Celestron/Vixen 90mm f14.4 First Light

[A McEwan]

Well, my first views through this lovely old scope were of two archetypal refractor targets: Jupiter and the Moon.

I set the tube up on my modified AZ3 and found that the mount with counterweight handled the tube no problem. It is actually quite a lightweight tube, easily carryable with one hand. It was quite blustery in the garden but I couldn't resist!

Lined up on Jupiter, popped in the 25mm Plossl (thanks Dave) and focused...

Ooooh, nice sharp image! Little bit turbulent but it actually settled almost in front of my eyes after 15 minutes or so! Then I was given a lovely CA-free view showing at least four bands and the GRS approaching mid transit! This at 52x magnification!

I popped in my BGO 18mm buit found that focus was only achieved when I had the focuser fully racked in. I was using my Astrotech dielectric, and looking at it it has a rather long light-path. The image though was just as good, but a little bigger and easier to see the details.

I swapped back to the supplied Prism diagonal and the focus point returned to a more "normal" position an inch and a bit beyond the focuser body end. The image though was softer and not nearly as bright or sharp.

I swung over to the almost full Moon for a quick look.... Very nice view with the very slightest hint of false colour around the limb and at some terminator features. The overall globe was a very stark slightly off-white though. Certainly very aesthetically pleasing. Then I put the Astrotech diagonal back in.

Only just focused up against the focuser end but the view was much better. Sharper and less CA visible. I wished there was less wind and more of a terminator to explore. I packed up after half an hour or so - the wind was biting right through me.

Overall I think this scope has incredible potential. I must see if I can shorten the light path through the Astrotech a bit to achieve a little more leeway when using my ortho's, but the optical quality looks and feels sublime.

Know how I felt, sitting there with this great long tube extending towards the celestial orb above me, huddled against the wind with a simple alt-az mount to guide me? I felt "old-fashioned"... and LOVED it!

Ant

[John]

That all sounds very promising Ant

Interesting about the lack of inward focuser travel when the Astro Tech 90 deg diagonal is used - I've had similar issues with 2" diagonals but not 1.25" ones (I'm assuming that it's a 1.25" that you are using). It just set me wondering if the scope may have been originally designed for the Japan market ? - I recall reading somewhere that the Japanese astronomers are keen on using their scopes "straight through"

Definitely a very interesting and desirable scope you have there - I do know what you mean about being on the eyepiece end of a long tube

[A McEwan]

Yep, well the Astrotech is quite chunky for a 1.25" model. I'm sure there are "shorter" ones out there. Certainly the included prism is. Straight-through I have tried with othr refractors and found that quite rewarding too. Yes, I gather it is popular in Japan, or at least was in the past?

Ant

[spaceboy]

Sound like a result Ant.

[johninderby]

Nice first light. Glad to hear the f/14.4 is living up to expectations. What was the depth of field like when focusing?

Encouraging report as I'll be starting the Carton 100mm f/13 build shortly, and can't wait to see how well it performs.

John

[A McEwan]

It wasn't ideal conditions for determining depth of field, especially as with the good diagonal in the focus point was very limited anyway! But I will have a look at that when I get a chance.

Ant

[nightfisher]

Nice one ant, of to a flying start with a lovely classic, will be interesting to see how it shows saturn and double stars

[A McEwan]

Funny isn't it, in this age of multi-lens designs, super efficient coatings and 100-degree eyepieces, that a long narrow refractor with two bits of glass and a 42-degree orthoscopic should give such a rewarding observing experience.

However, back to reality - I can't remove the eyepiece holder part of the diagonal, so it looks like I'll have to invest in another good quality 1.25" diag, ideally with a shorter lightpath than the Astrotech. Any recommendations?

Ant

[A McEwan]

Actually, I've ordered a visual back adapter with a lower profile, so that will reduce the "height" of the adapter/diagonal combo by a few millimeters - enough to gain focus with room to spare.

The tiny focuser tension adjustment screws are very tough to move and have a deposit on them. It looks like they've possibly been loctited in place (sort of reddish chemical?). Any hints on how to undo this so I can adjust the tension more easily?

Ant

[F15Rules]

Nice first light report Ant, glad you like the Tal plossl:). You are absolutely right, there is something about looking through old glass - at either end!

I had focussing problems with diagonals and eyepieces (2") and on doing some searching around I found that a Zeiss/Baader prism diagonal works really well..I had the added problem that my Lomo Mak can't accept 2" eps without some intervention: I first bought a 1.25" to 2" adapter from the USA, which fits fine, but wouldn't come to focus with 2" eps. So I decided to find a Zeiss/Baader prism to try..soon afterwards I found one, as new condtion,with a 1.25" male to 2" female fitting on one end (the prism comes without either as standard) and I ordered a 2" female threaded tube for the other end (the one into which the ep goes). It all works really well, and using the prism instead of the diagonal gives a significantly shorter light path.

Maybe a prism diagonal would be worth trying Ant?

clear skies

Dave

[A McEwan]

Thanks Dave. However, I found that things with the words "Zeiss" and "Baader" in the description cost more than others, and the reduced height visual back adapter was pretty cheap. Plus I get to use my tried and tested mirror diagonal, so happy to go that route.

Only thing to worry about now is the pesky tension screws which are "locked" in to too high a tension setting. If I could free them I could get a smoother focusin action. It's not "bad" but I can sense that improvement is possible....

And yes, that Plossl is proving to be a real workhorse in all my scopes now!

Antony

[nightfisher]

Thanks Dave. However, I found that things with the words "Zeiss" and "Baader" in the description cost more than others, and the reduced height visual back adapter was pretty cheap. Plus I get to use my tried and tested mirror diagonal, so happy to go that route.

Only thing to worry about now is the pesky tension screws which are "locked" in to too high a tension setting. If I could free them I could get a smoother focusin action. It's not "bad" but I can sense that improvement is possible....

And yes, that Plossl is proving to be a real workhorse in all my scopes now!

Antony

Ant can you post a close up pic of the offending tension screw, might help to solve problem

yes have to agree about the TAL 25mm plossl, i use one for my A-focal imaging work:D

[A McEwan]

Will do Jules, but not until tomorrow at earliest... thanks.

Ant

[nightfisher]

i have just bought a celestron 90mm frac on the fleabay but its the astromaster eq with 11.11 f ratio, should make a great grab an go though