Its all about the F ratio

[Earl]

currently the rig im using is at F4.7, however im not impressed with the Blue at all (WO ZS71)

Im considering either the 5 element WO ZS71 at F4.9 coming in at £800 or the Borg 71 at F3.9 coming in at £1700..... humm maybe that answeres it in itself.

1k for an extra 1 F?

I know good and fast dont come in cheap in refractors however.

[perfrej]

I bet there is more to the extra k than just -1.0 f... Maybe a slightly better glass or optical design? Just thinking out loud

My TEC-140 is f/7... It is pretty good, actually 

/per

[Earl]

I bet there is more to the extra k than just -1.0 f... Maybe a slightly better glass or optical design? Just thinking out loud

My TEC-140 is f/7... It is pretty good, actually 

/per

I do agree Per, however on doing some research im not reading posative things about this blue bloat with Borgs either, and im doing my damndest to not just go baby Q,(its more than I want to spend on a seasonal rig) which I know just "Delivers".

[ronin]

To my thinking F4.7 in an ED refractor (WO ZS71) is going to show CA in one form or another. Basically too fast for the glass to handle. Many of the good triplets are slower then f/4.7 so I cannot see any doublet at that managing to control colour sufficently.

If the ZS71 was about f/6 then better (preferably f/6.5), for some reason the thinking is the faster the better and all other aspects are ignored. It might be if the glass can take it but you will need some expensive glass and more then 2 bits to manage it.

Personally I am not keen on a triplet at f/5, f/5.5 maybe but I would not be comfortable at f/5.

Have a look round and see how many apo triplets are f/4.7 - not a lot. There is less chance that a doublet will manage it when a triplet cannot.

[JamesF]

Unfortunately I have to inform you that I had almost managed to completely forget about Meghan Trainor and now you've gone and spoilt it.  If that damn song doesn't shift from my head by the morning and I have to come up there, tie you to a chair and force you to listen to it on auto-repeat for hours on end, you will understand that it's nothing personal, won't you?

James

[wxsatuser]

I do agree Per, however on doing some research im not reading posative things about this blue bloat with Borgs either, and im doing my damndest to not just go baby Q,(its more than I want to spend on a seasonal rig) which I know just "Delivers".

I know my Borg needs some effort put into it, I must knuckle down and try and sort it out.

May be I'm asking to much of it in the fast stakes with a dslr attached, but if you don't try you never know.

[Earl]

I maybe missing one detail, I can just stick to narrowband and as a F4.7 scope forNB is pretty damned good.

[ollypenrice]

The Baby Q is one of very few instruments which doesn't have a rival. It can work without blue bloat at F3.9. However, for NB there are aternatives. In natural colour, though, only the Baby Q hits the sweet spot in this aperture class.

Olly

[Mike Hawtin]

Earl, I have the Borg 71 and 0.7x reducer/corrector, in all honesty I would recommend you avoid it.  It just doesn't perform well at the blue end of the spectrum with my Astronomik filters, Astrodon filters apparently cut off a bit more but I'm reluctant to go to even more expense on the off chance they will reduce the bloating.

[swag72]

I've already said elsewhere Earl but you do tend to chop and change kit until you have the very best that you can get. By all means get a different scope, but you will end up getting an FSQ85 in the end, perhaps after a season of frustration of not being able to achieve what you want. Why waste time and money now.... just get what you know will perform from the start.

[Phillyo]

Earl, I have just taken delivery of the WO 5 element Star 71 and although I've only used it once I have to say I'm very impressed with it. You can see my first light image on the second page of the Deep Sky thread. For me it's perfect and for the price I couldn't be happier. The same as everyone else, I would love a baby-Q...who wouldn't? But at over £3k it's a lot of money to spend on a scope. I wanted to find something that just worked, and the Star 71 does.

I had the Megrez 72 before that but it was a faff. Not getting a flat field, trying to get the perfect spacing between the scope and the FF/FR to avoid elongated stars in the corners. No rotation option etc etc. The Star 71, again, just works. I connect my QSI583 to the scope, rack it out about 12mm and I'm imaging. It has the rotator so I can just move it to suit my framing needs.

My only caveat is that I only do NB imaging so not sure how it'll handle LRGB pictures.

IKI may let you trial one before purchase?

Phil

[Astroscot2]

Earl , I see in your sig you have a FSQ and reducer all ready, im trying to work out if your looking for a shorter fl instrument or

a faster f- ratio instrument or both? If blue bloat is a main concern have you considered a newt?

[Earl]

My secondary rig is evolving, the scope on it at present is the ZS71 which is not up to what i want for LRGB, however im considering just using it for SHO, just need a good night to finish my Rosete to see if it will do the job, which i think (hope) it will. IF it delivers what i want ill just upgrade the CCD to a 460 for the extra sensativity over the 683 i have currently plugged in.

[Earl]

Earl , I see in your sig you have a FSQ and reducer all ready, im trying to work out if your looking for a shorter fl instrument or

a faster f- ratio instrument or both? If blue bloat is a main concern have you considered a newt?

I have considered the Epsilon 130 it looks quiet impressive.

[Phillyo]

Would you be selling the 683 for the 460 Earl? Are they that much more sensitive? I have the 583 and love it...though it's my first and only CCD so nothing to compare it to.

Phil

[Earl]

Would you be selling the 683 for the 460 Earl? Are they that much more sensitive? I have the 583 and love it...though it's my first and only CCD so nothing to compare it to.

Phil

Oh No thats a great camera on my 106.

[Astroscot2]

Im also pulling together a secondary rig, something portable for quick trips to a dark sky site and astro parties.

I no longer own a frac but would like something that does not break the bank, another fsq aint gonna happen, ive been looking

at the Orion ED 80T CF with reducer, its more apealing price wise than a borg or fancy TS refractor.

I have some nice APO medium format lenses that I want to also try with my ccd.

The last year im been trying to sort my kit out, im getting there.

Mark

[laser_jock99]

I have considered the Epsilon 130 it looks quiet impressive.

The only true apochromat would be an all mirror system. Unfortunately the necessary coma correction optics adds an element dispersion.

An often forgotten aspect is the full spectrum capability of all mirror systems. If you use a full spectrum camera (UV thru NIR) like I do- then you can make use of the extended wavelengths as they still all be at the same point of focus (in theory). Lens based optics can only bring a limited spectrum to a focus. Hence the need for UV & IR blocking on all filters to limit haloes from out of focus wavelengths when used with lenses.