From: Ray Byrne <ray@in4media.co.uk>
Date: January 8, 2010 6:25:11 PM MST
To: Astro_IIDC@yahoogroups.com
Subject: Re: [Astro_IIDC] solar beginnings...
Hi Mark,
Yes Alan is right about the commercial ones the Baader film is superior but the off-axis mounting of the film still has merit. Even though the commercial filters Thousand Oaks, Orion Telescope Centre etc. offer off-axis filters the filters themselves are not Baader film but coated glass that is why they are quite as good not the fact that they are mounted in an off axis fashion.
IHTH
Ray
On 8 Jan 2010, at 21:35, Mark Gaffney wrote:
Hi Ray,
& all the best for the new year to you! It`s about 8.11 am here in the morning (daylight savings time) & the sun has just risen over the bushes I have in the east. I set the utilites menu to allow slewing to the sun & after inputting the settings (time etc..) it`s slewing a bit below true position. I very quickly mastered the smallest shadow method for alignment & centred & aligned. Then I left the scope & began playing around with my spring form taping bubble wrap around the inside. It fits quite well around the very rim (the rail below is in the way of having it more than 2-3 cm down the tube. I had the scope in after my successful PA in early December because of all the rain so will have to do that again more accurately. It`s a cloudless day today ( probably will get very hot later!) My solar film still hasn`t arrived despite being posted Christmas eve. I think the postage was quite an economical price so may be a longer time for delivery. The trouble with getting up 4-5 am in the morning is I`m tired directly after dinner at around 7 pm & have to have a lie down for 2-3 hours! So I don`t usually do any scoping until it`s around passing the meridian time for it. I`ll keep in mind the off axis option you`re speaking about but I think Alan was advising against the commercial ones you can buy both for price & other reasons I think..? At least with the sun it`s a more civilised time of day for the telescope! Before the heat of the day now & at a time I don`t have to fumble around in the dark! It`s now 8.35 am & the scope is still happily tracking the sun outside there!
Mark.
On 09/01/2010, at 7:54 AM, Ray Byrne wrote:
Hi Mark,
Happy New Year to you.
I'd be inclined to have an off-axis aperture to fit your Baader film into. Measure the largest area of the corrector plate that is free of any obstruction and cut a hole in some card that will fit in you cake making spring that will avoid the secondary mirror and the ring that holds the edge of the corrector (probably 3" or so). That way you will have no secondary obstruction to interfere with the light path, effectively like a refractor, and being that seeing is nearly always poor during the day a smaller aperture will help combat the poor seeing. Also the Sun is obviously extremely bright and you don't want or need all that light so a sub-aperture mask will help there too. Do a Google on secondary obstructions and also smaller aperture in poor seeing and you'll see what I mean.
IHTH
ATB
Ray
On 8 Jan 2010, at 04:19, Mark Gaffney wrote:
Hi Alan, Ray & others,
My Baader solar film (1 foot square) is I believe in the mail
somewhere & I now have a 280mm cake making spring form as per the
following site & some cardboard. Here`s the site I`m using for advice
on the construction of my filter; http://www.backyard-astro.com/equipment/filters/baader.html
I can`t find an email link to the author so am asking here. How much
of the aperture of my C9.25 can I use i.e. how big a circle should I
be cutting in the cardboard? The spring form does seems to fit the
scope & & I`d be using a reducer...
Mark.