Sun Filter for 100mm dobsonian

[Mr__W1zz4rd]

Hell all

Firstly I would like to apologise if my question is in the wrong forum. I have a 100mm dobsonian telescope and was wondering if it was passable to fit a sun filter on it to view sunspots and taking photos of the sun.

If so can anyone recomend a filter and where to get them from.

Thanks

James

[laudropb]

What ever you do do not purchase a cheap eye piece filter. They are extremely dangerous. You can purchase safe solar filters from the site sponsors, FLO. Just click on the heading at the top of this page. Also remember to remove any optical finder scope before viewing the Sun to prevent any accidents. Safety has to be your first concern when viewing the Sun.

[Mr__W1zz4rd]

Thank you for the info Laudropb. I have done some solar photography in the past with my Canon 7D and 300mm f4 L lens with filters but wasn't sure where to buy a safe and recomended filter.

[Steve Ward]

Any made from Baader ND5.0 Solar Film is what you need , there are other types available but non come close to the Baader in terms of detail achievable ... 

Either a suitably sized ready made filter like this ... http://www.firstlightoptics.com/solar-filters/astrozap-baader-solar-filter.html

[Steve Ward]

Or if you are handy in the 'Blue Peter' sense you can make your own with an A4 sheet of the film ... http://www.firstlightoptics.com/solar-filters/baader-astrosolar-safety-film-nd-50.html

For some reason the link to the film does not work but you'll find it under Solar filters on the FLO site ... http://www.firstlightoptics.com/solar-filters.html

[Mr__W1zz4rd]

Thanks Steve. I love a bit of Blue Petering so I think I will try and make my own. I will design is so I can fit it to my 100mm dobsonian telescope and possibly a step down cone to 77mm for my Canon 300mm f4 L lense as I only have a cheap filter currently for my lense.

Other that the safety implications and the filter is there anything else I should consider before proceeding with this?

Not sure if this is a stupid question or not but here gose!

Is there a best time of day light hour to view the sun? Dusk, Dawn, Noon etc.. Would the amount of atmosphere the light passes through at Dawn and Dusk have a negative affect on the clarity.

[Dave In Vermont]

The light/image of anything & everything up there will usually look clearer when it's as high up in the sky as possible. This is because the image is traversing through less of the atmosphere. So yes - you will likely get a cleaner view at high noon then when the Sun is just rising, or setting.

There's a filter you may be interested in learning about. It's from Baader Planetarium in Germany, and is the Solar-Continuum Filter. There's a thread on it here:

http://stargazerslounge.com/topic/150905-baader-solar-continuum-filter-review/

It can help tease out better views of the granulation on the solar surface when used with a foil-filter such as what you're planning on making. It also turns the Sun bright green in the bargain. It took me awhile to get used to that!

Enjoy -

Dave

[Mr__W1zz4rd]

That you all for your info on this topic. Im thinking of getting a Baader 81-113 adjustable solar cap for my 100mm dob and make a step down cone to 77mm for my 300mm f4 L canon lense.

The light/image of anything & everything up there will usually look clearer when it's as high up in the sky as possible. This is because the image is traversing through less of the atmosphere. So yes - you will likely get a cleaner view at high noon then when the Sun is just rising, or setting.

There's a filter you may be interested in learning about. It's from Baader Planetarium in Germany, and is the Solar-Continuum Filter. There's a thread on it here:

 Dave i have been reading up on this type of filter and it looks fantastic so i will be looking at getting one of these also in the new year, thank you for your reply.

[DRT]

Hi James,

Is your Dob the solid tube or open truss type? Just checking as it is a bad idea to view the Sun through a truss Dob as the Sunlight can strike the mirror through the open sides and cause all sorts of damage to you and your scope.

Also worth noting that you don't need much aperture to view the Sun as there is so much light to play with. When viewing through my Explorer 200P I keep the front dust cap on the tube and just remove the small 2" cap with the small hole covered with Baader film. If the dust cap on your Dob has a similar small cap you could do the same.

Good luck and stay safe

Derek

[Mr__W1zz4rd]

Hi James,

Is your Dob the solid tube or open truss type? Just checking as it is a bad idea to view the Sun through a truss Dob as the Sunlight can strike the mirror through the open sides and cause all sorts of damage to you and your scope.

Also worth noting that you don't need much aperture to view the Sun as there is so much light to play with. When viewing through my Explorer 200P I keep the front dust cap on the tube and just remove the small 2" cap with the small hole covered with Baader film. If the dust cap on your Dob has a similar small cap you could do the same.

Good luck and stay safe

Derek

Hi  Derek

It is a solid tube, i have the Sky-Watcher HERITAGE 100P table top Dob. Yes mine has a removable 2" cap as well so i will look into doing that. Thank you.

[Steve Ward]

The light/image of anything & everything up there will usually look clearer when it's as high up in the sky as possible. This is because the image is traversing through less of the atmosphere. So yes - you will likely get a cleaner view at high noon then when the Sun is just rising, or setting.

In theory yes ... unfortunately when applied to Solar viewing/imaging the theory tends to fall apart somewhat ... 

By the time midday arrives the Sun has had a good few hours to heat up the ground surrounding you , especially tarmac , concrete , metalwork , rooftops etc , etc ... all these things will radiate heat and create their own 'low level' plumes of rising warm air , and if they happen to be between you and the target the effect can be disastrous regarding 'seeing' ... 

Generally a sweetspot can be found early to mid-morning , after the Sun's reached a reasonable altitude and before things get too hot .

In all honesty I would not get too bogged down with trying to view at a particular time , you will very quickly come to realise that Solar work can be as frustrating as nighttime astronomy as far as working round the weather is concerned ... you will generally find yourself viewing as and when a break in the grey blanket allows , regardless of time of day ... 

Best bet is to have your Solar rig all set up as a "grab 'n' go" unit ready to deploy at a moment's notice and a keen eye on the weather ... a lot of time you will only get a five minute patch of blue sky to play in ... 

[DRT]

James,

The easiest way to cover the 2" hole it to cut a 3" square of the Baader film and tape it over the hole on the inside surface of the dust cap. You can then just remove the 2" cap when you want to use it

Be sure to use strong tape. Electrical insulation tape works well.

Derek

[Mr__W1zz4rd]

Thanks Derek will do. 

[ArmyAirForce]

I made a ply disc for the baader film for my 80ED scope. I use two strips of Velcro to attach it securely to the end of the tube. Like night time viewing, the smaller the aperture, the less detail you will see, so I would go for a full aperture filter, not just the 2 inch cap.

[ArmyAirForce]

If you want to add a DSLR, video mode is the better way to get a solar image than a single shot. With a non-tracking mount like a dob, try aligning the width of the sensor to the diagonal path of the Sun as it climbs across the sky. This will keep the Sun on the sensor as long as possible, allowing a good number of video frames to be captured. The best percentage of these can then be stacked in Autostakkert or Registax to give a single tiff for final processing.

I use my 600mm focal length Evo 80ED, with a x2 teleconverter, giving a 1200mm focal length. On a non-tracking mount, I can get about 2 minutes of DSLR video as the Sun moves across the sensor.

[Dave In Vermont]

Speaking of our local star - a large sunspot has erupted, sending an M-class solar-flare in our direction. The upshot of this is a 60% chance of auroral-activity. For further information:

http://www.spaceweather.com/

And:

http://www.softservenews.com/

As well as:

http://www.aurora-service.eu/aurora-forecast/

'ta,

Dave

[DRT]

Like night time viewing, the smaller the aperture, the less detail you will see, so I would go for a full aperture filter, not just the 2 inch cap.

I don't disagree, Stephen, but with the scope (and presumably standard Plossl eyepieces)  that James has the difference will be almost undetectable. The 2" cap solution is an extremely cheap, easy, fast and safe way to get your first view of the Sun, which is why I suggested it.

[ArmyAirForce]

Probably yes for visual, but the original poster also mentioned taking photos.

[niallk]

James,

The easiest way to cover the 2" hole it to cut a 3" square of the Baader film and tape it over the hole on the inside surface of the dust cap. You can then just remove the 2" cap when you want to use it

Be sure to use strong tape. Electrical insulation tape works well.

Derek

+1 works well on my 10" - very handy for protecting the film when not being used. Will someday make a larger mask, but I enjoy high mag views with even just this 2" aperture. Always inspect before use and check that it is stuck securely

Yep - that's a Rice Crispies box cell...

[Mr__W1zz4rd]

Thank you all for you input. i am looking forward to having a play with my filter.