At some point in the past I stumbled upon a vendor that offered “neutral density” filters that were actually thin metal with profuse small holes. I now cannot remember who this was or the industry term for such a product. Can anyone advise me?
Tom
It’s common for ND filters to be metal coated glass. But the “profuse small holes” may be a problem if you are solar observing! The ones I have are clean as a whistle (Questar solar filters).
Peter
Tom,
I can’t help you about these filters, but I am curious to know what interest a PEP observer might have in them.
Roy
Roy:
I have an observer with a PMT photometer who cannot work with the brightest stars that are our group’s major focus right now. The idea is to put the ND over the “nosepiece” of the photometer to knock down the light level without changing the transformation coefficients.
Thanks Tom,
When I composed the question I was thinking of photometers with photodiodes such as the Optec Inc. SSP-3 which can observe the brightest stars. Understand now.
Roy
Most of our observers do use the SSP3 but our man in Louisiana has an SSP5.
On a different topic, I am trying to find someone in Australia who can take up PEP. I can supply a photometer but I’m having a very hard time finding someone who is both willing and is having tolerable weather. I sent an SSP-3 to a fellow in Sydney about five years ago, and he proceeded to have two years of awful sky conditions. Can you think of anyone who might be interested? We have an active research project on alpha Cygni stars and I also need data on Antares. Most recently I tried contacting the astronomical society in Tasmania but I have yet to get any response.
Tom
The weather in Australia has been atrocious for optical astronomers for a few years now.
I don’t know of anyone who would be interested in PEP. However, I do have a list of email addresses for 36 astronomical societies across Australia. There are more, but the ones I have are the ones I could confirm at the time I put the list together late last year.
Would you like me to send it to you by private message (provided I can attach images to it - I’ll need to take screenshots of the list)?
Roy
Roy:
Thanks. Right now I think I will South Africa instead of Australia. I’m hoping they have better weather.
Tom
Tom,
All the best. October to March where I live has very few completely clear nights. It’s starting to improve now.
Roy