Any BF10 or BF15 owners out there, if you could d a simple experiment for me.
Could you hold your Blocking filter (BF10) up to your eye and look at a fluorescent light source (or compacth fluorescent) and let me know what colout the light appears.
I think I have a faulty BF10, through the BF5 the lights are easy to see and are greeny coloured and clear. Through the BF10 they are nearly impossible to see and are deep red.
Looking at the sun with the BF10, I see no proms no matter how much etalon tuning on the PST, with the BF5 I get lots of proms and surface detail.
hi peter
placed mine under bright led down lights and a lovely deep red was seen,used my scope 2 days ago and was seeing nice proms and plenty of detail especially around 1429..damm looks like we just missed a m7 flare
Peter,
Is it a gold body Coronado blocking filter? How are you connecting it to the PST?
It may be worth checking that the front "mini ERF" at the eyepiece end of the diagonal is OK...just unscrew the chrome nosepiece and have a look. ( for imaging - this part of the blocking filter can be safely removed.)
No, it looks exactly like the standard BF that comes with the PST, just with a 10mm hole instead of a 5mm one.
It came as part of a DENK 60 upgrade I believe.
Peter,
Hmmm it may not be a Coronado filter - don't know.
Just check where it screws onto the black box and see if there's a secondary filter.
The blocking filter is "tuned" to Ha CWL and is only 6-8A wide...so normally not much to be seen.
I'd assume it was designed to work?
Apparently it *used* to work, I've seen images taken through it.
Just took it outside again, definitely no proms visible no matter what I do.
Pop the standard BF5 back in and the proms are all there.
It isn't mine, I was given the scope to assess the problem with it. The etalon seems fine, though not quite as good as mine, but the BF seems to be the problem, no proms on either scope.
Can they just die over time? The eye-side surface is a deep red/purple and the lens side is nice and gold, appears unblemished.
It would be unusual for the BF just to stop working...
The only thing that comes to mind is that the tuning position has been lost.
You could try holding the filter assembly onto the black box, not screwing it into place; low power eyepiece and just slightly tilt the assembly..the CWL varies slightly with tilt....worth trying.
(If I had access to a spectroscope I could quickly advise the possible problem)
It would be unusual for the BF just to stop working...
The only thing that comes to mind is that the tuning position has been lost.
You could try holding the filter assembly onto the black box, not screwing it into place; low power eyepiece and just slightly tilt the assembly..the CWL varies slightly with tilt....worth trying.
Tried tilting and rotating various ways, no change. Nice sharp image, but no Ha details. Looks just like a pink version of a white light image. Weird. The owner showed me pictures that prove it *was* working a year ago, but it has apparently just faded to none working.
On the ones that suffered from rust, what did that look like?
Could be a sneaky combination of tuning and the setting of the BF....
Re Rust...
This normally shows as a brown speckled "coating" on the mini-ERF. I've never seen a final blocking filter ( the little filter nearer the eyepiece) deteriorate!!
Hmmm, a couple years ago now I had a Coronado diagonal that showed oxidation of the energy rejection filter. This is the filter in the diagonal thats in the focuser end of the diagonal. Its actually two discs of glass with the erf coating between the two discs. This glass sandwich is supposed to be sealed at the edge to prevent oxidation of the coating by contact with the atmosphere. Over the period of a year the coating degraded from the outside edge gradually creeping in towards the centre. Solar detail became increasingly difficult to discern. See the attached image showing the mottled appearance of the degraded coating and the remnant of unaffected coating at the centre of the filter.
It looks pristine compared to those. With the bf5 no matter how much I tilt or turn, or even put it in backwards I still get proms. On any of the PSTs
With the BF10 I get no hint of them no matter what convolutions into try. Really strange, especially as it apparently did work some months ago, but the views of details slowly faded away.
If there werent photos to prove it, I would be doubtful. The cell has a dot of clear nailpolish marking it, so I can tell it hasn't been undone or tampered with.
For curiosity i opened up the cell holding my BF5, it is a single square of sanwhiched glass, purple one side, gold on the other, nothing to adjust or go wrong really. The BF10 I have appears much the same.
Not sure what else I can try, it is bloody expensive to replace, but the PST is useless without it.
Well, Denk have confirmed that the BF filters they were supplying have had some issues with performance fading and then disappearing. They had them made by a 3rd party and have had no joy in getting a solution.
They are going to return the customer's original BF5 and throw in a machined clamshell for the PST, even though the filter is out of warranty.
Not as nice as getting a replacement BF10, but at least they are looking after him.
I'm still intrigued as to *how* the filter has died.
Merlin, if you have time, and if the customer doesn't want it, could I post you the 3rd party BF10 to run through your spectroscope? I'm just intrigued as to what has happened.
Peter,
yes, I'd only be too pleased to run it through the specrtroscope and return it to you.
Drop me an email, we'll take it from there.
Interesting problem!!
