arad85 Posted June 19, 2009 Share Posted June 19, 2009 I want to get a 2" diagonal for my C9.25 (and C6S, and 80ED!). As far as I can see, I have the choice of (for premium pieces)- Dielectric (£115)- Prism (£185)- Quartz Dielectric (£220)I've read reports elsewhere that the dielectric and quartz dielectric are visually "the same" (by someone who owns both) so I'm kind of discounting the quartz.Anyone have any experiences of the standard dielectric vs the prism? An added advantage of the prism is that the image is the right way up/around, which would be much easier for targets such as the moon...TIA Link to comment Share on other sites More sharing options...
Milamber Posted June 19, 2009 Share Posted June 19, 2009 The prism would indeed be good for the Moon, and also terrestrial targets, but for DSO's and the like, you really need as little between your eye and the target as possible... this would sort of imply that putting a *big* lump of glass in there is probably not a good idea. If you think the benefits of right way up viewing outweigh the light loss then that's fine, but be aware of it as a factor. Also bear in mind you would be likely needing to have a similar arrangement for your finder also, to stop confusion when swapping eyes between the two.Arthur Link to comment Share on other sites More sharing options...
johninderby Posted June 19, 2009 Share Posted June 19, 2009 Just keep in mind that most prism diagonals are really for low powered use. For any high powered observing and in particular for use with reflecting scopes such as your SCTs go for a mirror diagonal. The real advantage of a dielectric diagonal is that the coatings are really tough and won't scratch or degrade over time so it is well worth getting.Quartz will cool down faster, but with such a small mirror any advantage is hard to dectect. I've used both and really haven't noticed any diference.WO diagonals are very good, if not quite the best. Televue, Baader and Stellarvue are a bit better but more expensive, and most observers probably wouldn't notice the difference.John Link to comment Share on other sites More sharing options...
philsail1 Posted June 20, 2009 Share Posted June 20, 2009 Hello "arad85."As it happens I have a WO 2" "Dialectric" 90 degree mirror Diagonal, and a recently bought (from FLO) WO 2" 45 degree Prism Diagonal.I use them with my Celestron C8i SCT scope.I bought the 45 degree Prism to make using the scope a bit more comfortable (especially when using my binoviewers) when observing objects at between 18 degrees and 60 degrees.First thing I noticed was thet the prism diagonal gave slightly (but noticeably) sharper views when observing the Moon and Planets.Can't really comment on any loss of light - mainly as I haven't compared both diagonals on deep sky objects yet.As soon as I can, I will let you know hew they compare.Hope this helps.Regards,philsail1 Link to comment Share on other sites More sharing options...
arad85 Posted June 20, 2009 Author Share Posted June 20, 2009 First thing I noticed was thet the prism diagonal gave slightly (but noticeably) sharper views when observing the Moon and Planets.Can't really comment on any loss of light - mainly as I haven't compared both diagonals on deep sky objects yet.As soon as I can, I will let you know hew they compare.Hi Philsail1, yup, it does. Please post your findings here when we get more than 1 hour of darkness and you can actually see a DSO .... Link to comment Share on other sites More sharing options...
philsail1 Posted June 20, 2009 Share Posted June 20, 2009 Yes, certainly "arad85."philsail1 Link to comment Share on other sites More sharing options...
beetlejuice Posted June 24, 2009 Share Posted June 24, 2009 I wouldn't waste my money on a quartz diagonal given the highly variable sky conditions we have in this country. I have both the WO 2" dielectric and the Stellarvue 1-1/4 dielectric. They are both excellent, being very nicely built. I would recommend the Stellarvue as an excellent all-round digaonal (far superior to the cheapo diagonal that came with my SCT). I don't know who imports them in the UK - I bought mine in the US 3 years ago. Link to comment Share on other sites More sharing options...
Rob Posted June 24, 2009 Share Posted June 24, 2009 Hi,Altair Astro - Nature Optics - Astronomy Telescopes & SkyShed POD Observatory equipmentSell stellarvue. Give them a try.Rob Link to comment Share on other sites More sharing options...
Rob Posted June 24, 2009 Share Posted June 24, 2009 Altair Astro Nature Optics CATALOG - Astronomy Telescopes & SkyShed POD Observatory equipment UK & Europe Link to comment Share on other sites More sharing options...
beetlejuice Posted June 24, 2009 Share Posted June 24, 2009 Altair Astro Nature Optics CATALOG - Astronomy Telescopes & SkyShed POD Observatory equipment UK & EuropeThat's a very good price indeed - only about a fiver more than I paid in the US. Bargain. I'm well chuffed with mine. Link to comment Share on other sites More sharing options...
FLO Posted June 24, 2009 Share Posted June 24, 2009 I want to get a 2" diagonal for my C9.25 (and C6S, and 80ED!). It would be a shame to put a 1.25" diagonal on an ED80. The 2" diagonal will almost certainly be better (imperfections occur at the mirror edge, where it is cut, the edges of a 2" mirror are further from the centre) and will allow the use of 30-40mm wide-field eyepieces. HTH Link to comment Share on other sites More sharing options...
arad85 Posted June 26, 2009 Author Share Posted June 26, 2009 Hi all,Thanks for the feedback. I ended up with a second hand 2" quartz off here.... Now we just need some decent weather (was away Tues/Weds night at a wedding - how typical). Link to comment Share on other sites More sharing options...
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