Scratched ITF on Coronado PST

[Mark_C]

Hi all,

I recently bought a second hand Coronado PST from ABS and of course as expected since receiving it we haven't had one decent day of weather so haven't had a proper chance to test it out. As the scope won't be getting used for a few days more, this morning I decided to unscrew the top eyepiece just to make sure there was no accumulations of dust in-between the blocking filter and ITF. I noticed there was quite a bit of dust on the surface of ITF filter so I gave it a gentle blast with the rocket blower which got rid of most of the dust, however I've noticed there seems to be a nasty mark on the surface ITF filter (see pic below). Should I be concerned about this? And most importantly will it affect performance of the scope?

It also looks as though the prism in the black box has been attempted to be cleaned some way or another, as there appears to be smear marks on the surface of the glass... will this adversely effect performance?

I'm a little disappointed to have made these discoveries and am hoping I can just write them off as being a non issue... but I'm beginning to wonder whether they are or not.

Any input on this would be most appreciated.

[Merlin66]

Obviously these "issues" shouldn't be there.

The ITF seems to be in reasonable condition (other than the scratch) - it's not a safety issue but may affect contrast. You need to try it first. Worst case you could mask it with a black texta (just make 100% you don't do any more damage!)

The PST ITF can be replaced using the Maier filter ( a straight swap over...)

The prism - if it annoys you a clean with Baader fluid should do the job.

Hmmm Buyer beware!

[Solar_observer]

The seller should have stated,there were these problems. I assume you didn't pay pennies for it,even second hand.

I think it's out of order.....hope it dosent affect your viewing experience.

[Mark_C]

Obviously these "issues" shouldn't be there.

The ITF seems to be in reasonable condition (other than the scratch) - it's not a safety issue but may affect contrast. You need to try it first. Worst case you could mask it with a black texta (just make 100% you don't do any more damage!)

The PST ITF can be replaced using the Maier filter ( a straight swap over...)

The prism - if it annoys you a clean with Baader fluid should do the job.

Hmmm Buyer beware!

Hi Merlin,

Thanks for the info. I posted on another forum (CN) regarding this and a user there reckons that besides the scratch that the ITF is also rusted, which is another piece of great news to make my day. The only consolation is that I may consider doing a PST mod later on down the line, so that's something.. although I gather that I will still need the ITF afterwards. I have looked in to getting a Maier filter, although it will add another £50 on to the bill, it's at this point that you start questioning whether it was worth buying second hand.

The seller should have stated,there were these problems. I assume you didn't pay pennies for it,even second hand.

I think it's out of order.....hope it dosent affect your viewing experience.

I completely agree with you there. I will also have to give the seller benefit of the doubt as he may not have known about this issue, although I can't imagine many PST owners being unaware of the issue and not checking beforehand.

I'll be honest and say that I paid £410 inc delivery for the scope, so definitely not cheap and the possibly of having to replace the ITF filter makes me wonder whether it was worth buying second hand in the first place.

I guess it was also a case of myself being overly naive as I bought the item from a distance without being able to check for these issues.

I'm not sure whether I can be bothered with hassle of contacting the seller about this, although most people probably would. I really don't know what to do now.

[NGC 1502]

I'm not sure whether I can be bothered with hassle of contacting the seller about this, although most people probably would. I really don't know what to do now.

Sorry to hear of your problems.   But are you absolutely certain that that scratch in your pic is not a bit of debris etc ?   You mentioned  'a gentle blast with the rocket blower'  perhaps a stronger blast may work, or failing that, I'd try something like the corner of a clean micro-fibre cloth.

I may be entirely wrong, but worth a try.

Regards, Ed.

[Mark_C]

Sorry to hear of your problems.   But are you absolutely certain that that scratch in your pic is not a bit of debris etc ?   You mentioned  'a gentle blast with the rocket blower'  perhaps a stronger blast may work, or failing that, I'd try something like the corner of a clean micro-fibre cloth.

I may be entirely wrong, but worth a try.

Regards, Ed.

Hi Ed,

I was hoping this was the case, however I have given the filter a stronger blast with the rocket blower and have ran a very fine micro-fibre across the surface but the mark remains. I'm pretty sure it's a scratch as I initially feared.

[Moonshane]

could you soak a fine clean paint brush with isopropyl alcohol and gently try to lift it - you never know it may just work. there's nothing really to lose I don't think if it's a scratch

[Mark_C]

could you soak a fine clean paint brush with isopropyl alcohol and gently try to lift it - you never know it may just work. there's nothing really to lose I don't think if it's a scratch

Thanks, I shall have to give this a go, I will need to buy some isopropyl alcohol first though!

I still fear it is a scratch as I have gone over it a number of times with a micro-fibre cloth and the surface feels rough when gliding over it. It could well have been there from the start, it's difficult to know.

[Moonshane]

very true. it may possibly be worth just putting it all back together, and enjoy the views. that's the best way I think to forget it's even an issue.

[Moonshane]

if the surface feels rough that suggests something stuck on the surface. assuming that's some kind of epoxy glue I can see around the perimeter it may indeed have been there since it was made. the good news is that as far as I know it will be well away from the focal plane and should therefore have no discernible affect on the view 

[Merlin66]

Mark,

It's difficult to assess the state of the ITF re deterioration from your image..but what ever it is I've seen much worse!

[Mark_C]

very true. it may possibly be worth just putting it all back together, and enjoy the views. that's the best way I think to forget it's even an issue.

I would have preferred to have just forgotten about it but it's difficult.   I think it's just a case knowing how much money I spent on it, thinking I was going to receive it in flawless condition only to later on discover that was far from being the case. I forgot to mention that also there was an allen key bolt missing from the side of the black box which got me a little suspicious and which is what prompted me to look further to make sure nothing was tampered with. :-( I believe the scope may have had an owner before the last seller, so these issues may have been present without the last owners awareness.

if the surface feels rough that suggests something stuck on the surface. assuming that's some kind of epoxy glue I can see around the perimeter it may indeed have been there since it was made. the good news is that as far as I know it will be well away from the focal plane and should therefore have no discernible affect on the view 

Good point about the focal plane, it makes sense. I guess with the BF5 being so small that the marked part of the ITF filter will not actually form as part of the image.

Mark,

It's difficult to assess the state of the ITF re deterioration from your image..but what ever it is I've seen much worse!

Merlin,

Here is a picture of the ITF at a different angle, the photo isn't the best, sorry! I don't really know much about the ITF filter but it does appear to look like rust around the edge of the filter. When shining a light through the other side it appears as a deep crimson red colour, although it does seem a darker/deeper red around the edges. I'm not sure whether or not it is supposed to be like this.

I know it's ultimately for me to decide, but would would be a reasonable course of action to take if the filter is deemed faulty? Is it reasonable to bring this to the sellers attention? I have owned the scope just under a week.

Thanks for everyones help so far!