Sun viewing ?

[Dazraz]

Hi watched a episode of sky at night today and the bloke on there was saying that a reflector telescope is no good to observe the sun - is this true i have a 8" dob ?

[RichieP]

No, he was just referring to the eyepiece projection method, which would focus the Sun's full power on the secondary and would break it.

It's fine to use a full aperture filter with a reflector, which will stop 99% of the Sun's light from entering the scope in the first place.

Regards

Richard

[LukeSkywatcher]

I have read the same. I think its something to do with the material the optical tube on reflectors is made of. There is a lot more plastic involved in the reflectors while refractor tubes are mostly metal. Apparently reflectors allow more heat to build up inside the tube because they use mirrors instead of glass lenses and can melt bits of the inside of the tube.

I'm not saying it will happen................just it can happen. I've seen plenty of images online of people using reflectors to observe the sun.

Personally i'd be afraid of the primary or secondary cracking. I wonder how often that happens. I know BadderAstroSolar film blocks 99.999% of the suns light from entering the scope. I have not read anything about it blockling heat. But i guess if you block that much light that you are also blocking the same amount of heat?

I'm thinking about making a solar filter for my reflector but i'm too chicken to do it. I have one made for my refractor.

[brianb]

I know BadderAstroSolar film blocks 99.999% of the suns light from entering the scope. I have not read anything about it blockling heat.

The stuff is rather better at blocking or reflecting infra red (heat) and ultra violet than it is in the visible range. If it wasn't at least as effective it wouldn't be safe to use visually.

If a solar filter is installed at the objective end of the scope, there is no heating at all inside the tube, and the sun isn't shining on the outside walls of the tube either. No problem with any design of scope. But do NOT use any type of scope other than a small refractor for projection work ... and only then if you have brass & glass eyepieces (no plastic, no cemented components).

[LukeSkywatcher]

The stuff is rather better at blocking or reflecting infra red (heat) and ultra violet than it is in the visible range. If it wasn't at least as effective it wouldn't be safe to use visually.

If a solar filter is installed at the objective end of the scope, there is no heating at all inside the tube, and the sun isn't shining on the outside walls of the tube either. No problem with any design of scope. But do NOT use any type of scope other than a small refractor for projection work ... and only then if you have brass & glass eyepieces (no plastic, no cemented components).

Thanks for clearing that up Brian. So the Badder film DOES block the heat also, so is perfectly safe to use with reflectors?

Regarding solar observing with refractor:..............ok the lenses in most EPs are glass but the casing is usually plastic or aluminium. I dont think i have ever seen an EP with brass casing................unless the EP is about 100 yrs old and a bit of an antique.

I have used my Celestron 90EQ and supplied EPs to observe the sun. The casing on the Celestron EPs is certainly not brass.

[brianb]

Yes, Baader solar film is perfectly safe to use with reflectors ... assuming it's not pierced or torn, the filter mount is securely fixed so it won't blow off whilst in use, etc, etc.

Metal eyepiece casings ought to be OK but almost all EPs made in the last 40 years contain cemented lenses - the cement will melt if such an EP is used for projection with a good chance that it will be ruined - I wrecked a Kellner using it for projection with a 60mm refractor. No problems using modern eyepieces with solar film.