focal reducer on 12inch dob

[mindburner]

been trying video camera on the 300p dob with little success, mostly due to dire weather. I got a focal reducer (0.5) 1.5" but I cannot achieve focus with it. Is it possible to get a low profile tube or extender tube as I am not even sure which way to go to get focus. I understand there may be coma issues even if I get focus. The dob is great but comming to the conclusion that it's really just a visual scope.

I can always use the reducer with my old meade, until I get my new EQ kit

thanks

[angusb1]

A focal reducer will bring the focal plane farther in towards the secondary so a low profile focuser may help.

There are some formulae here that should enable you to calculate by how much. I was going to post the link to the calculator on TimosAstro website which would have done the maths for you but its down I have a copy at home - if I can get my webserver back up and running lafter work I'll post a link.

[mindburner]

A focal reducer will bring the focal plane farther in towards the secondary so a low profile focuser may help.

Many thanks for that. I think I can get one that sits flush inside the 2 inch tube. A 2 to 1.25 should maybe do the trick.

Love the Aphex avatar BTW

[angusb1]

You're welcome.

The Aphex Twin rocks

Liking the Space 1999 avatar too btw. Might have to revisit that one.

[todd8137]

hi there and hello from me ,well i use my 300p or the dark side when you say video cam i take it you mean a movie camera type one and not a web cam,i used the same reducer for a while on my 300p and it was cool it worked well with a webcam and my cannon 10 camera,no coma either.i do have a low profile dual speed caryford ,as the rack and pinion on the sky watcher for me did not have enough inwards travel

i would not say its a visual scope ,has i have had many a great nights out do in videos and take in pics

it does take a bit of messing about but take a look at my you tube videos and you will see the 300p is not just a visual scope cheers and keep at it you will get the results you are looking for but these handheld video cameras are a bit hard to use we have a sony and a jvc one and i have had not able to use them as i could not get the chip close enough to grab any thing

todd8137 - YouTube

take a look when you have a minute at some of my vids all done with a cheap 10 quid webcam some good filters the 300p and a lot of headeaches

[mindburner]

hi thanks for all the grat replies. The camera is actually a CCTV camera SCB-4000 used by quite a few people for live viewing of DSO's

I will try and see if I can get a low profile 2 to 1.25 reducer and if that doesnt work a better focuser. I will have a butchers at your videos as I love this scope and would like to do more with it. Got some good results with a web cam, it;s more the live DSO thing I am after.

cheers

[riklaunim]

I doubt that there is backfocus for any focal reducer in the dobs.

[mindburner]

I tried removing the 2 inch to 1.25 skywatcher supplied adapter and made a very ghetto cardboard tube, just to try and see if the video camera would be able to focus with the .5 reducer on. It did but was pretty low. I think I may need to get one of the low profile adapters that actually sit inside the 2 inch hole to have any hope of focus. But I think it should work.