SCT Collimation

[robindurant]

I read some where that you can collimate a SCT by removing the EP from a Diagonal and viewing through the opening ? Any comments ? I have collimated roughly by viewing through the Corrector which turned out to be more accurate than I expected.

[barkis]

Robin. I am not sure what you mean by viewing through the corrector. The secondary mirror is fixed on the corrector, so you can only look either side of it or over and under it. I am missing something here ?

Ron.

[robindurant]

Hi

If you stand a little way say about 3' from the corrector plate and level with it, you will see even circles when it is correctly collimated, if not the centre refector mirror will look lop sided, just like night time on a star. I hope I have explained this OK, maybe someone knows a website which explains this. It is the way I found out but cant remember the site.

[Kaptain Klevtsov]

I've done this with a maksutov as the primary mirror is moved for collimation. Other than star testing I don't know another way for a Mak.

Kaptain Klevtsov

[barkis]

Hi

If you stand a little way say about 3' from the corrector plate and level with it, you will see even circles when it is correctly collimated, if not the centre refector mirror will look lop sided, just like night time on a star. I hope I have explained this OK, maybe someone knows a website which explains this. It is the way I found out but cant remember the site.

Cheers Robin, I guess it will give an indication of a close proximity to being collimated, but I have no doubt you would verify it with a star test. Anyway, I guess SCT's will fall out of collimation whilst in use due to mirror flop, unless of course you have a mirror lock, and use a Crayford focuser. I have an LX90 12", but as I have not used it in anger yet, I am not sure how bad the aforementioned would be.

Ron.

[dogfish]

Hi all,

Here's a link explaining what Robin has been doing.

http://www.mira.org/ascc/pages/lectures/collim.htm

I've still to attempt this with my 6" SCT, but I'm thinking of getting Bob's knobs first. There seems to be no hurry though as the West of Scotland has had about 7 weeks of almost total cloud cover

Cheers, Martin

[robindurant]

Thanks Dogfish, yes this is the method. If you take care you will find that you dont have to make major alterations when fine tuning on a star.

[Helen]

I was amazed that my collimation was spot on when I tried it on a star after doing it indoors (after attaching Bob's Knobs). Well chuffed!

Helen

[dogfish]

Robin and Helen

That sounds reassuring. I'll have a crack at it as soon as my Bob's knob's arrive (assuming the skies ever clear). Ordered them today. £10.31 delivered (Paypal rates). I'll let you know how I get on.

Cheers, Martin

[moonie]

Hi

I've just fitted a set of BKs to my 8" LX10 and used the collimation method that you speak of.

I had the scope out last night looking at Jupiter, did a star test and it was spot on, no adjustment needed. :) well chuffed

[Albireo380]

I tried the daytime collimation method on my 8" LX90. I only needed a wee tweak that night when doing a star test. So it does seem to get you into approximate collimation.

Tom