starting out with apo's. takahashi vs evostar

[valefor]

as it states in the title. im about to buy my first apo refractor. ive read alot of reviews and the evostar 80ed sounds like a perfect start. but i do have some newb questions.

first of all i have seen 2 scopes in green witch that to the untrained eye seem identical.

the takahashi fc 76ds and the evostar 80ed.

both doublets and both around 80mm objective lens. (tak is 76 but hey hoo)

both are around f7.5. the tak is slightly shorter by 50mm.

so can someone explain to me why the tak is £2000 more expencive than the £450 skywatcher? is it the difference between aston martin and jaguar? or jaguar and mondeo for example?

my second question. this one will really make me sound like a dumb newb. but i have a 8" newtonain at f5. with a FR the 80ed will go to f5. but that doesnt meen i will be able to see what i can see in my f5 newt does it?

also i asume that a heq5 is the perfect mount for AP with a 80ED. am i right in assuming this?

thanks everyone for your time and sorry for the level of stupidity.

[astrosathya]

Hi Newb

Quality of the optics is what dictates its price. The Takahashi for example may have guaranteed optics with a Strehl ratio of above 0.9 while the Evostar may be diffraction limited. Its not the type of glass they use that only dictates the quality, but also the surface finish. Also the Takahashi will undergo strict quality control, the Japanese are very particular when it comes to perfection. The Evostar is made in Taiwan and for all I care it may be a farmer assembling the lenses. Yes, you are correct when you compare it with a Jaguar and a Mondeo.

By the way, the Tak will weigh far more than the Evostar, they are built like tanks.

Hope I was some help.

[Mr Bond]

F number is a focal ratio. It doesn't mean it has the same brightness or light transmission( even on the same diameter, as coatings and baffles have a part to play!).

the f number is how many times the diameter will divide into the focal length. So a 200 f5 has a F/length of 1 metre (1000mm).

A 200mm f5 reflector and a 80mm f5 refractor are different animals. Hope I helped but I doubt it!

[John]

Hi Newb

Quality of the optics is what dictates its price. The Takahashi for example may have guaranteed optics with a Strehl ratio of above 0.9 while the Evostar may be diffraction limited. Its not the type of glass they use that only dictates the quality, but also the surface finish. Also the Takahashi will undergo strict quality control, the Japanese are very particular when it comes to perfection. The Evostar is made in Taiwan and for all I care it may be a farmer assembling the lenses. Yes, you are correct when you compare it with a Jaguar and a Mondeo.

By the way, the Tak will weigh far more than the Evostar, they are built like tanks.

Hope I was some help.

Optically, I think the scopes will not be as far apart as this. Tests I've seen show an average Strehl for the Skywatcher ED's of around .95 or better and for Takahashi doublet's .97 or .98 so not much in it by that measure.

The Tak optics will be polished to a higher standard and better coated though so that will deliver some improvements. The overall mechanical quality and build of the Tak's will be much, much higher than the Skywatcher ED's though. The latter are OK but just that in the build and finish department.

[valefor]

astrosathya that does make a bit of sence. however i still dont think its worth 6x the price of a sw apo.

so mr bond. you have come with answers. (that was fun to say.)lol

i understand how f ratios work tho i didnt know if light transmittion was the same princible. i see its not. thanks for the info. so a galaxy i can see in my 8" newt may not be visable in a 80mm refractor.

so how do i find them for imaging with a frac without being able to see them. and without using a goto?

[ollypenrice]

Takahashi are premium scopes, mechanically very well made and optically excellent. However, I very much doubt that a Tak doublet is likely to represent all that good a buy. To get the best out of Takahashi you need to move to their top end quadruplets (for photography) and triplets. The high end FSQ quadruplets are wonderful for imaging. In visual use the SW ED80 will get much closer than you might think. But when you put a camera in you see why the FSQs have such a following. You have a huge flat field, superb colour correction right into the blues, reliable focus control, etc etc. They can produce world class images on very large format cameras. They also have fast F ratios and are even faster with their reducers. It is worth paying Tak prices for these instruments but, quite honestly, their doublets are way too expensive.

Olly

[Mr Bond]

Also less obvious but true is that as you progress as an astronomer, your interests may drift.

Two things, will you wish you hadn't spent all that money on an apo, or will you be pleased you did as it'll make a fine travel 'scope!

thus it begins.......

;-D

[Mr Bond]

Or of course, justify to buy both or more...

[valefor]

i see. thanks guys. although the price of the tak still hits hard. i think i would rather put the 4 grand into a deposit for a mortgage than ap and live with a house and a sw ed80. lol. at least till im 55 and mortgage is payed off.

to reitorate a previous question. how do you find objects for ap if you cant see them to lign them up? piggyback on a newt with duel mounting would be my only guess for someone who dont have goto.

[Mr Bond]

Star maps and using "sign posts" as a guess. I'm assuming you want to do a long exposure on a dim dso?? Someone more knowlegeable will be along shortly

All my stuff is visual.

[ronin]

If you cannot see them then you use the finder scope or equivalent to aim at the object (hopefully) then take a shortish exposure assuming a DSLR, say 10 or 20 sec. Hopefully the object will show up on the image captured. If it does and is central then great, take the series that you want. Otherwise repeat again until the object is located and central.

The option on a goto is to perform the alignment then you goto a star near the object and centre that accurately, on some you can then use that as a new datum point and then make the short move to the object wanted. There are similar options sometimes provided under an assortment of names.

[ollypenrice]

Use GoTo for AP. Time is far too precious to waste.

Olly

[dmahon]

Consider an equinox 80 as well. Only £100 more but F6.25 (F5 with a reducer).

[Dabajeh]

Taks are worth every penny