Dust in new Coma Corrector

[MrB (Simon)]

Hi guys,

I just took delivery of an ASA 0.73x coma corrector/reducer, pretty happy when it arrived.
However having looked thru the corrector at white and black sheets of paper, there is obviously dust and very small flecks (fibre's) on the internal element surfaces.
At quick count without looking too hard, there would be about 10 specks easily visible. A more thorough inspection would probably reveal more.
Surely these things are put together in clean rooms?!!

On top of this, the objective element was rattling in the body, I was able to gently apply a quarter turn on the threaded retaining ring to bed it home.

My question is... should I be concerned? Will these have an affect on contrast etc?

As much as I would hate to have to do it, should I be returning it to Europe for a replacement?

I would try taking a photo(s) but don't like my chances of getting anything usable.

[blink138 (Pat)]

personally i dont think there is an excuse for this..... i mean they would surely be asssembled under an extractor to avoid this and of course lint free gloves
also it seems to have passed quality control!
pat

[brian nordstrom (As avatar)]

Just knowing they are there will forever play on your mind , they might or might not produce artifacts ? , but you know they are there and will never be satisified ,, .
Is it easy for you to return this ?
I would if it was mine .
Brian.

Originally Posted by MrB

Hi guys,

I just took delivery of an ASA 0.73x coma corrector/reducer, pretty happy when it arrived.
However having looked thru the corrector at white and black sheets of paper, there is obviously dust and very small flecks (fibre's) on the internal element surfaces.
At quick count without looking too hard, there would be about 10 specks easily visible. A more thorough inspection would probably reveal more.
Surely these things are put together in clean rooms?!!

On top of this, the objective element was rattling in the body, I was able to gently apply a quarter turn on the threaded retaining ring to bed it home.

My question is... should I be concerned? Will these have an affect on contrast etc?

As much as I would hate to have to do it, should I be returning it to Europe for a replacement?

I would try taking a photo(s) but don't like my chances of getting anything usable.

[Astro_Bot]

If it were me, I'd publicly ***** and moan in a semi-coherent manner until I felt better, tear it apart, put it back together, then say, "stuff it", bin it and open a beer.

However, my approach hasn't exactly been successful ... or appreciated ... so perhaps it's better to do the opposite.

That means politely getting in touch with the supplier about a replacement.

[clive milne]

Simon... I have experienced receiving optical equipment from overseas in worse condition than that, ie) dirty great thumb prints on internal lens elements, etc).

Customs officers get bored occasionally....
And who can blame them for protecting us from {fill in the blank}, it stands to reason that an optically transparent item the size of a coffee cup could be used to smuggle significant quantities of contraband in to the country undetected.

The targeted selection process for employment in this service is unlikely to weight the attributes of intelligence or 'being reasonable' too highly (at a guess).

I expect it would have left ASA in pristine condition.

[Astro_Bot]

That raises an interesting point. If it had been opened by Customs, wouldn't the package have been re-sealed with a sticker saying, "This package was opened and inspected by Australian Customs ..." (or something like that)?

[brian nordstrom (As avatar)]

You have a point Simon and as Clive pointed out if customs did open it , your point of them telling you they did is a valid one , any chance of a few close up photos , the contamination and the mechanisim that holds it together to see if it been touched ?
Thanks , I am most interested as either way its not good enough .
Brian.

[clive milne]

Whilst not disputing the point that receiving a corrector in the condition described is unacceptable. In reality, the extent to which these dust specs will effect the performance of the optical train will probably not be in any way discernible after flat fielding. Your secondary mirror for example is functionally equivalent (in context) to a spec of dust 2 inches in diameter. (give or take)

[MrB (Simon)]

Thanks for the replies guys.
The dust I might be able to live with, def not happy about it but as Clive said, there should be minimal effect on the image, particularly after flats.

I am however awaiting feedback on another possible issue from someone else that has the exact same corrector. If theirs doesn't exhibit the same problem as mine, it is definitely going back.

Originally Posted by Clive

Your secondary mirror for example is functionally equivalent (in context) to a spec of dust 2 inches in diameter. (give or take)

I ran the numbers... an equivalent sized central obstruction as that on my scope, for the corrector, would be a speck of dust of 16mm diameter! (43% central obstruction)

[Moon (James)]

Did you get the 2 inch (2KORRR) or 3 inch (3 KORRR) version?
James

[MrB (Simon)]

I got the 2".
I would have gone the 3" but would have had to upgrade the feathertouch too.
It's on my to do list.