Teslar Posted May 2, 2013 Share Posted May 2, 2013 (edited) I leave the Baader at mid point, focus with the Mak knob and then use the Baader to get fine focus. The instability shows with light winds and just the lightest touch on the mount for instance when adjusting the alignment screws Don't be put off though the scope can produce tremendous images and there is satisfaction in doing the mods Edited May 2, 2013 by Teslar Link to comment Share on other sites More sharing options...
tuckstar Posted May 2, 2013 Share Posted May 2, 2013 But i thought all achromatic reflectors suffered with CA, irrespective of what they were made of, as they are still achromaric and apopchromatic. A suspect a small, fast, 80mm, doublet or triplet would be nice in the future, but i think i'm after the aperture for the time being with a set of slow optics. I don't want a 150mm mak as i don't feel it is a worthy step up from the 127mm mak, so 180mm or more i feel would be necessary on the mak front. The russian mak is hellish expensive new, and i would get a second hand one if i found one. I need to feel the weight of one of these celestron 8" or 9" s-c scopes. Apparently 7kg for the 8" and 10kg for the 9.25" but both are only f/10. James My refractor is a Zeiss c63/840 F13.3, with T coatings (Zeiss's ed) very nice lenses. Jupiter at 210x very little if any c/a! Splits doubles like nothing I've ever looked through. Just cus its an achro doesn't mean it has to suffer from c/a. Link to comment Share on other sites More sharing options...
dawson Posted May 2, 2013 Author Share Posted May 2, 2013 That's interesting, i'd just assumed all achros had issues with CA. Have you done any imaging of DSOs with it? Jd Link to comment Share on other sites More sharing options...
dawson Posted May 2, 2013 Author Share Posted May 2, 2013 Teslar, i am put off a bit by the shaking issue i have to be honest. I'll do some more digging. Jd Link to comment Share on other sites More sharing options...
dawson Posted May 2, 2013 Author Share Posted May 2, 2013 Just found another thread on SGL about the rings... Does putting cork on the inside of the slightly larger rings which are more easily availble do the job? Jd Link to comment Share on other sites More sharing options...
tuckstar Posted May 2, 2013 Share Posted May 2, 2013 (edited) That's interesting, i'd just assumed all achros had issues with CA. Have you done any imaging of DSOs with it? Jd Haven't imaged dsos but don't have the kit. I have taken planetary and Luna with a webcam but only CMOS not CCD. See my gallery, there my first attempts though so don't laugh. Aperture prob a bit small for dso, and to be honest i havent tried, but it will perform as well as most 80s due to the quality of glass, it is rated as 1/7.1 PV, 1/40 RMS and 0.95 strehl by zeiss but apparently most perform above this rating. It is a bit of a classic though and quite sort after. Have you looked at the sw schmit newt? Different i know but a fast scope with glass. Edited May 2, 2013 by tuckstar Link to comment Share on other sites More sharing options...
dawson Posted May 2, 2013 Author Share Posted May 2, 2013 Andy, i looked at the 190mn (i think that's its name), which looks to have a curved corrector plate like the maks and a tube like the newts; it's too fast for that i'm after, but looks good for DSO stuff primarily. I think i'm pretty much sold on the 189 mak idea now, f/15. I'm just exploring the focus and stability (tube ring) options first. I'm looking forward to seeing your scope in action though. I'll have a look at your images when i'm on a computer, on my phone at the moment. Jd Link to comment Share on other sites More sharing options...
tuckstar Posted May 2, 2013 Share Posted May 2, 2013 Any time matey, its so confusing deciding which one to go for. Think that's why most people end up with a mixture of scopes. Its horses for courses. Good luck mate. Link to comment Share on other sites More sharing options...
Brantuk Posted May 2, 2013 Share Posted May 2, 2013 Most of the top quality refractors have inherrent field curvature which is why you nearly always find them paired with a flattener. Depending on how fast they are a reducer may also be needed - or you can get combined flatener/reducers. Three objectives focusing the primary colours all in the same focal plane takes a fair bit of glass bending. Link to comment Share on other sites More sharing options...
dawson Posted May 2, 2013 Author Share Posted May 2, 2013 I think the refractor will be a subsequent purchase, along with its associated purchases.... It would be cheaper and no less rewarding to just buy a better pair of binoculars Link to comment Share on other sites More sharing options...
Brantuk Posted May 2, 2013 Share Posted May 2, 2013 For around £250 to £350 you can get a very nice little doublet second hand which will give you the opportunity to take very reasonable LE widefield snaps of dso's. Worth bearing in mind. Link to comment Share on other sites More sharing options...
dawson Posted May 3, 2013 Author Share Posted May 3, 2013 Yes, i would like something like that in the future kim. I'm keeping an eye on abs just in. Case a bargain appears. Jd Link to comment Share on other sites More sharing options...
+RonC Posted May 3, 2013 Share Posted May 3, 2013 My final scope will be a 190MN James, got to save for it, they just don't come up second hand!! Ron Link to comment Share on other sites More sharing options...
dawson Posted May 3, 2013 Author Share Posted May 3, 2013 There was a SW MN190 on either ABS or ebay for £595 for several days a few days ago. It looks lovely, but too fast for me. Good luck finding one. Have you thought about putting a wanted advert on ABS, it might just encourage someone to sell theirs if they are no longer using it. James Link to comment Share on other sites More sharing options...
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