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WO GT/F 81 and/or 102 question

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#1 N1ghtSc0p3

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Posted 26 March 2014 - 11:14 PM

I've read Timm's review of the GTF102 and the Astronomy Technology Today review of the GTF81. I'm interested in both of these scopes, but have a question about what's needed in addition to the scope...do I also need the camera adapter?

I currently have an A2FF and 0.8 FF/FR from Astro-Tech, so I was also contemplating the GT models as well...though the primary intention is imaging, I might use it visually from time to time. Do I need the WO-specific reducer if I went with the GT scope instead of the GTF?

Thanks.

#2 Scott Rose

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Posted 27 March 2014 - 06:15 AM

If you get the GT model, then you should use the WO FF/reducer that they make specifically for each of those models. Each scope has its advantage. The built in field flattener raises the native focal ratio of each one of those scopes. I have the GTF102 because when I bought it, the website said it was f6.9. Only to learn later that was wrong and it was actually f7.7. Had I known this, I probably would have gotten the GT102 and separate FF/reducer. That said, I have found it to be an excellent visual scope, but have not yet tried it for AP. If going only visual the GTF102 would be my pick. If AP is your goal, then think of the targets you want to capture first. The GT81 will give a much wider target than the GT102. And yes, you will need a camera adapter for either the DSLR or CCD.

#3 timmbottoni

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Posted 27 March 2014 - 01:14 PM

Hi,

Thanks for feedback on my review, and Scott is correct on the focal ratios, etc. I think regardless of which way you go, you will need some sort of camera adapter. The focuser accepts any standard 2" (or 1.25" with included reducer) accessories. If you have one you can use it, if you need one, then WO has some good options.

If you want to image a wider field of view, then the GT102 with the FLAT 6A is the way to go. I'm not sure if options you mentioned that you already have will produce optimal results, but if you have them you can try them and see just how well they work. If you decide to, you can always try them first, and then if you don't get the results you hoped for, buy the WO FLAT 6A. That way you aren't buying the Field Flattener from WO only to find out that you didn't need it.

Also - the optics in the front are the same high quality FPL53 triplet whether you get the GT or GTF model of each size. And one final note... The GTF 102 can be used without the built in field flattener, by unscrewing that section, and reattaching the focuser, and then using it like a GT102 (with a 2" extension tube), and even adding the FLAT 6A. The GTF81 can't do that, because the design isn't built that way. If you look at the pictures you might be able to see what I mean. If you need more info on that just let me know.

Hope that helps!

Timm

#4 N1ghtSc0p3

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Posted 27 March 2014 - 06:49 PM

Hi Timm,

I really enjoyed your review of the GTF102. I didn't know that one could turn the GTF 102 into a GT like that...that's really good to know! I am definitely leaning towards the 102 for the following reasons:

- I have a 72mm f/6 scope
- I've actually pre-ordered the upcoming WO Star 71 APO imaging scope
- I'd like to try something with a little longer focal length for some of the slightly smaller targets
- Seems to me that the GTF102 is one of the best deals around for a full APO w/ FPL-53 glass and a built-in (but changeable!!) field flattener

I should make a decision in the next day or so.

Thanks all for the input and advice.

Cheers,

#5 N1ghtSc0p3

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Posted 27 March 2014 - 07:50 PM

For the WO GTF 102, I see the 'standard length Canon' (P-PA-C), 'long Canon' P-PACL, and 'standard T-ring' P-PA2 adapters. Does anyone have experience with the standard and/or long Canon adapters? Just want to make sure I order the right one for my 450D.

Thanks!

#6 timmbottoni

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Posted 28 March 2014 - 08:07 PM

For the WO GTF 102, I see the 'standard length Canon' (P-PA-C), 'long Canon' P-PACL, and 'standard T-ring' P-PA2 adapters. Does anyone have experience with the standard and/or long Canon adapters? Just want to make sure I order the right one for my 450D.

Thanks!


Hi,

Get the long version for a refractor, the short version would be better for something like a reflector.

Does that make sense? I can explain further if you want, but just picture where it goes in the optical path, and remember that in a refractor you need the extra length to take the place of what would normally be a diagonal. An SCT could use either most likely.

Timm :grin:

#7 timmbottoni

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Posted 29 March 2014 - 10:57 AM

I did a comparison showing the 2 fields of view (in SkySafari 4 on Android) of the GTF102 (smaller field) to the GT102 with .8X flattener (larger rectange), using my Canon 60D as the chip (APS-C).

See if this helps you see the difference. I think if you already have a FF, I would go GT102.

Timm

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#8 timmbottoni

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Posted 30 March 2014 - 03:52 PM

I shot some actual test pictures last night comparing the GTF102, to the GT102, to the GT102 with the WO FLAT6A. As soon as I can look at them in detail I will post them.

Timm






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