View Full Version here: : Another Diagonal question.
I wasn't sure if I should use the other thread or not but my question is more basic than the other.
The diagonal that comes with the Celestron astromaster isn't exactly the greatest so I would like to upgrade it but I don't know much about diagonals.
So I was wondering what are some good affordable makes that I can use with the astromaster?
Baring in mind that I eventually want to get enough of the kit together to do a stage 1 PST mod with this scope eventually so I'm only going to need the diagonal for a small amount of time.
Thanks for looking.
22-02-2012, 08:23 PM
The Bintel and Andrews diagonals are excellent value for money and as good as anything that is under $200.
For what you want to do, they are ideal.
The Bintel ones look reasonable, but I'm not sure if they supply them to any European dealers. Any price save would probably be taxed by customs here, maybe.
23-02-2012, 09:06 AM
They are the same as the Orion branded ones, you should be able to get one locally cheap.
23-02-2012, 09:13 AM
Type in BK7 into the search section and find a great article by DavidU on diagonals for refractors. I have a GSO 2" dielectic and cheaper BK7 and can't see any difference when using GSO plossils. Matt
23-02-2012, 09:36 AM
From my searching of the Net. GSO = Bintel and Williams = Orion
Some have found the GSO better in comparison to the Williams.
Some have stated that the field stop on the GSO is 2mm greater than that on the Williams.
Some indicate look for wave front quality in front of reflectivity. Based on that, and given that only few quote wave front after placement of the dielectric coatings, tends to head you towards the quartz substrate.
Now the clinch.........who's eyes are good enough to pick the difference in wavefront........did come across one rather technical article in my travels.
I was going to go for the GSO 2inch quartz dielectric........1/12-1/15 before the dielectric coatings. Unless, the infocus becomes insufficient to allow for a 2inch.............then AstroTech produce a 1.25inch with excellent reviews....Sky and Telescope hot product for 2007.
In terms of if money is no object, then if you are after a mirror then look to Vernonscope and if you are after a prism then look towards Tak.
My budget has me at GSO and am please with the comparative reviews that it has received on the Net.
At the end of the day.....best that the optics can deliver is without the diagonal. I need an extender to test how good the optics can get.
Hope this helps,
23-02-2012, 10:14 AM
with the astromaster i don't think you need quartz - i had one & didn't notice any difference over the standard dielectric, if it were me i would get the standard GSO & concentrate on getting a better eyepiece
Thanks guys for the useful information, looks like I have some checking up to do today then and some reading.
I know I should probably get a good fixed eyepiece but I do have a Hyperion zoom mk3 which I find to be really good.
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