11 mm tv plossl and coronado pst.

[andre2]

Hi, i order the 11 mm TV plossl eyepiece for the coronado pst, but the image remains blurry. I try to focus in all directions but iT wouldn't reach focus. I also want to try/ order  another 15 mm TV plossl, but affrait that that one maby  will  fail too(??). Do someone have experiens with this or maby know whether someting is wrong with the eyepiece or the scope ?  all other eyepieces i have works...i am curious what's going on , especially with an TV eyepiece! thanks for the information! 

Edited May 29, 2019 by andre2

[Ags]

What other eyepieces have you used?

Have you tested the eyepiece at night? Can it make night stars look like point sources? If so there is nothing wrong with the eyepiece.

[andre2]

I use a solar telescope. Thats the only scope i have , so i cant test the eyepiece. I hope i  find someone that has the same issue with the same scope and eyepiece.

Edited May 29, 2019 by andre2

[Stu]

I have used a Televue 11mm  Plossl in a Coronado PST and it worked very well, very sharp. If your PST works well with other eyepieces then it may indicate there is a problem with the eyepiece. That is quite a rare thing but I guess it is possible.

[andre2]

Yes. I agree, probably there is someting wrong with the glass . Maby i will order a new  15 mm tv plossl , hope that one will work!

 

 

 

Edited May 29, 2019 by andre2

[Stu]

5 minutes ago, andre2 said:

Yes. I agree, probably there is someting wrong with glass. Maby i will order the 15 mm tv plossl , hope that one will work.

 

 

 

Presumably you can return the 11mm to your retailer for a refund or replacement?

[Paul73]

Can’t remember any problems with 11mm TV Plossl. Try losening off the screw and skidding the eyepiece our as you look through it. If it comes to focus. You will just need a cheap extender.

I’ve got an 11mm and an 15mm somewhere. I’ll give them a try in the PST when I next see the sun (probably the weekend).

Paul

[Peter Drew]

An 11mm TV Plossl worked with my PST. Overall I preferred to use a 8mm-24mm zoom eyepiece.   😀 

[Paul73]

Another zoom fan here. So much of solar is about tweaking things as seeing fluctuates. The Baader one is better corrected too (the sun is rounder).

But I will check the TV Plossl/PST pairing again. 

[John]

The only thing that I can think of that might prevent a Tele Vue plossl coming to focus is that the TV plossls reach focus around 8mm further outwards than many other eyepieces. If the focusser mechanism of the PST in question had an issue of some sort (it works by moving a prism within the body of the scope I seem to recall) then that might prevent it being able to allow the focal plane of the eyepiece to reach that of the scope optics.

 

[johninderby]

I find it highly unlikely that there is something wrong with the eyepiece assuming that it is a new one of course. Quality control is one reason TV eyepieces aren’t cheap.

A Televue plossl does need more outfocus as I found using one in my Quark scope. 

[Stu]

9 hours ago, johninderby said:

I find it highly unlikely that there is something wrong with the eyepiece assuming that it is a new one of course. Quality control is one reason TV eyepieces aren’t cheap.

A Televue plossl does need more outfocus as I found using one in my Quark scope. 

I agree John, but we know an 11mm TV Plossl works very well with a PST from experience, so something must be wrong.

I tend to also agree with you and John that it is more likely to be the PST than the eyepiece itself, but personally I have had one faulty brand new TV eyepiece (Ethos 3.7mm) so whilst it is highly unlikely, it is still possible.

If out focus is the issue then presumably if the op winds the focus all the way out then pulls the eyepiece out slowly it should come to focus?

[John]

4 minutes ago, Stu said:

....If out focus is the issue then presumably if the op winds the focus all the way out then pulls the eyepiece out slowly it should come to focus?

Thats worth a try.

The focus mechanism of the stock PST can have issues as well:

https://www.cloudynights.com/topic/571477-trouble-with-pst-focus/

 

[andre2]

I will try that and let you know if it come that way to focus. Pesonally i think there is nothing  wrong with the focuser , iT always focus well with other eyepieces ( up to 9mm is the highest have used) but, if the focuser has a limited range, why others can reach focus with that eyepiece.....and there most be probably also ( a lot) pst's with more or less the same focus range i have.  Hmmm  its almost getting  interesting to figure this out!  Experience will tell.

 

 

 

 

 

 

Edited May 30, 2019 by andre2

[andre2]

Hi , i lifted the eyepiece a bit up, while i look through it and it came to focus! But the seeing was somewhat average and i compere iT with an 12 mm plossl and the view through the 11 mm TV  was slightly better but worst then 20 mm plossl ( due to the average seeing) the eyepiece is a little short for my scope. What is the conclusion of this? And, Can i order savely the 15 mm TV plossl? ( witch is i think even a better eyepiece for an normal pst, especially for general seeings)

Edited May 31, 2019 by andre2

[Mark at Beaufort]

I use a 8-24 TeleVue zoom on my PST which I prefer to the stand alone EPs. To be honest I set the zoom, in the main, to the 16mm position because I find the view is much sharper and brighter. I occasionally move up to the 12mm settings to view individual areas but never higher.

I hope you sort your problem without too much expense.

 

[John]

When I had a PST and a Lunt 50 I found that a zoom eyepiece was a great tool. Like Mark, I rarely used more than 12-15mm with these scopes.

 

[Stu]

I'm sure the 15mm would work well. As I mentioned earlier, I used to use an 11mm most of the time and it seemed to cope with most seeing conditions. Alot comes down to personal preference of course. I sometimes used a 12.5mm Ortho which was good too.

Zooms do seem to work surprisingly well, in part due to the f10 focal ratio of these solar scopes. Avoid the very low cost Seben ones though.

[andre2]

Hi there!  I take my seben super zoom in use again ( 8=24 mm) and compere iT with the 11 mm TV plossl lifted up. I put the zoom at 11 mm setting = the seeing was pritty decent for a moment= And compere the fews of the prommences , and the zoom was better then the 11 mm TV plossl!  Now i forget that 15 mm TV plossl and what caused the focus problem . i will just use the zoom again in decent and good conditions. And will order a cheeper 15 mm and 20 mm plossl and use that for average  and decent seeings.

 

 

 

Edited May 31, 2019 by andre2

[andre2]

Update. My pst had probably a shorter focus range, thats why the 11 mm tv plossl not reach focus.  the focus range of the pst prism is in general short,but mine was probably  a bit shorter then usual. ( no problem, what really a problem is are the poor seeings and activities which every solar telescope sucks without, the only solution here is patience)

Edited September 29, 2019 by andre2

[John]

19 minutes ago, andre2 said:

Update. My pst had probably a shorter focus range, thats why the 11 mm tv plossl not reach focus.  the focus range of the pst prism is in general short,but mine was probably  a bit shorter then usual. ( no problem, what a problem is are the poor seeings and activities which every solar telescope sucks without)

The TV plossls require around 8-10mm more outwards focuser movement to reach focus than many other eyepiece types. That might be the problem. Pulling the eyepiece a around 1cm out of the focuser drawtube might let you reach focus with it.

[andre2]

Ooh yes. I have do that, but was not so impressed by the fews and find iT a bit uncomfortable. I find out that in decent/ good conditions the seben zoom at 11 mm setteng works even better for prommences , and use this one instead. And two simple plossl for less then decent conditions 20 and 15 mm.

Edited September 29, 2019 by andre2

[John]

I'd agree that the 8-24 zoom would be more comfortable to observe with than the 11mm TV plossl.

Zooms work really well for both white light and H-alpha solar viewing I've found.