Using a 10” dob for Solar

[Littleguy80]

On telling my wife that I’d read that with some solar film my 10” dob can be used for solar observing, she suggested this as a possible Christmas gift. I have two questions. Firstly, is this a good option for solar? I’m thinking about getting a little frac, probably next year, as a travel scope. Would this be a more suitable candidate? Secondly, if the dob is good for a bit of solar, what do I need to get? 

Many thanks!

[Zakalwe]

Solar film would be grand.

Is your dob a truss design? If so, be very careful as the sun can catch the exposed mirror and the focused light will do a LOT of damage very, very quickly. If it's a solid tube and you'll be fine.

[Littleguy80]

1 minute ago, Zakalwe said:

Solar film would be grand.

Is your dob a truss design? If so, be very careful as the sun can catch the exposed mirror and the focused light will do a LOT of damage very, very quickly. If it's a solid tube and you'll be fine.

Thank you. It is solid tube so all good  

[Peter Drew]

If, as is most likely with a 10", you would be using an off axis mask, the aperture you would be using would probably be around 4". It could be argued that a similar size refractor would be more convenient to use and even be travel suitable.       ?

[Victor Boesen]

I've had the same dilemma myself and come to the conclusion that I will wait until I get a small travel refractor.. not because it isn't possible, but simply because I don't think I'll use it enough..

[cloudsweeper]

Baader film in some suitable home-made housing is easily done Neil.  Might be simpler to do it for the smaller opening.  Also - I got a Solar Continuum Filter - it shows better detail with the sunspots.

Here's the solar filter I made for my 120 frac......

Doug.

[Size9Hex]

I’ve used a 10" SW solid tube dob with film for solar. Worked well, but now I exclusively use a small frac with solar wedge. Similar sentiment to Peter - it’s more convenient, plus, in my view, less prone to my own user error. The sun is quiet at the moment and also low in the sky, so I’d say no rush. In your shoes I’d wait for the frac and buy a wedge at some point, although the film is a cost effective entry point for sure. I use the shadow that the scope casts upon itself or upon the ground to work out when it’s lined up, so in my view, no additional finder strictly needed.

[Whistlin Bob]

+1 for the cheapy film in cardboard option and +1 for the shadow method for aligning. 

I did both of these things as an interim a few years back on my 8 inch dob and it worked well enough that I've never bothered improving it.

I do also use an orange filter which makes it look nicer.

The shadow method works well on a straight through finder with the caps on, but you should never do this if anyone else is around in case they take the caps off.

[Highburymark]

Do bear in mind that the sun is almost completely blank at the moment and probably will be for at least another year, so there's not much to see in white light. 

[rwilkey]

2 hours ago, Peter Drew said:

If, as is most likely with a 10", you would be using an off axis mask, the aperture you would be using would probably be around 4". It could be argued that a similar size refractor would be more convenient to use and even be travel suitable.       ?

I agree with Peter, a refractor with a 100 or 102mm (4") aperture would be just right for solar observing, I certainly find it so with my C100ED.  Also the Baader Solar Film would not be suitable for a 10" Newt as it is not wide enough, it is A4 (20x29.5 cm) or 8¼" wide.  You would have to get a ready made filter (a type I use for my 4") measuring 294-304 mm found here:

 

https://www.firstlightoptics.com/solar-filters/astrozap-baader-solar-filter.html

 

Good luck with your choices!

[Littleguy80]

2 hours ago, Highburymark said:

Do bear in mind that the sun is almost completely blank at the moment and probably will be for at least another year, so there's not much to see in white light. 

Interesting comment, Mark. While will it be so long without much to see?

[Littleguy80]

Many thanks for all the responses. Greatly appreciated! Plenty of food for thought. 

[niallk]

Yeah perhaps wait til there is sunspot activity, but for the cheapness, a bit of film is remarkable fun for such low cost - basically nothing to lose trying.  I erm messed up a full aperture filter (don't ask...), so I stuck a bit on the inside of the 250px dust cover lid with the 2" off axis hole.  Works very well, but I will go back and make a full aperture cell again.

Maybe keep an eye out for a second hand Ha scope - they seriously rock - even during solar minimum

[Highburymark]

On 11/11/2018 at 16:15, Littleguy80 said:

Interesting comment, Mark. While will it be so long without much to see?

Sun goes through 11 year cycles of activity and inactivity - measured predominantly by the number of sunspots, which are visible in white light. Unfortunately we are right at the most inactive time at the moment - and it's not likely to start picking up for another year  at the least ☹️

[cletrac1922]

First of all welcome from land down under

There is a simpler way to solar observe with a 10" dob

The hard plastic cover has a small removable cap

Just sticky tape some visual Baader film on the underside, and this will also reduce the amount of light coming into the tube

Also remove the spotting scope,

Attached pic was taken through my 10" collapsible dob, solar eclipse several years ago in Oz

Taken holding mobile phone camera to eyepiece

John

 

[Louis D]

Also consider Thousand Oaks Optical films.  They have their Silver-Black Polymer Sheets and SolarLite Filter Sheets available in 12"x12" sheets for $25 and $49, respectively.  The former is suggested up to 100x while the latter is supposed to be good beyond 100x.  They also make cell mounted SolarLite filters ready to mount on your OTA with a bit of felt shimming in sizes up to 17.625 inches.  Your 10" size would run about $119.  I used their Silver-Black Polymer solar eclipse glasses for the 2017 eclipse and everyone around us thought the view through them was much sharper than through ordinary solar glasses sold everywhere.  The nice orange color of the sun was a plus.

I've been using Baader solar film on both an ST-80 and an 8" Dob full aperture since it was introduced nearly 20 years ago.  You definitely see more detail with the 8", but the ST-80 was fine for viewing partial phases of the solar eclipse.  I'm thinking about trying the TO SolarLite filter to see if it is any better than the Baader.

[JOC]

In terms of aligning without a finder this was much more difficult that I had anticipated.  However, I've discovered a sneaky tip which helps me.  I use the shadows of the telescope to help with rough alignment.  Then making sure my solar filter is in place I take out the EP and leave the focal tube empty, I find then that finding and centralising the sun in the primary is much easier than it would maybe be. All I do is peep into focal tube and align the big orange disc on the primary.

[Louis D]

15 hours ago, JOC said:

All I do is peep into focal tube and align the big orange disc on the primary.

Also handy at night for the nearly full to full moon if you don't have a finder to mount on a Dob (forgot it, laziness, etc.).  First use the shadow method to get it roughly pointed at the moon.  Then, if the telescope is pointed anywhere close to the moon, its bright reflection will be projected onto the inside of the tube somewhere, so just look down the front of the tube from a slight distance to see it.  Next, just move the tube to send the image up the tube wall and out the front.  Then, you should be able to get the reflection projected onto the secondary mirror in short order with a little trial and error.

[JOC]

2 minutes ago, Louis D said:

Also handy at night for the nearly full to full moon if you don't have a finder to mount on a Dob (forgot it, laziness, etc.).  First use the shadow method to get it roughly pointed at the moon.  Then, if the telescope is pointed anywhere close to the moon, its bright reflection will be projected onto the inside of the tube somewhere, so just look down the front of the tube from a slight distance to see it.  Next, just move the tube to send the image up the tube wall and out the front.  Then, you should be able to get the reflection projected onto the secondary mirror in short order with a little trial and error.

Yes, I can see it working for that, although obviously with the sun you are limited to viewing the primary in the secondary via the focus tube as the sun filter is over the main aperture!

[Louis D]

3 minutes ago, JOC said:

Yes, I can see it working for that, although obviously with the sun you are limited to viewing the primary in the secondary via the focus tube as the sun filter is over the main aperture!

Noticed you have a FlexTube.  My lunar method wouldn't work so well without a shroud in place to project the image onto.