Using a laser power meter with thermopile sensor to check ERF filters

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Rusted
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Re: Using a laser power meter with thermopile sensor to check ERF filters

Post by Rusted »

Hi Andrew,

Yes, I now have an external D-ERF followed by the 2" filters at 30cm inside focus of my 6" f/10 H-a iStar.

A Beloptik KG3 and Baader H-alpha 35nm CCD. These filters screw into a 2" x 37mm Baader Click-Lock adapter in the tailpiece.

The Beloptik KG3 is not female threaded in the front of its cell, unlike most filters, so cannot be placed second to the Baader.
Which is a shame, really, because the Baader H-a 39nm is far more obviously, surface reflective.
Making the Baader a safer option to have nearest the objective to avoid heat absorption in sustained use with a larger [6"] objective.

A new layout of PST etalon/filter stack with direct screw connection to ZWO ASI174 camera and 2" helical focuser. All nicely stiff now!
The (PST) ITF and BF filters reside inside the threaded adapter just before the camera.
The "Skywatcher" PST, etalon tuning motor uses a 16T timing pulley, 240T GT2 belt and 64mm screw [hose] clamp.
It is controlled by a HitechAstro DC focuser controller.

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http://fullerscopes.blogspot.dk/

H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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Re: Using a laser power meter with thermopile sensor to check ERF filters

Post by AndiesHandyHandies »

Hi

In your reply to my question about the laser pointed remote thermometer you said

2" Baader CCD

I assume you meant a Red CCD filter but from your last comment is it in fact the Baader 35nm dielectric filter, you said 39mm which I assume is a typo.

Yes its a shame the beloptik is not front threaded.

You could swap the filter glasses over in the two holders if they are the same size or move the Beloptik to a cheap coloured filter holder? As it would be best with the 35nm first as you say.

Cheers. Andrew.


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Re: Using a laser power meter with thermopile sensor to check ERF filters

Post by Rusted »

Thanks Andrew,

Rewrite: I have just read the earlier posts from 2013. Where Oliver at Beloptik discusses a KG3 temperature tolerance of 300C!
Which makes my 120F measurement at focus behind the D-ERF look like rather, small beer. My filters are also well within focus.
Hopefully these filters will not be remotely as stressed as trying to use them as a D-ERF in their own right.
There were no filters, at all, to protect my PST etalon after the sub diameter, internal D-ERF.

The obviously higher, visual reflectivity of the Baader H-a 35nm may have no relevance at all in the red light following the full aperture D-ERF.
I may need to make some large holes in my main tube so I can monitor filter temperature with a "fever" gun. [To give it its topical name.]
If need be, I can then add a cooling fan to the "ventilation" hole for those long, hot, summer days of imaging at 55N, later in the year. ;)
Last edited by Rusted on Sat Feb 29, 2020 7:07 am, edited 1 time in total.


http://fullerscopes.blogspot.dk/

H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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Re: Using a laser power meter with thermopile sensor to check ERF filters

Post by Merlin66 »

Ok
Can we get a little more rigor in the testing and reporting.
Use one filter at a time and record the results, then move on to adding one filter and recording results , repeat. Etc.


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Re: Using a laser power meter with thermopile sensor to check ERF filters

Post by Rusted »

Merlin66 wrote: Sat Feb 29, 2020 7:07 am Ok
Can we get a little more rigor in the testing and reporting.
Use one filter at a time and record the results, then move on to adding one filter and recording results , repeat. Etc.
Point taken. :D

If only it were possible in the present, seemingly endless, heavily clouded, with showers, weather regime..

If it were not for the high speed of my ASI174 there would be no chance [at all] to capture a cloud-free sun!

2000 frames at 320 & 390fps, for 800x600 and 640x480, 1-2ms, in 5-6 seconds, is only just, fast enough!

Three heat bands running for hours at 80F and I'm still struggling to stay ahead of the dew point using an additional hairdrier! ;)

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http://fullerscopes.blogspot.dk/

H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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Re: Using a laser power meter with thermopile sensor to check ERF filters

Post by AndiesHandyHandies »

Hi

The Baader 35nm is reducing heat on the etalon by 33%. And the Beloptik stopping long IR. Providing more protection for the expensive blocking filter.

You can unscrew the retaining ring in the Beloptik and then screw the Baader 35nm in and it will act as the retaining ring and they are then in the best order.

Andrew.


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Re: Using a laser power meter with thermopile sensor to check ERF filters

Post by Rusted »

Or, I could swap the filters over between cells.
I just need to find my screw-adjusting dividers to loosen the retaining rings.


http://fullerscopes.blogspot.dk/

H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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Re: Using a laser power meter with thermopile sensor to check ERF filters

Post by Rusted »

AndiesHandyHandies wrote: Sat Feb 29, 2020 2:55 pm Hi

The Baader 35nm is reducing heat on the etalon by 33%. And the Beloptik stopping long IR. Providing more protection for the expensive blocking filter.

You can unscrew the retaining ring in the Beloptik and then screw the Baader 35nm in and it will act as the retaining ring and they are then in the best order.

Andrew.
I tried swapping around various filter mounts but the KG3 glass was much too thick.
So I used your clever idea of stacking the Baader 35nm H-a in front after removing the KG3 front locking ring.
I even remembered to wear disposable nitrile gloves to avoid marking the filters with fingerprints.
Now I just have to remember not to unscrew them, in the usual manner, or I might drop the KG3 glass! :oops:

Thanks for the useful suggestion. ;)


http://fullerscopes.blogspot.dk/

H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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