Cleaning and respotting

[Shelster1973]

After house move, noticed that the primary on my Newt had become rather grubby and in need of some TLC.

Have been looking at some guides for cleaning and am failry happy with that (no agitation, rubbing and clean off with distilled water).  Have got a template and spot so that I can re-spot the primary but in reading the guides noticed that people were on about marking where the mirror came out so that it goes in the same way (shiny side up  ).

Does this make any difference as the scope will be collimated fully after re-fitting so any changes will be cancelled out here?  Must be the same as when it is first assembled, am sure the manufacturers just pop the miro in and then carry out the adjustments.

Quite looking forward to doing this.  Mrs S is away on the last weekend of the month, so have plenty of 'alone' time to get it sorted without interuptions or distractions.

[Peter Drew]

It shouldn't really matter if it's a "normal" Newtonian mirror. If you have been happy with it so far, no harm in marking it to retain the original position. Large thin mirrors sometimes have a preferred axis of orientation, I would recommend marking them. My 30" mirror improved significantly with a 90 degree rotational shift.  

[Shelster1973]

Cheers for that. Nothing quite as extravagant here....just 8" for me. Think I will just put it back in which ever way really

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[Shelster1973]

Well...there is interesting.

Have taken out the primary ready for the clean and respot tomorrow and did a test fit of the catseye hotspot template to see if it actually is 8" and will fit.

Turns out the centre spot that was on there from when I got it over 14 months ago is in fact slightly off centre by what looks to my engineers eye about 5mm, which I am guessing is a raher lot when it comes to optics.

Wonder what the images will be like after I have re-spotted and put it all back together........

Also make me wonder how many other OTA's out there may be slightly off centre with their centre spots too.

[russ.will]

I think the center spot on all of my Newts have been off to a greater or lesser degree. You think this would be a comparatively simple thing for a manufacturer to get right.

Russell

[Shelster1973]

Shouldn't be too much difficulty for them.....use a simple template like the one I have and Robert is your father's brother....also wonder if there is a way to permanently chemically etch the centre spot too....in a way that does not balls up the mirror though

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