Pst problems

[solarboy]

I borrowed my astro clubs PST that has been on a shelf in a cupboard for about 3 years . Don't know where they got it from . Tried it yesterday and the  image is very dim I have cleaned the  optics but it's  still the same. Any tips or info would be appreciated. 

Thanks for looking. 

Edited February 25 by solarboy

[Elp]

What colour is the front objective (tint)?

[solarboy]

Just took a couple of photos of the Pst lense. 

 

[Elp]

Have you checked the ITF filter in the bottom of the eyepiece holder tube, if clear it should be similar to the front objective, a nice clear bluey/green colour. They are prone to clouding over yellow if moisture is present which will reduce the effectiveness of the filtering.

See the last image in this post, the whole eyepiece tube screws off the prism box so you can see the ITF filter, on top of that filter is a red one which you can see from the open side before you insert an eyepiece. You can also see the ITF filter if you remove the side panel from the prism box but the narrow gap between the top of the pentaprism and the filter doesn't allow you to assess it that well from this angle.

The ITF filters can be replaced in the age of scope you have, the earlier scopes (with a gold/brown front objective) this wasn't possible.

Edited February 25 by Elp

[solarboy]

[Elp]

The ITF one you have to angle in light to tell, the yellowing/clouding over almost looks like paint splodges or some sort of mold.

The red one as far as I know normally doesn't need replacing, at least not periodically like the ITF.

Edited February 25 by Elp

[Elp]

Also have a look at the pentaprism, there's no grease/gunk stuck on the surfaces perpendicular to the light path. The grease that's used to allow the prism to slide on the guide rails can be quite messy. Just be careful loosening the bolts on the side of the prism box, they're quite soft and can strip on the heads, obviously make sure you're loosing the bolts from above.

[solarboy]

I will  clean it with lens cleaner and check for grease on the other bit I will keep you posted 

[Peter Drew]

As Elp has posted it's almost certain that the ITF has failed.  If the eyepiece/filter holder is too tight to unscrew warm the unit with a hair dryer, this softens the threadlock material,     🙂

[Rusted]

Poorly PST ITF.