Hey Julian, love your videos man, they are very detailed and easy to understand. I wanted to chat with you on a couple of topics, if you can, which platform can we do that on? thanks Xee
That is a great question, and a very difficult one to answer. Up to 6” in aperture, refractors are better due to the lack of central obstruction and a higher transmittance. Additionally, refractors have a very stable optical design which does not require frequent collimation. The only downsides of a refractor are mainly the chromatic aberration (can be mitigated in a myriad of ways) and the cost (they are generally more expensive than reflectors) Beyond 6” in aperture, refractors become prohibitively expensive, at which point a reflector becomes a better option. Hope this helps!
@@darkskygeek yes it helps- but the point I don’t get: the cost of that telescope could easily afford a 10’, maybe 12’ reflector, right? Wouldn’t it be a better choice? I’m a newbie to astronomy, and the reflector just seems to be a better choice under my limited knowledge.
A 10” reflector will be massive and will therefore require a large and expensive mount. The telescope will require re-collimation on a regular basis. Thermals will be an issue. The surface of the primary will be at best 1/4 wave (unless you pay a lot of money) And you’ll have to contend with a central obstruction, which reduces contrast. Then, you realize that resolving power is limited by the atmosphere, not be the diameter of your telescope, etc. There is a long list of reasons as to why refractors are preferable over reflectors, at least up to 6” diameter. CS!
@@darkskygeek thanks a lot! I haven’t considered these points before and your feedback improves my understanding. I just didn’t understand what you meant with “primary will be at best 1/4 wave” could you explain it further?
“1/4 wave” refers to the surface accuracy and smoothness of an optical surface. It means that it deviates by as much as 1/4 of the wavelength of light (usually in the green, so 500nm / 4 = ~ 125nm) compared to a perfect paraboloid.
I still don’t understand purpose of advanced sequencer. I can plan everything in simple sequence mode plus refocusing every 1.5 degree drop in temperature; framing target with rotation and meridian flip.
@@darkskygeek I can use advanced version, but it really doesn’t give any extra advantages. By the way, how do you decide on integration time. For example, 8h Ha. Maybe it needs 80h.
Here is a simple example. As you probably noticed, I have an automated telescope cover. In order to open / close that cover as part of my sequence, I *have* to use the advanced sequencer. There are many other reasons why I only ever use the advanced sequencer, and I certainly encourage you to give it a try, but if you are satisfied with the basic sequencer, there is no reason to switch. As far as the total integration time, the more the better 😉 But I am also limited by how many nights are clear, and other factors like work and family life. In the end, I try to get about the same amount of time on all 3 narrowband filters.
