Title says it all! Check my signature for my current setup regarding what I'm working with currently, but i'm looking for a newtonian astrograph to complement my wider FOV that I get from my AT72EDII.
I have a deep love affair with diffraction spikes, and have always loved the aesthetic a newtonian brings to a final image, and am well aware of the added complexity of collimation/light leaks/etc that comes with a newtonian! I've had a decent amount of practice on my 8in. dob, so that aspect doesn't necessarily scare me away!
I'm thinking of something around 600-800mm that would allow me to get decent shots of larger galaxies and really hone in on center cores of DSOs (Cygnus Wall, Eagle, Orion, Etc. A decently fast one as well would be helpful, as my sky horizon is a bit limited by trees and houses, and I can't always get 6hrs on a target in a single night. 4.5hr is about the max I can manage at the moment. I'm in a bortle 6 suburb, so light pollution is an issue as well.
I know they Sky Watcher 150p is a popular go-to, but I've also heard quality issues as well with the focusers and excessive light leaks near the main mirror.
I've also seen tons of ads for the Apertura CarbonStar 150p. Anyone have experience with that guy yet? Thoughts?
Thanks CN! Any wisdom/feedback is really helpful!
Since you're ready to accept the challenges of a fast newtonian astrograph, and depending on your available budget, my suggestion is to either buy a "descent" one like the TS-Optics ONTC line (to have descent mechanics to support the tight collimation tollerances of such an instrument), or built one from readilly available quality parts.
In the long run, either of those choices will prove cheaper than buying a "budget fast newtonian" from far East and trying to improve things later on by replacing parts = $$$ (with all the frustration of trying to make it work...).
My approach was to start building one from descent quality parts that are readilly available on the market:
I already had a budget 8'' f4 mirror & 85mm diagonal so:
- bought a custom made carbon fiber OTA directly from Klaus Helmerichs in Germany per my specs (to have a rigid tube to support the mechanics of the scope, increase collimation accuracy and stability in every alt, eliminate ota sag/tilt, avoid collimation/focus shift due to temperature changes, reduce weight etc)
- OTA specs where carefully designed in order to avoid any drawtube protruding in the light path, and also to have the coma corrector front lens hidding further into the drawtube to avoid any strange reflections from direct light that could hit the front lens (from light polution or even from a flat panel)
- flocked the entire OTA inside to eliminate any further reflection issues
- bought an TS ONTC mirror cell which (after minor twinking) works extremelly well (to have the ability to maintain precise collimation in every alt, support the mirror in a proper flotation way without excessive rms errors resulting from mirror stress & without mirror pinching since the mirror cell has appropriate & adjustable side supports and clips)
- bought an aftermarket CNC machined spider (for better secondary stability vs alt since diagonals of fast newts are large and heavy, and to avoid issues of non-parallel vanes)
- bought a descent and adjustable R&P focuser (to help eliminate any image shift/drawtube tilt etc while supporting heavy camera & coma corrector)
- install a custom made stainless stil reinforcement plate under focuser to further eliminate any focuser/ota sag under image train loads
- install a vibration-free mirror fan for the back of the ota
- eliminate any possible light leak under focuser/ota back
Also, quality collimation tools are an ABSOLUTE MUST for fast f4ish newtonians (I have Catseye tools as well as a quality and well collimated laser with tight beam). An F4 is a completely different beast vs F5 or slower....collimation tollerances are VERY tight. Same for the critical focus zone....your mechanics must be able to achieve & maintain all those tight tolerances....
I also installed an autofocus (ZWO EAF) to further improve my focusing (huge advantage over bahtinov masks, mainly from the easy focusing process that allows me to run autofocus more often and avoid temperature shifts)
- Next step will be way better optics (Mirrosphere - France) & better coma corrector (I use an ES HR2, will use a Paracorr 2 to yield a focal length of 920mm)
Newtonians are amazing (if you enjoy fine-tuning as I do!)
Best,
Argyris
Edited by Argyris, 30 May 2024 - 04:04 PM.