- Adding some edits to include answers to questions in original post.... (bullet pointed items)
I have a 12''/F5 Dobsonian on the way... I have a couple of questions/clarifications as I have not purchased a full range of accessories. Guidance would be appreciated.
- I should have mentioned that this was for an Explore Scientific Truss Dobsonian
I have a decent range of eyepieces (for a fast reflector) and am replacing the RDF with a RACI finder. (arthritis in neck).
Collimation: I am intending to get a catseye set, but do not know if there are any hidden "gotcha's" in that selection. (AKA, are laser collimation or other things needed? That is, a cheshire, sight tube, and AC are all that are needed and border on overkill for a beginner (and the AC is realistically optional)... Or am I missing something?)
Note: My brother has a 90mm Newtonian without collimation tools which I have "hand" collimated, so any tools will probably be "super" to me!)
- Added: All of that is overkill for a new person with no equipment. Get a collimation cap and learn to use it. It is inexpensive and generally useful no matter the situation. Once you have that you can know your weak points in collimation skills and get tools specifically to address those needs. (Also, using your highest power eyepiece and a star test. Polaris is probably your friend for a newbie with a non-tracking mount for this.)
Barlow/Focal Extender: I have not purchased these at this point. I know that they work somewhat differently in the optic behavior, but want to verify whether or not a focal extender disqualifies "Barlowed laser collimation". This is not something which I have seen answered clearly in my research.
It seems to me that the main advantage of a Barlow is for those with removable optics which can be screwed on "like a filter" but with reduced magnification. (Slight extenson --- If going focal extender, then Glatter+Tublug is the optimal choice if "laser collimation" is desired?)
- See above, but if Barlowed laser collimation is in play, if you need/want to do this, you can get away with just getting a laser if you already have a Barlow lens. Better results would be expected if you get a specialized tool for this (e.g. HG laser + TuBlug)
Also, are there any good rules for what to evaluate as far as the quality of the scope are? I have found some articles on evaluating optics and such, but don't find a clear checklist to make sure that I am not missing something.
- Careful evaluation of the diffraction pattern for the star test should allow for gross level evaluation of the optics for faults
Edited by tmossman01, 29 October 2020 - 12:11 PM.