Baader Triband and white light

[DavidP]

I’m wondering what energy filters people used to image in white light using the Triband telescopes. Do you use to a Herschel wedge? Or maybe a reflective filter and then neutral density?

[Dennis]

Good question. Personally i dont use any for imaging. Im just making sure that the filters are hardcoated and behind barlows at higher f-ratios.
Only for OIII i use a 10nm Baader 2" OIII filter as "ERF" for the Antlia OIII 3nm.
Dont try this at home.

A Herschel would be an option, but it also will kill the lightflux down to 4% which is a disadvantage for calcium k imaging. So basically i see that as a good option if you want to visually observe.

[marktownley]

I've used a herschel wedge with the 8" HaT.

[Dennis]

The Altair G-Band filter survived too with todays first test. So basically with the triband i never had anything damaged or getting too hot by not using additional filters (second year of use now). Hell of a scope and coatings.

[vineyard]

That's encouraging Dennis, thanks. I pulled the trigger on an Altair Astro triband D-ERF for my little 5" Mak but have not had a chance to use it yet. It's mostly for HA & Ca closeup with quarks. But the D-ERF on it is ND4 in continuum frequencies. Still too bright for visual (and ofc letting a LOT of light through in Ca & HA frequencies that need managing for visual).

But I think if you put a G-Band (or a 540nm solar continuum) filter, that would block the Ca and HA frequencies which are still coming through in high transmission, and basically make it close to having an ND3.8 astro solar film in place for imaging. I've got a Q into Nick at Altair to check I'm not missing something there.

I agree that putting a wedge behind an ND4 filter would make it quite dark, but perhaps instead of that just putting an additional ND0.9 (as well as a G-band or 540nm filter) would make the whole thing safe for visual? Overkill just for WL ofc, but a nice little additional versatility without having to change the front of the scope.

Mark did you find the wedge behind the HaT too dark? And Dennis how are the images with the G-band?

[Dennis]

That's encouraging Dennis, thanks. I pulled the trigger on an Altair Astro triband D-ERF for my little 5" Mak but have not had a chance to use it yet. It's mostly for HA & Ca closeup with quarks. But the D-ERF on it is ND4 in continuum frequencies. Still too bright for visual (and ofc letting a LOT of light through in Ca & HA frequencies that need managing for visual).

But I think if you put a G-Band (or a 540nm solar continuum) filter, that would block the Ca and HA frequencies which are still coming through in high transmission, and basically make it close to having an ND3.8 astro solar film in place for imaging. I've got a Q into Nick at Altair to check I'm not missing something there.

I agree that putting a wedge behind an ND4 filter would make it quite dark, but perhaps instead of that just putting an additional ND0.9 (as well as a G-band or 540nm filter) would make the whole thing safe for visual? Overkill just for WL ofc, but a nice little additional versatility without having to change the front of the scope.

Mark did you find the wedge behind the HaT too dark? And Dennis how are the images with the G-band?

Well i can only speak for the baader system, i dont know how the altair triband filter will behave with regards to residual energy or transmission of certain wavelenghts.
For visual you would need a Herschel wedge of course. You dont want to experiment with ND filters when it comes to eyesight.

The G-band filter seems to work for the fact that the triband D-ERF curve is actually "zero" at this wavelength. I managed to get about 85 fps with a mid ranged gain setting on the imx432 camera. But i couldnt test more because of haze and clouds.

[marktownley]

Mark did you find the wedge behind the HaT too dark?

Not at all.