Post by mojocvh on Mar 29, 2014 12:40:53 GMT -6
Right off we go!
First up References. This isn't my idea. I just found it on the 'net one day. I have taken info from a number of sources found via Google so If I have stepped on anybodies toes please contact myself or Joe and we will sort it out. OK.
So what's it all about? It's about collimating your SCT with very little effort or indeed distress.
The instructions are quite straight forwards, with a mask fitted, you go out of focus and you are left with a pattern of lines, centre and correct those lines using your secondary adjustment screws and you're done.
Of course there are a couple of points to ponder.
If your scopes MECHANICAL primary/secondary alignment is WAY out you might have severely tilted your secondary WAY out to correct the apparent VISUAL discrepancy, it is possible that your primary is moveable on the baffle tube or the adhesive that sticks the primary in place has started to fail. Bad News and beyond the remit of this thread BUT if you are interested [and it's no bad thing IMHO] ....
Ref. www.wilmslowastro.com/tips/c14_optics_alignment.html
.....gives some superb background into how these problems can be resolved...
Coarse alignment.
So firstly you want to check from the front of the scope that things are tickety boo.
Ref. www.bobsknobs.com/faq/faq.html#How_do_I_perform_coarse_collima
Hopefully you will be looking like
and not like this
In all but a very small number of SCT's there is no way to adjust [easily] the primary so you will have to correct your coarse collimation using the secondary adjustment screws. We will now assume that all is OKAY with the back end of the scope and that coarse collimation is good.
Duncan Masks.
OKAY I first tried to make up a Duncan style mask as detailed below.
Ref.
alpha-lyrae.co.uk/2013/12/31/schmitt-cassegrain-collimation-made-easy-using-a-duncan-mask/
I will now admit to being sup optimal when it comes to cardboard circles and scissors. I am in fact garbage at it [and that's where my efforts at DIY mask making ended up] LOL.
So this project stalled, until one day, surfing the various uk astro forums, I spotted an article/thread that had a reference to Laser cut Duncan Masks!!!
In fact it was a reference to Keith Morris from who I had purchased a bahatsov[sp?] mask for my C8 many moons ago, and was now producing these as well. Brilliant!
On receipt of the mask made to the dimensions I supplied [Keith is a Meade man and his original masks are based on Meades] I was able to ensure that not only was my secondary was centred wrt the actual tube itself but that the mask gave me the confidence [of finding proper collimation again] to loosen then re torque ALL my bob's knobs to the same "value" whilst tightening up collimation.
On the downside, I had to use a 10mm eyepiece with a barlow to give me the curved lines, thus they were attenuated by all that glass....
Minor points aside this method works and is a great boon for us SCT owners, even for that little bit of confidence boosting re collimation.
cheers and all the best
Mo.
PS I almost forgot. If you get hold of a 35mm film cannister [yes] you can centre the secondary holder by simply adding a pinhole peep at the rear of the OTA and looking UP the baffle for extra reassurance.
Ref. www.wilmslowastro.com/tips/c14_optics_alignment.html down at the bottom of the list...
First up References. This isn't my idea. I just found it on the 'net one day. I have taken info from a number of sources found via Google so If I have stepped on anybodies toes please contact myself or Joe and we will sort it out. OK.
So what's it all about? It's about collimating your SCT with very little effort or indeed distress.
The instructions are quite straight forwards, with a mask fitted, you go out of focus and you are left with a pattern of lines, centre and correct those lines using your secondary adjustment screws and you're done.
Of course there are a couple of points to ponder.
If your scopes MECHANICAL primary/secondary alignment is WAY out you might have severely tilted your secondary WAY out to correct the apparent VISUAL discrepancy, it is possible that your primary is moveable on the baffle tube or the adhesive that sticks the primary in place has started to fail. Bad News and beyond the remit of this thread BUT if you are interested [and it's no bad thing IMHO] ....
Ref. www.wilmslowastro.com/tips/c14_optics_alignment.html
.....gives some superb background into how these problems can be resolved...
Coarse alignment.
So firstly you want to check from the front of the scope that things are tickety boo.
Ref. www.bobsknobs.com/faq/faq.html#How_do_I_perform_coarse_collima
Hopefully you will be looking like
and not like this
In all but a very small number of SCT's there is no way to adjust [easily] the primary so you will have to correct your coarse collimation using the secondary adjustment screws. We will now assume that all is OKAY with the back end of the scope and that coarse collimation is good.
Duncan Masks.
OKAY I first tried to make up a Duncan style mask as detailed below.
Ref.
alpha-lyrae.co.uk/2013/12/31/schmitt-cassegrain-collimation-made-easy-using-a-duncan-mask/
I will now admit to being sup optimal when it comes to cardboard circles and scissors. I am in fact garbage at it [and that's where my efforts at DIY mask making ended up] LOL.
So this project stalled, until one day, surfing the various uk astro forums, I spotted an article/thread that had a reference to Laser cut Duncan Masks!!!
In fact it was a reference to Keith Morris from who I had purchased a bahatsov[sp?] mask for my C8 many moons ago, and was now producing these as well. Brilliant!
On receipt of the mask made to the dimensions I supplied [Keith is a Meade man and his original masks are based on Meades] I was able to ensure that not only was my secondary was centred wrt the actual tube itself but that the mask gave me the confidence [of finding proper collimation again] to loosen then re torque ALL my bob's knobs to the same "value" whilst tightening up collimation.
On the downside, I had to use a 10mm eyepiece with a barlow to give me the curved lines, thus they were attenuated by all that glass....
Minor points aside this method works and is a great boon for us SCT owners, even for that little bit of confidence boosting re collimation.
cheers and all the best
Mo.
PS I almost forgot. If you get hold of a 35mm film cannister [yes] you can centre the secondary holder by simply adding a pinhole peep at the rear of the OTA and looking UP the baffle for extra reassurance.
Ref. www.wilmslowastro.com/tips/c14_optics_alignment.html down at the bottom of the list...
