What size aperture for solar observing.

[Aaf146]

Hi guys, I have a question. I have an 8" dob and am going to make a filter using solar film.

Is it worth making one for the full 8" aperture or will the off axis aperture stop be better for it. 

I don't know how much more detail will be gained from using the full aperture so any advice would be greatly appreciated.

Thanks, Adam

[Roy Challen]

I have a 60 Ha scope and a 76mm a achro I use for white light. The achro shows far more sunspot detail due to the extra aperture.

For an 8" scope, maybe there won't be much difference between a, say, 6" or 8" mask. Try it and see.

I'm pretty sure you'll get great views either way.

[Stu]

I would probably go for full aperture if you can. A lot will depend on seeing, but under good conditions the extra resolution should show.

[nfotis]

Logically, you should receive more details with the larger aperture.

That's, if you can cover the whole eight inches with the Astrosolar film, of course.

N.F.

 

[inFINNity Deck]

I created a full aperture filter from aluminium and Baader ND5.0 foil for my C11 EdgeHD. It gives magnificent views, but only when seeing allows. So, if that is your only scope for solar observing, you may want to have a second filter with a smaller aperture. You will loose some detail, but may still have better views than with full aperture.

Nicolàs

[CraigT82]

Bigger is better IMO. But whether your seeing allows you to capitalise on the larger aperture is another matter. 

You could go ahead and make a full size aperture and then experiment with masks over the front of it to give you different sized apertures? I think a single A3 sheet of the Baader film would cover an 8” aperture. 

[Steve Ward]

I'd make a full aperture filter with Baader film and some masks that you can add to reduce the aperture as and when.

If you have exceptional seeing for the majority of the time the views full-bore will be magnificent , but I suspect you'll be quickly disappointed if your seeing is generally so-so.

I try the Mak180Pro now and then when I think the seeing will allow it but invariably as soon as I get set up I realise that it's not worth the extra hassle , generally speaking 100mm aperture is about all the usual UK conditions allow.

[PeterStudz]

I made one recently for my 8” Dob. A single A3 sheet of Baader film has a width of ~202mm and of course you have to allow a bit each side in order to stick it down. With some careful sticking it made an aperture of 185mm. I don’t think you’d notice any difference - and it covers the mirror clips

Used it a few times now. Each time the view has been significantly better than on my 4.5” Newtonian.

Edited June 18, 2022 by PeterStudz

[Spile]

This is how I made mine for my 8” Dobsonian

https://astro.catshill.com/solar-filter/ 

[ollypenrice]

I've found that more aperture usually improves the view using a white light filter.

Olly

[BGazing]

Unless your seeing is great you will be seeing-limited probably at 100mm already. So either 80mm off center or full aperture and then be prepared to lower magnification and use ND and/or polarizers/binos.

Edited June 20, 2022 by BGazing

[inFINNity Deck]

This is about what I can achieve with my full aperture C11 EdgeHD (imaged with ASI174MM, 2x Barlow, ND5.0 filter and Baader Continuum filter), but I have to admit that I get this kind of seeing only a few days a month (in this case it was just below 2").

Nicolàs

Edited June 20, 2022 by inFINNity Deck