Chroma UBVRI not produced anymore?

Community
1

Hello everybody

I went to a lot of online shops and they all have Chroma photometric filters out of stock.
Do you know if Chroma stopped producing them?
Do you know of any alternative brand that produces 31mm unmounted filters with 3mm thickness?

Thanks a lot
Nicola

2

These filters are expensive so most retailers will not stock them. It is too much money to have this inventory on hand as it does not sell quickly.

You could try ordering directly from Chroma.
For example, here’s a link to their website and a likely set of filters:
https://www.chroma.com/products/sets/27103-bessell-ubvri/

As an alternative, there are Baader Planetarium filters:
https://www.baader-planetarium.com/en/baader-ubvri-bessel-filter-set-photometric.html?sku=2961751

Andover Corporation also makes good quality filters:
https://store.andovercorp.com/product-category/johnson-bessel-ubvri-filters/

Clear skies,
Colin

3

So no options, I have to go with Chroma.
Baader’s thickness is 2mm
Andover Corp. is 5mm if I’ve correctly read, price the same as Chroma

4

What filter wheel do you have? Many will take 2mm or 3mm.
A lot of the professional scientific filters are 5mm.

5

I need the filter to be 3mm so it is parfocal with the other I have and with the OAG

6

Optolong is another manufacturer of photometric filters. I have a 2inch set, but don’t know if they have 31 mm.

7

I had a look at their website. They haven’t got the 31mm unmounted and moreover are 2mm thick.
I wish I had purchased the Astrodon one when it was still in production…

8

I use 36mm I think and suspect that they may be loose in the filterwheel. When i get around to verifying that, I try one of the industrial supply houses for flat fiber washers to snug them up.
Ray