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Old 28-03-2014, 09:33 PM
AstroTom (Tom)
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Solar Viewing and Heat Effects on Telescope

Hi Everyone,

I have just joined this forum and thought it would be good to get some of my questions answered by other fellow astronomy enthusiasts. I have been interested in astronomy for nearly 20 years and have had many telescopes. At present I own a Celestron CPC 800 SCT telescope with equatorial wedge. I have recently started in the field of astrophotography too.

Anyway I have recently bought an Orion solar filter that covers the front of my SCT telescope and have the hydrogen alpha filters for the eye piece as well. I live in Brisbane, Australia and during the summer it gets pretty hot here. I was wondering whether having the telescope pointing at the sun for a long period of time with all filters on may cause damage to the telescope due to the telescope heating up. I am thinking about the expansion of the metal casing and the mirrors. At present I am thinking of doing the solar viewing earlier in the morning before the sun gets strong and also during the winter months. My primary use for the telescope if for the night viewing and I don't want to damage the telescope just on the sun. I may be worrying a bit too much on this but I am as structural engineer and I have to consider thermal effects a lot on the different structures I design.

Anyway I'm interested if anyone has any comments on the above.

Regards,

Tom
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Old 28-03-2014, 11:14 PM
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alocky (Andrew lockwood)
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The front solar filter will reject enough heat for you to safely use the scope outside all day. The drive electronics might not appreciate a lot of direct sunlight though -I cover mine and the camera with alfoil to shade them.
Sadly, unless your h-alpha filter is a solar observing one with a passband less than .7 angstrom, it will not do a lot for solar viewing, and should certainly not be used without the front filter. These filters are not something that can be screwed onto an eyepiece.
Cheers,
Andrew.
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Old 29-03-2014, 05:51 AM
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Merlin66 (Ken)
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Tom, welcome on board!
As Andrew has said, using a white light filter up front will protect the optics and is 100% safe.
Adding filters just improves contrast but will not show the Ha proms or detail.
I also use the alifoil wrap when using for extended periods.
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Old 29-03-2014, 07:23 AM
glend (Glen)
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Yes Tom please take that advice as solar observation can be dangerous. Whether a glass Orion or Baader Safety Film filter they pass white light and not the wavelengths that would allow the H-a to be visible, for that you need a dedicated solar scope like a Lunt that has optics designed for that purpose. Your eyepiece filter might be useful for viewing the horsehead nebula but it will not enhance solar viewing. With your solar filter you will be able to see the sunspots and potentially some of the granularity detail but not flares or prominances.
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Old 29-03-2014, 09:59 AM
Dennis
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I live in Brisbane and usually set up around 8:30am and can often run through to maybe 11:00am if the seeing is good. I use a full aperture Baader Astro Solar Film filter on the front of my Mewlon 180 F12 with the ZWO ASI120MM CCD camera.

With the filtered OTA pointing at the Sun and the telescope mount tracking, the OTA body is shaded, as is the focuser and CCD camera by the shadow of the filter on front of the OTA.

I sometimes put a Telegizmo tripod/mount cover over the tripod and mount for extended sessions, just to keep the mount cool, especially when it can get into the mid-30’s in Brisbane.

Cheers

Dennis
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Old 29-03-2014, 07:32 PM
AstroTom (Tom)
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Hi Everyone,

Thanks very much for the information and advice. It sounds like I need the dedicated solar telescopes for getting the more detailed images of the sun. But to be honest the solar equipment I have is more of a in the side activity that allows me to do some observing through the day.

I will look into wrapping the tube in the alifoil wrap when I do get the telescope pointing on the sun.

Thanks all again for the information,

Tom
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