Thousand Oaks solar filters

[scoobee]

Has anyone tried or still using these filters, would like some advice but mainly are they worth it?

[JamesF]

I don't have one, so don't take my word as gospel by any means, but the impression I have from other people's comments is that they aren't as good as the ones based on Baader solar film and if you want to buy a ready-made one then the Astrozap ones are better.

James

[DrRobin]

Hi,

I have made several filters from one sheet of Baader solar film, all of which worked really well. I haven't tried a pre-made filter as the Baader film is about half the price of a single filter and according to most reports performs better than all but the most expensive glass filters. If you want to see how I made mine, send a message and I will post a few pics.

I had thought about trying the Thousand Oaks Etalon and ERF, for Hydrogen Alpha observing, but have seen mixed reviews. Don't know if anyone has any experience of these?

[scoobee]

thanks for the name drop, from my research a double stack of some Solar Continuum Filters are the ideal set up with the astrozaps was trying to avoid the extra £££££'s

[scoobee]

Robin, thanks for the offer of the homemade one, I all ready have a magazine article dealing with that. H-alpha is the way to go as long as i can save up!!!

[DrRobin]

Hi,

I found the Baader film gave great results very quickly, possibly the easiest imaging I ever did. I bought a second hand PST and through the eyepiece the views are outstanding, but trying to get them recorded on video seems a lot harder. Still we have a lot of hours of daylight at the moment, so plenty of opportunity for practice.

[Peter Drew]

Robin. I had a secondhand Thousand Oaks 125mm ERF, it was rather thin compared to the Baader ERF's but I have to say that I was very pleased with the results in conjunction with a PST mod.

[michael.h.f.wilkinson]

I have an 8" Thousand Oaks solar filter (nickel coated), which gives very good views indeed. I bought it in the days that the alternative was mylar-based, which was not as durable as the current solar films. I have a Baader solar film filter for the kids' 4.5" Dob and it is fine as well. The Thousand Oaks filter delivers a slightly less blueish image, and it is certainly sharp. The main problem with white-light solar observing is that you are often limited by seeing more than anything else. My big C8 delivers images which are not really sharper than those in the little 4.5" (if the latter is properly collimated), under most conditions. Given the current prices, I would go for Baader film every time.

I have found the following confusion in (negative) comments on Thousand Oaks glass filters: Many state that creating an 8" optically flat filter of sufficient quality would be way more expensive than the Thousand Oaks filter, but this is not true. Making the filter is no more expensive than making the corrector plate of my C8 (the latter is aspheric, and arguably more difficult to make). The confusion stems from optical flats which are more difficult to make and way more expensive, because they need to be corrected to 1/50th lambda or better. This is because and optical flat is a flat surface used in interferometric testing to determine the figure of optics. To make this test accurate, the flat must be more accurate than the lens undergoing the test by at least an order of magnitude. By contrast a flat optical surface used for a filter requires 1/6th lambda or better.

Thus Thousand Oaks filters are a lot better than is claimed by some ("just window-pane glass" is a comment I have heard), but Baader film is so much cheaper that I cannot recommend buying such a filter now.

[DrRobin]

Hi Michael,

I wouldn't want to knock anyone's product and your comparison was fair and balanced. If you are looking for the best you can get then a correctly engineered glass filter is going to outperform a floppy sheet of film everytime, but it comes at a price. I think for most, the better performance of the glass filter is probably not realised in most peoples set up and therefore it is very hard to justify the price.

Perhaps if you had a Televue scope and eyepiece or other 'expensive' make then it might make sense to spend more money on the filter, but I wouldn't recommend spending more money on a solar filter than say the cost of the scope or eyepiece.

It's the 80:20 rule, spend 20% of the price and get 80% of the performance. Spend the other 80% of the price to get the extra 20%.

[michael.h.f.wilkinson]

Yep, best quality comes at a price. You have to wonder if even the likes of TeleVue and Questar would really get better results in practice. After all, seeing is the real bugbear here. I have heard that for best performance many people recommend a Herschel wedge (but not for a catadioptric or reflector, unless you want to shatter a secondary mirror!!) which gives excellent results in refractors. These are also expensive however.

[DrRobin]

Hi Michael,

Best quaility.... always does.

Interesting that your kids' 4.5" dob produces almost the same images as your C8. I haven't tried my C11 but made a small aperture filter for my 200mm dob, partly as to have made the whole aperture would have let too much light in for my camera. The pictures are better through the dob than through my ST80, mostly because I have a 10:1 driven focuser on the dob and only the stock manual focuser on the ST80.

The C11 would certainly give higher magnification, so perhaps I will give it a try one day. I think I would again make a small aperture filter, approx 70mm to make sure I don't overload my camera.

[rwilkey]

I have found the Baader solar film quite adequate for the job, I have the ready-made 114mm for my C100ED-R and it is great, perfect for white light, I also use Lumicon filters to colour the image and make it more interesting. You have to go careful with the film though and be extra careful not to damage it.

[michael.h.f.wilkinson]

Hi Michael,

Best quaility.... always does.

Interesting that your kids' 4.5" dob produces almost the same images as your C8. I haven't tried my C11 but made a small aperture filter for my 200mm dob, partly as to have made the whole aperture would have let too much light in for my camera. The pictures are better through the dob than through my ST80, mostly because I have a 10:1 driven focuser on the dob and only the stock manual focuser on the ST80.

The C11 would certainly give higher magnification, so perhaps I will give it a try one day. I think I would again make a small aperture filter, approx 70mm to make sure I don't overload my camera.

The C8 definitely has the edge when seeing is good. However, those occasions are quite rare. I think that if I put both on say Pic du Midi, the C8 would consistently beat the 4.5" by quite a bit. My Thousand Oaks filter does not overload cameras, despite being full aperture. I used 1/125th second exposure time on 100 ASA Fujichrome in the past.

[DirkSteele]

I purchased a Thousand Oaks glass solar filter for my 11" SCT to watch the 2004 Venus transit and was highly impressed. I would not hessitate to recommend one, but as others have pointed out they are quite pricey relative to alternative solutions and I am not sure that it warrants the increased cost under most conditions.

One positive to highlight though is the fit over the telescope gives me confidence that it is not going to fall off which is perhaps more of a risk on a homemade filter using a solar filter material like the Baader.

[scoobee]

To All, thanks for your input in this topic which has been a tremendous help.

Just one more little question, if I go down the route of buying a thousand oak then would a continuum filter be any good or are they used just to enhance white light?

[michael.h.f.wilkinson]

I haven't used the Baader solar continuum filter myself, but I have heard it brings out detail. I know it has been used in conjunction with the Baader Herschel wedge, so I do not see why it shouldn't bring out detail when combined with either solar film or a glass filter.

[scoobee]

Michael, I have seen many good pictures of Baader film and continuum filters either stacked or single use, I think it does bring the pictures alive showing granulation on the surface.

I think I will be going down the road with the Oaks and filters at £207 a tad over the top but a third of the cost of a PST!!!!!

[michael.h.f.wilkinson]

Michael, I have seen many good pictures of Baader film and continuum filters either stacked or single use, I think it does bring the pictures alive showing granulation on the surface.

I think I will be going down the road with the Oaks and filters at £207 a tad over the top but a third of the cost of a PST!!!!!

I might get a Baader continuum filter as well. It should indeed bring out detail. It is not the same as H-alpha viewing however. I was lucky enough to get a Lunt LS35THa for a very reasonable price a few weeks ago. The images are amazing, even with an aperture of only 35mm. White light is still a lot of fun, though.

[scoobee]

depending on how things go next year I am wanting to get a coronado solarmax 60