Poor man double stack

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pupak
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Poor man double stack

Post by pupak »

I'm going to use the unplated Newton 250/F5.6 in H-a, so I'm testing how to get the narrowest possible band with minimum attenuation in H-a, because there will be very little light. I tried a combination of BF, TZ2x, BF, Quark on the AR150/F15 and the results look pretty encouraging. It's not a real DSII, but it's definitely a lot better than the single BF variant. I wonder if the N250 will shed enough light on that.
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Re: Poor man double stack

Post by KMH »

Very nice results, but I guess I don't understand what you're doing. How does using two blocking filters decrease the bandpass? Sorry if I'm missing something obvious.

Thanks!
Kevin


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Re: Poor man double stack

Post by pupak »

KMH wrote: Thu Jun 01, 2023 5:41 pm Very nice results, but I guess I don't understand what you're doing. How does using two blocking filters decrease the bandpass? Sorry if I'm missing something obvious.

Thanks!
Kevin
Adding a second BF before the TZ2 increases image contrast similar to DSII. Not that much, the 3D effect is not as noticeable, but it's an improvement. By what mechanism does this improve contrast if not by narrowing the band? I'm not an expert on etalons and BF, maybe someone more experienced can explain it to us. I'm just sharing my knowledge from practice. I'll leave the theory to the experts.


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Re: Poor man double stack

Post by Dennis »

Nice closeups!
about your mod: the results look good, but a comparison with the single bf would be king (or is it shown on the images? if so, what image is what?).
As far as i understand double stacking or using 2 bfs will not narrow the bandpass. What leads to improvements is usually the "cutting of the skirts" of the bandpass, so that parasitic light is reduced.
I still can see a double limb on the images, this would indicate that parasitic light hasnt been reduced much.


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Re: Poor man double stack

Post by arnedanielsen »

Very nice Petr!

Best regards,
Arne


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Re: Poor man double stack

Post by pupak »

One BF only.
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Re: Poor man double stack

Post by marktownley »

Promising results Petr.

To get the best out of both of those blocking filters they need to be tilt tuned.


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Re: Poor man double stack

Post by pupak »

marktownley wrote: Fri Jun 02, 2023 7:31 am Promising results Petr.
To get the best out of both of those blocking filters they need to be tilt tuned.
That probably won't work. I have them stored without the possibility of tilting, but I might figure it out somehow. That's a good idea, thanks.


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Re: Poor man double stack

Post by Averton »

Impressive images Petr.


Clare & Peter
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