Transits of Mercury

Robin Lee · Post by **Robin Lee** » Sat Nov 04, 2006 10:47 pm

Who is going to observe this event? Anyone has a solar telescope? I can leave for Singapore and meet you guys! It's gonna be fun.

By the way, does the transit always mean that a planet pass over its host stars?

jiahao1986 · Post by **jiahao1986** » Sat Nov 04, 2006 10:58 pm

Hi,

I'm going to observe it in NTU campus with my ETX-125, possibly trying to take some photos. I don't have a solar telescope, but I remember one or two folks on the forum owning Coronado PSTs, one is local vendor Joo Beng( www.astrobargains.com); the other one I can't remember...

Here wish that all of us having a clear, haze-free morning sky at transit time!

Robin Lee · Post by **Robin Lee** » Sun Nov 05, 2006 10:22 am

Do you have the solar filter for your ETX-125?

I think I can contact Joo Beng for the event!

jiahao1986 · Post by **jiahao1986** » Sun Nov 05, 2006 11:19 am

I do have a solar filter for my ETX-125. It sounds like you don't have a solar filter for your LX90 right? Better go and get one

Besides, at Joo Beng's place, the eastern sky is blocked by a big apartment building...

mrngbss · Post by **mrngbss** » Sun Nov 05, 2006 12:58 pm

There are readily available solar film from some local vendors. You can spend a little time to make a filter for it too. Maybe faster.

Using a PST (with its supplied ep) to observe the transit maybe a little challenging(mercury will be very small). Darker and smaller. If there is less clouds, maybe you will be more awed by the prominences and features on the Sun. Changing the ep(to magnify your view) on PST may not enable focusing to be reached.

I'm observing it from 7am-8am. Gonna use a c8 and 5i in white light. Normally the sky is not clear enough during this time (especially this hazy period). Hoping for the best.

Robin Lee · Post by **Robin Lee** » Sun Nov 05, 2006 3:40 pm

Wee Nhgee, do you have the solar filter ready? What should I buy for my 8" LX90? Time is reaching.

mrngbss · Post by **mrngbss** » Sun Nov 05, 2006 3:48 pm

Kim Miau wrote:Wee Nhgee, do you have the solar filter ready? What should I buy for my 8" LX90? Time is reaching.

Not too sure what you meant by the first question...

I have 3 sets of white light filters (80mm, 5", 8"). All are Thousand Oaks'.

If you can afford, buy a ready made 8" filter. Otherwise, you can use the solar film (A4 size) to make a off-axis white light filter for your 8". Off-axis construction will require about 3-4" aperture of solar film. I've never had time to make one yet. You could come earlier to singapore to buy the film and make one. Otherwise stay at your hometown, get the film and view using your 8".

Off-axis viewing is quite similar to full aperture. Below shows a 8inch whitelight filter.

Robin Lee · Post by **Robin Lee** » Sun Nov 05, 2006 4:02 pm

Can you explain more about the off-axis? How much is the solar film?

mrngbss · Post by **mrngbss** » Sun Nov 05, 2006 4:11 pm

Kim Miau wrote:Can you explain more about the off-axis? How much is the solar film?

A picture says a thousand words... heehee..

Attached is a Energy Rejection Filter for the H-alpha solar filter set.

Off-axis filters are for SCTs and those with a secondary mirror in the middle. Uses less material. Since aperture reduces, therefore f-stop increases. Similar for photography the image is darker. but viewing wise, to me is not much of a diff for the Sun. With a A4 size film sheet, I can make a few off-axis filters for large aperture telescopes.

Hope the picture explains a little.

Robin Lee · Post by **Robin Lee** » Sun Nov 05, 2006 9:34 pm

I see. In this case the image seems larger as the focal ratio increases, am I right?