Collimation after cleaning

[badnit12]

I recently purchaced a Meade 114 goto scope on eBay (probably a newbie "schoolboy error") and I was thinking about cleaning the mirror, as when I look down the tube I can see several largish specs of dirt, and quite a bit of dust.

I'm thinking that if I remove the screws holding the mirror cell in place, I can remove the whole assembly, wash the mirror with some distilled water etc and reassemble. The trouble is, I'm not sure if the mirror will still be aligned - how much could the mirror move if all the screws lline up the cell in the tube, I assume it would be a small amount, so would it make any difference to the collimation, and how hard it it to make the adjustment if needed?

I hope this makes sense, and that someone can point me in the right direction.

Thanks in advance

Andy

[Peter Drew]

I think the "right direction" is to leave well alone , specks and dust will make no real difference to the performance. The secondary mirror is larger than anything else that will get on the primary mirror. 

[Alan64]

Hello Andy,

Until you feel comfortable with the process of collimating a Newtonian, then it would be best to leave well enough alone, for now.  At most, you could blow the tube out with compressed air, but not canned air.

I entered "Meade 114 goto scope" into Google Images...

https://www.google.com/search?q=Meade+114+goto+scope&biw=1680&bih=916&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi7pvnY9_jKAhXHJiYKHV1sB58Q_AUIBygC

Which one is yours?

Cheers,

Alan

[Dave In Vermont]

As Alan says above - avoid the so-called 'canned-air' products. They're not 'air' at all - they're propellants such as CFC's. And can come out in liquid form and make a mess. Worse than when you started. A bit of dust doesn't impair the light-gathering ability of a mirror. If you decide to take out the mirror for a cleaning (read up on how-to safely first), you will need to collimate once you re-assemble. And one of these days, you will need to - so here's a link to what many consider the most lucid and simplest guide going. And the writer is a member here - and a very nice person at that! Astro_Baby:

http://www.astro-baby.com/collimation/astro%20babys%20collimation%20guide.htm

Tuck that away for a cloudy day. Someone here will be happy to hold your hand when you decide to venture into the dreaded art of collimation. Then, after you've done it and understand it - you'll wonder what all the fuss was about!

Dave

[badnit12]

Thanks for the advice everyone,  and thanks for the link Dave - I'll file it away

Alan, "which one is yours?" is a good question - I cant find any model number anywhere! I checked on the Meade website and the nearest I can find is the DS 2114, although that model is shown with an optical finder whereas mine has a red dot.

I've trid to  attach a shot of the mirror (which looks horrifying in the photo, but almost "normal" to the naked eye) but for some reason I'm getting a warning about the size of the file even though it's only 551 kb.

Andy

[Alan64]

You'll want to reduce the size of the files to at least 1/10th of that when posting.  This one of my 6" f/5 Newtonian's primary mirror and cell from my files is only 30 KB in size, and quite ample to illustrate...

 

It appears that you have a Bird-Jones reflector.  I'm sorry to be the one to tell you.  Those are especially difficult to collimate, and have proven to be almost impossible for most.  They can be fun as a diversion, and with which to tinker and putter, but don't expect too terribly much in so far as optical performance.

Cambridgeshire is just north of London...

...yet far enough removed perhaps to afford some relief from the excessive light pollution to the south.  Computerised go-to mounts are most helpful in areas plagued by such.  Is it that bad there where you live, and is a go-to mount an absolute necessity? 

[badnit12]

Alan, as I said - probably a schoolboy error (still making them at the age of 60 )  I must say, I've never heard of Bird-Jones, but if what you say is true, I'll take the advice and leave well alone.

I bought the goto hoping it would help me find things more easily, and hopefully help to identify them too. I've since ordered Turn left at Orion as it seems highly recommended on here.

I live in a village about 20 miles north of Cambridge, it's so dark in my back garden I can't see anything - except when my neighbour comes out and triggers his 500w security lights Arrrrrgh!

Andy

[Alan64]

Hi Andy,

...51 here. 

 

That sounds promising, in so far as the darkness.  This is my view to the south, presently, and with my neighbour's "security" lights blazing away in the distance...

The situation improves in the spring and summer, when my deciduous trees leaf out.  I have no such light on my lot, and as I had stipulated twenty years ago when I moved here from the city.

A Bird-Jones reflector incorporates a built-in barlowing lens-element, a 2x most likely, doubling the focal length and usually positioned at the end of the focusser's drawtube.  If you shine a torch down the focusser, you may see it glint.  It enables a longer focal-length to be had within a shorter tube.  The main mirror is of a spherical figuring instead of the more desirable parabola.  The spherical mirror and barlowing element is intended to reduce manufacturing costs, and ultimately at the consumer's expense.  Have a look at this.  It makes for an interesting and often humorous read...

http://www.cloudynights.com/topic/479897-i-really-hate-my-bird-jones-and-cant-collimate-it-help/?hl=+hate%20+my%20+bird#8208jones=&page=3

For consideration in future, these go-to Newtonian kits are popular, reasonably priced, and equipped with parabolic primary mirrors...

http://www.firstlightoptics.com/reflectors/skywatcher-explorer-130p-synscan-az-goto.html

http://www.firstlightoptics.com/reflectors/sky-watcher-star-discovery-150p.html

Although, even those Newtonians cannot be collimated in the traditional manner.  In the desire for go-to technology within the less expensive kits, the telescopes themselves must take a back seat, this being due to the necessity that the go-to systems must operate adequately.   Then there are the go-to equatorial kits, and whereby the Newtonians are fully functional...

http://www.firstlightoptics.com/reflectors/skywatcher-explorer-130p-ds-eq3-pro-goto.html

 

I've never had a go-to mount myself.  Admittedly, I'm a bit backwards in that regard...

Cheers,

Alan

[badnit12]

Alan, Thank you so much for taking the time to pass on your much needed advice, I read through the "I really hate my bird jones" saga - oh dear!

After I had dried my eyes, I decided that I will probably have to look for something else, although, ultimately, I would like to build my own scope. It looks like the meade will end up back on eBay at some point (stand by to offer the same advice to the next unfortunate owner :D)

The other links to your recommended alternatives have certainly given me food for thought!

Thanks again.

Andy