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Burnt Mini ERF

Posted: Tue Mar 10, 2015 12:48 pm
by seti_v2
Hi all,

New here. Got a used PST and started my mod.

Got it all taken apart and the mini erf looks pretty bad. Anyone else see one like this? Is it still usable or should I replace it with kg3 glass? I will be using dichroic uv/ir cut and dichroic r29 filters before the telescope objective as an incoming ERF.

Thanks!

Re: Burnt Mini ERF

Posted: Tue Mar 10, 2015 12:55 pm
by seti_v2
Or is this the safest way to go?

http://maierphotonics.com/656bandpassfilter.aspx

Re: Burnt Mini ERF

Posted: Tue Mar 10, 2015 2:24 pm
by Bob Yoesle
Yep, very "rusted" out. Replace with the Maier ITF, add a 2" Red Baddder CCD filter in front of the PST objective to act as an IR blocking filter to reduce the heat load and thermal cycling. This should help preserve the new ITF.

OR use the Beloptik KG3 ( http://beloptik.de/en/left/if-uv-ir-cut ... ng-filter/ ) with a suitable 2" RG630 or RG 610 in front of the objective, such as the Baader 35 nm H alpha filter. This combination should not be so easily susceptible to deterioration as the ITF is.

Re: Burnt Mini ERF

Posted: Tue Mar 10, 2015 2:53 pm
by marktownley
Bobs answer is the best option, the maier is the cheapest option...

Re: Burnt Mini ERF

Posted: Tue Mar 10, 2015 3:37 pm
by seti_v2
A new 25mm thorlabs kg5 lens just popped up on ebay for $12.

As a temporary fix I can use this with my uv/ir and red filters. I know the kg5 transmission is a little less than the kg3 but the price is great for a quick fix, especially since i have the other uv/ir and red filters already.

Thanks guys!

Re: Burnt Mini ERF

Posted: Tue Mar 10, 2015 7:15 pm
by marktownley
seti_v2 wrote:A new 25mm thorlabs kg5 lens just popped up on ebay for $12.
make sure it is anti reflection coated...

Re: Burnt Mini ERF

Posted: Tue Mar 10, 2015 7:40 pm
by swisswalter
Hi Stephen

yes that ERF needs replacement as Bob and Mark suggsted