Good make of 254/1250 Newton for DSO

[Gerry Casa Christiana]

15 hours ago, wimvb said:

Btw, Lacerta offers a photo newton with quartz mirror. It costs 300 € more than the non-quartz version, and is marketed as "zero expansion". With a carbon tube, it's supposed to be veeery stable. That may very well be true.

Ah yes had a look at those. Very nice! Might be out of my budget though. I'm interested in these TS PHOTON ones but doesn't seem to be many people using them but the specs seem good. Also 70mm secondary! Bit more research I guess. 

[Alan64]

Hi Gerry,

A 70mm secondary is not that bad for that sized aperture...

The secondary for my 150mm f/5 is 47mm, and I don't even have a 2" focusser.  The reason that one may seem too large is because it has a 2" focusser, and so to illuminate 2" oculars.  The Bresser linked to previously, its secondary is 74mm in diameter.  If you like the specs overall of the TS, give it a go.

[wimvb]

You really need to ask yourself what you want to do with the new scope, and how accurately you want to do that.

For astrophotography, requirements are different than for visual use. Do you just want a larger aperture, or do you require a stable mechanical system? AfaIk, the most stable ap reflector you can get has a carbon fibre tube with a quartz or pyrex mirror and a fan to speed up cooling. The focuser needs to be stable as well, which often translates to: needs to be upgraded. Within your budget, that may mean that you should be willing to a) buy used, or b) settle for a smaller aperture. An 8" f/4 or f/5 ts photon with carbon fibre tube can be had for 949 €. The metal tube equivalent is at least 500 € cheaper. Regardless, you need to add a coma corrector. One which gets very good reviews is the SW/GPU coma corrector, for 235 € (Baader mpcc is about 170 €, I believe).

Personally, I would (and am) save up for quality. "Buy once. Cry once."

[Gerry Casa Christiana]

28 minutes ago, wimvb said:

You really need to ask yourself what you want to do with the new scope, and how accurately you want to do that.

For astrophotography, requirements are different than for visual use. Do you just want a larger aperture, or do you require a stable mechanical system? AfaIk, the most stable ap reflector you can get has a carbon fibre tube with a quartz or pyrex mirror and a fan to speed up cooling. The focuser needs to be stable as well, which often translates to: needs to be upgraded. Within your budget, that may mean that you should be willing to a) buy used, or b) settle for a smaller aperture. An 8" f/4 or f/5 ts photon with carbon fibre tube can be had for 949 €. The metal tube equivalent is at least 500 € cheaper. Regardless, you need to add a coma corrector. One which gets very good reviews is the SW/GPU coma corrector, for 235 € (Baader mpcc is about 170 €, I believe).

Personally, I would (and am) save up for quality. "Buy once. Cry once."

Yes I think that is very good advice. I'm just a little unsure of the TS PHOTON as there don't seem to be any real examples of DSO shot with them. Maybe they are fairly new. I can compromise on the carbon fibre but the focuser has to be fairly good. Yes I know those GPU ones they are excellent. Worth the money. Just mirror quality that I'm worried about as this is the vital part of the setup. There seems to be a million pictures of the SW 250pds on astrobin but was hoping my next scope wasn't another SW. 

Gerry

[wimvb]

The optics in a SW is good enough. It's the mechanical part that's their weak side. Focusers are most often the first to go. The standard crayford can be replaced by something more sturdy. Maybe a Baader diamond steel track? TS even sell a carbon tube as a replacement for the 150pds steel tube. All the holes are pre-drilled or pre-cut.  If you consider a Newton telescope as an optical platform, rather than one single instrument, then swapping parts makes sense.

The TS Photon scopes are fairly new, but probably a good alternative to sw. As I wrote before, the Photons are one part in a TS offering, from budget (ts photon) to high end (ts n-ag). And while the parts may come from the same factory, it's the difference in quality that sets them apart.

[Alan64]

The TS "Photon" is Teleskop Service's house-brand.  I would venture to guess that the manufacturer of its mirrors is Guan Sheng Optical in China, aka GSO.  I say this because the vendor High Point here in the U.S. carries a house-branded 150mm f/5 Newtonian, and manufactured by GSO.  Mind you, I'm not stating that it is indeed, but only that it's quite probable.  GSO manufactures the very popular Apertura AD8(formerly Zhumell Z8), a "Dobsonian" which is also marketed here in the U.S.  The vendor Agena Astro of California sells all sizes and focal-ratios of GSO primary-mirrors and optical-flats.  In addition, a U.S. manufacturer of premium "Dobsonians" sports within its base-model offering: GSO mirrors.  Give TS a call and ask.

Edited June 1, 2018 by Alan64

[Science562h]

Well, Synta makes bit better mirrors, if you see them in person. 1% more reflectivity & better coating.  I agree, with the post, DOBs are for viewing first, anything else is a plus. 

[johninderby]

Having had a 10” Skywatcher dob and now a Bresser 10” dob find the Bresser optical performance  better than the Skywatcher. 

Bresser uses a proper 9 point mirror cell and a really good focuser and has a black rubberised anti-reflective coating inside that is far better than Skywatchers thin coat of blackish paint.

Probably why the performance advantage.

Edited December 29, 2019 by johninderby