Solar viewing - what is there to be seen?

[KeithB]

Hi,

I have made a solar filter using Baader film.

This is relatively small, just fitting the offset 58mm hole that is in my Dob's lens cap.

With the filter firmly attached and the lens cap taped on, I've got some good views of sun spots.

Is there any more that can be seen with this sort of setup? E.g. Solar eruptions/flares.

Is there any advantage to a filter that is the full diameter of the scope(10")?

Any more things I could look for?

Thanks in anticipation.

[Naemeth]

Hi,

I have made a solar filter using Baader film.

This is relatively small, just fitting the offset 58mm hole that is in my Dob's lens cap.

With the filter firmly attached and the lens cap taped on, I've got some good views of sun spots.

Is there any more that can be seen with this sort of setup? E.g. Solar eruptions/flares.

Is there any advantage to a filter that is the full diameter of the scope(10")?

Any more things I could look for?

Thanks in anticipation.

I've got a full aperture filter for my scope, and sunspots are definitely visible, but it's not enough aperture to get granulation on the surface. I should think a 10" full aperture filter should start to show granulation on the surface, for anything else though you'll probably need a solar scope.

HTH

[KeithB]

As I bought a single A4 sheet of the film, I don't actually have enough to make a filter for the whole aperture, but I might make one about 8" diameter and see if it helps.

[Freddie]

Sun spots and some surface detail but you would need a Ha filter for anything else.

Be VERY careful, sensible idea to tape the cap on, you may also want to take the finder off (if fitted) just in case you go to look through it without thinking.

[KeithB]

I leave the caps on the finder to avoid that very problem. I find I can line the scope up quite well using its shadow.

[KeithB]

Sun spots and some surface detail but you would need a Ha filter for anything else.

What is an Ha filter and would it work with the setup I have?

[KeithB]

Hydrogen alpha filters just transmit light produced in a very narrow band by excited Hydrogen atoms - the sun is mostly hydrogen. Not a cheap thing that you can easily add on. The cheapest way to view in H-alpha is to buy a Coronado PST - personal solar telescope. You can see sunspots, flares, prominences and the granular surface. A popular tool in the summer - when northern nights are short - and of course totally immine to light pollution.

Sounds like something to add to the endless list wishlist.

The other advantage to solar viewing seems to be the temperature. It's a lot warmer!

[mullac2001]

http://www.wexphotographic.com/buy-coronado-personal-solar-telescope/p1528002?cm_mmc=googlebase-extension-_-telescopes-_-solar-telescopes-_-coronado-personal-solar-telescope_1528002&utm_source=googlebase-extension&gclid=ckgwuatagbycfw_ktaodmlaa3q

[KeithB]

The PST seems to have a tiny aperture, 40mm.

is aperture almost irrelevant, because there is so much light from the sun?

[Naemeth]

The PST seems to have a tiny aperture, 40mm.

is aperture almost irrelevant, because there is so much light from the sun?

It's not irrelevant, there is just a lot of light in hydrogen there. Large solar scopes are immensely expensive, but offer a lot more resolution and detail.

[RichieP]

I would disagree that you need large apertures to see surface granulation in white light solar observing,

I use a full aperture filter on my SW127 and, given good seeing conditions, can make out some granulation on the surface, as well as the umbra/penumbra structure of sunspots.

Richard

[RichieP]

It's not irrelevant, there is just a lot of light in hydrogen there. Large solar scopes are immensely expensive, but offer a lot more resolution and detail.

Very true. People sometimes forget that aperture gives you resolution and well as light gathering ability (it's why I would always use a full aperture filter). The PST is 40mm because that's about as much Ha aperture as you can get in an affordable scope (if you count 500 quid as being affordable). Bigger solar scopes cost many thousands.

[Naemeth]

Very true. People sometimes forget that aperture gives you resolution and well as light gathering ability (it's why I would always use a full aperture filter). The PST is 40mm because that's about as much Ha aperture as you can get in an affordable scope (if you count 500 quid as being affordable). Bigger solar scopes cost many thousands.

Although a "regular" scope can be made into a solar scope with the right blocking filters, it does require a lot of DIY and you need to be precise about it, it is much cheaper, but personally I wouldn't trust myself to do it , I'd rather take it to a specialist or someone very knowledgeable on here, Peter Drew knows a lot about this sort of stuff .

White light is certainly the cheapest, but certainly try and make a full aperture filter, maybe even buying more than one sheet, FLO should be able to advise whether you would be able to combine two sheets, but I'm sure you could if you were careful .

[Stargazer_00]

A dedicated solar scope is a true luxury

[nytecam]

The PST seems to have a tiny aperture, 40mm. is aperture almost irrelevant, because there is so much light from the sun?

40mm via PST is adequate for solar Ha [red] and CaK [blue] light - some of my old shots mainly proms @ http://home.freeuk.com/m.gavin/pstmg.htm Sorry some links broken - have fun

[Stu]

I think in general there's not too much to be gained by going over around 150mm aperture. The theoretical gains in resolution tend to be outweighed by tube currents and seeing limitations because of the heat during the day.

I have a PST and think it is great. Plenty of detail to be seen and I love seeing the prominences which often change very rapidly. I would love to do a PST mod with an 80 or 100mm scope some day.

With white light solar, I think with an optimum aperture you should be able to see surface granulation. The Baader solar continuum filter can help with this, though I think you probably need more than the 80mm aperture I tried with.

Stu

[RichieP]

I use the Baader Solar Continuum filter. It does help with seeing granulation, but isn't strictly necessary. It also has the nasty habit of reflecting stray light entering the eyepiece fron behind, so I get to see a reflection of my iris! An observation hood (or in my case a tea towel) cuts down on this.

Richard

[nephilim]

Although a "regular" scope can be made into a solar scope with the right blocking filters, it does require a lot of DIY and you need to be precise about it, it is much cheaper, but personally I wouldn't trust myself to do it , I'd rather take it to a specialist or someone very knowledgeable on here, Peter Drew knows a lot about this sort of stuff .

White light is certainly the cheapest, but certainly try and make a full aperture filter, maybe even buying more than one sheet, FLO should be able to advise whether you would be able to combine two sheets, but I'm sure you could if you were careful .

You can buy the film 'off the roll' from Baader.

[KeithB]

White light is certainly the cheapest, but certainly try and make a full aperture filter, maybe even buying more than one sheet, FLO should be able to advise whether you would be able to combine two sheets, but I'm sure you could if you were careful .

Thanks to everyone for all the useful information.

As a next step, I think I'll try to make as big a filter as possible from the rest of the A4 sheet of film. About 8" diameter.

incidentally, am right in thinking that it doesn't have to be round?

Could I put a rectangular hole in a circular piece of card and still get good images?

[Naemeth]

Thanks to everyone for all the useful information.

As a next step, I think I'll try to make as big a filter as possible from the rest of the A4 sheet of film. About 8" diameter.

incidentally, am right in thinking that it doesn't have to be round?

Could I put a rectangular hole in a circular piece of card and still get good images?

You should be able to , as long as it covers all 8".

[Stu]

Stick to a round aperture otherwise you might introduce some nasty diffraction effects in the image.

Just to cover off an earlier comment, I certainly wouldn't attempt to join together two sheet to make a larger filter - no need and far too risky.

On good, steady days the 8" may give better results but I suspect the stopped down one will perform better more of the time. I assume it is positioned between the vanes of the secondary spider?

Have fun with it, when the sun eventually shines!

Stu

[Bizibilder]

I would recommend making your filter about 4" (100mm) diameter and putting the filter offset so the light can pass between the supports of your secondary mirror (thus eliminating diffraction spikes). As said above there is little to be gained with apartures over about 4" as it is the atmosphere that limits resolution rather than your optics. With a Baader filter in place you can see sunspots, surface granulation and faculae (bright ribbin like features associated with spot groups). Not bad for a £20 sheet of film.

Forget Ha filters. You will need a Ha telescope to see prominances etc and these start at £599 with the Coronado PST and then leap to the £1500-2000 and beyond for anything bigger!

By the way - NEVER try to join two pieces of filter sheet. You can buy 50cm wide sheet from Baader if you really need to - but it costs about £50 and really is unnecessary.

[KeithB]

I would recommend making your filter about 4" (100mm) diameter and putting the filter offset so the light can pass between the supports of your secondary mirror (thus eliminating diffraction spikes). As said above there is little to be gained with apartures over about 4" as it is the atmosphere that limits resolution rather than your optics. With a Baader filter in place you can see sunspots, surface granulation and faculae (bright ribbin like features associated with spot groups). Not bad for a £20 sheet of film.

Forget Ha filters. You will need a Ha telescope to see prominances etc and these start at £599 with the Coronado PST and then leap to the £1500-2000 and beyond for anything bigger!

By the way - NEVER try to join two pieces of filter sheet. You can buy 50cm wide sheet from Baader if you really need to - but it costs about £50 and really is unnecessary.

Following your advice I've now made myself a larger filter.

Using corrugated car , I made two circles with a 110mm diameter hole offset to one side. This was close to the largest that would fit between the mirror supports. The film is sandwiched between them and they are attached to a card ring which fits around the full aperture.

Following all this work I am anticipating cloudy days (and nights) for the foreseeable future!

P.S. I still haven't managed to see comet Panastarrs, because of cloudy weather.

[KeithB]

Sunny day today, so I got to try out the solar filter.

I've attached a picture of the filter on my scope.

I only managed to see a few sunspots, but the seeing wasn't superb.

Hints of granulation seemed to be there. Either that or I have an over active imagination!

(Picture is upside down for some reason)