I was having a clear out this morning and selling some bits and pieces second hand and was going to sell my ETX90 but couldn't bring myself to do it.
Have I read somewhere that a reflector like this has no spherical aberration or I am just hoping?
I tried my 85mm Beloptik tri-band ERF and it fits really nice in the ETX90 screw on dew shield, might give it a try when the sun is out.
Anybody any thoughts? Valery?
Thanks
Mark
ETX90 for CaK Work
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ETX90 for CaK Work
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Re: ETX90 for CaK Work
Sell it and use your TAL100 !
Valery
Valery
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.
Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.
Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.
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Re: ETX90 for CaK Work
Ha ha ha! Fair enough!
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Re: ETX90 for CaK Work
Hopefully should be a bit of sunshine today, I have it all set up ready so will give it a quick blast...
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Re: ETX90 for CaK Work
Lol, I know, I like themDerek Klepp wrote:One things for sure Mark you,ve got to appreciate Valery,s honest replies.
I did try earlier today and the results were dog awful! Won't be using this. At least i'll be a few quid up selling it
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Re: ETX90 for CaK Work
Hi Mark,
I don't think that scope is corrected that far down in the blue. If the AR is a standard TIO2,SIO2 4 layer then it will be absorbing a lot below 400nm.
I have seen them used at Ha but not at K-line. That my be why it didn't look good when you tested it.
Mark W.
I don't think that scope is corrected that far down in the blue. If the AR is a standard TIO2,SIO2 4 layer then it will be absorbing a lot below 400nm.
I have seen them used at Ha but not at K-line. That my be why it didn't look good when you tested it.
Mark W.
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Re: ETX90 for CaK Work
Thanks Mark! Definitely not well corrected as the following image testifies. Very interesting about the coatings too, makes perfect sense as I had to rack the exposure right up, and also fits in with similar findings which i've had with my Meade AR5 refractor at 393nm in terms of having to get the exposure time right up. Also backed up with my observations visually with my Meade series 4000 plossls giving dimmer views with a Daystar CaH I have been testing compared to brighter views with Tele Vue plossls of same focal length. I wonder if the TV are using MGFl2 coatings compared to the TiO2 of the Meade?
Anyway, a view through the ETX90... (80mm aperture) pretty yuck I think! Compare this to the same area with the ED80 stopped down to 60mm
Anyway, a view through the ETX90... (80mm aperture) pretty yuck I think! Compare this to the same area with the ED80 stopped down to 60mm
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