Chromacor on buy and sell

[spaceboy]

http://www.astrobuysell.com/uk/propview.php?view=120486

A very rare item indeed but £725 rare ? I totally get that the average 6" apo refractor will put a dent in your kids inheritance so if it is possible to match a chromacor with an already well corrected achromat your laughing but at £725 and no guarantee you will find the ideal match wouldn't you just be better off getting a used ED refractor to get those true apo views?

I appreciate the chromacor as far as I am led to believe will if matched work with any size achromat refractor so if you have the money for a mount and an observatory large enough to house an 8" + refractor then the chromacor is well worth it's weight in gold.

I know chromacor are rare as clear, transparent nights in the UK so demand a higher price but how much were they when they were available ?? And if they were so good at correcting achromatic refractors why didn't they consume the market.

[F15Rules]

My thoughts exactly. 

I know John, our resident eyepiece guru?, had one a while back and although he did get it to work well I don't think it was totally straightforward and I doubt it cost him anything like that. As you say, you could get a very nice ED120 or equivalent for the cost of this plus say £200 for a 6" F8 Synta achromat..

Dave

[Chris]

Yeah that's probably double what I'd pay. Besides the price, Knowing that John has tried these a couple a times yet ended up with a gaggle of ED's tells me all I need to know.

[mikeDnight]

They were expensive from the start. Your question about the ED apo is extremely valid. When the chromacors were first introduced the ED apo market was to many folk, out of reach due to the extreme high prices. Around £2000 for a 4" fluorite doublet from Tak or Vixen was just too high a price for many. £3,850.00 for a 5" Tak thirteen years ago, EEK! ? So, you can see why the chromacor had appeal.

If the chromacor's were truly excellent they would still be a major player in today's market, but with the superb SW 100 & 120 ED Pro available for only a little more outlay, its a no brainer. The achromatic telescopes from SW varied greatly in quality of figure, where as the ED's are all of high standard, some very high standard. Optical quality really does count and Id put money on it (your money) that no 152 SW achromat with chromacor would give anywhere near the performance level of a  100 or 120 SW ED.  I've seen a 152 SW achromat die alongside a 102mm Vixen fluorite with regard to its planetary performance. There's simply no way that trying to correct CA by adding corrective elements will ever produce the pure laser etched views given by the FPL53 ED doublets.

Mike

[alan potts]

As said I know John had one a good while back, I don't believe they are easy to use and I am also sure they didn't cost that amount new. For that price you could get a few nice different types of s/h telescope, I would feel you could pick up a nice 12 inch Dob for 725 quid.

Alan

[John]

I actually owned 3 of these including one of the very rare version II's which is the type being sold. I believe the seller is a member here.

If properly matched to the objective characterisics and installed these devices certainly do transform the performance of an F/8(ish) achromat to that of a good ED doublet of the same aperture.

When you witness the effect that both the reduction of the CA by around 80%-90% and (if properly matched) the removal of spherical abberation has on the performance of the scope it does make you realise where many of these achromats are optically before correction.

The cost of a 6" ED doublet is around £2300 I think (the APM / LUNT ED doublet is the lowest prices I think) so with a chinese used chinese achromat OTA plus probably a focuser upgrade plus some careful installation you could have an ED doublet equvalent for around 50% of the cost of an off the shelf one.

The price being asked is what they can go for but most change hands in the USA.

 

[Peter Drew]

I'm sure that the value of a Chromacor, both financially and in performance is in some way proportional to the size of objective it is applied to. I have a 8.5" F12.5 achromat but the residual CA is not enough for me to feel minded to use a V block filter let alone stumping up £700+ for a Chromacor. Had my objective been F8 or faster it may well have been a different matter! I'm also not convinced that the suppression of CA and SA in a "cooking" achromat is sufficient to raise it to the level of a high end APO. 

[spaceboy]

3 hours ago, John said:

The price being asked is what they can go for but most change hands in the USA.

 

Had the distance not been an issue I would have had myself one 4-5 years ago. I think I PM's you for advice on price of chromacor at the time John. The seller was offering a chromacor II with "matched" EVO150 for $550 CAD on the Canadian version of Buy and Sell. Not sure if it ever did sell as the owner wasn't going to split and shipping the lump that is an EVO150 to the UK was never going to be cost effective.

All said and done though I have to say I'm REALLY happy with my ED120 and despite loving the whole big frak thing with my EVO150 I let it go as it was just too frustrating to mount compared to the dainty ED. A chromacor may save you a tidy sum over an equivalent APO but having a big refractor comes with it's own set of challenges which encourages further spending.

[John]

2 hours ago, Peter Drew said:

I'm sure that the value of a Chromacor, both financially and in performance is in some way proportional to the size of objective it is applied to. I have a 8.5" F12.5 achromat but the residual CA is not enough for me to feel minded to use a V block filter let alone stumping up £700+ for a Chromacor. Had my objective been F8 or faster it may well have been a different matter! I'm also not convinced that the suppression of CA and SA in a "cooking" achromat is sufficient to raise it to the level of a high end APO. 

Not a high end apo I agree Peter (now that I now own a couple ) but I certainly noticed the difference when I put a chromacor into a Synta 150 F/8 and a Meade AR6.

If one wanted to get into the really big league refractors (I know you are already there !) then you could combine the chromacor with a 7.1" Istar R30 F/8 which is on sale and get a pretty special refractor for a bit over £3K 

The chromacor was developed when the chinese 4.7" and 6" acrhos first started shipping. They probably made more sense back then but the advent of affordable and good ED doublets (thanks again to Synta) was a bit of a game changer.

@Spaceboy / Nick: I agree with you on the ED120 and the mounting challenges of larger aperture refractors.

It was fun playing around with the chromacors that I've owned though and the 6" achromats that came and went as well. I think I learned a bit about refractor optics during that time although I'm no E S Reid thats for sure !