SkyWatcher Explorer 130PDS struggling to focus + Ra&Dec control questions

[DebatedNothing]

Hello all, complete beginner here.

 

Recently bought my first telescope and mount but am struggling a bit with it. The scope is a SkyWatcher Explorer 130PDS and was second hand but like-new still in box etc. Anyway, the scope came with a 28mm lens and what I think is a barrows lens (hollow tube to fit between telescope and eyepiece, similar in appearance to a macro extension tube for a DSLR). Without the barrows lens I cannot focus on anything as far as I can tell. The further "out" (more extended from telescope body) I bring the eyepiece the closer things get to focused (for example the moon) but they do not reach focus before I run out of extension distance on the focuser. I can bring the moon to focus with the barrow's lens on the telescope, which makes sense to me as (as far as I understand it) as well as increasing magnification, the barrow's lens should allow you to focus on closer objects. This has me concerned however as, obviously, you shouldn't be struggling to get the plane of focus close enough to focus on the moon... So what could be wrong with the scope or am I just missing something?

Secondly, I have a few questions about the use of an Ra and Dec mount. So as I understand it, if you consider the sky to be a sphere that we on earth are at the centre of, Ra and Dec consists of moving your telescopes "line of pointing" along latitude lines (RA) and along longitude lines (Dec) or the other way around, not really relevant which is which. Anyway, my question is, am I being an idiot or is there no way of pointing the telescope south without it ending up upside down? So, going from a Declination of basically 90 with the telescope where you want it, you have to decrease declination to get to something in the southern sky, which as far as I've been able to figure always results in the telescope being the other way up. Is this just something you have to deal with or am I being profoundly stupid in some way?

 

Thanks a huge deal for any advice you can give.

[ronin]

The scope is designed for imaging, that usually means the DSLR has to get in closer so that the image and the sensor will coincide. The tube is for visual use - you need the eyepiece to sit further back so you put the tube in then pout the eyepiece in the tube.

Will add the second bit when I have read it.

Basically at present I think it is: No tube = imaging, Tube = Visual. By the way it is an Extension Tube, the barlows have, or should have, a lump of glass in it somewhere. Quite a few makes are now supplied for imaging as a default as then all they need do is throw a short extension tube in for visual use ES and Bresser do it on just about all their scopes.

[ronin]

The looking south bit. There is an action called a "meridian flip" and I suspect that you need to perform this manually - not overly sure as I cannot recall the chaos that the meridian flip causes. Need to go get my EQ's out again and work it all out again. I do know of a big scope on a big mount with big weights and when that performs an automatic meridian flip you get well out of the way of it. There is a LOT of weight being thrown around. That at present is all I can suggest, hopefully someone else will be more familiar with one then I am. I ahve used Alt/Az's for too long.

[bobro]

As ronin has explained, the 130PDS is designed for photographic use, often with a DSLR camera. The image sensor on a DSLR is typically about 44mm behind the front flange of the camera, so when an eyepiece is used instead an extension tube is used to take up this distance so that the eyepiece can focus. The good news is that, once focused on the Moon, everything else in the sky will be in focus.

The scope is on an equatorial mount - great for astrophotography but not so easy to use for visual as you have found. The mount needs to be pointed at Polaris (polar aligned) in order for the RA and DEC controls to operate properly. The attached photo shows what the mount and scope positions will typically look like when the mount is polar aligned and the scope tube is pointing towards the Moon in the south.

This video explains different co-ordinate systems and why they are used : https://www.youtube.com/watch?v=zQB6UnrTEEM&t=974s

Hope this helps - and welcome!

 

[spillage]

You might find it easier to attach a collar to the scope just above the top tube ring. Either another ring or some use a needle work wooden hoop thing. This is attached tight to the scope only, allowing you to slacken off the two rings that attach the scope to the mount and rotate the scope inside the rings without the scope sliding down and becoming unbalanced to adjust the position of the eyepiece.

What is the model of you mount.

 

cheers

Spill.

 

[DebatedNothing]

9 hours ago, spillage said:

What is the model of you mount.

 

Thanks for the advice regarding the use of a collar to fix the telescopes position in it's rings, that's a really clever idea I probably wouldn't have thought of

The mount I have is an EQ-3-2 skywatcher mount, why?