21st May 2023 Altair G-band filter test

[Montana]

Last week I received my Altair 430nm G-Band filter which I was very excited to try out ( https://www.altairastro.com/altair-2nm- ... 3245-p.asp ). The weekend was forecast to be sunny, but we had to travel to Dover to visit and care for an elderly relative who was in need of assistance. However, when we got back at lunchtime Sunday it was still sunny so I set up the TEC140 and the Baader Herschel wedge.

Seeing isn't usually that great in the afternoon and I usually try to image early morning, but last week even early morning was terrible so I didn't hold much hope.

I started with Baader Continuum filter as I know what this should look like and I should be able to gauge seeing conditions. It was not too bad, I took a full disc, then went to 5x Powermate with the ASI174. Seeing was shaky but there were moments of nice clear seeing when the wind blew, so it was obviously local currents which were the issue.

I then swapped for the Altair 430nm G-band filter. It didn't screw easily to the nose piece of the ZWO, it would only bite and screw one turn. The exposure time seemed similar to the Continuum filter. I then decided to use a UV/IR cut filter with it but as there are no threads on the outside of the filter I had screw this to the ZWO nosepiece and then screw the G-band filter to the outside of the Baader UV/IR filter which it did perfectly. This knocked the exposure down a little more but not significantly.

Oh my!! what a delight this filter is. I think it is the best solar purchase I have made for a long time. I love granulation and my word! the view is breath taking. The contrast is phenomenal! when I said the seeing through the Continuum filter was shaky, the added contrast meant I could see everything at 5x so easily. It didn't seem to be more subject to seeing than the continuum filter. Also, I was concerned that the TEC140 is terrible at 393nm and I have to stop it down to 100mm, but no, I could focus easily and stayed at full 140mm and 5x powermate easily.

I also compared the view with a Wratten 29, but here I seriously had to use the UV/IR cut filter with this as there was so much leakage. The main differences were:

Wratten 29 (red)- least contrast, granulation is very rounded like bobbles, sunspot umbral/penumbral detail the most pronounced, seeing most stable
Baader Continuum (green) - more granulation contrast, more angular granulation, less umbral/penumbral detail
Altair G-band (blue) - phenomenal granulation contrast, very angular granulation, least umbral/penumbral detail (very dark contrast)

Full discs (1x, 140mm aperture)

Wratten 29 / UVIR cut filter
Sun_130237_21_05_2023_Wratten29_UVIR by Alexandra Hart, on Flickr

Continuum
Sun_122813_21_05_2023_ WL_Contin by Alexandra Hart, on Flickr

G-Band / UVIR cut filter
Sun_132735_21_05_2023_G-Band_UVIR by Alexandra Hart, on Flickr

5x Powermate (140mm aperture)

Wratten 29 / UVIR cut filter
Sun_131614_21_05_2023_a Wratten29_UVIR by Alexandra Hart, on Flickr

Continuum
Sun_123149_21_05_2023_Contin by Alexandra Hart, on Flickr

G-Band / UVIR cut filter
Sun_133155_21_05_2023_G-Band by Alexandra Hart, on Flickr

and just because I loved the granulation so much, I couldn't help myself take more with the G-Band, and the seeing wasn't perfect either
Sun_134056_21_05_2023_G-Band by Alexandra Hart, on Flickr

Sun_134155_21_05_2023_G-Band by Alexandra Hart, on Flickr

I couldn't spot those intergranular bright points yet but I hope with better seeing I may.

I fully recommend this filter, what a cracker / game changer!

Alexandra

[OlegLviv]

vERY GOOD TEST!

[pupak]

Superb test.

[Dennis]

Very nice test Alexandra!
I have the same thing with the rough threading of the g-band filter, but its no big deal. Until now just clouds and haze for me.
Why do you combine the g-band with the uv/ir block filter? I thought the g-band filter will block that anyways.

[Montana]

I did because, I do now add it with all filters, it is not guaranteed they block distant UV/IR and as there is some light reduction it must be blocking something! I have learned that most datasheets only show the near and not far ends of the spectrum and this is a belt and braces approach for me from now on.

Alexandra

[Dennis]

I did because, I do now add it with all filters, it is not guaranteed they block distant UV/IR and as there is some light reduction it must be blocking something! I have learned that most datasheets only show the near and not far ends of the spectrum and this is a belt and braces approach for me from now on.

Alexandra

I see, makes sense.

[vince22]

stunning photosphere !!!

great pic Alexandra ...

and so, after that .. I buy the filter .. shipment under way .. maybe 29 may is here ... :-)

[oriolestation]

Very exciting results! Bravo!

[Montana]

Thanks guys
That's great Vince, they should give me a commission

Alexandra

[marktownley]

These are excellent Alexandra! A great compare and contrast. I'm very tempted by one for a try...

[arnedanielsen]

Wonderful test and results Alexandra!

I'm so looking forward to receiving my filter - which should arrive tomorrow!

Best regards,
Arne

[rigel123]

Great comparison Alexandra, that filter almost looks like it's reaching some of the CaK band.

[GreatAttractor]

Lovely shots, Alexandra.

Adding this filter to my shopping list.

[banjo]

thank you for these tests.
I received mine on the 16th, it's the first one that gives me fairly good results, despite the not great sky in the south/west of France and like every time I have new equipment, 3 weeks without sun
Paul

with the G bande Altair 2nm

16mai23bandeG.jpg (1.7 MiB) Viewed 1483 times

[Carbon60]

Excellent, Alexandra. Looks like a great investment. All of the images look great in their different ways, but the additional contrast provided by the narrowband 430 nm filter is clear to see. Very nice.

Stu.

[christian viladrich]

Great test Alexandra ! This is exciting news.

The comparison between W29, 540 nm and G-band is very informative. The G-band seems to be a killer with the TEC 140.

Some bright filament points are visible in the penombra of the big spot :-)

I've done some testing today. Sounds good too :-)

[rsfoto]

Hi Alexandra,

Very interesting

[DeepSolar64]

Very nice work Alexandra! I LOVE the granulation images and the big spot of AR13110 looks very detailed. You should try coloring your last two. I bet they would look even better. But would you use the typical orange-yellow or a bluish color more suited to 430nm?

I have taken a few images using my 430nm Edmund Optical 10nm bandpass Gband filter. It takes good seeing to get it to outperform the 540nm filter on sharpness. However the view is a bit different than 540nm and white light. In my images the penumbrae of sunspots seem to appear darker than they do in white light or 540nm and the faculae do show up a bit better away from the limb than they do in the former. Your 2nm bandpass filter should show Gband details much better than mine does. Hopefully Marty Wise will see your images and post. He took some awesome pictures using the Edmund Optical 430nm filter that I now have but stated that a narrower than 10nm bp filter was needed. And now you have one!!

Again, great images. Give yourself a SPOD. You have my vote!

viewtopic.php?t=38392

viewtopic.php?p=380298&hilit=430nm#p380298

James

P.S. I have used my 430nm filter and posted images from it several times here but most suffer from my often poor seeing conditions. You did VERY well for a first light on that filter. Big scope and good enough seeing to use it. And better processing skills than I have. Cudos to ya!

[nicspenceryork]

Fascinating comparison.
They’re all gorgeous!
Nic

[Montana]

Thanks everyone for all the kind words, I enjoyed testing and comparing these filters. I did notice that my TiO filter was clouded over and degraded and I couldn't get focus another solar filter bites the dust! one in, one out.

Alexandra

[DeepSolar64]

Thanks everyone for all the kind words, I enjoyed testing and comparing these filters. I did notice that my TiO filter was clouded over and degraded and I couldn't get focus another solar filter bites the dust! one in, one out.

Alexandra

Your TiO filter must have been a soft coated one.

[arnedanielsen]

My filter arrived safely this afternoon... together with some rain. :-(

346111294_2436806539829830_6084165738717791948_n_resize.jpg (304.89 KiB) Viewed 1214 times

Well, well... maybe I can try to catch up on some processing instead.

Best regards,
Arne

[DeepSolar64]

Of course! Any new piece of astronomy equipment always comes with clouds and/or rain.

[Bojan]

I couldn't gather from the post, did you use it visually? Could you discern a difference between it and the baader visually ?

[ffellah]

Thank you, Alexandra, for testing this filter and sharing results. This is what this forum is about: all your images are superb.

Franco

[Peterm]

Amazing images Alexandra!

[Montana]

Thanks guys

Bojan, I didn't look visually because my Herschel wedge is currently set up for imaging (low ND filters). I would have had to add a few more ND filters for visual use.

Alexandra

[christian viladrich]

I couldn't gather from the post, did you use it visually? Could you discern a difference between it and the baader visually ?

Hi Bojan,

I have three different G-band filters : Edmund Optics 10 nm, Andover 1.9 nm and Altair 2 nm.

The Andover 1.9 nm is the best overall filter I have for visual observation with my Taka TOA 150. It vastly outperforms the 540 nm continuum in terms of contrast, visibility of granulation and facular plages. I find the violet color most pleasant, but this is just a personnal taste.

I don't expect the Altair 2 nm to be much dfferent than the Andover 1.9 nm. I have not tried it yet visually.

Christian

[DeepSolar64]

Christian,
I also have the Edmund Optical 10nm Gband filter. What is your assessment of it?

James

[Rob63]

Ordered, you really should be on commission Alexandra

[SteveZ]

Alexandra,

Thanks for the test report. The G-Band captures look great. I need to get one on order.

Steve

[vineyard]

Thanks for sharing Alexandra - looks very interesting. I'm looking forward to seeing some comparison shots between the G-band and CaK or CaH to see whether there is a huge difference between them or not. Cheers!

[christian viladrich]

Thanks for sharing Alexandra - looks very interesting. I'm looking forward to seeing some comparison shots between the G-band and CaK or CaH to see whether there is a huge difference between them or not. Cheers!

So, keep tuned :tomorrow, I'll post a comparison between Antlia 393-3 nm, Altair G-band, Alluxa Ca K 0.37 nm, 0.14 nm, and 0.37 + 0.14 nm ;-)

[DeepSolar64]

Thanks for sharing Alexandra - looks very interesting. I'm looking forward to seeing some comparison shots between the G-band and CaK or CaH to see whether there is a huge difference between them or not. Cheers!

So, keep tuned :tomorrow, I'll post a comparison between Antlia 393-3 nm, Altair G-band, Alluxa Ca K 0.37 nm, 0.14 nm, and 0.37 + 0.14 nm ;-)

430nm Gband 10nm?

[christian viladrich]

Thanks everyone for all the kind words, I enjoyed testing and comparing these filters. I did notice that my TiO filter was clouded over and degraded and I couldn't get focus another solar filter bites the dust! one in, one out.

Alexandra

BTW, what is the bandpass of the TiO filter ? Where did you buy it from ?

[p1taylor]

Excellent, Alexandra. All of the images look great, Very nice.

petr

[Montana]

Thanks

Christian, I bought it from Omega optical about 10-12 years ago, it was one of the first filters I bought. To know the details of it would require me to be a lot more organised than I am. It may take a big search to find the order sheet with the spectra on it

Alexandra

[robert]

Hmmm
Thanks for an interesting post!

[christian viladrich]

Thanks

Christian, I bought it from Omega optical about 10-12 years ago, it was one of the first filters I bought. To know the details of it would require me to be a lot more organised than I am. It may take a big search to find the order sheet with the spectra on it

Alexandra

Don't bother with it Alexandre. It was just out of curiosity ;-)

[vince22]

Thanks guys
That's great Vince, they should give me a commission

Alexandra

:-). Yes they should !!!

The filter arrive superfast … 3 days ago … and extra cost are really expensive ( duty cost , more than 30% )
But for me the filter worth the buy ..

I test yesterday and today … with my fs 128 …
I will post the pic when i find the time to work on the avi ..

But, i am happy with the filter ..
thanks Alexandra

[DeepSolar64]

I test yesterday and today … with my fs 128 …_vince22

Vince, you have a Tak!!?

[MapleRidge]

Hi Alexandra...

Thanks for the post on this filter

It convinced me to buy one...I should have it by the end of the coming week.

Brian

[PEterW]

Be interested in a visual comparison on a medium sized scope between continuum, “improved” continuum and this new g-band filter. Time to dust off the old kit and see what new things have come along!

Peter

[eroel]

Alexandra:
A super comparo session.
Thanks.
Eric.