Sun Damaged Scope - Questions

[Novarius]

Before the transit tomorrow (little confused with the dates, assuming we in Europe see it on the 6th?) I decided a trial run of sun projecting was in order with the scope. I found it, rain cloud rolled in (think this was a warning to stop, more later), it eventually passed and the sun was shining once more.

After some faffing around I got the sun, then 15 - 20 seconds later an awful stench of melting plastic filled the air. I think the clouds were warning me lol.

Now, the 'my stupidity' part. I assumed a solar filter was required, ONLY if you intended to look at the sun directly, not if you intended to project it as I was attempting to do. As soon as the smoke was pointed out to me I moved the scope immediately away. I was in the process of changing eyepieces.

Question.

The lens I used was a bog standard came-with-the-scope one, 10mm. The glass itself is slightly cloudy, it stinks and the internal plastic housing is, for the most part, wrecked. It is, 'usable' still. This I know, is easily replaceable.

Now, the focuser was smoking when I noticed it myself after the comment from dad and a friend of "whats burning?", the glass inside is slightly marked, but not as bad as I assumed it would be. Can it be cleaned, or is the entire focuser KIA?

I did test the scope upstairs and visually, the lenses and focuser aren't too bad, sure as hell isn't perfect now but it's not as bad as I feared. If area is cloud free tonight, will be testing properly.

I am quite astonished at just how quickly this occured though. I know magnifying the sun causes heat issues (poor ants) but not in less than 20 seconds. Very valuable and respected lesson was learnt today. Will not happen again.

[jimmyjamjoejoe]

For projection you need to use eyepiece designs that contain no cemented elements, otherwise the cement gets fried and wrecks the eyepiece. Aside from that, a frac should be fine for solar projection so long as the focuser is mounted and aligned properly. What scope were you using?

[Bizibilder]

You have to be really careful! (I "cooked" my new DSLR a couple of weeks ago!!) You may find that the vapour from the melted plastic has fogged your lenses a little. If you are lucky you should still be able to use them for the Sun but you may need to clean or replace them for fainter objects at night. You can get hold of Skywatcher basic eyepieces quite cheaply as many folk upgrade and have them to spare.

[Novarius]

For projection you need to use eyepiece designs that contain no cemented elements, otherwise the cement gets fried and wrecks the eyepiece. Aside from that, a frac should be fine for solar projection so long as the focuser is mounted and aligned properly. What scope were you using?

Celestron Astromaster 114

[LukeSkywatcher]

I cant find many pages online that say a solar filter is needed for the projection method. I'm amazed that your EP got fried. Maybe the focuser was not tightly screwed in and this cause a bit of give and misalignment.

[Adrian]

Two things really:

1) the Astromaster 114 is a reflector. These are not ideal for projection as the sun's heat is focussed onto the secondary which can get hot enough to crack - Refractors are preferred for projection.

2) that scope has a barlow type lens in the focusser in order to give the 1000mm focal length in a shorter tube and it is this which may have been part of what was smoking. If so then the view may be damaged for all eyepieces

[Novarius]

Cheers for the posts thus far people. I am, annoyed with myself but, on the bright side, atleast it wasn't my eyeball.

@Luke - You may be right, looking at the eyepiece the melting has occured only on one side.

[LukeSkywatcher]

Two things really:

1) the Astromaster 114 is a reflector. These are not ideal for projection as the sun's heat is focussed onto the secondary which can get hot enough to crack - Refractors are preferred for projection.

2) that scope has a barlow type lens in the focusser in order to give the 1000mm focal length in a shorter tube and it is this which may have been part of what was smoking. If so then the view may be damaged for all eyepieces

Ahhhhhhhhhhh good points. It makes sense now.

[John]

..... You may be right, looking at the eyepiece the melting has occured only on one side.....

That might mean that your scope is not in accurate collimation, ie: the point of focus is off centre a bit. Rather a drastic way to find that out though

[LukeSkywatcher]

That might mean that your scope is not in accurate collimation, ie: the point of focus is off centre a bit. Rather a drastic way to find that out though

Very true. If the mirrors are out by even a fraction, while observing/projecting the Sun, this could cause the same damage.

I had not considered that.

I suppose the moral of this story is to use a refrac for any solar work if at all possible or a full aperture/off axis solar filter if you are using a reflec.

[Novarius]

That might mean that your scope is not in accurate collimation, ie: the point of focus is off centre a bit. Rather a drastic way to find that out though

Most likely, never done it before, everything seemed fine but, I think it is way off. Are there any budget Collimators out there? Had a look at FLO and there is no way i'm spending £30+ on what is effectively a £5 laser pen with a bit cut out. There has to be a more budget friendly way.

[LukeSkywatcher]

The most important thing is that your eyeball was not on the end of that EP pointed at the Sun.