meade 10" dob focusing query

[chardie]

hi all,
my names is leslie. i bought a second hand mead 10" dob at xmas drove it back from melbourne to stanthorpe on the front seat of the car after visiting my brother. may as well kill two birds with one stone so to speak;) . i am expecting collimation to be out after a trip of about 1600 k's. i am guessing that a laser pointer is the easiest way to collate it ? .the weather at night hasn't been very accommodating at all so much so i have not moved it from my bedroom door to outside a distance of some six feet until today being bored and not having much to do i dragged it outside to have a look at some pine trees on a ridge some kilometers away just for curiosities sake. apart from the heat shimmer they looked a lot like pine trees. not sure how collimation would affect looking at pine trees either my actual question relates to the eyepiece focuser it seems to slip when i focus in or out and when pointed to the sky the eyepiece tends to slide back down towards the tube. i down loaded the manual but theres not much in there that is applicable. too me it seems like the focuser could use a bit more tension or contact between the focusing knob and the eyepiece tube. just wondering what my options are whether it needs to be pulled apart or if its a screw that needs to be tightened. thanks in advance for any thoughts

[Allan_L]

Hi Leslie,
Congratulations on a nice scope purchase.

Re Focuser:
I am not certain about Meade, but it is probably similar to my skywatcher DOB focuser, which has two screws on the underside of the focuser.
(May be a combination of Screw and thumbscrew, or two of the same).
Anyway, one is to tension the focuser as you suggest (the screw in my case) and the other is to "lock" the focuser in position temporarily - like if you have a heavy camera attached - (this is the Thumbscrew in my case).

Re Collimation:
There are four main things to check:
1. That the secondary is located at the correct height up the tube, ie directly in line with the focus tube.
2. That the secondary is pointing in the correct direction ie that it looks "Round" when looking down the focus tube.
3. That the secondary aligns with the central dot on the primary
4. that the primary is properly aligned with the secondary.

1. and 2. can be done naked eye, and once correct, only needs to be checked occasionally (depending on how well the secondary holds its positioning).

A laser collimator (not a laser pointer) will help with 3. and 4.
But the collimator itself could be subject to misalignment of the laser and so many people don't like them.

A chesire is generally regarded as the better option by many. Not subject to collimation issues of some lasers. But these are a little more difficult to use alone.

Personally, I use a laser (that has been tested) and check it occasionally with a chesire.

IMHO lasers are easier to use in the dark, whereas the chesire is easier to use in the light.

IMHO, this is a very good guide for collimating:
http://www.astro-baby.com/collimation/astro%20babys%20collimation%20guide .htm

not sure about collimating effects on pine trees.

clear skies

[chardie]

thanks for that link to the guide. i spent all but ten dollars of my last weeks wages before the holidays on acquiring the scope. the collimation tools will have to wait a week or two sadly.
yes i know the two thumbscrews that you mention. i could lock the focuser quite easily the other thumbscrew maybe meant to tension the focuser however it doesn't seem to work like that for me. well to further clarify my point even with both thumbscrew really loose turning the focuser only moves the eyepiece about 5 mm outwards at the start then it slips and the eyepiece doesn't move any further regardless of how much i turn the focusing knob. i can rack the eyepiece in and out by hand quite easily. not sure if thats a good or bad thing. im working away from home till friday night perhaps my thinking is flawed and i need to tighten that second screw to make contact to the focusing knob i'll have another look at it this weekend.
the trees were only for visual gratification just to see that i didn't break it on the trip somehow considering the nights had been really ordinary i had to do something :)

[david booth]

from memory there are 2 screws under the focacer one locks it and the other one is for ajustment may have come loose check that first i hope you enjoy the scope

[chardie]

ok got it sorted. got home with few minutes to spare before dark took the scope outside for a quick play the closest thumbscrew to the tube does locking the other one does tension on the eyepiece all good now. thanks for the help guys. its good to see the moon except for high level cloud there's a fair bit of haze around it but at least i can see something :) . got the scope cooling down under the veranda i'll have some tea then hopefully go find a star. one more question do you find the secondary mirror or diagonal very blurry or almost discernible in the eyepiece ? should you notice the diagonal when looking through the eye price or is it something you get used too?