Omni XLT 120, 150 Refractor, 8" or 6" Newtonian

For people new to astronomy who want to ask those questions that they were afraid to ask. Receive helpful answers here.
Bomia
Posts: 15
Joined: Mon Apr 06, 2015 6:43 pm

Re: Omni XLT 120, 150 Refractor, 8" or 6" Newtonian

Post by Bomia » Thu May 21, 2015 8:26 pm

Junwei, I was considering the 120 over 150 because not only it's cheaper but also less CA, but the length set me back since it means a dry-cab 2 size up.

Kochu, are you able to show me a untouch photo of the moon with the scope without filter? While I hear all about the CA, I really don't have a feel how bad it is.

Hardwarezone
Posts: 266
Joined: Fri May 17, 2013 2:50 am
Favourite scope: maksutov

Re: Omni XLT 120, 150 Refractor, 8" or 6" Newtonian

Post by Hardwarezone » Thu May 21, 2015 9:47 pm

Bomia wrote:Hi hardware zone, The reason why I am not getting 6se, it is not EQ mount and I like to consider AP in near future. And can teach me how to use US proxy?
google search "facebook proxy"
the first page results just pick one that doesn't look too dubious , be sure to not key in personal info with these proxy
https://www.proxfree.com/facebook-proxy.php

The celestron omni cg4 mount (also called skywatcher eq3-2) , I think you may need to get more info on it because I've seen comments in other forum that it is inadequate(gears and bearings) for anything but the brightest targets.... and also the counterweight & pier issue for our local 1degree north latitude



this CA chart pops up at the usual forums .... don't know created by who
Image
for more info you can google search "sidgwick focal ratio"

User avatar
antares2063
Posts: 687
Joined: Sat Jan 22, 2005 3:34 pm
Favourite scope: Newtonians
Location: Bedok North Street 2, Singapore

Re: Omni XLT 120, 150 Refractor, 8" or 6" Newtonian

Post by antares2063 » Sat May 23, 2015 6:09 pm

Hi Bomia,

Speaking from Visual p.o.v : I think you should try looking through some achromats to decide on your acceptable level of CA . Different people have different limits. Myself Im not bothered with the false colour as I could only see it on 1 target : Jupiter at med-high power during the mersing trip. During the trip there were alot of first timers coming on second night and I asked if any of them saw any blue fringing on various objects : Nil. Locally i tried it on moon with also almost undetectable CA.

No one single scope suits all purposes , honest truth about this hobby. After some time, you can also decide if you are inclined to go down the visual observing route or the digital Imaging route. Hope this helps.

Regards,
Junwei
I miss the place where stars shine bright, to gaze upwards in awe of the sight

User avatar
Great Red Spot
Posts: 410
Joined: Sun Sep 29, 2013 3:55 pm
Favourite scope: Newtonian

Re: Omni XLT 120, 150 Refractor, 8" or 6" Newtonian

Post by Great Red Spot » Sat May 23, 2015 9:38 pm

Just to clarify, Junwei is using a good quality 100mm achromat at a good f10. His observation that there is negligible CA is consistent with the chart posted by Hardwarezone.

User avatar
Sivakis
Posts: 240
Joined: Mon Aug 10, 2009 12:55 pm
Favourite scope: Astrotech AT66ED APO

Re: Omni XLT 120, 150 Refractor, 8" or 6" Newtonian

Post by Sivakis » Sat May 23, 2015 9:48 pm

Hardwarezone wrote:
Bomia wrote:Hi hardware zone, The reason why I am not getting 6se, it is not EQ mount and I like to consider AP in near future. And can teach me how to use US proxy?
google search "facebook proxy"
the first page results just pick one that doesn't look too dubious , be sure to not key in personal info with these proxy
https://www.proxfree.com/facebook-proxy.php

The celestron omni cg4 mount (also called skywatcher eq3-2) , I think you may need to get more info on it because I've seen comments in other forum that it is inadequate(gears and bearings) for anything but the brightest targets.... and also the counterweight & pier issue for our local 1degree north latitude


All GEMs should have the pier issue when used in Singapore unless it comes with a half-pier or you buy one together when purchasing the GEM. I'm currently in the process of researching if I want to build one out of pvc (seen others do it before, so I'm tempted).

I'm actually using the Celestron Omni CG-4 but my scope + dslr comes up to under 3kg so that's perfectly fine, although the CG-4 does have a rated limitation of only 20 pounds so heavier scopes/gear may not be suitable. Tripod legs are single-piece metal so it's plenty sturdy (and heavy....). So far, using it with the dual-axis motor (although I'm only using the RA-drive), 60 seconds seem to be okay on my Astrotech AT66ED - haven't tried longer exposures.

Bomia
Posts: 15
Joined: Mon Apr 06, 2015 6:43 pm

Re: Omni XLT 120, 150 Refractor, 8" or 6" Newtonian

Post by Bomia » Sun May 24, 2015 11:22 am

Sivakis, if you are using PVC, try to find ABS plastic pipe, it's thicker and stronger.

User avatar
Airconvent
Super Moderator
Posts: 5596
Joined: Tue Sep 30, 2003 11:49 pm
Location: United Federation of the Planets

Re: Omni XLT 120, 150 Refractor, 8" or 6" Newtonian

Post by Airconvent » Sun May 24, 2015 12:39 pm

Hi Bomia,
Inspite of false colours and such, in Astronomy, Aperture wins. If you are seriously into astronomy, you will graduate from Planets and moon very quickly. And DSOs require more aperture, especially in Singapore where they are dimmer. Get the biggest aperture that you can easily carry around (Cats or Newts). The Skywatcher Heritage 130 would be a good starter although its not suitable for AP. You can always buy a EQ mount later for the OTA.

Refractors offers typically 3 advantages, wide view, portability and high contrast. But generally, when viewing DSOs, they do not matter as much.

And before you buy anything, do drop by any of the obs sessions to check out the scopes there, so you have a better idea what is needed.

Cheers
The Boldly Go Where No Meade Has Gone Before
Captain, RSS Enterprise NCC1701R
United Federation of the Planets

Bomia
Posts: 15
Joined: Mon Apr 06, 2015 6:43 pm

Re: Omni XLT 120, 150 Refractor, 8" or 6" Newtonian

Post by Bomia » Sun May 24, 2015 3:29 pm

Hi JunWei, I am actually seriously considering the 150R pairing with AVX mount as my first scope after reading all the comments and other acticles. My plan next will likely be a 6" Newtonian or 8" SCT to cover the whole sky. I guess I should be able to accept the CA as a imperfection of the refractor. Nothing is perfect in the first place.
I am prepared to the scope home next week and will very wish to join you guys in some gathering.

User avatar
Sivakis
Posts: 240
Joined: Mon Aug 10, 2009 12:55 pm
Favourite scope: Astrotech AT66ED APO

Re: Omni XLT 120, 150 Refractor, 8" or 6" Newtonian

Post by Sivakis » Sun May 24, 2015 11:31 pm

Bomia wrote:Sivakis, if you are using PVC, try to find ABS plastic pipe, it's thicker and stronger.
Thanks Bomia I'll take note of that.

User avatar
antares2063
Posts: 687
Joined: Sat Jan 22, 2005 3:34 pm
Favourite scope: Newtonians
Location: Bedok North Street 2, Singapore

Re: Omni XLT 120, 150 Refractor, 8" or 6" Newtonian

Post by antares2063 » Sun May 24, 2015 11:39 pm

Hi Bomia,

150mm refractor (in your case the achro which is a f5...I think) and a 6in newt f5 seems to be overlapping . unless if you are getting a ISTAR 6" achro f10 or f15 please invite me to admire the scope ;)

Sure! we are also waiting for more suitable weather on weekends...because of work and family..past few nights have been totally overcast, till tonight it clears but its monday tmr...

Regards,
junwei
I miss the place where stars shine bright, to gaze upwards in awe of the sight

Post Reply