SkyWatcher 200P Help and advice.

[sonicninja]

Evening everyone. I recently made the purchase of a used but in superb condition SkyWatcher 200P and I have a couple of immediate questions im hoping someone might be able to help me with.

Firstly, i noticed that the focuser is 2" but comes with 1.25" eyepieces and a step-down converter. Is this ideal or should I aim to purchase some 2" eyepieces?

Secondly, the primary mirror is a little dirty, is this something I can clean myself or best left to a professional?

Thirdly, I noticed that three screws are missing from the back behind the primary mirror. I believe these to be the locking screws (the other three large thumbcrews with springs are present). Are these vital and should I go about getting them replaced?

 

Many thanks in advance.

 

Keith

[FinleyChambers]

I’m not 100% sure on the screws so I’ll leave that bit out. The mirror shouldn’t effect anything and I wouldn’t clean it myself, you can ruin the coating on the mirror, I’m sure it would be best to get the 2” eyepiece because you’re loosing a lot of light I would’ve thought with the smaller eyepiece adapter. 

[banjaxed]

If the screws are missing from the primary mirror then they must be replaced or you won’t be able to collimator your scope. Unless your mirror is really dirty I would leave it alone as it will not make any noticeable difference. If your scope came with any eyepieces then see how you get on with them before you invest in replacements.

[Orange Smartie]

Other, more qualified people will be along shortly. However, quick answers:

Your mirror will take a lot of dirt before it needs to be cleaned, so unless it's really filthy, I wouldn't worry. It is something you can do, but needs to be done with care, so I personally wouldn't be in a rush to do it.

There are normally 6 screws on the base of the tube - as you note, 3 are to adjust collimation, the other 3 are to lock everything in in place. You can get replacements if you feel you need them, but they aren't strictly necessary for the normal function of the telescope. As it happens, I noticed this week that mine were all loose as I'd forgotten to retighten them after adjusting the primary mirror.

Pete

Edited to say that I wasn't implying that the above 2 posts weren't from qualified people - they must've posted while I was typing - merely that I myself am a relative newbie.

Edited January 8, 2022 by Orange Smartie

[John]

Great scope - congratulations !

2 inch eyepieces are only useful for low power / wide angle views. In due course you may want one but for now the 1.25 inch fitting eyepieces will be fine. You don't loose any light by using 1.25 inch fitting eyepieces by the way, they just can't show as wide a field of view as a 2 inch eyepiece.

Unless the mirror is filthy, leave it be for now. A little dust will not make any difference to the views.

Take a photo of the back end of your scope and post it on here so we are not "shooting blind" with regards to screws that may or may not be missing

On the 200P dobsonian scope there are 3 small screw holes that are empty, 3 large collimation screws and 3 inset grub screws which are locking screws. It would be good to see a photo to confirm what you have.

Edited January 8, 2022 by John

[Stu1smartcookie]

I have also just purchased a 200p .. its a great scope isnt it ? . I would try to get some replacement screws but I have had scopes before that I NEVER tightened the locking screws as collimation was thrown out by doing so . But , as I said , try to get some . As for EPs , I have used both 1 1/4 and 2 inch .. the 2" gives great wide field views and I usually start my viewing with that . 

[Louis D]

And if it's the Synta focuser I think it is, don't put the 1.25" adapter in the 2" adapter, you won't be able to reach focus.  Replace the 2" adapter with the 1.25" adapter.  Synta alone uses this scheme.  Every other 2" focuser uses 2" eyepieces natively, and then you insert a 2" to 1.25" adapter into it to step it down for 1.25" eyepieces

As @John points out, 2" eyepieces are best for low power, wide angle views.  I'd recommend picking up something in the 35mm to 42mm widest field range just to help center objects before moving to higher powers.  Of course, with Synta's focuser, this isn't as quick and easy to do as with other focusers.

Take a picture of the primary mirror to help us get an idea of how dusty it is.  It has to be really grungy to warrant a cleaning.  Cleaning microscratches are worse than dust because they cause light scatter.  Dust just tends to attenuate the brightness a bit.

You'll want to at least collimate the primary with something like a Rigel Aline to make sure you're getting decent views.  This assumes the mirror has a center marking ring, which it should have from the factory.

[Spile]

I suspect the “missing” screws are the Allen key bolts that are recessed so you can’t see them. I’ve published a number of pages that will explain what they are for and also my experience of a wide angle 2” eyepiece. The pages are based around the 200P, so take a look following the link in my sig.

Edited January 8, 2022 by Spile

[John]

24 minutes ago, Spile said:

I suspect the “missing” screws are the Allen key bolts that are recessed so you can’t see them.

My thoughts as well. There are also 3 threaded holes on the rim of the base which would hold a mirror cover in place if it was the 200P F/5 model. Skywatcher don't fit these plates on the F/6 dobsonian version but the screw holes are still there.

This is how it looks (for the benefit of the original poster): C = collimation screw, L = recessed hex / allen locking bolt, X = empty threaded hole as mentioned above

 

 

Edited January 8, 2022 by John

[sonicninja]

Thanks so much for all the replies everyone, its an absolute monster and Im looking forward to using it. The mirror isnt particularly dirty really, i just noticed a bit of dust when compared to my almost brand new 130P. This 200P is approx 4-5 years old and the amount of dust I can see is very light for a scope that old so as suggested I wont mess with it for now.  By the looks of it the previous owner took really lovely care of it all.

I'll attach a picture of the rear of the telescope. Im only really worried if the scopes' collimation will be affected in day to day handling without these missing screws. I havent collimated a scope as yet as its not something I want to do immediately without reading up on it first. Hopefully I can either leave this screws off entirely or get some replacements if needed. Let me know what you think!

 

[John]

The ones missing are the locking screws. I don't use them on my scope unless taking it somewhere in the car. You collimation screws look to have been upgraded from the stock ones so perhaps the previous owner decided to dispense with the locking screws altogether ?

You should be OK without them but if you feel the need to replace them, any screw that fits the thread and is long enough to bear against the inner section of the cell would do. Many folks, like me, don't use these though.

 

[sonicninja]

Thanks John. Could you just eloborate a bit for me? Why would you need them in the car? Do these screws stop the  primary mirror from moving whilst in transit?

 

[John]

10 minutes ago, sonicninja said:

Thanks John. Could you just eloborate a bit for me? Why would you need them in the car? Do these screws stop the  primary mirror from moving whilst in transit?

 

They stop the inner section of the primary mirror cell from moving during transit. The mirror is held into that inner cell with 3 clips so it won't move around itself. What it might mean if the locking screws are not there is that more collimation adjustments might be needed after transit than might otherwise be the case. The mirror won't become detached from the cell or anything horrible like that !

 

 

 

 

[sonicninja]

Thanks John, much appreciated. I may look to get some in future in that case. 

[Spile]

You can see what is “beneath” the 200P here. https://astro.catshill.com/mirror-cleaning/
There is also a collimation guide on the same site.

[Doasqa]

On 08/01/2022 at 11:51, sonicninja said:

Evening everyone. I recently made the purchase of a used but in superb condition SkyWatcher 200P and I have a couple of immediate questions im hoping someone might be able to help me with.

Firstly, i noticed that the focuser is 2" but comes with 1.25" eyepieces and a step-down converter. Is this ideal or should I aim to purchase some 2" eyepieces?

Secondly, the primary mirror is a little dirty, is this something I can clean myself or best left to a professional?

Thirdly, I noticed that three screws are missing from the back behind the primary mirror. I believe these to be the locking screws (the other three large thumbcrews with springs are present). Are these vital and should I go about getting them replaced?

 

Many thanks in advance.

 

Keith

Don’t clean the mirror, I once did this successfully alter days of research, it was pretty dirty. After all the stress there wasn’t a difference so I’d never take that risk again. As far as 2” eyepieces the only one I have is a Pentax 40mm. It has an AFOV of 70°. I love it for sky surfing enjoying the wider FOV, in my case it is 3.12°   You might add an additional 2” eyepiece with moderate magnification but when I do the math the TFOV isn’t worth it. My other 1 1/4” eyepieces suffice for my needs. I don’t know what the screws do so I can’t comment. 

[cajen2]

You could always splash out on some Bob's Knobs: something like these: https://www.firstlightoptics.com/bobs-knobs-collimation/bobs-knobs-stellalyra-celestron-sky-watcher-newtonian-collimation-knobs.html

But check with Flo to see if they're the right ones. 

[Arthur Hucksake]

Hello Keith.

                  I have a 200p, big girl isn't she?  I replaced the Focuser on mine with a Baader Steeltrack.  Not trying to be insulting but compared to the Crayford the Baader is far Superior.  It makes the original feel like it was made in the dark, out of old horseshoes by Stevie Wonder.  2" Eyepieces are more expensive than 1.25" obviously but worth it in an 2" Tube.  Send Skywatcher an email regarding cleaning the Mirror as they are coated and easily ruined.  Send me a pic of the missing screws, or rather a pic of the bottom of the Tube and I'll send you a link of where you can get replacements.

[powerlord]

are they actually missing ? have a look in there for the head of an allen grub screw. if they, are they are just metric allen grub screws - gets from ebay,. etc.

sounds like mirror is fine, but really, cleaning mirror is not difficult - folk do tend to over egg stuff like this - mirrors are not made of unicorn tears - maybe like me you just can't stand that it looks dirty and want to clean it - get a bit of calotherm calocoat and some good quality lens cloth. I've cleaned all my newts like this. they are now like a mirror (sic). Obviously don't have at it with a wire brush or alcoholic wipes, etc.

you don't mention if you've collimated it ? if not:

https://www.astro-baby.com/astrobaby/help/collimation-guide-newtonian-reflector/

all the best

stu