Celestron 8" F5 Newtonian's First Light Session

Canopus Lim · Post by **Canopus Lim** » Sun Jan 07, 2007 11:33 pm

Hi Cataclysm,

Advantages of Newtonian (reflector)
1. Only 2 optical surfaces (2 mirrors) and hence higher transmission than Cat which has 3 optical surfaces (1 glass and 2 mirrors)
2. Central Obstruction tends to be 20 percent region compared to 30 plus to 40 percent Central Obstruction on Cat. This translate to better contrast on planets for the Newtonian.
3. Less likely to dew because of design (no front corrector plate)
4. Can be figured to very high standards and optically excellent. There are less Cats that are of that high standard optically unless they are those Russian Maks or better SCTs.
5. Tend to operate at f/8 and lower and hence wider field of view. Cats are usually f/10 and above and hence the maximum field it can go is rather limited. My 12.5 inch f/5 Newtonian has the same field of view as a Celestron 6inch SCT!
6. Ability to collimate. Once you have the correct tools and knowledge, you can ensure a well collimated scope out in the field unlike an SCT which cannot be collimated with tools and requires a star test which is troublesome and time consuming and even more troublesome when using grab and go alt-azi mounts.
7. Cools down faster than Cat due to open tube.
8. It is CHEAP for its aperture and quality!!

Disadvantages:
1. Its size! Although the bigger Newtonians are more portable than Cats of equivalent aperture. However, for smaller apertures, Newtonians tend not to be as portable as Cats.
2. Collimation (it may be a disadvantage as it usually needs collimation of the optics almost everytime when observing). However, if one is accustomed to it, it is a breeze and less than 3 min time to collimate a scope.
3. More maintenance than SCT because of open tube and optics exposed to the air.

kayheem · Post by **kayheem** » Sun Jan 07, 2007 11:38 pm

Canopus Lim wrote:Looks like Weixing holds the Singastro Ironman title! The last contender carried 8inch f/4 newtonian and now you are carrying 8inch f/5 newtonian.

The last contender may be out of action now, but he may be back after his injury has healed. Maybe a 8" F6?

jermng · Post by **jermng** » Mon Jan 08, 2007 12:03 am

Who is this contender??

kayheem · Post by **kayheem** » Mon Jan 08, 2007 8:59 am

He was the original Singastro Commando.

http://www.singastro.org/viewtopic.php? ... t=fracture

Post by **weixing** » Mon Jan 08, 2007 9:34 am

Hi,
Hmm... I thought Ariefm is the record holder... his 7" and 10" Newtonian.

Have a nice day.

Tachyon · Post by **Tachyon** » Mon Jan 08, 2007 9:41 am

Wow! That is one big scope!

kayheem · Post by **kayheem** » Mon Jan 08, 2007 9:45 am

Ahh...having big scopes do not count! You have to man-pack the whole lot to the field to qualify!

rlow · Post by **rlow** » Mon Jan 08, 2007 9:55 am

Hi,
Hmm... I thought Ariefm is the record holder... his 7" and 10" Newtonian.

Ahh...having big scopes do not count! You have to man-pack the whole lot to the field to qualify!

Arief is already catching up... didn't you see his EQ6 case?

Post by **weixing** » Mon Jan 08, 2007 10:08 am

Hi,

how well does your MPCC work visually? Is the effect noticeable?

I can't use it yet as the 2" adapter of the scope focuser is too high causing it not able to reach focus. I'll test it once I got my 2" low profile adapter for my focuser.

Anyway, base on testing at near terrestrial objects which it can reach focus, the image at the edge does seem better than without it.

Have a nice day.

Post by **weixing** » Mon Jan 08, 2007 10:20 am

Hi,

Arief is already catching up... didn't you see his EQ6 case?

Ha ha ha... that's a big and heavy mount. I think it'll be very impressive to see the whole setup and what's he going to mount on it. Hope that he won't mount just a C8 on it...

Have a nice day.