Solar Newtonian?

[Alan White]

Does anyone who Solar Observes use a Newtonian for this?
If you do what are you using and how filtered.

I am reading my recent Solar Astronomy book and realise you can make a Solar Newtonian, with uncoated mirror etc.
So it set me wondering if folks here do such things?

Be interested to hear and see what folks are doing.

 

[apaulo]

hi alan, i use a dob mounted 200p newt , only scope i have. i made 2 filters using thousand oaks solar foil. it shows the sun as a yellow image, some other  foils baader i think shows the sun as a white image. this foil is surprisingly strong.  you dont need a full aperture size foil but obviously the whole filter unit Must cover the full aperture of the scope. i made a small 1 for the finder. keeps life simple for me. hope the pic helps. 

[maw lod qan]

I also use my 8" for solar WL.

I don't remember the brand of film but one sheet was large enough to do the OTA and finderscope.

I use the full 8", no reduction in size.

[vineyard]

Its worth checking out solarchatforum on this.  Yes it has been done by some of the folks on there & is pretty interesting.  I'm part way through ATM classes, making a 6" newtonian.  Mirror is almost done but not yet coated etc, so whenever the classes resume, I'm definitely pivoting the rest of my ATM to an uncoated primary mirror and truss tubes for the body.  Should be a v nice WL scope, perhaps even adaptable for CaK w a PM (depending on coated or uncoated secondary I suspect) but I'm by no means an expert on that - solarchat v v helpful (mountains of expertise & folks are happy to share their insights).

[vlaiv]

Just be careful with that idea of using uncoated glass for solar.

Reflection of uncoated glass is about 4% or 0.04 per surface.

You'll have two uncoated surfaces (don't forget to use uncoated secondary as well!) - so that is 0.0016 (0.04 x 0.04)

This means that uncoated newtonian can reduce sunlight to 1/625

Baader solar film is ND 5.0 - it reduces sunlight by 1/10000 - or 16 times more.

It would be good to include ND filter as well in the system (much like Herschel prisms do - they have 4.6% reflectivity and add ND filter to get needed combined neutral density / light reduction).

You would need ND 1.2 filter to reach total ND 5.0 levels. Simple moon ND filter is something like ND 0.6 - 0.9, so I would add one of those and variable polarizing filters so actual brightness can be tuned at the eyepiece.

Good thing about Herschel wedge is that it polarizes the light - so you need only one polarizing filter at the eyepiece to control level of the light (by turning the eyepiece).

[Alan White]

Solarchat already looked at as a source of information, and highly reccoemend that.

The design specifics are indeed additional filtration in use.
I am fully aware that I would not just have ago, my eyesight is far too valuable.
As we all remind those less technical, do not look at ths sun without suitable filtration

 

[vineyard]

Thanks @vlaiv that is v helpful re the calculations - yes definitely some form of filter to be used.  And a good idea re the variable polarising filter.  May end up w two different Hoya filters depending on whether imaging or visual.  Will need to do the calcs carefully once the mirror is finished - sadly classes have been shut down (understandably) since the lockdowns.  Hopefully will begin again at some stage this year.  Cheers!

[Guest]

I am too lazy to make them so I just buy them lol

https://www.telescope.com/mobileEnsemble/Accessories/Telescope-Eyepiece-Filters/Orion-Safety-Film-Solar-Filter-for-Reflectors/pc/3/sc/48/403.uts

 

[Paz]

12 hours ago, Mike Q said:

I am too lazy to make them so I just buy them lol

https://www.telescope.com/mobileEnsemble/Accessories/Telescope-Eyepiece-Filters/Orion-Safety-Film-Solar-Filter-for-Reflectors/pc/3/sc/48/403.uts

 

Me too. I bought a sheet of A4 baader solar film ages ago with a plan to make a solar filter for use with my C8 and VX14 (I often use a 137mm off axis aperture stop on the VX14 for doubles/lunar/planetary and thought it might be good for solar) but I still haven't got around to making anything with it.

[Guest]

1 minute ago, Paz said:

Me too. I bought a sheet of A4 baader solar film ages ago with a plan to make a solar filter for use with my C8 and VX14 (I often use a 137mm off axis aperture stop on the VX14 for doubles/lunar/planetary and thought it might be good for solar) but I still haven't got around to making anything with it.

I bought some basic solar filters for my 20x80 binoculars.  They work pretty well.  I spent 20 minutes watch the sun.  I could see sunspots quite easily.  I wish they would make H alpha filters for binos

[cajen2]

That's good going.