TheSkySearchers

DEnc wrote: ↑Sat Sep 11, 2021 6:28 pm I whine frequently about my “learner telescope”, an SV110ED achromatic refractor: blue bloat, nasty internal reflections, shaky focuser, and its unsuitability for spectroscopy. Also most of the Landolt reference stars for photometric calibration are too faint to calibrate my rig, that much I know. But here’s a new one: it just isn’t fast enough for some variable targets.

I compared my observations of the variable V603 Aql with an observer in Spain, who imaged with the same camera (STT-8300M with a JC-V photometric filter), but a larger scope—10” as a I recall, versus my 4” refractor. The AAVSO alert (743) called for a fast cadence since this star shows high frequency oscillations. At magnitude 11.5 I had to image for 60sec with 80sec between saves, compared to his cadence of 20sec. Sure enough he caught a lot more detail than me (black, versus red for my observations).

I’ve been locked in analysis paralysis regarding the next scope, trying to anticipate features that would limit its performance for my applications. There are just too many variables: local weather, the mount, the camera, and the details of the design and construction of the OTA....

DEnc wrote: ↑Sat Sep 11, 2021 7:17 pm Thanks nFA. My aspirations:--
1. Astrophotography of dimmer/smaller targets. I'm envious of Steve/starfield's recent image of LBN1235, taken in Anza Borrego. I image in the same general vicinity but I can't touch a dim target like that due to poor flat correction/internal reflections. Blue bloat's a mess too.
2. Spectroscopy would be nice, ruling out an achromat.
3. Speckle imaging of close binaries. (A new camera is planned too.) Presently I'm only tracking STE16, rho ~20asec. It'd be great to have a longer list.
4. As noted, fainter photometry targets. Also with my current rig exposures in JC-B are too long to be practical.

I have a Mach 1 mount so between its specs for payload and my fading muscle tone it'd be good to have a total weight of <35 lbs on the mount. I'm heading to cloudy coastal skies in northern CA, so portability for travel inland is important (i.e., collimation issues and weight). I'm jonesing for at least 9.25" of aperture.

notFritzArgelander wrote: ↑Sat Sep 11, 2021 8:13 pm I used to own a 9.25" Edge, a great scope and I miss it rather. The most critical item on your list is the spectroscopy. Is is "nice to do" or "must do"? I ask that because I think an under appreciated fact is that the f-ratio of the spectrograph needs to be approximately matched to the f-ratio of the scope or else the spectrograms suffer from vignetting and photon waste. If you are really interested in spectroscopy that will give more of a clue. Most SCTs are f10 and most available spectrographs are optimized to work well with that f ratio fortunately.

DEnc wrote: ↑Sat Sep 11, 2021 8:32 pm

notFritzArgelander wrote: ↑Sat Sep 11, 2021 8:13 pm I used to own a 9.25" Edge, a great scope and I miss it rather. The most critical item on your list is the spectroscopy. Is is "nice to do" or "must do"? I ask that because I think an under appreciated fact is that the f-ratio of the spectrograph needs to be approximately matched to the f-ratio of the scope or else the spectrograms suffer from vignetting and photon waste. If you are really interested in spectroscopy that will give more of a clue. Most SCTs are f10 and most available spectrographs are optimized to work well with that f ratio fortunately.

There's a subforum on CN where gear for spectroscopy is a regular topic, and this has come up. For that reason I am leaning towards an EdgeHD, 11" or 9.25".

Thanks again!

DEnc wrote: ↑Sat Sep 11, 2021 10:16 pm On the contrary, thank you for bringing that up. I consider it an authoritative confirmation.