Solar advice please

[bosun21]

I have never attempted any solar observation before but with the summer months approaching rapidly I feel like it’s the opportune moment to start. I intend to use my Starfield 102 for this and I’m about to pull the trigger on a Starfield wedge. Do I need any additional equipment like filters etc before I can begin observing? I thought about making a filter from Baader solar film to begin with, but I may as well take the step I would inevitably make anyway and buy a wedge. I just want to ensure that I do it safely and properly from the beginning. Any advice and tips would be very much appreciated. Thanks.

[inFINNity Deck]

A Baader foil filter is one of the cheapest ways to start observing, but please mind you that you use the right type of foil. These foils can be bought at varying Neutral Densities, most common are ND5.0 and ND3.8. The figure tells you how much light is blocked ND5.0 means 1/10^5 = 0.00001 = 0.001% of the incoming light is being transmitted to your eye. At ND3.8 this is 1/10^3.8 = 1/6310 = 0.00016 = 0.016%, so 16 times as much as the ND5.0 foil. The ND3.8 foil therefore is not safe for visual observation, only for imaging.

A Herschel Wedge has a glass wedge and internal filters that take care of the transmission. Wedges too come at varying transmission types: there are photographic and visual wedges. The Starfield Wedge appears to combine the two. They state that it is safe for observing (we need to presume that that is visual observing) and it can be used for imaging. The amount of light can be regulated by its internal double polarizing filter, which (partially) blocks incoming light. Baader too sells a very nice wedge.

By far the cheapest solution to observe the Sun is by projection on a white surface or (even safer) by using a Solar funnel (but the view will be less detailed): https://eclipse2017.nasa.gov/make-sun-funnel

Using above methods you should be able to see sunspots, pores and granulation. If you want to see prominences and surface detail you would need a H-alpha filter like a DayStar Quark or a dedicated Solar Scope like those from Lunt or Coronado.

Nicolàs

[JOC]

@bosun21 You might find useful this thread which shows how many of SGL have made filters from Baaders solar film 

 

[Franklin]

Most solar wedges come with a factory fitted ND3.0 filter which makes the whole thing safe. But it will still be rather bright so most people fit a single polarizing filter to the eyepiece when viewing and with that you can tune in the light intensity by rotating the eyepiece/polarizing filter combo. Baader do a solar continuum filter which is very good with a wedge, it helps increase contrast but does turn the Sun green.

[JOC]

There are details of the Baader film that a lot of people use here:

 

[apaulo]

i use thousand oaks foil, i think the main difference between thuousand oaks and baader foil is, oaks gives you a yellow sun, and baader a white sun, so its purely a choice of what colour you want the sun. i think performance ways they are both very similar. 

[bosun21]

17 minutes ago, Franklin said:

Most solar wedges come with a factory fitted ND3.0 filter which makes the whole thing safe. But it will still be rather bright so most people fit a single polarizing filter to the eyepiece when viewing and with that you can tune in the light intensity by rotating the eyepiece/polarizing filter combo. Baader do a solar continuum filter which is very good with a wedge, it helps increase contrast but does turn the Sun green.

I’m going for a wedge over the foil as I’m led to believe that it has better contrast at higher magnification. When you say a single polarizing filter that can be rotated on the eyepiece does that work due to the prism polarizing the sunlight before it reaches the second installed filter? This is all new to me.

[inFINNity Deck]

The polarizing filters usually come as a set of two: one is fixated in the diagonal or wedge, the other fixated to the eyepiece. By rotating the eyepiece along the optical axis, the combined action of the two filters darkens/lightens the view.

I use a set like that when observing the Sun with my C11 EdgeHD in combination with ND5.0 foil as I still find the resulting view somewhat on the bright side.

Nicolàs

[Franklin]

The light from the wedge is already polarized so you just need a single polarizing filter on the eyepiece. A variable polarizing filter is used when a full aperture solar film/glass filter is used. Some people also fit a UV/IR cut filter just to be on the safe side but a wedge with internal ND3 is certified safe, just too bright and this is why you would use either alone or together a polarizing filter and solar continuum filter (a green filter is a cheaper option). If imaging through a wedge then a UV/IR cut is needed as cameras are more sensitive to IR.

[Alan White]

I use a Lunt 1.25 wedge at present,
I moved to this from Baader Film a good few years ago, no regrets other than I should have bought the 2" one at the time.

Filter wise, single Polariser (Baader) and a Solar Continuum Filter (Baader) which gives better detail /contrast and does indeed turn the sun green.
But after years of using this, the sun goes yellow in my brain, even though for 20 seconds or so its clearly not, it shows as a vivid green.

 

Edited April 25, 2023 by Alan White

[Franklin]

20 minutes ago, bosun21 said:

When you say a single polarizing filter that can be rotated on the eyepiece does that work due to the prism polarizing the sunlight before it reaches the second installed filter?

correct

[Carbon Brush]

Another vote for the wedge - not film.

I use a Lacerta Wedge. Unlike others, these are a 'Brewster' Angle. This means the light is strongly polarised.
I can then use a single polarising filter for extreme brightness control.

If you read the Lacerta hype, you wonder why others don't do this.
I have asked retailers about 90deg vs Brewster - and asked someone giving a talk at PAS. But nobody has the answers.
All I can say is that I have been happy with the Lacerta/Brewster. But have not done side by side with others.

Another useful filter is a solar continuum.
This dims the image a little if you have a 'too bright' wedge. Importantly you start to see the granulation.

Choosing a 'too bright for visual' wedge is a good idea.
If imaging you can use a fast shutter to freeze the turbulence.
Dimming an image for eyeball comfort is easy with a polarising, or further ND, or continuum filter.

If you go for a 2" wedge, think about light path. It is something like 115mm.
You can run out of focus on some scopes.

HTH, David.

 

[bosun21]

1 hour ago, Carbon Brush said:

 

If you go for a 2" wedge, think about light path. It is something like 115mm.
You can run out of focus on some scopes.

I am definitely going for a 2” wedge and will be buying it from FLO so I can always return it if it’s unsuitable. I think it will be fine on the Starfield 102 as I use a 2” WO diagonal for nighttime viewing and there’s quite a bit of inward travel left on the focuser. I may make a post asking other owners with Starfields who use a wedge.

[Stu]

I think most info has been covered already, but for clarity the Wedge MUST have an ND3.0 fitted for safety, and also one of either a polarising filter or something like a Continuum filter to reduce the brightness to a comfortable level. In my CoolWedge I use a Continuum, and as Alan says, you quickly forget that the Sun is green! I will be moving to a Mark II CoolWedge which will allow me to add a single polariser too, giving me brightness control when I use binoviewers.

Regarding the Lacerta Wedges, they do get good reports, although personally I prefer a 90 degree angle as I find it easier to view, particularly when the sun is up high.

I’m sure the Starfield will work very well for you. I would certainly try a Continuum if funds allow, and the polariser is a good option too. The views through a good 4” and wedge can be pretty stunning when conditions are favourable, and don’t be afraid to use high power (x100 to x200) when the seeing is good, and you will really see the detail pop out!

[bosun21]

5 minutes ago, Stu said:

I will be moving to a Mark II CoolWedge which will allow me to add a single polariser too, giving me brightness control when I use binoviewers.

I was also looking at the CoolWedge II as well as the Starfield wedge but the back order time is quite long for the CoolWedge II with FLO. Would I be able to use a single polarizing filter along with a continuum with the Starfield wedge?

[Nik271]

You could stack the continuum and the polarising filter if at least one of them is threaded on both ends. Btw an OIII filter is very close in performance to a continuum one.

For me the main advantage of the wedge over the film is not the resolution but the fact that the wedge is about 2 times brighter, so it allows more magnifiication with binoviewers.

[Stu]

1 hour ago, bosun21 said:

I was also looking at the CoolWedge II as well as the Starfield wedge but the back order time is quite long for the CoolWedge II with FLO. Would I be able to use a single polarizing filter along with a continuum with the Starfield wedge?

You can add the polarising filter to the bottom of your eyepiece and then you can rotate the eyepiece to tune the brightness. Not sure where the Continuum goes on these so I’ll leave that to someone else to answer.

Yes, I’m hoping the lead time isn’t too bad, although I do still have my Mark I until the II arrives!

[Carbon Brush]

Any filter is fitted after the wedge. That way it only has to deal with a tiny fraction of the suns energy.
The ND filter is immediately after the wedge. In some wedges (including Lacerta 2") it is impossible to remove without dismantling the wedge - a safety feature.
After that, it doesn't matter about order of filters. Unless someone knows otherwise?

HTH, David.

[Stu]

59 minutes ago, Carbon Brush said:

Any filter is fitted after the wedge. That way it only has to deal with a tiny fraction of the suns energy.
The ND filter is immediately after the wedge. In some wedges (including Lacerta 2") it is impossible to remove without dismantling the wedge - a safety feature.
After that, it doesn't matter about order of filters. Unless someone knows otherwise?

HTH, David.

Baader info says Continuum immediately after the wedge, then ND3.0 then polarising filter. I think this reduces reflections from the Continuum.