#1  
Old 12-02-2008, 07:36 PM
OneOfOne's Avatar
OneOfOne (Trevor)
Meteor & fossil collector

OneOfOne is offline
 
Join Date: Jul 2005
Location: Bentleigh
Posts: 1,386
F3.3 focal reducers

I had just started to have a play around with my DSI II in the last couple of weeks, until the cloud came back again. The first night out I tried the C11 on the Moon and of course could only get a tiny sliver onto the laptop screen Basically, no big surprise with a focal length of around 3000mm. I haven't had a chance to try the 6.8 on there yet, but I was also thinking of the benefits of using a 3.3? This will drop the focal length to around 1000mm which is comparable to 80-100mm scopes, so it would give a much wider field. At the moment the budget won't stretch to a refractor, but I could stretch to play around with a reducer.

Does anyone have a C11 with a 3.3? Any recomendations on brand? Any better than others? Or anyone using a 3.3 on other SCTs? Pros and cons?

So I can use the 6.8 for visual but you can't use the 3.3, why not? Is the curvature too great, can't focus, severe vignetting.

Any suggestions or recomendations appreciated!
Reply With Quote
  #2  
Old 12-02-2008, 07:56 PM
astroturf (Bryan)
Registered User

astroturf is offline
 
Join Date: Mar 2007
Location: Old Bar NSW
Posts: 247
Hi OneofOne

I would say that once you have used a 3.3 red. with your SCT you'll never go back
I use one with my DSI pro & LX90 (2500 mm F/L) and can fit things like the swan neb in one frame whereas without it seemed like less than half,or 80-90% of M42 with, or just the trapezium & surrounds without.
it would seem that the DSI has to work a lot harder without it & it's harder to focus
It's not really so useful if you are taking shots of planets where you want the magnification
the Meade 3.3 comes with fittings so that 3 different F/L's can be used, the fittings mate with the DSI & require aa SCT/2" adapter if you have a 2" focuser

Good luck
Bryan

Last edited by astroturf; 12-02-2008 at 08:17 PM.
Reply With Quote
  #3  
Old 12-02-2008, 08:31 PM
Zuts
Registered User

Zuts is offline
 
Join Date: Mar 2007
Location: sydney
Posts: 1,830
Quote:
Originally Posted by OneOfOne View Post
The first night out I tried the C11 on the Moon and of course could only get a tiny sliver onto the laptop screen Basically, no big surprise with a focal length of around 3000mm.
If you want to take moon or planet photos then 3000 mm is not enough. A .3 reducer will make the moon and planets even smaller.

For moon and planets you need to increase and not reduce your focal length. With a 4 by powermate you will have 12000 mm focal length and Jupiter will look great. With a .3 reducer it will be the same as through a refractor with a low power eyepiece, i.e very very small.

For DSO's it is the reverse. You want the zoom but not so much maybe and F10 requires very long exposures. In this case a .63 reducer would be the go.

Although I havnt tried I have been told that a .3 reducer will cause severe vignetting. Though on a small chip like a DSI II this may not be the case. Certainly on a DSLR it would. Another option is a lumicon giant easy guider. These things are supposed to give no vignetting at all. I was lucky enough to get one second hand for around 200 bucks, normally they are around 500 AUD.
Paul
Reply With Quote
  #4  
Old 13-02-2008, 06:37 AM
OneOfOne's Avatar
OneOfOne (Trevor)
Meteor & fossil collector

OneOfOne is offline
 
Join Date: Jul 2005
Location: Bentleigh
Posts: 1,386
Imaging of planets from home would be a little difficult from my place as there are a number of large trees that block the ecliptic out this time of year, I can only see Mars if I set up in the front yard and look over the neighbours roof. At least with the street light, I could read the newspaper while the laptop is taking shots! Jupiter and Saturn will be a little better later this year.. I can see Venus when it is at its highest for about half an hour after the sun sets, but that is looking over the roof of my house. So imaging of planets would be destined to be frustrating...

So my main interest at the moment is to get a large part of the Moon in a single shot rather than zooming in on a crater. I tried a few test shots on M42 and all I could get was the trapezium, which is pretty boring on its own! Eventually I hope to get a DSLR, but that is a few years away at the moment. Of course I would not need the 3.3 then.
Reply With Quote
  #5  
Old 13-02-2008, 09:11 AM
astroturf (Bryan)
Registered User

astroturf is offline
 
Join Date: Mar 2007
Location: Old Bar NSW
Posts: 247
The 3.3 will open up a whole new world - so to speak
Looking back I can't think of anything more frustrating than using the DSI without it - you will manage almost 1/4 of the moon in one frame & as I said before, a lot of nebula's will become more satisfying to capture
You are right ,the 3.3 is useless with a DSLR (severe vignetting) & I suspect this is the case visually as well - I cant think of a reason to use it visually anyway

Cheers
Bryan
Reply With Quote
  #6  
Old 13-02-2008, 12:37 PM
Domol's Avatar
Domol (Domenic)
Bring on the night!

Domol is offline
 
Join Date: Jan 2007
Location: Dingley Village
Posts: 162
i tired my C11 with a borrowed 3.3 and my Canon 400D, and can confirm you get a large coma around stars, which you can't focus. All fine with my Celestron 6.3 reducer, i can fit the whole of M42 in my canon.
try the free CCD camera program at http://www.newastro.com/newastro/boo...camera_app.asp
you can see the results of various telescope/CCD combinations
Domenic
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 06:01 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Testar
Advertisement