How do Dobs/Newtonians fare in singapore light polluted skies

[akdwivedi]

Hi skywatchers,

I have been primarily using SCTs (previously C8s and now a C6) and refractors (Orion 120ST, SW 80ED, Stellarvue 102ed, SW120ED) for visuals from my patio. So far the SCTs and refractors are doing fine as I mostly view planets and luna. I tried some DSOs and star clusters but the view wasnt so good, due to bright skies and bad seeing.

I wanted to check with the community about the scopes used for visual astronomy from Singapore. I dont drive, so going to darker skies across the border is out of question.

Will a larger dob/newtonian - say something like 10"-14" f/4-5 work better. Which dobs do you use, which eyepieces do you use. looking forward to your advice and tips.

thanks

[joachim.ong]

I have a C8 and a 10 inch self-built dob, have briefly used an 8 inch dob for a while, also had the chance to compare the 10 inch side by side to a 12.5 inch in SG.
I am a firm believer that "aperture is king" and would say the difference in aperture is as expected. Mainly small, noticeable increments but don't expect a miracle; dim objects just appear less dim. You probably get the same feel in going from your 120mm refractors to the C8.
For me stars are nicer and more colourful in the dob for some reason, maybe because it is possible to use larger exit pupils, or maybe because SCTs have a spherical primary mirror. But I think this preference is quite personal.
The one thing I can recommend for light polluted skies is a proper UHC/OIII type filter if you have yet to try one. That said, I'd pick an 80mm in dark skies over any scope in Singapore.

[akdwivedi]

Hi Joachim

thanks for your feedback. I do think the aperture of a 10-12" dob might give better views than refractors/SCT (which I have). However, I was concerned about heavy light pollution in singapore skies (specially my place is surrounded by these light emitting buildings all around).

Fpr planetary and lunar, SCT certainly gave me better views though I must say 120ED/80ED do have more sharpness/resolution.

I was looking at 10"-12" skywatcher flextube prices are decent. and skywatcher claims 94% reflectivity on their mirrors. I think the flextube also allows the tubes to be adjusted a little shorter so that a binoviewer may be used. But then I watched Ed's youtube channel where he said a 8" gets twice as much used as a 10" and a 12" gets used even lesser.. :-).. choices/decisions..

[joachim.ong]

Making sure stray lights don't enter the scope should be the top priority. If that means you need to walk a little, a lighter scope might be better. Get a trolley too, if you have space at home you can leave the dob on it all ready to go.

[rlow]

I have used those telescopes (or similar) that you mentioned. For newtonians, I have used from 4 to 15 inch and bigger. So I share what I see in the scope performance etc.

There is a big jump from C6 to 10-12 inch dob, both in size/weight as well as performance. A 10-12 inch newtonian will show brighter and better details on planets and brighter open/globular clusters than C6 and other smaller 4 to 5 inch refractors. This is so, as long as the newtonian is properly cooled, well collimated, light-baffled, and most importantly have good quality optics.

Good quality optics refer to one which has lesser optical aberrations. Mirror reflectivity is important but may not be that critical. I've seen SkyWatcher newtonians which have good mirrors, and some not so. Either try your luck on mass-produced optics, or pay more for premium optics.

Eyepieces of higher quality may perform slightly better but not as significant compared to upgrading to a bigger aperture telescope with good quality optics.

Unlike on planets, the bigger newtonian show more but may not perform in the same significant way on fainter DSOs like nebulae and galaxies under our urban night sky,. This is due to the limiting factor, which is the light-polluted sky. If you don't drive but can move the scope to observe DSOs from the outskirts of Singapore under darker skies viewed towards the sea, you may get better DSO views compared to the views from your patio.

Viewing under truly darkest skies away from cities' light domes is significantly better for all DSOs. For planets and moon, observing under our urban night sky is already optimum.

The SkyWatcher 10 to 12 inch flextube has a relatively massive and heavier base. The SW 10 inch base is 12.0 kg, while the SW 12 inch base is 17.4 kg..If you intend to primarily observe planets from your patio, then these size/weight portability issue may be less of a concern, compared to moving it to a darker observing site. The original base can be replaced with a lighter compact "home-made" rocker box/base with better movement.