Solar Image 7th March 2021 Baader K-Line

[Nigella Bryant]

Hi all, only managed one image today due to cloud. 80ed stopped down to 60mm plus Baader K-lIne filter. Lovely spot group and AR region coming onto disk at the North Eastern Limb at 10 O'clock position.  

[JeremyS]

Well done Nigella 👍🏻

[Nigella Bryant]

Thanks Jeremy. I was surprised I got anything as it was only a 50% stack of 250 frames. I usually like to get 1000 frames and stack 40%.

[Davey-T]

Nice one Nigella, Sun appeared here too late though.

Dave

[Highburymark]

Really nice Nigella. Could you briefly explain your set up - you’re getting some lovely surface detail from that filter.

PS - nice to remotely meet you the other week on the Solarchat meeting.

[Nigella Bryant]

16 minutes ago, Highburymark said:

Really nice Nigella. Could you briefly explain your set up - you’re getting some lovely surface detail from that filter.

PS - nice to remotely meet you the other week on the Solarchat meeting.

Hi, it was really nice to meet up on zoom and put names to face's. 

For the K-Line I use a 80mm ed refractor@ f6.8 which I reduce with an aperture mask to 60mm because of the wavelength. Mark on solarchat suggested that I do that and it does make a difference. I use a Lunt hershal wedge with a ND1.8 filter instead of the installed ND3. I place a 0.5 reducer in the mix with the Baader K-Line filter. I use a Zwo ASI 178mm on both the HA and Baader K-Line scope's. 

Hope this makes sense.

[Nigella Bryant]

52 minutes ago, Davey-T said:

Nice one Nigella, Sun appeared here too late though.

Dave

It's very hit and miss this week unfortunately. Last week was amazing.

[Highburymark]

20 minutes ago, Nigella Bryant said:

Hi, it was really nice to meet up on zoom and put names to face's. 

For the K-Line I use a 80mm ed refractor@ f6.8 which I reduce with an aperture mask to 60mm because of the wavelength. Mark on solarchat suggested that I do that and it does make a difference. I use a Lunt hershal wedge with a ND1.8 filter instead of the installed ND3. I place a 0.5 reducer in the mix with the Baader K-Line filter. I use a Zwo ASI 178mm on both the HA and Baader K-Line scope's. 

Hope this makes sense.

Thanks for the info. Impressed at what can be achieved.

[David Smith]

Good result. Seeing was horrible here today, looks like it was better down your way.

[Nigella Bryant]

7 minutes ago, David Smith said:

Good result. Seeing was horrible here today, looks like it was better down your way.

Thanks David, transparency was good I think albeit between the clouds.

[mog3768]

Nice have you got a magic wand that makes the cloud disappear  

[michael.h.f.wilkinson]

Nice images with great detail. Am I right in thinking the Baader K-line filter is wider in spectral transmission than the Lunt Ca-K modules?

[Nigella Bryant]

1 hour ago, michael.h.f.wilkinson said:

Nice images with great detail. Am I right in thinking the Baader K-line filter is wider in spectral transmission than the Lunt Ca-K modules?

Hi, yes, much wider than the Lunt CA-K module. Nonetheless it's a good filter for the price compared to the Lunt. It's pretty much like a higher contrast of the continuum filter. 

[michael.h.f.wilkinson]

13 minutes ago, Nigella Bryant said:

Hi, yes, much wider than the Lunt CA-K module. Nonetheless it's a good filter for the price compared to the Lunt. It's pretty much like a higher contrast of the continuum filter. 

I was considering one of these filters until I got a bonus for working 25 years at the University of Groningen. That allowed me to go for the Lunt (one of the comparatively rare pieces of new kit I own). They are very pricey. I have heard of people double-stacking the K-line filter to get a narrower band. Would that help, do you think?

[Nigella Bryant]

1 minute ago, michael.h.f.wilkinson said:

I was considering one of these filters until I got a bonus for working 25 years at the University of Groningen. That allowed me to go for the Lunt (one of the comparatively rare pieces of new kit I own). They are very pricey. I have heard of people double-stacking the K-line filter to get a narrower band. Would that help, do you think?

Hi, yes, that's my idea eventually, when I too get the Lunt CA-K module. 

[Macavity]

27 minutes ago, michael.h.f.wilkinson said:

I have heard of people double-stacking the K-line filter to get a narrower band. Would that help, do you think?

Heheh - I haven't! But it is theoretically possible? You'd have to work out light
levels (obviously) - Each *DS* CaK equivalent to an ND2 filter (If I remember?). 🤔
The superposition of gaussians should give you a (calculable!) improvement...

Aside: Even saw "peak minus wings" subtractions with "nearby" near-UV filter!
(All very "Particle Physics", I thought! lol.) The only prob I had with my DS CaK
was inter-filter ghosting reflections - Notably with mirror scopes (MAK 150). 🙃

I [too] sense that once-planned REAL CaK scope receding into the distance. 😐
 

Edited March 8, 2021 by Macavity

[michael.h.f.wilkinson]

2 minutes ago, Macavity said:

Heheh - I haven't! But it is theoretically possible? You'd have to work out light
levels (obviously) - Each *DS* CaK equivalent to an ND2 filter (If I remember?). 🤔
The superposition of gaussians should give you a (calculable!) improvement...

Aside: Even saw "peak minus wings" subtractions with "nearby" near-UV filter!
(All very "Particle Physics", I thought! lol.) The only prob I had with my DS CaK
was inter-filter ghosting reflections - Notably with mirror scopes (MAK 150). 🙃

I [too] sense that once-planned REAL CaK scope receding into the distance. 😐
 

Much depends on the exact shape of the passband. Double-stacking two H-alpha filters generally gives a 1.4x reduction of bandpass, as you would expect from Gaussian profiles. If however the bandpass has a roughly square profile, the resulting passband will not be much narrower. Much also depends on the centre transmission. If it is near 95% the result will be a maximum transmission of around 90%  (0.95 squared). If it is much lower, the image will be much dimmed.

[Nigella Bryant]

2 hours ago, michael.h.f.wilkinson said:

Much depends on the exact shape of the passband. Double-stacking two H-alpha filters generally gives a 1.4x reduction of bandpass, as you would expect from Gaussian profiles. If however the bandpass has a roughly square profile, the resulting passband will not be much narrower. Much also depends on the centre transmission. If it is near 95% the result will be a maximum transmission of around 90%  (0.95 squared). If it is much lower, the image will be much dimmed.

I love experimenting with equipment so as I'm eventually going to buy a Lunt CA-K module and I've already got a baader k-line filter what's to loose, lol. I've been experimenting with light path today with a hershal wedge+ ND3/ND1.8 with one or the other + 0.5 reducer+ the Baader K-Line filter without Baader K-Line filter in different positions of the light path to get the largest disk possible with the Zwo ASI 178mm. 

The results are:- Hershal wedge + ND1.8 + 0.5 reducer + Baader K-Line filter. 

I've got a hydrogen alpha 7nm filter that I'm going to put in the mix instead of the Baader K-Line filter just because I can, lol.

After all science is about experimenting isn't it. As long as we're very, very careful with our eyesight what's to loose. 

[michael.h.f.wilkinson]

20 minutes ago, Nigella Bryant said:

I love experimenting with equipment so as I'm eventually going to buy a Lunt CA-K module and I've already got a baader k-line filter what's to loose, lol. I've been experimenting with light path today with a hershal wedge+ ND3/ND1.8 with one or the other + 0.5 reducer+ the Baader K-Line filter without Baader K-Line filter in different positions of the light path to get the largest disk possible with the Zwo ASI 178mm. 

The results are:- Hershal wedge + ND1.8 + 0.5 reducer + Baader K-Line filter. 

I've got a hydrogen alpha 7nm filter that I'm going to put in the mix instead of the Baader K-Line filter just because I can, lol.

After all science is about experimenting isn't it. As long as we're very, very careful with our eyesight what's to loose. 

Double stacking a Lunt Ca-K module (1 nm bandpass) with a Baader K-line filter (8 nm bandpass according to Baader) should not have any discernible effect on passband, but can reduce overall throughput. What does help a lot in imaging in Ca-K is the use of an ERF that transmits Ca-K, to reduce heat and therefore turbulence in the optical tube. I was lucky enough to get a second-hand Beloptik Tri-Band ERF (apparently, there are only six of these), which transmits bands around Ca-K, Solar Continuum and H-alpha, but I gather that Aries Instruments makes dual band ERFs.

I really notice an improvement in sharpness if I install the ERF.

[Merlin66]

I use a 2” Baader CCD Blue filter as an ERF on my DIY CaK set-up.

Seems to work well for me.

 

Edited March 8, 2021 by Merlin66
images added

[Peter Drew]

I also have one of the rare six Beloptic triband  ERF's that I use on my 150mm solar telescope.  Works well.      🙂