7 February 2013 at 8:41 pm #573239
Posted by A R Pratt at 20:41 on 2013 Feb 07
Sir Patrick was always very cautious when discussing solar observing and he had one piece of advice for beginners – Never look at the Sun through a telescope!He would have been dismayed to see the solar filter (a thin sandwich of mylar and cardboard) loosely placed and lying barely inside the dew shield of a refractor! Just waiting for a gust of wind to displace it – then the observer would ask his friends to guide him to the nearest A&E Department.Solar projection with a small refractor is a safer option for beginners.If you use a solar filter make sure that it is securely fixed over the front of your ‘scope. Fiddling with ‘Blue Peter’ sellotape is not a method I would recommend.Please, never take any risks with your precious eyesight.
Attachments:11 February 2013 at 9:30 am #576209
Posted by Marlyn Smith at 09:30 on 2013 Feb 11
Of course you are quite right with your warning that the Sun should be treated with respect and any method of observation should be well checked out and made completely safe.I watched the programme and thought the presenters did emphasise the dangers. Many solar observers use a mylar/cardboard type filter (including myself on occasions) as it’s the cheapest method for direct solar viewing. A good fit is essential and the filter should not be loose or "flapping about". The presenters commented on wind blowing the filter loose and suggested sellotaping the filter to the telescope tube as a precaution. I thought this was entirely sensible as the filter is light and any additonal method of securing it to the telescope would enhance safety. I didn’t get the impression of a "Blue Peter" type fix!Solar projection is a very safe method for solar observation but of course the observer still has to "find" the Sun safely. During projection, the telescope is NOT "safe" and there is always the risk that someone will try to look through the eyepiece. At least with a filter in place, this danger is eliminated. Solar observing is a very rewarding aspect of astronomy but the observer must be aware of the dangers and take proper precautions. I wouldn’t recommend any method of solar observation as safer than any other and I have no criticism of the Sky at Night team.12 February 2013 at 11:31 am #576214
Posted by A R Pratt at 11:31 on 2013 Feb 12
Hi Marlyn,Yes, I agree that the presenters stressed the dangers of solar observing. Unfortunately, the programme didn’t discuss the pros and cons of solar projection, which was the only method available to me in the 1960s and ’70s, when my mentor was Harold Hill. Since then I have made – and purchased – a number of solar filters.I was concerned that a member of the Flamsteed Society used a home-made mylar filter that was loosely seated inside the rim of the dew shield of his refractor. We didn’t see the filter secured in place.A few years ago a member of a local astronomical society mentioned that he’d made a solar filter for his 20cm SCT, but it gave very dim and blurred images of the Sun. I inspected his mylar filter, which was well made and was tightly secured over the front of his ‘scope. Then I noticed his design flaw – the mylar aperture was in the centre of his cardboard disc, sitting precisely in front of the secondary mirror obstruction! No wonder he couldn’t see the Sun through it. :-)Clear skies, Alex.
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