Solar resolution with Baader film over smaller insert aperture

[SteveBz]

Hi Guys,

I made a full aperture solar filter for the c114eq, instead of just for the aperture of the smaller insert cap.  It gives me quite nice resolution.

I want to make a filter for the c8n, if I just make a filter for the cap (about 58mm), will I notice any degradation of resolution?  A quick play with the lambda over diameter formula (I can't remember it's name, Raleigh formula?) suggests not.

What do you think?

Regards

Steve.

• R=λ/D (wavelength over diameter)

[John]

You will get the resolution and light grasp of a 58mm aperture scope, basically. For white light solar viewing that will still give some nice views though.

Sorry that I can't comment on the maths - it's not my forte really !

 

[SteveBz]

Just now, John said:

You will get the resolution and light grasp of a 58mm aperture scope, basically. For white light solar viewing that will still give some nice views though.

Sorry that I can't comment on the maths - it's not my forte really !

 

Oh, the Html came out wrong.  I'm going to fix it.

[SteveBz]

3 minutes ago, John said:

You will get the resolution and light grasp of a 58mm aperture scope, basically. For white light solar viewing that will still give some nice views though.

 

That's what I guessed, but will I (or you) be able to tell the difference for an object as large as the Sun?

[xtreemchaos]

it all depends on the seeing, if the seeing cracking i see no difference between  using my cap filter or full aperture, but in less good conditions which is the norm full aperture wins the day by a mile and the bigger the better.  charl.

[SteveBz]

5 minutes ago, xtreemchaos said:

it all depends on the seeing, if the seeing cracking i see no difference between  using my cap filter or full aperture, but in less good conditions which is the norm full aperture wins the day by a mile and the bigger the better.  charl.

Ok, so maybe the answer is to use the leftover film from the c114 to make a small 58mm cap filter, and then upgrade to to a 200mm filter when I get round to it. 

The other issue with the 200mm filter is storage.  The 114mm filter already takes up a lot of space, I can't even imagine what a 200mm filter would require.  Maybe I should wait and get a properly made glass filter.  Might take up less space than a fragile baadfer film filter.

[xtreemchaos]

yer storage, i keep mine in the box it came in but i dont take my kit out, a tupperwear container would keep it safe, i moved to a lunt solar wedge earlyer this year ,a big step forward for me, thay dont work with mirrored scopes only refractors i use mine with a ed80 and sw 120mm f5 and AR127l f9.5, it gives amazing views and images.  charl.

[SteveBz]

Hi Charl,

Yes I saw they don't work with reflectors, why is that?

Steve

[michael.h.f.wilkinson]

The main issue with reflectors is that the build up of heat on the secondary can shatter it, especially with fast primary mirrors, like my F/2 primary in the SCT. I have used a slow  (F/8) Newtonian in EP projection mode, and checked that the secondary only ever became lukewarm. Solar Newtonians use a non-silvered mirror which keeps levels safe for the secondary. All other reflectors need a way to keep the light and heat levels low, so Baader film or the like is the only solution. I personally prefer full-aperture filters to sub-aperture.

[SteveBz]

2 minutes ago, michael.h.f.wilkinson said:

The main issue with reflectors is that the build up of heat on the secondary can shatter it, especially with fast primary mirrors, like my F/2 primary in the SCT. I have used a slow  (F/8) Newtonian in EP projection mode, and checked that the secondary only ever became lukewarm. Solar Newtonians use a non-silvered mirror which keeps levels safe for the secondary. All other reflectors need a way to keep the light and heat levels low, so Baader film or the like is the only solution. I personally prefer full-aperture filters to sub-aperture.

Hi Michael,

Nice answer.  Do you have a thermostat on the secondary?  How do you monitor the heat buildup?

I imagined that the full aperture would be nicer, and I'll probably go that way in the fullness of time.  I'm now finding that storage is a major issue with two fully erected Newtonians in the garage and a dish on the lawn, I really need to start pushing in the other direction, unless I'm going to invest in a permanent second residence!!!!

Steve.

[michael.h.f.wilkinson]

33 minutes ago, SteveBz said:

Hi Michael,

Nice answer.  Do you have a thermostat on the secondary?  How do you monitor the heat buildup?

I imagined that the full aperture would be nicer, and I'll probably go that way in the fullness of time.  I'm now finding that storage is a major issue with two fully erected Newtonians in the garage and a dish on the lawn, I really need to start pushing in the other direction, unless I'm going to invest in a permanent second residence!!!!

Steve.

 

The Newtonian I had was a home made 6" F/8 on alt-az mount (we are talking 1979 here), and I just felt the side of the secondary

[xtreemchaos]

 hi Steve, great imfo from Michael, he said it a lot better than i could, and i do prefer full-aperture but with the solar wedge instead of solar film with my fracs.  charl.

[SteveBz]

So, with my Newtonians, Baader film is the only choice?

[michael.h.f.wilkinson]

13 minutes ago, SteveBz said:

So, with my Newtonians, Baader film is the only choice?

That or removing the coatings of the primary to turn them into solar Newtonians

Not a path for the fainthearted