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| I have a 10" Truss RC with an ASI071 (APS-C) and the A-P CCDT67 (.67) reducer and get a flat field on my 10". No reason to think that you will not get one with your 12". And I verified my flat field with CCD Inspector. |
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| Perfect... Thanks Jim. |
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| New mount arrived! |
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| Trace - If you have the CCDT67, use the formula on the AP website to determine the correct spacing to get a large enough image circle so you don't get vignetting. |
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| I have an edge 1100 and a Hyperstar. I obtained both of them used substantially below new prices. I'm really happy with my choice because of the versatility. I have not been using it much at full magnification but use it mostly with the 0.7 focal reducer. A couple of my images are up here under my name Peter Bresler |
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Hi Peter, Thanks for that, and getting a good price is certainly a factor. I think the Edge + Hyperstar is an amazing combo and it's images are amazing, especially the planetary. I haven't settled on the RC, but it's still the front runner for me for several reasons. And, by choosing 1 scope at long FL and 1 at wide FOV, there's more options and I like that. CS Trace |
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| If you are bothered by reflections around bright stars, you should be aware that the hyperstar exhibits the same reflections as the RASA. The design is quite similar. |
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| Erlend, I was not thinking about that issue with the Hyperstar. Thank you for pointing that out. |
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Trace:Actually, Bob had pointed this out with his Edge HD 11 which was part of my path to the RC preference. |
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| I hadn't seen the new Starizona 0.4x NightOwl reducer mentioned yet. I have the 8"EdgeHD with Hyperstar but probably would have considered one of these if I hadn't gone the EdgeHD+Hyperstar route. (Note, this is only for non-Edge scopes) |
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Trace I appreciate you rose the discussion, but in my opinion, you should get more experience before spending so much money. Of course you were right Alessio, and it was great advice. After a year of climbing the auto guiding learning curves of the CEM120 & then Paramount, and purchasing and getting experience imaging with two nice low cost Newtonian f4's (6&8in), I now find myself back in this topic to resume my search for the right long FL scope. It's back to the EdgeHD 11 vs. 10"RC. As I return to the topic, your post was the most apropos place to return 🤗. Grazie mille! |
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Hi @Chris Sullivan , Reading your previous posts about using your RC8, I was wondering how you managed to get stars in your OAG when using it without the your astrophysics 0,67x reducer ? I am using an OAG with a zwo ASI120MM, and at f/8, stars are crazy dimmed and I am lucky when I get one in the field of view.... and my guiding really suffers from it. I am planning to use the same astrophysics reducer as you do (I am living in Paris - same Bortle 8 SNR problems :-) ), and use the native focal length when I do a bit of planetary, but I still would love to understand how to optimize my OAG at native focal length, in case I need a closer look at a dim object (last night I tried again to image the Tiger’s eye galaxy, but my stars were elongated - probably weak PA - and after an hour, the field of view had changed dramatically like everything was shaking, until it settles again - I suspect I lost the guide star). Anyway, thanks for your feedback ! |
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You need a guide camera with a larger sensor like the ZWO 174; the 120 is way too small. Peter |
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Peter Bresler: That makes sense... should have thought about it : sensor is 2x larger AND pixels are almost 2x larger as well, and therefore catch 4x more photons... But that is a totally unexpected expense for me. God this hobby can become a ruin if you don’t take care... :-) |
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Hi Jérémie, I think your issue is that the 120 just isn't sensitive enough. I tried doing OAG with a camera with that Aptina sensor and I couldn't get any stars. I switched to a Lodestar X2 and had no issues whatsoever. From my experience, a 290MM works almost just as well as a Lodestar, but the 120 just isn't compatible with off-axis guiding. Good luck! Chris |
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I'm really surprised by all the RASA hating in these posts! I own a RASA11, and I'm *extremely* happy with it. I've combined it with a OSC (ASI183mcPro) and a full-time Hoya UV/IR filter (replaced the clear optical window). The result is a 1 degree field with pinned image quality (wavelength pinned by UV/IR & spot quality pinned by off-axis distance). It has a platescale pretty nicely matched for galaxy work (0.799 arcsecs, 0.399 Drizzle). My main issue is the mount I have (Celestron CGX-L), but I don't have any complaints at all about the RASA11 (and I have the first gen...before the focus upgrade). If someone could please point out the RASA issue with bright stars via an image, I'd appreciate it. Imaging at f/2.2 is just such a pleasure (comparitively speaking)! I do have the benefit of a dark and dry site, but I'll also add that I travel a lot with my RASA 11 and I haven't yet had to collimate it (and I use CCD Inspector to verify). I'm fairly new to AP, so be gentle, but my images can be seen here: www.astrobin.com/users/dmsummers/ I can't give advice about the other options, but I think some of this RASA hating may be overdone. I think the RASA is a fine option (probably among many fine options). Cheers, Doug p.s. I will note that focus on f/2.2 pretty much requires a motorized focuser and some decent software. I use Ekos with ASI EAF focuser and custom (available) automatic focus adjustment software to give updates between exposures. I can autofocus once and hold focus throughout an imaging session which makes it really nice. |
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Doug Summers: Hi Doug, Thanks for joining the discussion and your images are stunning, very nice! Sorry for any bad feelings regarding comments on the RASA 11, I certainly think everyone here will agree it's an amazing instrument and I think all would be thrilled to use it!! A quick google search yielded this image, clearly a beautiful image, and it does show the circular highlight around the bright star. Similarly, but less severe, it is also seen in your Pleiades image on n-Tau star. Kind regards and CS Trace |
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| Argh....you are absolutely right! I never noticed the ring in that image (and there's more than one). I suspect that this could be a function of over-exposure/saturation. I will be interested to re-image that field at lower gain and/or shorter exposure to see if I can influence the result. Thank you for pointing this out; I will watch for it more carefully now. As I've taken many exposures and not seen it, I suspect I can (mostly) control for it. Anyway, I didn't retain any bad feelings; it was more curiosity than anything else given my good experience(s) with the RASA 11. I'm glad I asked and you answered! Best, Doug S. |
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| And to be sure each scope design gives it's own particular treatment to bright stars. Here's an RC example, and these diffraction patterns are well known on the 8" f4 fast newtonians. I've certainly had them on mine, and to some extent but less so on the 6"f4. |
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Trace: Thats a poor RC example though. There are plenty of amazing RC images that don't exhibit these characteristics. The stars in that image arent even aligned *facepalm* |
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| Yikes I see that, poor example, and by the imager's own comment it was just a quick test shot. |
