Testing Antlia CaK filter plus one documentary Ha image, 15.6.

[RomanH]

Hello,

today morning was one of those bad seeing condition that I though I will not do any image. But I wanted to do some filter tests. I did use Daystar CaH for "between photosphere and chromospehere" images, but since I didnt liked it (doublestacked Lunt CaK would be much much better) I decided to sell it.

So today I come up with idea to increase resolution of my continuum/photosphere images I normally do with green filter (540nm CWL, 40nm wide) by using Antlia CaK filter (396nm CWL, 3nm wide). Despite the seeing I came up with better resolution than with green filter so I probably stick with CaK for granulation details.

Equipment used: TS CF APO 155mm f8 on SW EQ6R, Antlia CaK, TV Powermate 4x and Daystar Quark for Ha, ASI 485. More info and resolution on click on the images or here: https://astrofotky.cz/~rick.

CaK image:


Ha image:

[christian viladrich]

This TS Triplet seems to be quite convincing. Your Quark is quite good too.
You're gone have fine when seeing conditions are good !

[RomanH]

Thank you. Report that came with telescope says that Strehl is 0.96 (I assume its for 555nm). It looks like that Strehl is still above 0.84 at 396nm.

Here is comparison how resolution changes between that Green and CaK filter. Difference isnt tremendous, but still noticeable. Refractor looks to be holding average seeing better than my previous 8" and 10" newtons fortunately.

[rigel123]

Great shot!

[DeepSolar64]

The Antlia CaK wedge does nice on those granules!! I’ve also seen that they are good for faculae/plage too.

Very nice Ha too!

I may end up getting an Antlia CaK wedge.

James

[LauraMS]

Great images! The TS appears to be doing well, even at CaK.

[JochenM]

Very interesting results, Roman (in a good way).

[marktownley]

Good results and informative comparison.

[Montana]

Great shots but I am confused why you sold the Daystar CaH and bought the Antlia CaK? surely the Daystar CaH wins hands down with the chromosphere? the Antlia only shows a photospheric white light view with tough seeing conditions in the blue.

Alexandra

[Dennis]

Looks like it is a great filter from Antila. What do you think about using 10nm OIII Filters for whitelight imaging?

[RomanH]

Montana: thank you! I understand the confusion. Well, I did not like the output from the CaH. Images did not looked like PST CaK (especially reversed granullation) but more like through normal CaK (8 or 3 nm) with higher contrast. Not sure what was the reason - maybe more factors were involved, like:
1. Daystar CaH is 5A wide (and due to QC it might be 7-8A) compared to Lunt which is 2.4A (probably major factor)
2. CaH line is 396nm compared to Lunt K line which is 393nm (minor factor I think)
3. I use color camera which is not very sensitive in UV (minor factor)
4. Internal ERF filter I used was Baader Blue filter and it degrade the original CaH filter transmission quality (minor factor)

The problem was that even if I would go with double stack, it wouldnt help much:
1. With 2x Daystar CaH I may get about 3-4A (if the second unit would be 5A), so not worth for me
2. Since Lunt CaK and Daystar CaH are centerend on different wavelength I couldnt stack them.

So only option for me would be go with Lunt CaK and eventually DS option. But since they are nowhere to get I ditched this idea for a while ... (Yes, I saw other filter options here, but they are too expensive for me).

Since I already had Antlia CaK filter (for Venus clouds) I tried if its worth to use it also for solar imaging. It looks like that refarctors holds pretty good against average seeing and with 155mm of diameter of my APO, I can use CaK filter most of the time, so looks like solution (and upgrade from Green filter) for me for now - CaK for hi-res granulation/photosphere images and Daystar Quark Ha for chromosphere ...


Dennis: I used OIII once in past and it worked well. But it was sensitive to seeing. I mean photographic OIII, using with camera. I did not tried visual. Btw, I also have Antlia dualband and SII filter, all of them great (I can say better than Baader/Astronomik I have so far).

[arnedanielsen]

Excellent images - both of them! And a very nice comparison between Green and CaK.

Best regards,
Arne