Quintuplet (5 lens) for visual?

[kriss13]

Hi

I was wondering if an 80mm quintuplet APO is suitable for visual.

I will purchase an 80mm for astrophoto, but also using it as a portable g'n'g telescope too.

The Orion 800mm triplet FPL53 carbon is what I want

but for 100 euros more I can get this one.

Will the quint have too much glass for visual (compared to a doublet or triplet FPL53 whre I can remove the FF)?

I don't know if the corrector is removable (screw in) form the quint.

thank you.

[ronin]

The extra 2 bits of glass are simply a flatener and will therefore make the final image flatter across the view. They will no cause a problem, I suspect that will make it better. It is not a reducer so you do not in effect lose focal length.

It is only 2 bits of glass so that will not upset the optics, look at eyepieces: a plossl has 4 elements a BST has 6. That is 2 more, go look at the number of bits of glass in an Ethos.

It appears to be something very much like the WO GTF81, that has 5 elements in it, and that is the same as the GTF-102 and the new Star-71.

APM make an 81mm imaging scope that is 6 elements, 3 at the normal objective end and 3 acting as a flatener reducer. For imaging building these is had the advantage of the user just alters the ficus to get the camera at the right location so no trying to get spacings just right.

Should be good for visual as well, very good I suspect and makes the focusing on the camera easier also.

[Davey-T]

When I was researching getting a new refractor I found reports of some astrographs not being able to reach focus for visual use especially with 2" diagonals and 2" eyepieces, I think the WO GTF102 was one of them.

Dave

[kriss13]

That's a new one, not reaching focus with diagonals... I wonder if it is in or out focus.

I could use extensions to get it to focus in one of the cases.

I may pull the trigger for the quint

[Davey-T]

That's a new one, not reaching focus with diagonals... I wonder if it is in or out focus.

I could use extensions to get it to focus in one of the cases.

I may pull the trigger for the quint

Something to do with lack of inward focuser travel I think, have a search on Cloudy Nights.

Dave

[lensman57]

That's a new one, not reaching focus with diagonals... I wonder if it is in or out focus.

I could use extensions to get it to focus in one of the cases.

I may pull the trigger for the quint

You can not use an ordinary diagonal with the 5 element Star 71, it won't reach focus. You either need to buy a special screw on diagonal or use it as a straight see through for visual. Most Japanese astrographs are like this too.

A.G

[Ruud]

I hope you buy the thing and find it perfect.

For myself, I have a four element flat-field refractor, all lenses air spaced, which causes no visible dimming, has invisible scatter and has no ghosting whatsoever. You can easily lose 5% of the light and notice nothing of it. I compensated for my many lens surfaces with a dielectric diagonal several percent brighter than the original enhanced aluminium one. Don't notice any difference from that either.

[kriss13]

Thank you all for clarifications of various aspects

BTW the other scope is this.(FPL51)

I have an offer that includes a FF 0.8x, baader APO filter, CNC rings+rail, case, 2" to 1.25 adapter... at the listing price 480€.

Makes it almost a contender for the quint... but less expensive.

Whould the 400€ more justify the 5 lens (taking into account that the other scope has a FF that corrects curvature and reduces the FL, and a filter to kill CA)?

Or should I spend better on 2 EP from ES (80* ones).

I heard that at 80mm the fringe is not very visible in photos ...

ps.

My astrophoto gear is complete because I just sold my last scope (102mm) being to heavy for my Astrotrac, so it is just a matter of what OTA to buy.

I hate it when I cannot choose from 2 different offers very different that are equally favorable to me .

[happy-kat]

Is there a weight difference?

Seeing as the number of lens is different between them I think reading your post

[kriss13]

Verry little, 2,2 vs 2,5 for quint... 300g difference, my NEX with adapters

Both are carbon, similar construction.

[happy-kat]

Too close to help you decide :-)

[kriss13]

yeah, weight is a non issue... I just whant the lightest 80mm APO (or close) for my Astrotrack , hence the carbon tube.

[kriss13]

Also there is no review or any one that talk about it the quint... i wonder if no news is bad news

[Ruud]

Davide Sigillò likes the Tecnosky. He wrote a review of it.

Does anyone know who makes this telescope and under which other brand names it is sold? It certainly looks interesting.

[kriss13]

Davide Sigillò likes the Tecnosky. He wrote a review of it.

Does anyone know who makes this telescope and under which other brand names it is sold? It certainly looks interesting.

I was talking about the 5 quintuplet

but thx anyway.

[Ruud]

Oh, sorry. I clicked the link in your post number 8 above. That scope looks looks very interesting for visual.

[kriss13]

Is it true that the quint will allow more magnification because of the corrected optics?

I search the net for an opinion about quintuplet for visual and didn't find detailed of what it behaves.

[NickK]

I use the Pentax SDP (double with inbuilt doublet flattener) for both visual and imaging.

It has a pancake flat field. I've only noticed that the TV 2x adds a little curve at the edges. I normally use Baader EPs but I've compared WO and TV 10mm pieces (WO<Baader<TV).

The visual is far better than most other scopes I've seen of the same size. Maximum magnification I've had was with 2x 5x stacked with a 10mm EP.. 

[Davey-T]

I think Olly has mentioned in the past that not all these scopes are equal just because they have the same lens system.

The Pentax would probably cost twice as much second hand as the Astro Pofessional new.

Dave