I've had the AR152 up for sale since I got the C9.25 reasoning that The C9.25 should be able to do everything the Refractor can do and with more aperture.
But I never had the chance to put them head to head. The SCT can operate at F/10 with a focal length of 2350 mm - a nice long focal length for planets.
With the reducer lens it can operate at F/6.3 an effective focal length of 1480 mm - getting down to reasonably low power for wide field cruising.
I had over spent the scope budget last year and so decided to liquidate the Refractor - despite it not really having a good chance to prove itself.
Previously the AR152 outgunned my Astro-Tech AT8in - an 8" Imaging Newtonian - on a Jupiter shadow transit.
Although the Astro-Tech has an oversized secondary mirror I still thought the 8" of aperture would over rule the 6" Achromat.
But not so, it was a clear shut out for the refractor. Conditions were a little murky and I could not even detect the shadow with the Newt.
It was clear on the refractor and I switched back and forth twice to make sure conditions hadn't changed.
So, finally tonight - nice warm and dry conditions on a weekend night - when does that ever happen?
I started with the SCT on the CGEM mount. I aligned and looked at the Ring Nebula. The Moon was about 3/4 phase so the sky was a murky light grey.
The Ring didn't look good and I decided not to use it for comparison. I slewed over to M27 and even in the light sky it was easily visible.
I inserted my new Celestron UHC filter in the 2" diagonal and it did improve the image quite noticeably.
I soaked in the view with a 22mm Ultima LX eyepiece (67x). Then I set up the AR152 on the Alt Az - T-Mount.
I eyeballed where the SCT was pointing and just tried to angle the Refractor in the same position. It was mounted very low on the alt az and I had to do some driveway crawling to maneouvre it.
I looked again at M27 through the SCT and memorised the view. Then to the AR152. I moved the whole Eyepiece/Diagonal/Filter combination over to the refractor. I centred M27 and then changed to the Ultima LX 13 mm e.p. (76x) to better match the magnification.
I looked - and Wow! - the refractor put up a view every bit as bright and distinct as the SCT. But that just should not be so - the refractor was giving up 3 1/4
inches of aperture. I looked long and hard and tried to imprint the view.
I moved back to The SCT - switching the optical train over again and then dropping to the 22 mm again.
Nope, the view was not quite as good. It was just less distinct - perhaps less contrasty is the best description.
I took out the UHC filter on The SCT and the view was worse - looking very grey.
Debra arrived home and I asked her to look through both scopes.
She immediately voted for the refractor and said it just looked 'crisper' there.
I started to think of the possible reasons why the SCT was not clouting the Refractor with its greater light grasp and higher resolution.
I figured while using the F/6.3 Reducer, the SCT was using 2 lenses and 3 mirrors before the eyepiece:
the primary mirror
the secondary mirror
the reducer lens
Whereas the refractor was using:
the objective lens
Since each time light is reflected or passes through a lens some if it is lost, it seems likely this must be a big factor?
But still - there's no way my C9.25 should be beat on deep sky by a 'big daft achro' as I have sometimes referred to it.
I've cancelled the sale (not kidding) of the achro pending a planetary shoot-out. There's just no way the Achro can win this one.
The C9.25 is legendary on planets and the Achro is going to have a blizzard of CA pouring out the eyepiece.
I'm thinking Jupiter here ....
But I would have dismissed any chance of it winning on deep sky - so who knows?
I tried the OIII filter but the sky was just too blown out by The Moon do find anything else worth comparing.
I did pull in Epsilon Lyra - The Double Double, and neither scope could cleanly split them - the stars appeared dazzling and a little spikey.
A clear tie on this object.