Hi, this question probably gets beaten around a bit but I couldn't find the specifics I wanted when I did a search.
I have just laser collimated my 200mm Newtonian by adjusting the secondary mirror. I unscrewed the back of the scope and looked around for where I might adjust the primary mirror but that looked fairly fixed, so I unscrewed my secondary mirror and moved it around until it was 'approximately' within the small black circle located in the middle of my primary mirror. I have done this before and have been happy with where I can get it.
My question is how close to the bullseye on my laser collimator/circle on the primary mirror do I need to get? The red dot is more in the middle of the black circle of the primary mirror than out of it and I am about 3mm away from the bullseye on the collimator. I'm pretty happy with it, I'm just using it for observation and it is far closer to the middle of the circle/bullseye than when I started (about 15mm out initially).
Closer is better, but no need to drive yourself crazy about it for most commercial tube units. There will be a way to adjust the tilt on that primary mirror. Have another look? But you need to know which are the right adjustment screws. Post a photo for us to check and tell us the make of scope. You will be able to get that beam returning from the primary mirror to the centre of the collimator "bullseye".
Closer is better, but no need to drive yourself crazy about it for most commercial tube units. There will be a way to adjust the tilt on that primary mirror. Have another look? But you need to know which are the right adjustment screws. Post a photo for us to check and tell us the make of scope. You will be able to get that beam returning from the primary mirror to the centre of the collimator "bullseye".
Thanks I'll take a few photos tomorrow. does it matter if I adjust the primary or secondary mirror as long as it's lined up?
John,
Your primary should have at least three adjustment bolts with three locking bolts (one for each). Adjusting only the secondary will not collimate the scope. The return beam needs to align with the transmitted beam and the primary needs to be adjusted for that.
What make is your scope, photos will help.
I live close to you and would be glad to help. You can PM me with contact details if you like.
Hi John,
Can you put up a photo of the back of the scope? Here is mine a SW 8" garden variety Black Diamond. Not a great photo but at 7 o'clock there are the knobs and locking screws for the mirror( 3 sets of Knobs and screws in total). Yours should look the same???
Matt
mine is slightly different I don't have the adjustment dials at the rear of the scope I have two screws next to each other (six screws in total). The Saxon manual states that each screw on the right hand side adjusts the primary mirror and that I need to loosen all of these first prior to making adjustments. I will give it a go tomorrow night when I have a chance, I am preparing for my son's 4th birthday tomorrow and we are still up wrapping and baking
All done all aligned. The back of the primary mirror had allen key adjusters which were just a hole in the back really and I didn't pick them up. I readjusted the secondary mirror again and then removed the lid from the back of the scope and adjusted the hexagonal bolts of the primary until the laser fed into the middle of the bullseye and out of view.
Thanks again Matt, always coming to the rescue and especially Sarge, who offered his own time to assist.
John
Just a word of advice. Be aware that a laser is not a be all and end all collimating tool. A a rule, I only use the laser for final tweaking, it has a role but only for the final check.
If you think about it it is perfectly possible to get a perfect looking alignement wit the laser, but have the secondary not even remotely centred under the focuser. Personally on my 12" I use a collimating cap, cheshire/sight tube and a laser and follow this little guide http://www.astro-baby.com/collimatio...on%20guide.htm .
I then use the laser to check collimation quickly before or during each session and do major checks every few months. Obviously if I do any work (installing a focuser, washing mirrors etc,) I collimate from scratch.
See what the stars and Saturn look like first before you become glum, John. I suspect you'll be happy. Unless something has gone terribly wrong or someone has massively "fiddled" with it, your secondary should be in reasonable position.
Sorry, I should have thought that there might be sunken hex-head screws. That is common on secondary mirrors but less so on primary mirrors. I'd be pulling them out quick-smart and replacing with a set of screws I can adjust with my fingers, for both mirrors.
[QUOTE=erick;872623]See what the stars and Saturn look like first before you become glum, John. I suspect you'll be happy. Unless something has gone terribly wrong or someone has massively "fiddled" with it, your secondary should be in reasonable position.
Sorry, I should have thought that there might be sunken hex-head screws. That is common on secondary mirrors but less so on primary mirrors. I'd be pulling them out quick-smart and replacing with a set of screws I can adjust with my fingers, for both mirrors.[/QUOTE]
Excellent advice next time I have to adjust my mirrors I will do this. I did mess with the secondary mirror a bit unscrewed it and moved it around to get the laser dot in the middle of the primary mirror circle???
Saturn looked good before I collimated, no problem at all could identify the divison and various faint bands around the planet. Stars were a bit harder to resolve so hopefully the mirrors are closer than before and they become a bit sharper. The proof will be in the pudding but this week does not look good at all. Thanks.
Hi John,
Hope I didn't give you a bum steer with the laser Malcom I thought the laser was the be all and end all of collimation....obviously not , will give astro babys method a go and see what happens, thanks for the link. John as Erick says when you get the scope back to where the views are good I suppose it doesn't matter about how far out or not you are according to lasers or any thing else. For me I guess I'm not that fussy about whats at the eyepiece, as my favourite scope is the 6" refractor, with all the CA that goes along with it! Coma in the Newt doesn't bother me either so maybe close enough is good enough for me.
A frustrating hobby at times but nothing worth doing is ever easy.
Matt
Hi John,
Hope I didn't give you a bum steer with the laser Malcom I thought the laser was the be all and end all of collimation....obviously not , will give astro babys method a go and see what happens, thanks for the link. John as Erick says when you get the scope back to where the views are good I suppose it doesn't matter about how far out or not you are according to lasers or any thing else. For me I guess I'm not that fussy about whats at the eyepiece, as my favourite scope is the 6" refractor, with all the CA that goes along with it! Coma in the Newt doesn't bother me either so maybe close enough is good enough for me.
A frustrating hobby at times but nothing worth doing is ever easy.
Matt
No way all good Matt, most of the YouTube vids I watched before you linked me to the Orion one only provided collimation by laser. I'm not looking for supernovas with this thing, if i get reasonable views of the planets and the odd DSO here and there I'm happy. I'm only observing at this stage. I need to get my eye in and learn how to work this eq mount properly before I start doing anything costly and time consuminng with this hobby. On the other hand I like to do the best job I can within the means of my control
Hi John,
Hope I didn't give you a bum steer with the laser Malcom I thought the laser was the be all and end all of collimation....obviously not , will give astro babys method a go and see what happens, thanks for the link. John as Erick says when you get the scope back to where the views are good I suppose it doesn't matter about how far out or not you are according to lasers or any thing else. For me I guess I'm not that fussy about whats at the eyepiece, as my favourite scope is the 6" refractor, with all the CA that goes along with it! Coma in the Newt doesn't bother me either so maybe close enough is good enough for me.
A frustrating hobby at times but nothing worth doing is ever easy.
Matt
Just another quick point. Coma in a newt is an inherent property of the design, it arises from using a parabolic mirror. No amount of tweaking collimation wil get rid of it. Having said that it varies markedly with the f ratio. At f6 it is barely noticeable, at f5 it is noticable but for visual use not significant, at f4.2 it gets annoying.
Erick is right, in my view. The important thing is the quality of the view, and especially with smaller, slower newts, spending hours trying to get colimation perfect is not time well spent, better spent actually observing.
Malcolm
Malcom I thought the laser was the be all and end all of collimation....obviously not , will give astro babys method a go and see what happens, thanks for the link. John as Erick says when you get the scope back to where the views are good I suppose it doesn't matter about how far out or not you are according to lasers or any thing else. For me I guess I'm not that fussy about whats at the eyepiece, as my favourite scope is the 6" refractor, with all the CA that goes along with it! Coma in the Newt doesn't bother me either so maybe close enough is good enough for me.
