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Posted by Paul A Brierley at 18:10 on 2010 Apr 06
I want to buy another telescope, that I will use for visual observing of the Moon and bright planets. Leaving my G11 and SPX 200-800 for CCD imaging of Deep Sky Objects.I am currently having difficulty in choosing the correct telescope for this purpose.The model that I am serious about is the 10" Orion (UK) OD250; but I can not decide which focal length instrument to choose.A. OD250L F6.3 FL 1600mmB OD250S F4.8 FL 1200mmI was wondering whether somebody on here could give me some advice please.
Posted by Callum Potter at 09:29 on 2010 Apr 07
If lunar and planetary are to be the main interest, I would suggest going for the longer focal length. You can then get the same magnification with more comfortable longer focal length eyepieces.Callum
Posted by Paul A Brierley at 17:42 on 2010 Apr 07
Thank you Callum,Yes the Moon and planets will be my main interest, but I will also be using this for casual tours of the sky, taking in bright DSO’s.I want something that is portable, which I will use mostly during the week during Spring and Summer when I don’t have the time for Astro-Imaging because of work the following day. The OD250L looks to be the ideal solution to my problem. Tonight is another case. It’s lovely and clear here in Cheshire, and looks like staying like this for tonight. Because of the day length, I don’t have the time for any imaging. And that is where I’d use my 10"I think I’ll go and order one in time for the Summer.
Posted by Andrea Tasselli at 12:12 on 2010 Apr 08
Get the shorter focal length one, much easier to use in dob configuration and less subject to wind buffeting. I know as I have the f/6.3 OTA.Andrea T.
Posted by Paul A Brierley at 18:49 on 2010 Apr 08
Thanks Andrea.I have to admit that I was worried that the F6.3 OD250L was going to be a monster! And that it could be difficult using it on Solar system bodies, especially when we consider the height of the eyepiece and focuser, with subjects like the Moon during winter.I think that I will probably ask John at OO for the OD250S. I can then use this telescope for deep sky observing from home, and also the peak district as well as Lunar and Planetary observing. Do you know if the F4.8 suffers badly with coma?
Posted by Andrea Tasselli at 12:55 on 2010 Apr 09
Hi Paul,Yes, there is coma but not so bad. A lot depends on what EPs your’e going to use as some of them make things worse and some better. If you’re really really picky you can get yourself a TV Paracorr and be done with it. Obviously for high magnification stuff coma is not an issue (at f/4.8 anyway).BestAndrea T.
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