APO Refractors

Hi all,
After about a year of researching refractors etc ive many questions as ive been looking to buy one for quite some time now!

What is the difference between ED and APO? Ar e they the same? Prob an obvious question here but it puzzles me! Also what does the doublet and triplet mean?? And whether its fluorite etc?

And then the glass type the FL 53 and 55 etc which is better and why?

I see all these specs but nowhere actually EXPLAINS the significance of them!

Also has anyone any experice with the new WO 72mm Scope??

www.williamoptics.com/telescopes/megrez72_spec.php

It seems very reasonably priced!

Also does anyone have experience with the 66mm scopes?

How might i go about mounting one of these scopes on my LX 90 or is there any point? Is my mount up to it? Would it be worth it with regards to imaging? I have an eq. wedge but would i be better off just getting an eq. mount such as a HEQ5 or Eq6 Ir HEQ6 mount to mount the 8" Lx90 and the WO scope aswell as imagers for astrophotography?? I really want to get into astrophotography and i know many peoples motto is that a good solid mount is primary!

Ill have to invest alot to get what i want outta this but ill wait and see!

All opinions and help is very much appreciated as im getting quite impatient atm with m setup and i think swaying away from the Lx90 mount would help!

Many thanks,
Matthew

How might i go about mounting one of these scopes on my LX 90 or is there any point? Is my mount up to it? Would it be worth it with regards to imaging? I have an eq. wedge but would i be better off just getting an eq. mount such as a HEQ5 or Eq6 Ir HEQ6 mount to mount the 8" Lx90 and the WO scope aswell as imagers for astrophotography?? I really want to get into astrophotography and i know many peoples motto is that a good solid mount is primary!

Ill have to invest alot to get what i want outta this but ill wait and see!

All opinions and help is very much appreciated as im getting quite impatient atm with m setup and i think swaying away from the Lx90 mount would help!

Matthew,

As you know, I've invested quite alot into my astro gear and based on this, if I were to start out again now, this is what I would do:

Decide first if you really want to get into astrophotogaphy. If you do, to get really serious into it with a v. expensive ccd camera and mount, it could cost a significant 4 figure sum and perhaps even a 5 figure sum. For the same money you can get a large goto dob.

If you do enter astrophotography, I would start off with wide angle imaging and get good quality equipment to do the job. Do not compromise your efforts buy buying inferior quality equipment as it will only drive you nuts and make your life mich more difficult. You already have a DSLR. A very good piece of kit is the Astrotrac mount. If you bought this and a Canon 50mm MKII lens for approx 90euro, you'll have a very nice piece of kit for wideangle images.

The next step up from here is to get a Canon L lens with a focal length in the range of 300-400mm. This will give you images of large DSOs and can still be mounted on the Astrotrac.

The beauty of the Astrotrac is that you will always have it and can bring it on hols with you.

I would recommend you take these 2 steps first before investing in a new mount. This way, you can still keep the LX90, which is a fine scope, and also do astrophotography at the same time. You will still be able to do planetary and lunar imaging with the LX90 if you use a good webcam or pick up a DMK camera at a later date.

Some sample images of plenets which I took with your LX90 and a webcam:







Images of the moon with your LX90 and Canon 300d:
www.astroshot.com/Lunar/images/2005_05_0...1_40thsec_iso200.jpg

www.astroshot.com/Lunar/images/2005_12_17_moon_lx90_300d.jpg

The purpose of this is not to "show off" my images, far from it. It's to show what a simple astronomer like myself can do with the exact telescope you have. If you have the interest and put in the time and effort, you'll get better images than these.

If you combine your existing scope and camera with a decent tracking platform and and one or two decent Canon L lenses, you'll have loads of gear to take astro images without spending a fortune. FWIW, I plan to get an astrotrac myself - gone around in a full circle you might say.

Hope this helps,

Hi Matthew, from what my puny brain does know



[/quote]What is the difference between ED and APO? Ar e they the same? Prob an obvious question here but it puzzles me! Also what does the doublet and triplet mean?? And whether its fluorite etc?

And then the glass type the FL 53 and 55 etc which is better and why?

I believe APO is the 'pure bred' top quality APO, whereas ED is slightly less quality, sometimes referred to as semi-apo.

Doublet/triplet refers to either 2 or 3 baffles inside the scope to dampen internal reflection, 3 is better.

I believe FL 53 is superb, I actually have'nt heard of FL55 so I don't know :oops:

Keith..

P.S. here is also a good company to deal with, they sell top notch APO'S would you believe up to 7" :shock:

www.astrotech.it/

Keith..

Hi Keith,

I too am looking for an APO or close enough to piggyback on the CGE, for wider field shots, would you recommend the Megrez 90? A Vixen 103 also came into the equation.

I believe APO is the 'pure bred' top quality APO, whereas ED is slightly less quality, sometimes referred to as semi-apo.

Doublet/triplet refers to either 2 or 3 baffles inside the scope to dampen internal reflection, 3 is better.

I thought that a doublet only used two pieces of glass in the lens, but a triplet uses 3 pieces of glass, each with different properties to correct for color and other aberration's. this is why triplets are so much heavier, due to the massive weight of all the glass used in the lens. is this not correct?