Solar fiter SW 200P

[MattGoo]

Thinking of making a full aperture solar filter for my Skywatcher Explorer 200P.

The A4 sheet of Baader AstroSolar film seems like it would be a tight squeeze since it's 210mm x 297mm and my 'scope aperture is 200mm?

Can I get away with the A4 (£20), or do I have to go for the bigger sheet of 1m x 0.5m (£55)?

Any input welcome.

[lex]

If your going to make 1 with 2 rings (donuts) of card then your aperture will be more like 170mm so you should be ok.

Apparently creating an offset smaller hole ala http://www.bpastro.org/index.php?page=how-to-build-an-off-axis-mask

would give better images and you'd have plenty of film with A4

Mines only 5" so i covered the full aperture, great views.

[Sammyb]

Hello MattGoo,

I have a 200P and made the solar filter below out of plywood (found a plant pot the exact same diameter as the outer diameter of the scope which I used as a template) and black card and gaffer tape. I cut the hole I think to about 3.5 inch or so (big enough hole to just fit in between two spider vanes). I then used a quadrant of solar film to cover the hole and stuck it with more tape. Plenty of black card on the inside to seal any gaps. As I understand it there is not much to be gained from a full 8" aperture solar filter - and 3.5 to 4 inch should be fine. I'm a solar novice though so feel free to correct me.

I got the kids to try it first so as not to damage my eyes (joke...).

Hope this helps,

Sam

[GreatAttractor]

As I understand it there is not much to be gained from a full 8" aperture solar filter

As in non-solar observing, bigger aperture gives better resolution and a larger, more comfortable exit pupil for a given magnification. Making subaperture filters is supposed to minimize the impact of bad seeing (I can't verify this from my own experience as I only have a 4" and a 6" scope; both use full aperture sheets and I haven't seen any difference in seeing effects). I'd suggest to start with a full filter and try resorting to smaller one if turbulence is a noticeable issue.

Of course when using only low powers a 4-inch hole will be enough (my 4" gives great views at 40x-80x).

[Bizibilder]

As above - go for a smaller filter that will fit between the spider vanes, or just make the filter round but only 150-180mm diameter - the choice is yours. By the way don't forget to either remove your finder or make a special little filter for it.

[jimmyjamjoejoe]

I'd go for the smaller filter. The a4 doesnt quite get full aperture, and by shrinking it you're only increasing the proportion of central obstruction. Although you gain resolution, you lose a lot of contrast.

[Matt Scunthorpe]

The 200p has a hole in the dust cap ready made. Those 2 bumps on the cap, one of them comes off, and the other is to store the cap. This is how i have done mine, and put the solar filter on the underside. I can attach pics when im home (at work atm) if you want some. One downside is that it makes your dust cap awfully fragile..

[spaceboy]

http://stargazerslounge.com/topic/157038-diy-solar-filter-for-my-200p/

HTH