Jump to content

1564402927_Comet2021Banner.jpg.a8d9e102cd65f969b635e8061096d211.jpg

Should the Sky-Watcher 200p have a base-plate?


Recommended Posts

Hi... I've just joined the forum and I'm a beginner so I hope you don't mind me asking a specific equipment question. I've just taken delivery of a Star-Watcher Skyliner 200p Dobsonian from FLO and although I've only had the chance to use it once, briefly, I'm very happy with it. But I'm concerned there may be a bit missing!

The base of the tube is open to the rear of the primary mirror. To me, that makes the mirror vulnerable to any knocks... Or worse. A small illustration in the instruction manual seems to show a three-armed assembly over the base, where the adjusting screws are. But my telescope doesn't have this, though it does seem to have spare screw holes. Further, while looking up collimation on the Astro-Baby site, I read that Sky-Watcher Dobsonians usually have a round metal plate screwed to the base, which of course I don't have.

Does anyone know if the 200p SHOULD have either of these base plates to protect the mirror?

I have contacted FLO to enquire but have had no reply as yet.

Many thanks in advance for any advice.

Julian.

Link to comment
Share on other sites

I don't know why this is but the F/5 equatorially mounted 200P does have the end plate but I've never seen one on the F/6 200P dobsonian. I've owned both scopes.

Personally I removed the plate from the F/5 version when I had it to speed up mirror / scope cool down a bit.

So, no, I don't think your scope is missing anything.

Welcome to the forum by the way :smiley:

Link to comment
Share on other sites

Hi,

I also have the 200p Dob - can confirm that I have no plate either, screws are also countersunk (both the holding and the adjustment screws) - it seems that the manual doesn't reflect the model it came boxed with in this circumstance :)

Link to comment
Share on other sites

My older blue tube Explorer 200P came with the base plate, but this was not present on my later black diamond 200P - so suspect Synta decided to dispense with this and save a few pennies. For visual use its probably not needed, though for long AP I have found that I get can get quite a lot of stray light in through the open end and this is definitely noticeable on my dark frames over 20 sec exposures (though much of this light probably comes from my laptop screen). I would advise making a cover or getting the FLO shower cap if you are doing any deep sky AP - I'm just making one up with three small fans to assist with the cool down.

Link to comment
Share on other sites

I'm not sure what I was thinking.

Reading Jake's post above has shook my memory :p

I actually found some stray light coming from the open end so I stretch a black woolly hat over the end which definitely makes a difference!

Dan

Link to comment
Share on other sites

As you see from my signature I have three Skywatcher scopes. The 200p was bought new in March 2012, came with no mirror cover plate, had crosshead countersunk collimation screws through neoprene O rings, and Allen head grub screws to lock the collimation. I replaced these screws with Bob's Knobs and the O rings by springs.

The other scopes (Black Diamond 150p and white Skyliner 250px) were second hand with no accurate way of dating them. Neither has a mirror cover plate, and they both have thumbscrews for collimation. Actually the collimation adjusters are 'thumbnuts' which are surrounded by metal springs and screw onto countersunk bolts which point backwards from the mirror cradle, and the collimation is locked by thumbscrews.

Link to comment
Share on other sites

Thanks all. Your replies have set my mind at rest. I was concerned that the open end could expose the mirror back to nasty accidental knocks when moving the telescope. Psychologically I think I will be happier with some kind of end cover, so I'll look into your suggestions. J

Link to comment
Share on other sites

Shower cap should do it!

When I first had mine I was picking it up by the bottom and inadvertently resting my fingers on the back of the mirror and then wondering why the collimation was slightly out!

They're fairly sturdy really.

Cheers

Link to comment
Share on other sites

What is the shower cap you mention? Is there a technical name for it I should search for on the FLO site?

Also (sneaky second question) should the factory settings be ok for the moment? I'm using the telescope straight out of the box and the moon seems pretty sharp... I haven't dared look into collimation yet!

Link to comment
Share on other sites

What is the shower cap you mention? Is there a technical name for it I should search for on the FLO site?

Also (sneaky second question) should the factory settings be ok for the moment? I'm using the telescope straight out of the box and the moon seems pretty sharp... I haven't dared look into collimation yet!

Julian,

I've been looking for the shower cap on FLO's site, but wasn't able to find this - might be worth e-mailing them an enquiry. To be honest for visual use you would almost certainly not notice the effect and would probably get a better return by flocking the OTA. For longer exposure AP then it can become an issue and can result in gradients and loss of contrast, but is easilly fixed. I like Longarms woolly hat sugestion - always useful to have a spare hat floating around when it gets colder.

Re the collimation, I would advise getting a long tube cheshire for this scope. Although they hold collimation pretty well between sessions, they tend to drift out over time and minor knocks, bumps and vibration can have a cumulative effect. Poor collimation will cause loss of contrast and resolution and will be a lot more noticeable than any visual effects from stray light. Astrobabe has a really good walkthrough collimation guide and there are some excellent tutorials on Youtube (including an 8 part detailed one by Astronomy and Nature Centre). Get the cheshire first and work through Mel's guide and it will soon be second nature - honest!

Link to comment
Share on other sites

Excellent advice Jake (and all). Many thanks.

I have emailed FLO and Martin there has found a shower cap for me. It will be a telescopic comfort blanket for me... I can see it gives no real protection as such :smiley:

J

Link to comment
Share on other sites

If it's any consolation my Orion Optics 12" dobsonian has an open back to the tube, probably more open than yours is due to the simple mirror cell design. My view is that the open back speeds up the cool down time of the scope. I've not had a problem with damage, dust intrusion or dewing as I recall. If I was storing the scope in a shed or observatory I would get a cover for the back end to discourage spiders etc.

post-118-0-66160300-1375198311_thumb.jpg

Link to comment
Share on other sites

If it's any consolation my Orion Optics 12" dobsonian has an open back to the tube, probably more open than yours is due to the simple mirror cell design. My view is that the open back speeds up the cool down time of the scope. I've not had a problem with damage, dust intrusion or dewing as I recall. If I was storing the scope in a shed or observatory I would get a cover for the back end to discourage spiders etc.

Definitely with you on keeping the spiders out - pesky critters! One had setup home in my filter wheel and made a right mess before I noticed and evicted him (or her)!

Link to comment
Share on other sites

John, thanks for the picture. Your Orion does at least though have the three-armed metal structure behind the mirror. I must admit I would feel safer with that extra bit of protection for the mirrow... even if it doesn't really make much difference :-)

Julian

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.