Help with understanding focus skyliner 200p

[JamesGlasgow]

I know this might sound stupid, however here we go!!

Bought my son a skyliner 200p classic of eBay, had a few ups and downs since, but with the help on these forums sorted most. However one hing that confuses me, is why the different eyepieces he has end up needing different 2” to 1.25 adapters. It didn’t come with any adapters, just 2 2” Celestron luminous eyepieces, got advised to buy an adapter. So bought one of these https://www.firstlightoptics.com/adapters/astro-essentials-2-to-125-reducer-adapter.html which works with a couple of plossl eyepieces he got for Christmas, but I got him a couple of bst in 8mm and 12mm as an upgrade and I can’t get focus with them. Have tried them in this https://www.firstlightoptics.com/dobsonians/skywatcher-heritage-76-mini-dobsonian.html which he got last year and they get focus fine. I take it I need a different type of adapter? Could anyone point me in the right place please.

 

thanks for any help given.

 

Edited January 18 by JamesGlasgow

[bosun21]

The adapter you bought is too short for 1.25" eyepieces. The telescope comes with two adapters. One is a 2" and the other a 1.25". Both are longer than the one you bought. What height is the adapter you bought? These are the two adapters that come with the scope.

 

[JamesGlasgow]

Thanks a lot, a picture paints a thousand words. The one I bought is only around 3cm high, I was just confused now I sort of know. Are the ones in the pictures around 2 inch’s high, just so I buy the correct one. As the telescope didn’t come with any, the person I bought it off used 2” eyepieces 

[Carbon Brush]

Good advice from @bosun21. Adding a couple of extra points.

As the scope is used, the main mirror may have been moved up the tube. This has the effect of moving eyepiece focus out of the barrel.
In other words a longer extension is needed. Or the mirror could be moved back down the tube.

If you point the scope in daylight at a distant horizon, rack out the focusser and the image should improve, even if you don't get focus.
Then release the eyepiece from the tube slowly pull it away from the scope, while looking through.
That will give you a good measure of how much extra focus travel you need.
If it is only a couple of millimetres, take a look at the back of the main mirror and see if the push/pull screws have enough travel.

If you move the mirror, you are into collimation. But that is quite easy on a simple reflector scope. Especially if someone shows you first time..
I won't offer to help collimate - hundreds of miles round trip🤥. But maybe someone nearer to you? Or a local astro club?
These are great scopes and it will give you a lot of pleasure.

Keep asking the questions.

[Mandy D]

1 hour ago, JamesGlasgow said:

Thanks a lot, a picture paints a thousand words. The one I bought is only around 3cm high, I was just confused now I sort of know. Are the ones in the pictures around 2 inch’s high, just so I buy the correct one. As the telescope didn’t come with any, the person I bought it off used 2” eyepieces 

My 1.25" adds about 37 mm and the 2" adds 48 mm. It is very handy that the Skywatcher Newtonians need these adaptors to reach focus with an eyepiece, as it makes them so easy to use for imaging with a DSLR which has the sensor buried deep in the camera body. For Nikons it is 46.5 mm, IIRC. If yours are too short, you can just pull the eyepiece out a bit and lock it with the screw until you get the right one.

[JamesGlasgow]

Thanks @Mandy D didn’t even think to pull out the eyepiece. Just been outside again with my boy, wife’s going to kill me keeping him up so late( he’s only 9). But it was worth it to see his face light up running up and down the street shouting ‘ I’ve seen Jupiter’ 

thanks a lot to everyone. You’ve made a boy very happy.

[Mandy D]

@JamesGlasgow glad to help. Tell your wife it is part of his education!

[PeterStudz]

@JamesGlasgow, when I got my Skywatcher 200p it didn’t come with an extension for 1.25” eyepieces. But I found this (link below) worked perfectly and was ideal. It’ll fit into the short adapter you’ve bought already and give perfect focus using BST StarGuiders - which I have too.

https://www.meadeuk.com/Opticstar-1-25-inch-Extension-Tube.html

[JamesGlasgow]

Thanks a lot @PeterStudz just ordered.