RC Collimation

[Saturn488]

I have read so much content on how to collimate RC telescopes.

Some using a cheshire to the expensive and hard to obtain Howie Glatter.

For those with RC's, what method do you use, what tools are involved and why do you do it the way you do?

[glend (Glen)]

The easiest collimation is no collimation. I sold my RC years ago and only use refractors now.

[Stonius (Markus)]

It sorta depends on which model you're talking about. Do you mean the cheaper GSO ones?

[Saturn488]

Yep the GSO.

[OzEclipse (Joe Cali)]

I have a Vixen VC200L. Triaxial collimation adjustment. Primary, Secondary, Baffle tube with internal corrector all adjustable.

I do the whole thing by star testing and incremental adjusting. Work slowly and carefully, take your time. Nights of full moon are good for this. I bought the Vixen second hand from someone who stuffed the collimation. I collimated the Vixen after I first bought it, then again last year about 7 years after the first collimating. It holds well and so it’s worth putting the time to do it well.

Joe

[mldee (Mike)]

The GSO Tilt ring, a well collimated generic laser collimator and the OCAL electronic collimator did a good job on my GSO 8 RC, with a final (and easy) conventional manual fine-tweak star check, the only bit you can't do on your kitchen table after lunch.

The OCAL is a good investment, will do Newts, SCT's and RC's. Pay no regard to the Chicken Littles, it works well. Google is your friend.

OCAL have a Youtube video for doing the RC: https://tinyl.io/6lpR, but you should first use the laser to check and adjust focusser tilt before using the OCAL to do secondary and primary adjustments. Rinse and repeat a few times and you should get a good final result before the final star test, which will just be a secondary mirror screws tweak if needed.

Small hint, put your phone camera in the mouth of the RC so you can easily see the secondary mirror donut (reflection on the primary mirror) when adjusting for tilt.

Not an overly cheap set of tools, but worth it if you want to make the GSO RC really hum.

[Marko of Oz (Mark)]

I have a GSO RC6 and use a generic Bintel laser collimator to align the secondary mirror and a Tri Bahtinov mask with a Tri Bahtinov Cover from our friends across the ditch at Skylabs to collimate the primary mirror.

Works for me once you understand the process.

cheers

Mark

[DJT (David)]

Hi Chrys
Bang for your buck, the GSO RC is well worth the effort. The mirrors are really good. At one point CFF were installing GSO mirrors in their RC Frames.
I had the 8” GSO and once tuned it holds collimation well.

It took a while to work out best approach for me but basically..

Upgrade the focuser. I switched to a moonlight.
Get the tilt adapter.
Get hold of the Takahashi collimation scope and the appropriate adapters. Threaded always works best

The GSO is (or was) so cheap, adding the extra for the upgrades makes sense. It’s still an economic proposition.

I use the DSO method. The principle is straight forward. Google it.

Whip out the baffle
Align the focuser using the tilt adapter
I used a farpoint laser for that. You should check the laser is collimated before hand which is straight forward using a simple jig. YouTube will help

Then iterate adjustments between the secondary and primary using the Tak. Tiny steps.

Would be a godsend if someone, maybe Joshua, machined up proper graduated adjustment knobs for the primary rather than the poxy hex heads they come with. Take a leaf out of CFF or other more expensive RCs. A little upgrade that will remove a lot of stress.

Get used to understanding the impact of push pull on your mirrors

If you go too far or have got yourself into a vicious circle, back off the primary until there is just a bit of tension evenly on the hex heads and go again. You can double check focal length by plate solving which helps identify if you have gone too far.


Remember, tiny adjustments on the primary at all times.

You asked why..
Be at one with nature and accept that the stock focuser is pants. Once you get through that then the rest is straight forward.

once the focuser is aligned, the tak collimating scope is really simple to use.

David

[lazjen (Chris)]

+1 to what David has said, plus this device: https://www.teleskop-express.de/shop...elescopes.html is another option. I found it very easy to use. I've also got the Tak collimation scope and that was good too.

[GOTO (Geoff)]

Originally Posted by mldee

The GSO Tilt ring, a well collimated generic laser collimator and the OCAL electronic collimator did a good job on my GSO 8 RC, with a final (and easy) conventional manual fine-tweak star check, the only bit you can't do on your kitchen table after lunch.

The OCAL is a good investment, will do Newts, SCT's and RC's. Pay no regard to the Chicken Littles, it works well. Google is your friend.

OCAL have a Youtube video for doing the RC: https://tinyl.io/6lpR, but you should first use the laser to check and adjust focusser tilt before using the OCAL to do secondary and primary adjustments. Rinse and repeat a few times and you should get a good final result before the final star test, which will just be a secondary mirror screws tweak if needed.

Small hint, put your phone camera in the mouth of the RC so you can easily see the secondary mirror donut (reflection on the primary mirror) when adjusting for tilt.

Not an overly cheap set of tools, but worth it if you want to make the GSO RC really hum.

Agree with Mike here. The RCs are scary and I sold my first one, an early model 8"GSO that did not have a secondary spot. I could not get it and gave up. Recently I bought another as they represent a good scope for galaxies.

So far I've also bought:
1. Howie Glatter laser collimator
2. OCAL camera
3. GSO title adaptor (VITAL imo)

I've still found it rather hard and it's a work in progress. But the one short test shot I did looked promising. Looking forward to trying again when we have some clear sky and no Moon.

Geoff

[Sayfog (Alistair)]

I've found the Deep Sky Instruments to be the best due to not introducing any extra errors from mored tools that don't live in an image train.

http://www.deepskyinstruments.com/tr...re_Ver_1.0.pdf

Main issue being is it doesn't account for mirror spacing, but neither do any other daytime methods, for that you'd need a ronchi grating - I was fine with these on my 1600mm but since upgrading to a 6200mm I'm seeing some residual (but balanced) coma in the corners which correct spacing + collimation should fix.

And Geoff I'm pretty its your RC8 I've got - its in a loving home!

[Saturn488]

Thanks for the replies all.

I decided to purchase the TS Colli as I have heard good reviews and feedback as well as not breaking the bank.

My RC arrived a few days ago so hopefully I can get some first light right out of the box soon.

I will be starting a new thread about mounting options for the RC as well.

[GOTO (Geoff)]

Originally Posted by Sayfog

I've found the Deep Sky Instruments to be the best due to not introducing any extra errors from mored tools that don't live in an image train.

http://www.deepskyinstruments.com/tr...re_Ver_1.0.pdf

Main issue being is it doesn't account for mirror spacing, but neither do any other daytime methods, for that you'd need a ronchi grating - I was fine with these on my 1600mm but since upgrading to a 6200mm I'm seeing some residual (but balanced) coma in the corners which correct spacing + collimation should fix.

And Geoff I'm pretty its your RC8 I've got - its in a loving home!

Hi Alistair,
I'm so happy you nailed it. If you've ever got time to help an old fella align his, to your high standards, please let me know.
Cheerio
Geoff

[TareqPhoto (Tareq)]

I was so worried about buying an RC due to collimation but it was my dream to buy one no matter what, so after little search and with a lovely sudden surprised budget i ended up buying TS [GSO rebranded] 10" RC truss, and some members elsewhere told me that this design is easier to collimate because the primary mirror and focuser are almost independent, i don't know if that is true or not, but i bought it as it is my dream scope.