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Refractors and a secret weapon !


John
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I thought I post some photos of my current dual and single refractor setup plus a new toy for the 6". The large yellow / orange one is a Konus "Konusky" 150mm F/8 achro (same as the 1st generation Helios / Celestron 150 F/8's), the smaller white one is a Vixen ED102SS F/6.5 ED and the mount is an Ambermille Aztech on a CG5 tripod with 16" pillar extension.

The strange Russian device plugged into the diagonal in the last photo is the new toy - an Aries Chromacor. These were marketed in relatively small numbers a few years back and were specifically designed for use with chinese 120mm - 150mm refractors. The version I have is designed to do 2 things, i) reduce the chromatic abberation (false colour) by around 85% and ii) correct spherical aberration by inducing a little compensating overcorrection. This is achieved through a 3 element lens made of glass with specific properties (or so I've read) rather than any form of filter.

From my 1st light tonight I'm rather pleased with it although I need to do some further fine tuning to the installation to maximise the benefits :)

I'm intending to bring this lot to the SGL5 Star Party in case anyone wants to have a peek :p

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WOW John!!! You have a chromacor???

How did you get your hands on that? Is it matched to the correction of the scope?

Gaz,

Well believe it or not, it came up on e.bay !. I'd read a bit about them a few years back but they were out of my league price-wise back then. When I spotted this one up for auction I did a bit of research, then did some star testing (over a couple of nights) which seemed to demonstrate undercorrection in my scope so the 0-1 Chromacor, which introduces 1/6th wave (approx) overcorrection, seemed a good bet. I made a bid and, hey presto, I won :)

I was the only bidder - I don't think many people would have given it a 2nd glance !.

Tony (whippy) reckons they are a bit uncommon so I feel lucky to have found this one, especially as it's in excellent condition.

I've got quite a bit of fine tuning to do on the "system" as a whole but the results tonight were very encouraging :p

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I was tempted by one on Ebay about a year or so ago but I would have had to then find the scope to match the chomachor rather than the other way round which seemed like it could have been bit difficult.

IIRC spacing is the key to getting the most out of it??

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....IIRC spacing is the key to getting the most out of it??

Yes - I've found lots of information on the web about setting them up. The designer, Valery Deryuzhin, posts on Cloudynights and there is a Yahoo Group for Aries products.

The critical factor is spacing between the eyepiece focal plane and the Chromacor optical assembly - my device was supplied with a number of spacers (empty 48mm filters) but last night I found the 28mm Hyperion fine tuning ring did the job OK though this is one of the areas I'm going to be experimenting a lot with. I'm also going to have to pay more attention to focusser and objective collimation - I think a replacement focusser might be worthwhile in due course.

Edited by John
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Oh well done John! :)

That's a great find and even better it went under the radar on Ebay. I remember they cost a fortune when new. And you will hopefully now have a well corrected 6" refractor......lucky blighter!

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Should be great. I still have a 150 as well, though sadly it rarely gets used and is worth peanuts despite being a fine visual beast even as it is. I look forward to hearing more. Well done.

Olly

Thanks Olly,

I agree that the 150 F/8's are good scopes, even in their standard form. I guess their value is partly due to fashion and the mounting / handling issues that the long and relatively heavy tubes present.

If somone has the mount and muscle I've noticed a number of 5" and 6" acrho's on the market for well under £200 at the moment.

There is something very satisfying about using a large refractor I find which seems, to me anyway, defy the logic of using more practical compound scopes of similar or larger aperture :)

Edited by John
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I've just picked up a 90mm f11.11 and absolutely loving it. Saturn has been a real surprise with no CA and a lovely sharp image upto 200x.

Must admit a 120 f8.3 or 150 f8 appeals a lot, always has. I have a real soft spot for refractors.

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Hi John,

That's a lovely set up you have there:)..

I actually saw the Chromacor myself and emailed the owner asking if he had a buy it now price...I did some net research and was put off by the fact that there seem to be different versions for different "abberations", and I thought knowing my luck I'd pick the wrong item for my needs:rolleyes:...

You seem to have landed a bargain there sir, well done!

Ref your mount, can I ask where you got your pillar extension? I would like to get one for my own CG-5 as I have a large long focus frac coming soon, and I don't want to spend all night lying on my back to get to the eyepiece:D..

Also an indication of the pillar price would be helpful if you don't mind sharing..

Good luck with the star party, bet you will have a large queue to view:hello2:

Dave

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I guess you're waiting for Jupiter with baited breath, eh John?

Yep :p. I had some great views of Mars and Saturn last night - the Chromacor seems to allow higher useful magnification so 343x gave me much crisper images than the standard scope did where performance nose-dived beyond 250x. There is a "snap" to focus that was not there before as well :)

Can't wait for Jupiter :)

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Hi John,

That's a lovely set up you have there:)..

I actually saw the Chromacor myself and emailed the owner asking if he had a buy it now price...I did some net research and was put off by the fact that there seem to be different versions for different "abberations", and I thought knowing my luck I'd pick the wrong item for my needs:rolleyes:...

You seem to have landed a bargain there sir, well done!

Ref your mount, can I ask where you got your pillar extension? I would like to get one for my own CG-5 as I have a large long focus frac coming soon, and I don't want to spend all night lying on my back to get to the eyepiece:D..

Also an indication of the pillar price would be helpful if you don't mind sharing..

Good luck with the star party, bet you will have a large queue to view:hello2:

Dave

Thanks Dave :p

I did take a slight chance in the purchase I guess but I was fairly sure about my scopes undercorrection before I bid - I'm not experienced enough to determine the exact extent of the undercorrection from the intra and extra focal star images like some though.

From the star images I saw last night (not an ideal night for it I have to say) I'd say that the whole system is just a touch overcorrected now, but I can live with that and I've some more experimenting with spacers and collimation to do yet. CA is really signficantly reduced though :)

I bought the pillar extension from The Widescreen Centre in London when there on a business trip a couple of weeks ago - £89.95. That sounds quite a lot but the thing is really well made - it's fit and finish is better than the rest of the mount in fact !. It's pretty heavy but luckily I only had to lug it as far as Paddington :)

I'm probably going to use the CG5 EQ head at the star party as it's steadier at high power than the alt-az, the motor drives help there - things do whizz across the FoV quickly when you get over 300x :)

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