#1  
Old 13-05-2020, 01:41 PM
jayconnor's Avatar
jayconnor (Jay)
Registered User

jayconnor is offline
 
Join Date: Mar 2015
Location: melbourne
Posts: 117
help with telescope

ok needing a little advice.

I have a Bintel BT200 f/5 scope that's quite banged up.
I have moved house 3/4 times over the 5-year period I have owned it and it's needing to be replaced.

Now im looking at buying the BT200 f4. is there a big difference between the f/4 and f/5 scope in terms on astrophotography wise?

just can't get my head around it all at the moment.

Thanks in advanced.
Reply With Quote
  #2  
Old 13-05-2020, 01:51 PM
jayconnor's Avatar
jayconnor (Jay)
Registered User

jayconnor is offline
 
Join Date: Mar 2015
Location: melbourne
Posts: 117
i take it the f/4 lets more light in?
Reply With Quote
  #3  
Old 13-05-2020, 02:31 PM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is offline
 
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 8,001
Jay,
It's the size of the main mirror that defines how much light gets in.
So, both the 200mm f5 and the 200mm f4 will receive the same amount of light.


Simplistically, the difference is that the f4 "concentrates" that light into smaller images, hence they can look brighter.


"Faster" optics like an f4 put demands on the eyepieces - better eyepices are required, which usually means $$$
Reply With Quote
  #4  
Old 13-05-2020, 04:59 PM
jayconnor's Avatar
jayconnor (Jay)
Registered User

jayconnor is offline
 
Join Date: Mar 2015
Location: melbourne
Posts: 117
Quote:
Originally Posted by Merlin66 View Post
Jay,
It's the size of the main mirror that defines how much light gets in.
So, both the 200mm f5 and the 200mm f4 will receive the same amount of light.


Simplistically, the difference is that the f4 "concentrates" that light into smaller images, hence they can look brighter.


"Faster" optics like an f4 put demands on the eyepieces - better eyepices are required, which usually means $$$



thanks kindly
Reply With Quote
  #5  
Old 13-05-2020, 05:58 PM
Startrek (Martin)
Registered User

Startrek is offline
 
Join Date: Dec 2017
Location: Sydney
Posts: 2,936
Jay
Collimating the f4 will require more skill and effort than the f5, thereís no argument about that
Iíve used my Bintel 200mm f5 for over a year now and has plenty of light grab , can image magnitude 9 to 10 galaxies
I was awarded image of the month for April across Australia by Bintel using my Bintel 8Ē f5 newt
Image attached
Go for the f4 if are worried about a little bit of extra weight on your mount ( 2 kg ) but my recommendation as a beginner go for the f5 mate you wonít regret it

Cheers
Martin
Attached Thumbnails
Click for full-size image (5480C18E-3B72-4260-8A89-310C270F27DC.jpg)
162.0 KB26 views
Reply With Quote
  #6  
Old 13-05-2020, 07:23 PM
astro744
Registered User

astro744 is offline
 
Join Date: Apr 2007
Posts: 931
Visually f4 is very demanding on eyepieces and you definitely need a coma corrector, (and at f5 if you are picky). However the OP did not ask for a visual recommendation, rather a photographic one. Put simply f4 is faster than f5 and in photography and astrophotography speed is desired, (f2 seems to be a goal of many).

An f4 telescope is photographically faster, is capable of a wider true field for the same aperture, is lighter, but does requires a better structure keep it in collimation. It is perhaps a good choice once some experience is built up with an f5 telescope first. Photographically both require a coma corrector.

I found the following discussion on this forum some years ago. See http://www.iceinspace.com.au/forum/s...ad.php?t=88094
Reply With Quote
  #7  
Old 13-05-2020, 07:48 PM
jayconnor's Avatar
jayconnor (Jay)
Registered User

jayconnor is offline
 
Join Date: Mar 2015
Location: melbourne
Posts: 117
thanks all so much for the comments.

i went with the F4 i have a Baadar coma corrector already also.

So now all that im struggling to get my head around is these f***ing clouds can anyone help with them?


P.S Martin that is such a nice image and what im aiming to achieve
Reply With Quote
  #8  
Old 13-05-2020, 08:01 PM
jayconnor's Avatar
jayconnor (Jay)
Registered User

jayconnor is offline
 
Join Date: Mar 2015
Location: melbourne
Posts: 117
Quote:
Originally Posted by astro744 View Post
Visually f4 is very demanding on eyepieces and you definitely need a coma corrector, (and at f5 if you are picky). However the OP did not ask for a visual recommendation, rather a photographic one. Put simply f4 is faster than f5 and in photography and astrophotography speed is desired, (f2 seems to be a goal of many).

An f4 telescope is photographically faster, is capable of a wider true field for the same aperture, is lighter, but does requires a better structure keep it in collimation. It is perhaps a good choice once some experience is built up with an f5 telescope first. Photographically both require a coma corrector.

I found the following discussion on this forum some years ago. See http://www.iceinspace.com.au/forum/s...ad.php?t=88094

great thread you sent me too. thanks for that mate.
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 12:15 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
Advertisement
NexDome Observatories
Advertisement
Testar
Advertisement
Bintel
Advertisement
Limpet Controller
Advertisement
Astronomy and Electronics Centre
Advertisement