Skywatcher 200p primary settings ?

[Alonsos]

Hi

After a week or more getting my head around collimating my 200 p I think I've got it

In doing so ive another problem at the (easy end ) the Primary,

I will try to explain -

Ok, when adjusting the mirror I can't get the mirror to go up down side to side hardly at all when trying to line it up with Cheshire

As I see it the home position is the mirror sits on small O-rings x3 with the adjusting screws going thro so when my setting is a bit high I turn the adj screw and that depresses the O-ring and so on and moves the mirror accordingly ,but I can't get it to come down far enough to line up with the Cheshire

The O-rings the mirror sits on are maybe 2- 2.5 mm thick so that's not much adjustment so ime finding that if I bring the lock screws into the equation I can push with them and get desired movement

So in effect ime adjusting with the lock screws & locking with the adj screws,that's not right,

If adj screws are turned anti clock they just undo & eventually would fall out obviously

3 nice springs instead of silly O-rings would work ime sure ?

Are the said O-rings past there sell by

Anyone else had this problem

Sorry I've gone on a bit but not easy to explain

Regards Alonsos

[dweller25]

You need to loosen the lock screws a good amount to allow movement for the adjustment screws, then collimate with the adjusment screws, then carefully re-lock the lock screws.

Apologies if this is what you have done

[Avocette]

Hi Alonsos and welcome!

From my experience of 4 Sky-Watcher Newtonian telescopes of various apertures, the o-rings are a 'value engineering' feature that can work, but are quite difficult to use since they are so thin and not very elastic after a while. Having said that they probably mean from SW's perspective that more new telescopes are still reasonably collimated after having been bumpted around when they are delivered by typical van services. Three of my SW Newt telscopes came fitted with the 'older' knurled knobs and springs, but the fourth newer one came with o-rings. I replaced them with 'Bob's Knobs' bought from the USA and unfortunately quite expensive. Some SGL members have found similar knurled knobs with the correct metric threads cheaper on ebay.

[Charic]

Your right about the home setting!

Without any scews or lock nuts fitted, and with the telescope in the vertical position, the Primary mirror cell should sit flush to the end cap, cushioned by the washers.

Your right too, in saying there is not much movement allowed?

The washers will allow some movement, but this movement is very slight, just a little tension on the screw is enough to 'tilt' the mirror.

Its the open end, the spider and secondary mirror that needs the critical alignment, concentric to the focuser, where the Cheshire tool is champion in this procedure. Then if any tilt is required to 'see' the three primary clips, carry out that procedure on the secondary, before preceding to the next stage.

The next stage, only a slight adjustment should be required to align the Primary to the secondary, job done, except a final Star test?

The use of 'Bob's Knobs is often quoted for ease of use 'tooless' adjustment to the Primary mirror, but imho, any addition of a spring will cause the mirror to bounce, under spring tension, over the more secure 'O-ring' fitting!

[Alonsos]

Thanks for all your replys & info

I had primary out today and fitted new beefed up O-rings that worked after a fashion , meaning larger is maybe getting harder to tighten down on , Ime pondering if it's practical to try the primary in another position ie move the whole thing around 1 set of holes or maybe 180 deg around I can't see that it would matter ( Ime probably wrong in that assumption)

I have some idea that the mirror cell has been fitted a bit [removed word] eyed in its holder giving me more to adjust out than available, daft I know but I

always have to adjust one (bobs nob) quite hard to get me in the ball park when the other 2 are just gently nipped or not doing anything at all

We used to have a saying about a car that keeps going wrong ( oh it's a Friday car) well Ime beginning to think this is a Friday telescope Ha

Regards & thanks you lot Alonsos

[Alonsos]

Re above post I see a word is removed so change fitted a bit( removed word) eyed , to maybe fitted a bit not level, offset or the like Ta

[Charic]

The system manages text for any undesirable words?

You may add any word, but if too close for comfort, the system removes that word for everyones safety, as this is an all ages forum.

[Alonsos]

Ta

Guessed that's what it was

Regards