for us

Cheers

[AlexN]

I did find it odd that the scope came with no collimation instructions (or any instruction manual what so ever).. You would think that with something as collimation touchy as an RC they would give you a run down on how to properly preform accurate collimation... Even a brief description of what to do if you see "insert description here" sort of deal..

I might call andrews tomorrow and see if we cant figure something out.. I need to get another vixen rail for the scope anyways.. may as well organise some sort of collimation instructions..

[leinad (Dan)]

Interesting. I guess then temporarily you could check out the Vixen coll. guide and get a feel for similarities if they exist.

here: http://www.vixenamerica.com/pdf/scop..._Collimate.pdf

[TrevorW]

I was wondering what the hex bolts and grub screws right next to each on the back plate where the focuser attaches are for and looking at the Vixen collimation guide it would appear they are to collimate the focuser



Cheers

[AlexN]

Trevor, those are for focuser collimation... to be sure that the focuser is square with the mirrors... I'd assume getting it right would be a real pain in the BUM!

[TrevorW]

Sorry Alex you must have psoted when I found the answer to my own question

I'm not touching those until a) I've replaced the focuser b) everything else fails

Cheers

[AlexN]

leinad - Cheers mate.. that actually might be helpful to at least get me started.. They are fairly similar, excepting that the VC200L has an adjustable primary, where as the GSO RC primary is fixed...

Alex.

[Peter Ward]

Originally Posted by AlexN

..... the GSO RC primary is fixed...

Alex.

OK this may take some effort.....Does the secondary have a central dot?
(usually applied with a permanent marker by kind manufacturers)

If no....then, make a thin cardboard mask with the same diameter as the secondary and put hole in the middle (cardboard..not the mirror ) , put it over the secondary and apply a dot via said hole.

Use a laser collimator to put laser spot over above dot on mirror.

Adjust the secondary to put the spot on the dot. You are almost done.

On a night where you can actually see an airy disk, have a look at a say mag 4 star.

Center it.

Do the diffraction rings look symmetrical?

No? then adjust the secondary to make it so. Remember *tiny* changes (eg Max 1/8th turn)

When the diffraction patterns are as round as you can make them, you are done.

Be happy or buy a better instrument!

[AlexN]

Cheers mate.. I just took a look through the scope with a cheshire eye piece and the secondary was off by quite a bit.. It doesn't have a center spot, that sure would be nice...

I'll look into the idea of centre spotting the secondary at a later date, for now, the cheshire made a big difference I now have all the rings looking down the scope concentric, they were quite a way out, somewhere in the vicinity of the 25" you mentioned.. I should have it out again this weekend, I'll point it at a star and see what I can do.. (provided the conditions are suitable...)

Cheers mate. I appreciate your input...

Ps. send me the cash and I'll buy an RCOS too

[TrevorW]

The Chesire helped, let me know for sure when you do a star test and I'll buy one

Analysis of an image using CCD returns varying results depending on whether you use monochrome, bayer matrix, what arc pixel size, camera pixel size, what saturation level etc etc

Cheers

Cheers

[tornado33]

Im glad I read this thread. I just installed CCD inspector and it returned this result with the 10 inch F5,6 scope. I had earlier collimated is using a standard laser collimator, first aligning secondary by putting laserspot onto centre spot on primary, then adjusting primary to get spot centred back at its source. Though the scope has a full thickness pyrex Sutching mirror, the tube is only thinnish gauge sheetmetal, and the cell is only a simple 3 point one, but the collimation still seems okay.

I used a 10 minute sub from my He2-72 image, taken with the modded 350D, as the test image. (baader MPCC coma corrector fitted)

FWHM around 3 arc secs, not bad for hand guiding on a mount with a plastic RA gear wheel

I am keen to try CCD inspector with my 6 inch F3.6 SN, it I suspect will be very finnicky due to fast focal ratio.

yes I thoroughly recommend centrespotting the primary mirror. Collimation errors with the secondary show up instantly with a laser collimator and the centrespot.

I also turn the laser collimator in the focusser, to make sure the laser is exactly parralell to the focuser axis. Mine wasnt and so i had to "collimate the collimator" till it was. When turning the collimator the laserspot should remain stationary.